>> Seed and Fruit Formation
Section 46. Formation of seeds and fruits
What happens in the ovule after fertilization? The fertilized egg divides in two cells... Each of the cells that arose in this process divides again, etc. As a result of multiple cell divisions, a multicellular embryo of a new plants.
From the largest ovule cell, which fuses with the second sperm, endosperm cells develop, in which nutrient reserves are accumulated. The endosperm supplies them to the developing embryo.
The seed coat develops from the ovule cover. So, after fertilization, a seed, consisting of a peel and an embryo, develops from the ovule.
Lesson content lesson outline support frame lesson presentation accelerative methods interactive technologies Practice tasks and exercises self-test workshops, trainings, cases, quests home assignments discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photos, pictures, charts, tables, schemes humor, jokes, jokes, comics parables, sayings, crosswords, quotes Supplements abstracts articles chips for the curious cheat sheets textbooks basic and additional vocabulary of terms others Improving textbooks and lessonsbug fixes in the tutorial updating a fragment in the textbook elements of innovation in the lesson replacing obsolete knowledge with new ones For teachers only perfect lessons calendar plan for the year methodological recommendations of the discussion program Integrated lessonsPalm trees - one of the largest families of flowering plants - has about 210 genera and 2780 species (G. Moore, 1973), and according to some sources - up to 240 genera and about 3400 species. Palm trees are widespread mainly in tropical and subtropical countries in total the globe, but especially richly represented in Southeast Asia and tropical South America; only a few species are found in extratropical regions (Map 13). The farthest to the north (almost 44 ° N) comes the squat hamerops (Chamaerops humilis), common in the Mediterranean from southern Portugal to Malta, as well as in North Africa. The Phoenix theophrasti date palm grows on the island of Crete. In the arid regions of Afghanistan, the nanorops Ritchie, or mazari palm (Nannorrhops ritchiana), is found, the range of which extends further into Pakistan, southeastern Iran and South Arabia. Trachycarpus fortunei reaches 35 ° N. NS. in Korea and Japan. This is one of the most cold hardy palms known to be cultivated in Scotland. Another species of the genus, T. takil, grows in the Western Himalayas at an altitude of almost 2400 m above sea level, where snow covers the ground from November to April. The genus Livistona enters Southern Japan and Eastern Australia (up to 37 ° S lat.). The northernmost American palm growing in the southeastern United States, Sabal minor, is found in North Carolina, and Washingtonia filifera (Washingtonia filifera) grows in the desert oases of Southern California and Western Arizona on the Pacific coast. The border of distribution of the family in the southern hemisphere passes through the islands of Juan Fernandez - the island of Robinson Crusoe (southern Juania - Juania australis) and the coastal regions of Central Chile, Southeast Africa, as well as New Zealand and Chatham Island.
Palm trees are characteristic components of many tropical ecosystems. They are found in a variety of habitats - from seashores and mangroves to high slopes, from marshes and swampy forests to savannas and hot desert oases, in lowland and mountain rain forests, and even in deciduous forests of warm temperate regions. However, it is in the tropical climate that palm trees find the most favorable conditions for their growth. Most palms prefer humid and shady habitats - along rivers and streams, at the outlets of groundwater, in lowlands, periodically flooded after heavy rains or flooded with tidal waters, in swamps, where they often form extensive, almost clean thickets. Most palms grow in humid and hot lowlands, and in the mountains usually at low to medium altitudes, but some rise high in the mountains. The latter include the genus Ceroxylon, or wax palm (Ceroxylon), which is found in the Andes of South America in the belt of mists. Thus, C. quindiuense was found in Colombia at an altitude of almost 3000 m, and useful ceroxylon (C. utile) rises to an altitude of 4100 m above sea level on Chiles volcano, meeting near the border of eternal snow. Some palms, such as the coconut palm (Cocos nucifera) or the Trinax and Pseudophoenix species in the Caribbean, are permanent inhabitants of the seaside. They are resistant to hurricane winds, salty sea spray, flooding sea water for at least a short period of time. Palm trees often grow in swampy coastal forests and marshes, along the inner rim of mangroves, in estuaries and on low tidal banks.
Washingtonia species, date palm (Phoenix dactylifera), and several other palms are excellent indicators of soil moisture in arid, extremely arid regions, as they are found only in areas where there is a source of water - a spring, stream or shallow aquifer ... The date palm grows magnificently in the oases of the Sahara and the Libyan Desert, in Algeria, Arabia and southern Iran. Intense heat, extremely dry air, lack of rainfall and even the sultry winds common in deserts are ideal conditions for cultivating the date palm. Moreover, it is not a xerophyte, since it is confined exclusively to oases. An Arabic proverb says: "The queen of the oasis bathes her feet in water, and her beautiful head in the fire of the sun." The date palm is able to tolerate and relatively low temperatures... It grows in areas where the absolute minimum temperature is -9 - -10 ° С almost every year, and in some years in some oases of the Sahara even -12 - -14 ° С. The date palm feels almost equally well on the loose sands of the Sahara and the Arabian Desert, and on the extremely heavy clays of the Iraqi interfluve, and on the stony soils of southern Iran. Its tolerance to soil salinity is especially striking. It sometimes grows on salt marshes, where the soil in summer is completely covered with white salt efflorescence.
Palm trees are the main components of palm savannahs in tropical Africa (for example, the Deleb palm tree, or Ethiopian Borassus - Borassus aethiopum and hyphaene species - Hyphaene) and in tropical America (Sabal species - Sabal, Copernicia species - Copernicia, etc.). Scorching heat and winds dry up the soil so much that few plants are able to survive. Palm trees will endure both prolonged flooding and a long dry season without visible damage. Palm trees found in savannahs and also in dry pine forests (for example, creeping saw - Serenoa repens) are surprisingly resistant to fires due to the absence of cambium. The non-dropping leaf bases at the bottom of the stem in carnauba (Copernicia prunifera) form a layer that protects plants from fire damage and can also function as water-storing tissue. In a number of palms, such as borassus, the seedling burrows into the ground due to the strong elongation of the cotyledon.
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Palm trees have a characteristic appearance that allows them to be almost unmistakably distinguished from all other plants. They usually have a well-developed, straight, unbranched ligneous stem with a crown of large fan or feathery leaves at the top. There are several forms of growth of palms. While maintaining the unity of the building plan appearance palm trees are unusually diverse. Their stems can be slanted or climbing, creeping and underground, or spread out on the surface of the earth. Along with the most common tree-like forms, there are lianas, as well as shrub-like and so-called "stemless" palms, in which the aerial stem is greatly shortened or completely absent and only leaves rise above the ground (Fig. 231). However, most palms are tree-like plants with a tall, slender columnar trunk (more precisely, a lignified trunk-like stem), like Washingtonia or Corypha species, striking with their majestic appearance and exceptional correct proportions. Their height can reach (60 m, like the wax palm of Ceroxylon of Kindyo, and the diameter is almost 1 m, like the Chilean wine palm (Jubaea chilensis), which is also called elephant palms for its size (Table 57, 4). Other low-growing palms with thin stems similar to bamboo or reeds and elongated internodes, they resemble miniature trees or shrubs.Dwarf palms are no more than half a meter high and as thick as a pencil (some types of Reinhardtia - Reinhardtia from tropical America), and tiny palm iguanura (Iguanura palmuncula) from the island and dwarf siagrus (Syagrus lilliputiana) - a true treasure of the Paraguayan flora - - no more than 10 cm tall, resembling more grass, they are in stark contrast to the majestic "princes of the plant world", as Karl Linnaeus called the palm trees.
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The Egyptian dum-palma, or Hyphaene thebaica, and some other species of the Indo-African genus Hyphane have an unusual appearance for palm trees: their stems usually branch dichotomously, giving the plants characteristic appearance (Tables 54, 4, Fig. 231). The dichotomy is also known in other members of the family, for example, in the South African Kaffirian Jubaeopsis (Jubaeopsis caffra), the mazari palm and the bushy nipa or mangrove palm (Nypa fruticans). In the palm family, the dichotomy is apparently secondary. Non-dichotomy branching of creeping shoots, usually in the American serenoa palm. Isolated cases of branching in Chrysalidocarpus lutescens and some other palms are probably associated with damage to the apical bud. In a number of large palms, the trunks are bottle-shaped or barrel-shaped swollen. An example is the endemic species of the Mascarene Islands bottle gioforbe (Hyophorbe lagenicaulis, table 50, 2), bitter-stemmed gioforbe H. amaricaulis) and the famous barrigona (Colpothrinax wrightii), growing in the sandy savannas of Western Cuba and the island of Juventud (Table 53, 1). Its trunk is barrel-wide in the middle part, and looking at it involuntarily suggests a comparison with an anaconda that has swallowed its prey. The African Deleb can have two or even three consecutive trunk extensions in the middle. The reasons for the appearance of such enlargements of the trunk and their biological significance are not yet completely clear. The stem of the pseudophoenix vinifera from the island of Haiti has the shape of a bottle, the long neck of which develops with the onset of flowering. In sabal, localized narrowing of the stems is noted in years unfavorable for the growth of a palm tree, as a result of which its trunk resembles an hourglass. Iriartea ventricosa, Socratea exorrhiza, Fig. 242, and some other palms - inhabitants of swamps, flooded lowlands and mountain forests of the fog belt of tropical America - have a peculiar appearance. The stems of these plants are equipped with stilted roots up to 2.5 m high, dotted with thorny thorns - modified lateral roots. In the early stages of development, the internodes of the stems of these palms quickly elongate, forming an unstable inverse conical axis, which is supported by stilted roots. They are formed from the lower internodes of the stem and provide support to the plant. After the base of the stem dies off, the palm rests on these roots, as if on stilts. Many palms have the form of shrub growth due to the formation of numerous stems from axillary buds at the base of the stem or on underground side shoots - stolons or rhizomes. In the first case, a compact bundle of stems appears, in the latter, the stems appear at some distance from the plant, forming thickets (Fig. 231).
Species of the American genus Sabal, Rhopalostylis sapida, endemic to New Zealand, and some palms from the coconut subfamily have an underground stem, which at first grows obliquely down into the ground (to a depth of 1 - 1.5 m in Attalea funifera ), and then, suddenly changing direction, bends upward (taking the shape of a saxophone), rises to the surface of the earth and forms an aerial stem in tree-like forms, like in Sabal palmetto, sometimes strongly shortened, like in a small sabal (Fig. 233 ), sometimes strongly curved and even twisted into a spiral, often S-shaped, from below with roots like ropes. When the vegetation is destroyed by fires in dry seasons, the underground stems of attalea and some other palms remain intact and soon produce new leaves. In the American oil palm (Elaeis oleifera), the old part of the trunk lays down, it is spread on the surface of the earth and is covered along its entire length adventitious roots; the younger ascending part raises the crown of large cirrus leaves to a height of 2 m. old plot the stem dies and rots, the palm tree almost imperceptibly moves away from the place where it was planted - "walks", say the locals.
Among the palms there are climbing lianas reaching the tops of the trees in the tropical rain forest (Table 56, 1). Their thin flexible stems with very long (sometimes up to 2 m) internodes and spread feathery leaves often reach a length of more than 100 m, and in some calamus species - up to 150 - 180 m. They climb with the help of modified leaves or sometimes inflorescences, firmly fixing itself, like an anchor, to the surrounding trees or shrubs, hanging between them with scallops. Climbing palms are found in all tropical areas. This form of growth arose independently in different groups of palms - in the New and Old Worlds. Rattan, or climbing, palms of the Old World, the most important of which are two large genera - calamus and demonorops (Daemonorops), are found in the rainforests of Asia, Australasia and Africa, but are especially diverse in the rain forests of Southeast Asia. Species of the genus Calamus are the largest and most specialized vines, forming dense, impenetrable thickets.
The vast majority of climbing vines are multi-stemmed plants, climbing stems usually arise from underground rhizomes, only Plectocomia has single stems. In Calamus, the seedling forms a rosette of leaves, from which several climbing stems rise.
Stems of palm trees are smooth, with annular scars from fallen leaves, like in the Cuban royal palm (Roystonea regia), or covered with a layer of leaf sheaths and petioles, sometimes thorny, like in American Acrocomia and Bactris palms. The thin stems of the Astrocaryum vulgare, an inhabitant of dry forests in the Amazon and Rio Negro, like other species of this genus, are armed with whorls of long sharp thorns. Straight or curved thorns on the stems of the Mexican dwarf cryosophila (Cryosophila nana), protecting the plant from being eaten by animals, are nothing more than modified adventitious roots with pointed hard root caps. In the lower part of the stem, common roots are sometimes formed. Root thorns also cover the trunks of the Amazonian palms of prickly mauritia (Mauritia aculeata) and armed mauritia (M. armatа). The extended stem base, characteristic of many palms, provides a solid foundation for a tall and powerful "column". Numerous rope-like adventitious roots extend from it. The primary root dies off early and is replaced by adventitious roots that appear on the lower internodes of the stems throughout the life of the palm. These roots are devoid of root spikelets; sometimes palms have mycorrhiza (coconut palm, peach palm - Bactris gasipaes - and others). Palm stems, always lignified and perennial, are composed of a crustal layer and numerous vascular bundles and fibers scattered in the main parenchyma. The fibers are tough, dark brown or black, often contain silica and are very hard. The vascular bundles are more concentrated towards the periphery of the stem, forming a much denser tissue than in the central part. This distribution of supporting fabrics provides maximum strength and stability to the trunk, although palms, due to the lack of cambium, do not form real wood like our regular dicotyledonous and coniferous trees. The design of the palm tree is in line with the best examples of civil engineering. The stalk of the palm grows to a considerable thickness as a result of primary growth, which occurs immediately below the apical meristem, located in the center of a small cupped or saucer-shaped depression at the apex of the stalk. The apical bud of a palm tree (figuratively referred to as "palm cabbage" or "heart of a palm tree") - a creamy, juicy, curly mass of young leaves - resembles a cabbage in appearance. It is deeply hidden in the crown and is protected from forest herbivores by the bases of the leaves, usually thick, rough, with a sharp edge or with thorns. Palm stems sometimes thicken (as, for example, in the royal palm) due to the division and stretching of the cells of the main parenchyma and fibers that surround the vascular bundles. This growth is called diffuse secondary growth or sometimes "continuous primary growth" (J. T. Wathaus and C. J. Queenie, 1978).
The leaves of the palms are alternate, usually clearly dissected into a petiole and a blade. The lower part of the petiole is expanded into the vagina, partially or completely covering the stem. The petioles are usually long, but may be very short or even absent. Palm leaf blades are extremely varied in size, shape and dissection. Their size ranges from a few centimeters (12.5 cm in the Guatemalan chamedorea of Türkheim - Chamaedorea tuerckheimii) to the largest in flora: in royal raffia (Raphia regalis), their total length with a petiole is over 25 m. The famous "shadow palm" - the umbrella-bearing corypha or talipot palm (Corypha umbraculiferа), has fan leaves up to 7 - 8 m long (petiole 2 - 3 m) and a diameter of 5 - 6 m. Its leaf is so large that it can shelter 15 - 20 people from the rain. The leaf blade in palms is complex, folded, fan or pinnate, in Caryota (Caryota) it is double pinnate; less often the plate is whole, not dissected into segments, palatine or peristonerous, and often bilobed at the apex (Fig. 232). Whole leaves of the American palm of manicaria saccifera (Manicaria saccifera), 9-10 m long and 1.5-2 m wide, jagged along the edge, under the influence of the wind they break incorrectly, like a banana. In fan leaves, the rachis (core) is greatly shortened. The plates are usually dissected into linear or lanceolate segments at various depths, sometimes almost to the base. The leaves of some species of the Malesian genus Licuala are palmate, dissected to the very base into narrow-wedge-shaped segments with a blunt serrated top, each consisting of several folds. In the so-called comb palms (for example, in species of the genus Sabal), the rachis continues into a blade and extends for a certain distance, sometimes almost to the very top, forming the median crest of the leaf and bending its blade. It gives large leaves great strength. Such leaves make up the transition from typical fan-shaped to feathery. Many fan and crested palms have a triangular outgrowth similar to a tongue at the top of the petiole at the point of its junction with the plate - gastula (Latin hastula - short end, dart, Fig. 232). It is usually present on the upper side of the plate, rarely on both sides. Sometimes the gastula reaches a significant size.
The presence of a median crest, or a powerful midrib of the blade, is a characteristic feature of the palm leaf. Segments of fan leaves and feathers of cirrus leaves - with a noticeable midrib or with several veins and have numerous and thinner veins, usually parallel to the median, but sometimes radiating from the base or from the midrib and ending along the edge or at the toothed apex of the feathers.
Palms are divided into two large groups depending on the nature of the attachment of segments and feathers to the rachis (Fig. 232). In some palms, the segments and feathers are V-shaped in cross-section (having the shape of a groove), that is, induplicate, or folded upwards with a noticeable vein below at the point of attachment to the rachis; the plate ends with an unpaired apical segment or feather. In other palms, the segments and feathers are Λ-shaped (roof-shaped) in cross-section, that is, reduplicate, or folded down with a noticeable vein at the top; the plate ends with a pair of segments or feathers with a thread located sometimes between them, representing the end of the rachis. Both pinnate and fan leaves are laid as one piece, and all parts of the leaf develop from the original whole tissue. The leaves of the palms are leathery, tough. They are covered with a thick layer of cuticle, often with a waxy coating, which in some palms reaches a considerable thickness. Many palms have a cover of tiny scales or hairs that can fade with age. The leaf blade is mostly smooth, but some thorny palms have thorns on the rachis and feathers. There is also a great variety in the structure of the base of the palm leaf. Many palms have long, closed tubular sheaths. They are often not expressed in adulthood, although in the early stages of development they form closed tubes that cover the stem.
Since palms do not have a specialized integumentary tissue like bark dicotyledonous plants Leftover leaves that remain in many palms may have a protective function. In Washingtonia species, the trunk is covered with a "skirt" of old, dry leaves, which persists in natural conditions for many years, forming a strong column in old plants up to 2.5 m thick (Fig. 231).
Numerous flowers of palm trees, usually collected in large, highly branched lateral inflorescences. In most cases, these are panicles with spike-shaped, ear-shaped or fleshy thickened and cob-shaped branches. Inflorescences, like the stems and leaves of palm trees, often grow to a considerable size. The giant apical inflorescence of the "shadow palm" - the coryphae of the umbrella - one of the largest in the plant world, reaches a length of 6 - 9 m. The female flowers of Phytelephas macrocarpa, mangrove palm, oil palm form heads. Rarely, the inflorescences are unbranched, spike-shaped (as in the species Licuala - Licuala or Geonoma - Geonoma). The vast majority of palms have axillary inflorescences; they develop among the leaves in the crown, like a coconut palm or sabal species, or below the crown, like a royal palm, opening only after the leaf has fallen off. Unusual arrangement of inflorescences in species of calamus and related genera: in them, the inflorescence grows to the sheath of the above-lying leaf.
Most palms are polycarpics; they form lateral inflorescences in an ascending sequence during many years of life. But in relatively few palms, inflorescences appear at the top of the stem only once in a lifetime after a long period of vegetative growth, and after fruiting, the plant dies off. Such plants are called monocarpics. There are only 16 known genera of monocarpic palms, and all of them (with the exception of torch raffia - Raphia taedigera) are limited to the tropical and subtropical regions of the Old World. It is curious that the monocarpic genus Metroxylon in general includes one polycarpic species Metroxylon Tong (M. amicarum), and the beautiful-fruited demonorops (Daemonorops calicarpa) is the only monocarpic representative of the largest genus of rattan palms. Perhaps the most a shining example monocarpic palms can serve as the umbrella-bearing corypha growing in South India and on the island of Sri Lanka (Table 53, 5, 4). This majestic palm tree bears a crown of large fan-shaped leaves. In the 40 - 70th year of life, the palm tree blooms, forming a giant apical paniculate inflorescence of many thousands of white flowers; branches of this huge "bouquet" reach a length of 3 - 5 m. Over many years of growth in the central part of the trunk in huge quantities accumulate nutrients in the form of starch, necessary for the only reproductive explosion in the life of a palm. On the island of Sri Lanka, many specimens of this palm tree bloom at the same time.
A similar group bloom is also observed in the giant Malay mountain rattan Plectocomia griffithii.
The peduncle of palms bears a basal two-tibial pre-leaf (profile) and usually from one to several covering leaves, which enclose a young inflorescence and, when flowering, split longitudinally or burst. They are called sterile covering leaves, since they are not associated with flower axes, in contrast to fertile ones, covering the branches of the inflorescence at the base and terminal axes that bear flowers. Covering leaves are tubular or scaphoid, leathery, webbed, fibrous or sometimes even woody, smooth or woolly, sometimes prickly. They fall off when the inflorescence opens or remain on the peduncle (sometimes long after the formation of fruits). Their number varies in different groups of palms.
Flowers of palm trees are small and inconspicuous (a rare exception are large, 7-10 cm long, female flowers of phytelephus and Seychelles palm (Lodoicea maldivica, or L. sechellarum). They are usually sessile, sometimes even immersed in the fleshy axis of the inflorescence, rarely on short pedicels. Flowers are sometimes bisexual, but much more often unisexual; in the latter case, male and female flowers are similar or noticeably dimorphic, like in borassus and geonoma.Plants are usually monoecious, less often dioecious (for example, date palm, phytelefas and chamedorea species). In monoecious palms, male and female flowers are located in the same inflorescence, but are usually placed in different parts of the axis, like in a coconut tree, or collected in independent male and female inflorescences, sometimes in male and bisexual. 2 circles, or rarely spiral, or single-row and irregularly lobed, or rudimentary, and sometimes completely absent (in male flowers of phytelefas). perianth tents are loose or accrete, membranous, white, yellow, orange or red. The sepals and petals of the least specialized palms are similar, but much more often the sepals are smaller than the petals. There are usually 3 sepals, rarely 2 or 3 - 7 or more (in female flowers of phytelefas); they are free and tiled or accrete. The petals are usually the same as the sepals, free or accrete, usually valve in male flowers (less often accrete with free lobes) and tiled in female and bisexual flowers, sometimes with short-valve tops or rarely valve. There are usually 6 stamens, located in 2 circles, rarely there are 3 (three-stalked wallichia - Wallichia triandra, mangrove palm, three-stamen areca - Aresa triandra) or much more than 6, but their number is usually a multiple of 3. In some specialized palms, for example, palandra (Palandra), there are from 120 to 950 - the largest number of stamens known in palms; they develop centrifugally. Polyandry (myogoticity) arose independently in different groups of palms. The filaments of the stamens are straight or bent at the top in the bud, free or variously fused together or adherent to the petals, or at the same time fused and adherent. Anthers attached at base or dorsum, rarely double or with separated pollen nests, straight or rarely twisted; they are opened by longitudinal slits. The pollen grains are most often mono-grooved, similar to the pollen of liliaceae, less often with a 3-ray groove, with 2 distal grooves, or 1 - 3-pore grooves. The pollen of nipa, annular and thorny, is different from that of all other palms. Female palm flowers often have staminodes - in the form of teeth, subulate or equipped with rudimentary anthers, free or sometimes fused into a cupula or tube with a lobed or toothed top and sometimes adherent to the petals. Gynoecium in the most primitive palms is apocarpous, of 1 - 3 (usually 3) carpels, but in most genera it is syncarpous, usually of 3 partially or completely accrete carpels, sometimes of 3 - 7 or 7 - 10; sometimes gynoecium is pseudo-monomeric with 2 reduced and 1 fertile nest and 1 ovule (as in Areca - Ares and many related genera). Most palms have septal nectaries located on the septa of the ovary. In some palms, they are small and, according to their position in the basal part of the ovary, are considered less specialized in this family (for example, in sabal, Livistona or coryphae). In the pseudophenix, the septal nectary, located at the base of the carpels, opens outward in pores opposite each petal. In other palms, nectaries with long canals that open with pores on the upper surface of the gynoecium (in Arenga, Latania) or between the carpels at the base of stigmas (in Butia, Butia, MacArthur poultry, Ptychosperma macarthurii). The trachycarpus has a rudimentary nectar spot on the sides of the three free carpels facing the center of the flower. The squat chamerops (Chamaerops humilis) has a rudimentary nectary on the upper surface of the bowl, formed by the fused, expanded and thickened bases of filaments in the male flower. Columns are free or accrete, long or short, and thickened or imperceptible. The stigma is straight or curved, sometimes elongated, rarely indistinguishable, in the form of a slit on the carpel or two-crested. In each carpel or in each nest of the ovary there is usually 1 ovule (rarely with 1 or 2 additional ovules - in the nipa). When the fruit ripens, 2 out of 3 carpels are often underdeveloped. The ovules are anatropic, hemitropic, campylotropic, or orthotropic. Rudimentary gynoecium is sometimes absent in male flowers.
Carpels of palms exhibit many of the characteristics of the primitive carpels of flowering plants. They are often leaf-shaped, can be pedunculated, and are usually conduplicatively folded, often with open abdominal sutures and laminar or sublaminal placentations. In Trachycarpus Fortune, trichomes develop along and to some extent within the open ventral suture, as in some primitive dicotyledonous plants. The stigma is sessile or nearly sessile. The genus nipa differs from the rest of the palms in a peculiar asymmetric cup-shaped carpel with a funnel-shaped stigma opening, the wide inner surface of which unfolds and folds back during flowering. The combination of bisexual flowers and apocarp is found only in primitive genera belonging to the subfamily of Coryphaeum. The apocarp is also characteristic of the date palm and nipe. Along with the archaic structural features of the gynoecium, inherent in some palms, in other representatives one can observe many signs of high specialization.
Palm trees are cross-pollinated plants with various adaptations that prevent self-pollination. The most reliable of these is dioeciousness, which is known in relatively few palms. In monoecious palms, the ripening of male and female flowers in the inflorescence is observed at different times, as a result of which the plant stays either in the male or in the female phase of flowering. These phases are sharply demarcated in time and, as a rule, do not overlap. The exceptions are palms, in which several inflorescences develop in the leaf axil (like in the arena) and male and female flowers can be opened simultaneously in different nodes of the stem, as well as bushy palms, which may have asynchronous opening of flowers on different stems. Dichogamy appears in palms in the form of both protandria and sometimes protogyny. Protandria is well pronounced in many palms (eg coconut and sago). Male flowers, which bloom first in the protandric inflorescence, are ephemeral. They usually open at dawn and fall off after a few hours. The female flowers remain receptive for several days. In triads, male flowers open sequentially, one after the other, (rarely two male flowers are open at the same time), and only after they fall, often after a few days or even weeks, female flowers open. Blossoming of flowers arranged in vertical rows proceeds in a basipetal sequence: the top flower falls before the next one blooms. This way of opening flowers in palms provides the plant with pollen for a longer period of time. Protogyny is much less common and is known, for example, in pipa, sabal saw palmetto and some palms pollinated by beetles.
Most palms appear to be pollinated by insects. Although the flowers of palm trees are small and, despite the sometimes brightly colored perianths, are usually inconspicuous, they are collected in large inflorescences that stand out noticeably against the background of dark green foliage. The flowers of many palms, such as the Clhamaedorea fragrans from the Peruvian Andes, are very fragrant. Sometimes palm pollen (like Acrocomia) has a characteristic odor or is brightly colored (like nipa). Bees, flies, hoverflies, fruit flies, beetles, thrips, moths, ants and other insects visit flowers for nectar, pollen, succulent flower tissue, or use the flower as a breeding ground, oviposition, and larval development. As a rule, a variety of insects are found in the flowers of palm trees, although not all of them are effective pollinators. Some palms are pollinated by beetles that feed on pollen and flower tissues. Various types of beetles carry out pollination, most often - weevils (Curculionidae). Palms pollinated by beetles, as a rule, are protogynous and form a large amount of pollen, while their flowers are devoid of nectar. Weevils pollinate flowers of two species of Bactris in Costa Rica (Bactris large - Bactris major and Guinea Bactris - B. guineensis), thorny palms from the coconut subfamily. Like nipa, they are protogynous, and flowering begins with the opening of the female flowers in the afternoon, which remain susceptible for 12 hours. Male flowers open 24 hours later than female ones and emit a musky smell, attracting beetles that eat their large thick petals. When male flowers open and lose pollen, beetles, loaded with this pollen, move to newly opened inflorescences with susceptible female flowers, pollinating them. The abundant pollen of male flowers also feeds on cuckoo (Nitidulidae), bees, and fruit flies on the tissues of the flowers. About 10% of visitors to bactris flowers are predatory beetles, rove beetles. The pollination mechanism of Bactris is very effective. Female flowers do not need to develop any special adaptations to attract pollinators and therefore can concentrate energy on their main function - the formation of fruits and seeds.
The pollination mechanism of Hydriastele microspadix from New Guinea is surprisingly similar to that just described. The flowers of the hydriastela are pollinated by weevils, which are found almost exclusively in the flowers of palm trees and are panthropic in their distribution (a remarkable example of the conjugate evolution of palms and insects). Weevils pollinate the flowers of Rhapidophyllum hystrix, a low shrub-like palm tree, which is called porcupine due to its numerous long (15 - 20 cm) sharp black needles on leaf sheaths. This palm tree grows in damp places and swamps of the coastal plain of the United States from South Florida to the Carolina. Short, tightly compressed inflorescences with 5 - 7 covering leaves are literally buried in a mass of needles and dark brown sheaths and never protrude even when the fruit is ripe. Male and to a lesser extent female flowers emit a musky scent. There is evidence of pollination of flowers of a number of other palms by beetles. Beetles are found in closed male inflorescences of Ammandra, and the release of heat by flowers of phytelefas - a phenomenon often associated with pollination by beetles - suggests cantharophilia in this genus. The milky white flowers of Johannesteijsmannia altifrons on the pale yellow velvety branches of the inflorescence partially hidden in the humus and plant debris accumulating at the base of the leaves of this "stemless" palm attract numerous insects with their sour milk and sewage scent. The flowers contain many beetles (adults and larvae), rove beetles, as well as larvae of flies, thrips, ants, termites, and beetles. In Ceratolobus, one of the most remarkable dioecious genera of rattan in the humid regions of Maleesia, the inflorescence is enclosed within a single cover leaf, which is opened by two tiny lateral slits at the apex. Numerous insects penetrate through them, attracted by the musty smell of flowers. In the inflorescences of the glaucous ceratolobus (C. glaucescens), an endangered species, the only small population of which is found in West Java, beetles, thrips and ants are abundant. The latter quickly colonize the inflorescences and the whole plant. They are attracted by nectar. In species with drooping inflorescences, pollen accumulates in abundance near the holes through which insects enter the inflorescence or get out. Ceratolobus flowers are closed from larger arthropod visitors, which cannot penetrate through small cracks. The "filter for pollinators" is also found in the American palmetto manicaria, the inflorescence of which is enclosed inside a saccular covering leaf with tiny holes between the fibers (Fig. 243).
However, there are many wind-pollinated plants among the palms. The date palm is a classic example. Under natural conditions, in the population of this dioecious plant, about half of the male specimens. A single cover leaf covers the entire inflorescence. The male and female flowers bloom as soon as the inflorescence is released from the cover leaf. The female flowers are apparently susceptible for 1 or 2 days. In culture, to obtain a sustainable harvest, the date palm is artificially pollinated by tying the cut branches of the male inflorescence to the top of the female. One male specimen is enough to pollinate 100 females. Artificial pollination was first applied by the ancient Assyrians and has been practiced for at least 3 or 4 millennia. This technique has survived to this day almost unchanged. Date palm pollen, which is produced in huge quantities, remains viable for one season or even 1 to 2 years. The fact that the pollen in palms retains its viability for a relatively long period of time was established for another dioecious wind-pollinated palm, the squat hamerops. In 1707, Joseph Kölreuter, whose name is associated with the doctrine of the field in plants, sent hamerops pollen, taken from a male specimen in the botanical garden in Karlsruhe, simultaneously to Berlin and St. Petersburg. The gardener Ekleben pollinated an old specimen of this palm tree, brought back under Peter I and located in the greenhouse at the Summer Palace. Although the journey took several weeks, the pollen did not lose its germination ability and the plant produced abundant fruits.
Perianth reduction in Trinax (Thrinax), a primitive genus with bisexual flowers with apocarpous gynoecium, is undoubtedly associated with wind pollination (Fig. 235). The cover leaves are relatively thin and the inflorescence opens quickly. Especially remarkable is the rapid elongation of the branches of the inflorescence, which grow in length by 15 - 20 cm in 10 hours before the anthers open. The flowers are protandric. In the small-flowered trinax (T. parviflora), the anthers open early in the morning, and abundant dry powdery pollen covers the branches of the inflorescence. During the male phase of flowering, the lips of the double-lipped stigma of the monocarpous gynoecium are tightly pressed together, which reduces the possibility of self-pollination. The stigma moves apart 24 hours after the anthers are opened. The funnel-shaped canal of the carpel is open distally. Trinax has been found to have pollen grains on the ovule in the nest, which is unusual for flowering plants. The open channel of the column appears to be a direct entrance for wind-carried pollen. Self-pollination occurs frequently and successfully, as indicated by abundant fruit setting on isolated specimens.
Until now, botanists have no consensus regarding the pollination of the coconut palm, one of the most studied palms. This plant is apparently pollinated by both insects and wind. Small male flowers open first around 6 a.m. and fall off at noon. Female flowers are susceptible for several days. The female flowering phase lasts 4-7 days. In addition, the flowers of the coconut tree are visited by birds - sunbirds and parrots, which feed on pollen. In the dwarf variety of this palm on the Malacca Peninsula, male and female flowers open, as a rule, at the same time, and self-pollination prevails here. In the smooth-covered butia (Butia leiospatha), an inhabitant of the Cerrados of Brazil, like the coconut palm, wind pollination is combined with insect pollination. Its flowers are visited by wasps, flies, and weevils and glitterlings grow in inflorescences. They use closed inflorescences and young fruits as egg-laying sites.
Self-pollination is also known in some palms. The bisexual flowers of the tall corypha (Sorpha elata) are self-compatible. Abundant setting of fruits with fertile seeds as a result of self-pollination is quite common in isolated cultivated specimens, which is of particular importance in connection with the monocarp of this species. In rattan palm, demonorops kunstleri, most of the fruits and seeds are formed, apparently, parthenogenetically.
The fruits of the palms are unusually varied. Their size ranges from a few millimeters to half a meter in the Seychelles palm, the fruits of which are among the largest in the plant world. In nipa, phytelefas and oil palm, the fruits are collected in large compact heads. Fruits are usually 1-seeded, but sometimes 2, 3 - 10-seeded. They represent a dry or fleshy syncarpous drupe with endocarp adherent to the seed or free, less often fruits, berry-like (for example, dates can serve). At the base, the fruits are often surrounded by a growing and hardening perianth. The vast majority of palms have non-expanding fruits. Only in a few species, when ripe, they split at the apex (Microcoelum - Microcoelum, Lithocarium - Lytocaryum, Socratea salazarii), and in Astrocarium species (Astrocarуum) they open completely, exposing sometimes brightly colored pulp.
The mesocarp of the fetus is juicy, sometimes with abundant needle-shaped crystals of calcium oxalate, often oily, juicy, fibrous or dry. The endocarp, enclosing the seed, is thin, cartilaginous or membranous, sometimes with a lid over the embryo (like in Clinostigma), or thick, horny or bony, then often with 3 or rarely more germinal pores (like in the coconut palm and other related childbirth). The number of pores corresponds to the number of carpels, and their location (in the middle, below or above the middle of the endocarp) corresponds to the position of the ovule micropyle. In a single-seeded fruit, only one of the pores functions, opposite to the ovule of the fertile carpel. The endocarp is sometimes provided with longitudinal ribs, while in the Seychelles palm it is deeply 2-, sometimes 3-, 4- and even 6-lobed. Palm seeds are very diverse in size and shape. Their size ranges from just a few millimeters to the largest in the plant world - 30 or 45 cm for the Seychelles palm. The seed coat is thin, smooth or fleshy (like the herring - Salacca), loose or fused with the endocarp. The endosperm is abundant, homogeneous or ruminated, in immature seeds it is often liquid or jelly-like, then it becomes very hard, and in some types of palms it is a source of plant "ivory" (phytelefas is large-fruited, hyphane is swollen - Hyphaene ventricosa, etc.). The endosperm contains a large amount of oil and protein. The embryo is small, cylindrical or conical. Several palm species have polyembryony.
Palm seeds do not have a dormant period, the embryo grows continuously. Seed germination can begin while the fruit is still attached to the plant. The embryo does not stop growing even while the seeds are spreading. In Malay villages, you can often see the sprouting of coconuts suspended from the posts of huts. The embryo receives water and nutrients from the endosperm. Seedling roots growing in the fibrous mesocarp are able to absorb rainwater seeping through the peel. However, the juicy pericarp (for example, in Livistona) inhibits or prevents the germination of the seed. When stored, seeds tend to lose germination quickly. They should be sown shortly after harvest. The exception is pseudophenix, whose “long-lived” seeds germinate after two years of storage. This ability to germinate after a long dry period is probably essential for survival in arid conditions such as sands and porous limestone in the Caribbean. Palm seeds germinate underground, with the exception of nipa, in which seeds germinate on plants or in floating fruits. The cotyledon never opens up as a green photosynthetic organ, since its tip remains immersed in the endosperm of the seed and is modified into a sucking organ - the haustorium. It dissolves and absorbs nutrients from the endosperm to support the growth of the embryo until the young plant forms leaves. In many palms, the cotyledon, when emerging from the seed, elongates in the form of a cotyledon tube and buries the seedling in the ground to a certain depth, which may be adaptive for palms growing in savannahs. The deepening of the cotyledon into the soil in different types of palm trees occurs at an unequal depth, which is largely determined by the habitat conditions. Deeper into the soil, the lower part of the cotyledon grows in the form of a tubular sheath at some distance from the fetus.
In palms, three types of seed germination are known (Fig. 233). In species with a noticeable elongation of the cotyledon, the seedling is distant from the seed and haustorium. In the date palm, trachycarpus, coryphae, the lower part of the cotyledon grows underground in the form of a long tubular sheath, and a shoot emerges from the cotyledon fissure formed in its upper part. In sabal, washingtonia, jubaea, the cotyledon in the lower part is expanded in the form of a much shorter tubular sheath, which forms a uvula in the upper part. In archontophenix, coconut palms, and some other palms, the cotyledon lengthens only enough to carry the embryo out of the endocarp. The lower part of the cotyledon, immediately after leaving the seed, grows outward in the form of a bell, forming a tongue. An embryo begins to germinate from the base of the cotyledon, parts of which are closely adjacent to the haustorium.
The fruits of many palms, juicy and brightly colored, are distributed by animals. Their main distributors are birds, although a wide variety of animals - from rodents to monkeys - also feed on the fruits of palm trees and distribute seeds. Large birds swallow the fruit whole, throwing out undamaged seeds near the palm trees or, more often, transferring them a certain distance. Certain birds, in particular pigeons, apparently played a large role in the spread of the range of palms. So, thanks to them, and also, obviously, ocean currents Pritchardia penetrated the Hawaiian Islands. The birds apparently introduced the seeds of the royal Haitian palm (Roystonea hispaniolana) to Little Inagua Island (Bahamas), where palm trees were recently discovered growing on the bottom of several large karst sinkholes. The list of palms, the fruits of which the birds feed on, is quite large. Cariotic fruits in Java feed on predatory mammals such as jackals, the Malayan palm marten and civets. Palm civets, wild pigs They feed on the fruits of the sugar palm (Arenga pinnata), and the black-armed and dwarf gibbons eat the mature fruits of the arenga (A. obtusifolia) in Indonesia. The fruits of rattan palms - calamus and demonorops - also serve as food for gibbons. Baboons feed on the fruits of the Egyptian doom palm. V Ancient egypt Thoth - the god of wisdom, patron of sciences - was revered in the form of an ibis or baboon, and since baboons often feed on the fruits of the doom palm, she became sacred tree Thoth. Images of baboons on palms are found in the paintings that covered the walls of ancient tombs. Monkeys are attracted by the fruits of the date palm Phoenix roebelenii in Laos, the American palms and Maximiliana maripa, as well as the African oil palm.
In the distribution of the fruits of some palms play an important role the bats that, like birds, can spread seeds on long distances... Large (15 - 20 cm in diameter) drupes of the Deleb, or Ethiopian Borassus, are the favorite food of the African elephant. It is to him that the palm owes its distribution throughout tropical Africa. The elephant eats the fruits, and the endocarp with the seeds enclosed in them are thrown out intact along with the excrement. However, the presence of the genus in Madagascar, New Guinea and, possibly, even in Australia, where there are no elephants, according to Harold Moore (1973), excludes the assumption of a conjugate evolution of elephants and Borassus, as well as the closely related small genus Borassodendron (Borassodendron). The African strata also feeds on the smaller fruits of the hyphana bloated, growing in the hot dry valleys of southern Zambia, and the African wild date palm (Phoenix reclinata). The fruits of palm trees that have fallen to the ground are eaten by tapirs, deer, fallow deer, bakers, goats, and cattle. Coyotes and gray foxes feed on the fruits of washingtonia filamentous. Squirrels and numerous rodents (paca, mice, rats) also take part in the distribution of fruits and seeds. They often drag the fruits to the nests or put them somewhere in the reserve, while some of the seeds are lost along the way or remain unused for some reason. In Brazil, rodents bury the fruits of Attalea funifera and Orbignya barbosiana in underground burrows, where their germination is stimulated high temperature due to the annual savannah fires. Fragrant fruit pulp and seeds with juicy skin of edible herring (Salacca edulis), an almost stemless, very thorny palm tree on the islands of the Malay Archipelago, attract not only rodents and birds, but also monitor lizards and turtles. The fruits of the Astrocaryum vulgare serve as food for fish, and the fish also eat the fruits of the Geonoma schottiana in South America.
Despite the abundant fruiting of palms, their fruits and seeds are often predatory destroyed by beetles and other insects, tree mice and rats, pigs and crabs. There is a close biological relationship between the coconut tree and the huge crab called the palm thief (Birgus latro). It feeds on the pulp of unripe coconuts: breaking the fibers, with powerful pincers punches a hole in the area of the "soft" eye, pulls out the pulp, sometimes breaking the endocarp with blows against the stones. The crab not only destroys fruits that have fallen to the ground, but, as you know, even climbs on a palm tree, knocking down coconuts. The crab lives on the tropical islands of the Indian and Western Pacific Ocean - in the area of distribution of the coconut palm. Chemical analysis of its fat has shown that it resembles coconut oil, having little to do with animal fat. This crab also feeds on the small juicy fruits of another palm, the Arenga listeri, which is endemic to Christmas Island.
Sea currents, rivers and streams, storm streams play an important role in the spread of seeds and fruits of a number of palms. Water contributes to the spread of species that inhabit the banks of rivers, such as meandering mauritia (Mauritia fiexuosa), and many other palms found in abundance on the banks of the "palm" Amazon River, Orinoco and their tributaries, as well as inhabitants of swamps and swampy forests (such as raffia and metroxilone). The fruits and seeds of a number of palms are picked up by the floods. The floating fruits of the coconut palm, nipa, pritchardia, sabal palmetto and others are carried by sea currents. Sometimes the fruits become buoyant only when they dry, like in Pseudophoenix sargentii, or when the seeds are destroyed. The fruits of manicaria are highly buoyant. Falling, they burrow into detritus or are carried out by rivers far into the sea, however, they cannot withstand prolonged exposure to salt water and soon collapse. Fruits with rotten or dry seeds can be carried by currents. They are found in large numbers on the beaches of the West Indies, on the Turke Islands (the southeastern tip of the Bahamas) and even on the west coast of Scotland. Of the seeds that have reached the Terke Islands, no more than 1 - 2% retain the ability to germinate.
A large role in the spread of many palms was played by man, especially such vital ones for him as coconut, oil, date, sugar, etc.
The classification of palms is based mainly on the structure of the gynoecium and the fruit, the type of inflorescence, the nature of the arrangement of flowers on the axes of the inflorescence, the number of covering leaves. Most modern authors accept the division of palms into 9 subfamilies: corythous (Coryphoideae), phoenix (Phoenicoideae), borass (Borassoideae), caryotic (Caryotoideae), nip (Nypoideae), lepidocaryoideae (Lepidocaryoideae) and) phytelephantine (Phytelephantoideae). With the exception of the largest and most heterogeneous subfamily of the Arecidae, which will obviously be further subdivided, they are all natural, well-distinguishable groups of palms. American palmologist Harold Moore (1973) divided the family into 15 large groups (without specifying their taxonomic rank), representing 5 evolutionary lines in the palm family; 8 of these groups fully correspond to the accepted subfamilies; the remaining 7 groups together constitute the subfamily of arecaceae, while most of them coincide (partially or completely) with individual tribes, and the group of arecoid palms embraces many tribes in palm classification systems. These large divisions of palms often correspond to those distinguished by P. Tomlinson (1961) on the basis of comparative anatomy data.
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Order of the Palm (Bincipes)
Palm family (Palmae, or Arecaceae)
Trees, sometimes lianas with unbranched trunks, without secondary thickening and a crown of palmate or pinnately dissected leaves. The flowers are small, bisexual, regular, in simple or complex, often very large inflorescences, sessile or, often, immersed in fleshy axes. The perianth is simple, 3-membered, in 2 circles, sometimes spiral, separately or somewhat intergrowth. 6 stamens in 2 circles, often 9 or more. Filaments are loose or fused at the base into a ring or tube. Ovary superior, 1-3-celled with 1 anatropic ovule with 2 integuments. Column. The placentation is central-angular. The fruit is a berry or drupe. The seeds are large, with endosperm, often closely intergrown with the endocarp.
235 genera and about 3400 species in the tropics and subtropics, especially Asia and America.
The concept of the tropics is rightly associated with palm trees. They often define tropical landscapes. They even talk about the "palm belt", referring to the area of coconut cultivation, between 20 ° latitude north and south of the equator. These latitudes roughly delimit the tropics from the subtropics. Rainforests are especially rich in palm trees on the alluvial soils of such large rivers as the Amazon and Orinoco. But there are many palms in savannas and in mountainous subtropical forests, where they can reach the frost limit. The only European species hamerops low(Chamaerops humilis), which lives in the south of Spain and Italy, even withstands temperatures of -7 ° C. The geographical distribution of the palms is generally remarkable. In America, 92 genera and 1140 species are known. In the Australian-Asian space, there are only slightly more species - 1150, but 167 genera, which is explained by the high number of genera endemic to individual islands. But Africa has only 50 species from 15 genera.
Many palms are characterized by high columnar trunks up to 20-30 m high, but they have the same thickness throughout, and sometimes the trunk in the upper part is even thicker than at the base due to the remaining petioles of leaves. The secondary thickening in palms, as in almost all monocots, is absent, but the primary thickening is very intense. Below the growth point, a large number of rapidly dividing cells are formed and quite a lot of incorrectly positioned vascular bundles with powerful sclerenchymal sheaths are laid. As the palm grows, the primary thickening may progress and then subside again. In some species, this leads to a swelling of the trunk in the middle part (resembling a boa constrictor that has swallowed large prey).
Palm trunks do not branch, except for the genus hifene(Hyphaene), which is supposed to have real dichotomous branching. Along with high-stemmed species, there are many short-stemmed and almost stemless species, in which a rosette of leaves emerges as if from under the ground. Climbing so-called "rattan" palms of the genus are very peculiar calamus(Calamus) living in the tropics of the Old World. Rattans have relatively thin flexible trunks set with strong curved spines. Cirrus leaves in a clearly regular arrangement (not typical for palms!), Have several pairs of lateral segments, as well as densely spiked rachis, which represents top part sheet. The length of rattan trunks reaches 100-200 m.
There are two main types of palm leaves. The original is the feathery type (Fig. 204). The cirrus-dissected leaves of palm trees reach the maximum size for leaves of 10 m or more, but the usual size is 3-5 m. A leaf of such a palm tree falling down with a noise can seriously hurt. The finger-dissected leaf is phylogenetically secondary and arose as a result of inhibition of the growth of rachis. Segments of the palmate leaf are more or less accrete at the base. The trunks of many palms (and even more often the petioles of leaves) are strongly thorny.
An interesting problem is the herbarization of palms. Of course, you can collect flowers for a herbarium, often fruits or parts of inflorescences. But what about the leaves, the inflorescence as a whole or with the trunk? Here, the herbarium is largely replaced by a sketch, accompanied by the necessary quantitative measurements, for example, the width of the petiole, the number of segments, etc.
Inflorescences of many species often branch intensively and reach significant sizes, sometimes up to 1.5 m or more. Their axes are often thickened and brightly colored. It's amazing that always small flowers palm trees form
Rice. 204. Palms. Coconut (Cocos nucifera): 1 - general view; 2 - inflorescence with male (a) and female (b) flowers; 3 - male flower (part - sepals); 4 - sectional view of the fruit (coconut). Calyptrocalyx spicatus: 5 - the upper part of the plant with fruits. Sabal (Sabal mauritiiformis): 6 - general view with inflorescences. Bactris (Bactris guineensis): 7 - part of a plant with fruits. Seychelles palm(Lodoicea maldivica): 8 - part of a female plant with fruits; 9 - bilobed endocarp with seed. Calamus (Calamus longisetus): 10 - cross section of the ovary
sometimes such large fruits as coconut(Cocos nucifera) or seychelles palm(Lodoicea maldivica). The fruits of the latter are the largest among woody plants, and the seeds are generally the largest. So in these respects, palm trees stand as champions.
The importance of palm trees in the life of the population of tropical countries can hardly be overestimated. Finger-cut leaves of many species are common material found on the roofs of so-called palm huts. From the trunks sago palm(Metroxylon) extract starch contained in parenchymal cells and used to make real sago. One of the world's most important oilseeds - undoubtedly oil palm(Elaeis guineensis). Fats in an exceptionally high concentration are deposited in this palm, not in the endosperm, but in the pericarp, so that they cannot be used by the seedling, but undoubtedly attract animals that distribute the fruits. This African feathery palm is cultivated in many parts of the tropics. Biologically, it is interesting in that it has dioecious inflorescences that bloom at the same time. In the male inflorescences there are up to 140,000 flowers, in the female - no more than 5,000. There are also purely dioecious varieties.
Perhaps the most famous among the palm trees belongs to the pinnate species. coconut palm, or coconut especially abundant in coastal areas. The landscape of the coastal regions of India, South Vietnam, Cuba, Ceylon is largely determined by the coconut tree. It is assumed that the homeland of the plant is the islands of Polynesia, from where it spread not only through humans, but also by transferring fruits through water. The middle layer of the pericarp is represented by the air layer. The seeds are capable of germination after 3 or even 4 months of swimming. Coconut fruit is not entirely common. Inside the powerful, 3-layered pericarp is a 1 cm thick "shell" of endosperm, to which is adjoined by a tiny embryo. The middle of the fruit is filled with a cloudy liquid rich in proteins - "coconut milk" (its taste, however, has nothing to do with milk). When the "nuts" are fully ripe, 9-11 months after flowering, the liquid solidifies. One inflorescence yields 8-10 "nuts", and the tree yields at least 25-30 years. Coconut endosperm (the so-called copra) is a valuable product used for the manufacture of coconut oil, as well as confectionery. The processing of coconut "nuts" is difficult to mechanize and is still done by hand, a skilled worker opens 2000 "nuts" per day.
In the huge family of palms, only a few species form edible fruits like the coconut. The latter also include dates - fruits date palm(Phoenix dactylifera). Its origin is unclear, but there is no doubt that it is one of the most ancient cultivated plants. In appearance, the date palm looks a little like a coconut, but the latter has a smooth trunk, while the date palm is densely covered with the remains of dead leaf stalks. The coconut palm is grown in humid seaside climates; the date palm, on the other hand, can grow in arid places, right up to desert oases. Its root system can reach deep groundwater. The date palm is dioecious. Mostly female trees are planted on plantations, and inflorescences from male palms, which are the subject of trade, are tied in the crowns of female individuals. Fruits - dates - single-seeded berries with juicy sugary mesocarp.
The fruits of the palm tree are of particular use. areca(Areca catechu). They are sold in abundance in any market in South Asia and go to preparation.
narcotic chewing composition - betel nut, which also includes the leaves of one type of black pepper and lime. The alkaloids contained in areca fruits strongly stimulate the central nervous system and inhibit the activity of the heart.
We see, therefore, that palms find a wide variety of uses. Here are some more examples. From young inflorescences wine palm(Raphia vinifera) receive the sweet juice used to make palm wine. By the way, the leaves of one of the species of this genus reach 15 and even 20 m in length; fiber is extracted from the leaf petioles of many types of palm trees, which is used to make ropes, nets, etc.
Palm trees are extremely decorative. They adorn boulevards and embankments of cities, right up to the coasts of the Mediterranean and Black Seas (however, only the most cold-resistant species can grow here). Several types of palm trees can be seen on national emblems and flags. Royal palm(Roystonea regia), which adorns the central squares of Havana, is the national tree of Cuba, and the tallest of the palm trees is Ceroxylon of Andean(Ceroxylon andicola), reaching 60 m in height, is the national emblem of Colombia.
Palms are undoubtedly an ancient family, which is also confirmed by paleobotany. Most scientists believe that palm trees have common origin with liliaceae. However, apart from some common features typical of monocots, palms, at least with modern liliaceae, have little in common. Important features of palms, as well as of the next family, are the tendency to aggregation of flowers into complex inflorescences and the complete absence of bolls. In any case, the position of palms in the system is rather isolated.
Many different concepts are studied in a botany course. One of them is endosperm. What is it, what functions does this structure perform in a plant? You will find the answer to these and other questions in this article.
Endosperm is part of the embryo
People have long been amazed at the ability of a tiny seed to give rise to an entire organism. It turns out that this is due to its unique consists of an embryonic root, stalk, bud and leaf. These embryonic structures are surrounded by nutritive connective tissue. She is the endosperm. Outside the seed has additional protection- the peel.
This term comes from two Greek words "endo" - inside, "sperm" - seed. Essentially, the substances required for the development of the tissues of the embryo.
The value of nutrients
Endosperm is tissue that forms during fertilization. In terms of chemical composition, it is a combination of starch carbohydrates, proteins and vegetable oils. Therefore, man uses seeds as a source of energy and vitamins. But beneficial features they are kept only raw. During heat treatment, the destruction of macromolecules of organic substances occurs.
Endosperm of gymnosperms
Plant nutritional tissue can be primary and secondary. In gymnosperms, endosperm is formed even before the process of gamete fusion - fertilization. It develops from a megaspore, which is a mother cell with a haploid set of chromosomes. The primary endosperm is tissue that forms in the ovule. As a result of its development, a female overgrowth, or gametophyte, is formed.
Double fertilization of plants
In the seeds, the angiosperm endosperm is formed during fertilization. In the course of this process, two sperm take part, which are located in the anthers of the stamen. The pistil ovary contains one female gamete and a central germ cell. Fertilization takes place here. One sperm is fused with the egg to form the seed embryo. The other connects to the germ cell. The result of the latter process is endosperm. This type of its formation is called secondary. The endosperm is located around the embryo, warming and nourishing it, creating conditions for the germination of the seed.
How is it formed?
Endosperm is formed in two ways. In the first case, the fertilized nucleus of the embryo sac divides many times. The formed structures are located along its walls. This type of endosperm formation is called nuclear. In this case, the nutrient tissue of the seeds is liquid. For example, coconut milk.
But in most angiosperms, after nuclear division, cellular division occurs. It changes the state of aggregation of the nutrient tissue. Moreover, during each division, cells are formed. So, if you collect the fruits of corn during the period of nuclear fission, it will be juicy and sweet. This is followed by the conversion of simple carbohydrates into polysaccharides. This chemical transformation accompanies cell division.
So, the endosperm, which is the nutrient of the embryo of the seed, performs essential functions. These include providing the embryo with energy, vitamins and microelements, transporting solutions of minerals from an adult plant. Also important is the regulation of the process of differentiation of embryonic cells into organs, which occurs due to the cytokinins of the endosperm.
The seed is a plant reproductive organ that develops from the ovule after fertilization.
During the formation of a seed and a fetus, one of the sperm fuses with the egg, forming a diploid zygote (fertilized egg). Subsequently, the zygote divides many times, and as a result, a multicellular plant embryo develops. The central cell, fused with the second sperm, also divides many times, but the second embryo does not arise. A special tissue is formed - endosperm. The endosperm cells accumulate reserves of nutrients necessary for the development of the embryo. The ovule covers grow and turn into a seed coat.
Thus, as a result of double fertilization, a seed is formed, which consists of an embryo, storage tissue (endosperm) and seed coat. From the wall of the ovary, the wall of the fetus is formed, called the pericarp.
Seed types
1.with endosperm (the seed consists of three parts: seed coat, endosperm and embryo. Seed with endosperm is inherent in monocotyledons, but can also occur in dicotyledons - poppy, solanaceous, umbelliferous);
2. with endosperm and perisperm (usually a rare type of structure, when the seed contains an embryo, endosperm and perisperm. It is characteristic of lotus, nutmeg);
3.with perisperm (the endosperm is completely consumed for the formation of the embryo. Seeds of this type are characteristic of cloves);
- without endosperm and perisperm (the embryo occupies the entire cavity of the embryonic sac, and spare nutrients accumulate in the cotyledons of the embryo. Together, the seed consists of two parts: the seed coat and the embryo. This structure of the seed is characteristic of legumes, pumpkin, rosaceae, walnut, beech, etc.)
Perisperm - Storage diploid tissue of the seed, in which nutrients are deposited. Arises from nucellus.
Endosperm - Large cell storage tissue, the main source of nutrition for the developing embryo. First, it actively transfers substances from the mother's body to the embryo, and then serves as a reservoir for storing nutrients.
Rice. Seeds
16. Classification of fruits. Fruitfulness .
The fruit is an organ of propagation of angiosperms, formed from one flower and serving for the formation, protection and distribution of the seeds contained in it. Many fruits are valuable food products, raw materials for obtaining medicinal, dyes, etc.
Fruit classification
In most classifications, fruits are usually divided into real(formed from an overgrown ovary) and false(other bodies also take part in their formation).
Real fruits are divided into simple(formed from one pistil) and complex(arising from the polynomial apocarpous gynoecium).
Simple ones are divided according to the consistency of the pericarp into dry and juicy.
Among the dry are distinguished single-seeded(for example, weevil, nut) and polyspermous... Multi-seeded fruits are divided into opening (bean, capsule, pouch, pod, etc.) and non-opening. Non-opening dry polyspermous fruits are divided into articulated (articulated pod, articulated pod) and fractional (crocodile, two-winged fruit, etc.)
Among juicy fruits, they also distinguish polyspermous ( pumpkin, apple, berry) and single-seeded(drupe).
Complex ones are called based on the names of simple fruits (polystyrene, manynuts, etc.).
In contrast to the fruit (simple or complex), the inflorescence is formed not from one flower, but from the whole inflorescence or its parts. In any case, in addition to flowers, the inflorescence axes take part in the formation of infructescence. Infertility is a product of modification (after fertilization) not only of the flowers, but also of the axes of the inflorescence. In typical cases, the compound fruit mimics the fetus and corresponds to it functionally. A classic example is pineapple fruit.
17, Vegetative propagation of plants and its biological value vegetative propagation of plants(from lat. vegetativas- vegetable) is the reproduction of plants using vegetative organs (root, stem, leaf) or their parts. Vegetative propagation of plants is based on the phenomenon of regeneration. During this method of reproduction, all properties and hereditary qualities in the daughter individuals are fully preserved.
Distinguish between natural and artificial vegetative reproduction. Natural reproduction occurs constantly in nature through the impossibility or difficulty seed reproduction... It is based on the separation from the mother plant of viable vegetative organs or parts that, as a result of regeneration, are able to restore the whole plant from its part. The entire set of individuals obtained in this way has the name clone. Clone(from the Greek. clon - sprout, branch) - a population of cells or individuals, which is formed as a result of asexual division from one cell or individual. Vegetative propagation of plants in nature carried out by:
Separation (unicellular);
Root shoots (cherry, apple, raspberry, blackberry, rosehip);
Korenebulbs (orchid, dahlias);
Layers (currants, gooseberries);
Mustache (strawberry, creeping buttercup);
Rhizomes (wheatgrass, reed);
Tubers (potatoes);
Bulbs (tulip, onion, garlic);
Brood buds on leaves (briofilum).
Biological significance vegetative propagation: a) one of the adaptations for the formation of offspring where there are no favorable conditions for sexual reproduction; b) the genotype of the parental form is repeated in the offspring, which is important for the preservation of the characteristics of the variety; c) one of the ways to preserve valuable varietal traits and properties; d) during vegetative propagation, the plant can be stored under conditions of impossibility of seed reproduction; e) the preferred method of propagation of ornamental plants; f) during grafting - resistance to external conditions increases in the scion plant. It should be noted that vegetative reproduction is also disadvantageous: a) negative traits are transmitted; b) diseases of the mother's body are transmitted.
18. SEXUAL REPRODUCTION, ITS ROLE AND FORMS Reproduction is a universal property of all living organisms, the ability to reproduce their own kind. With its help, species and life in general are preserved in time. The life of the cells is much shorter than the life of the organism itself, therefore its existence is supported only by the multiplication of cells. There are two ways of reproduction - asexual and sexual. During asexual reproduction, mitosis is the main cellular mechanism providing an increase in the number of cells. The parent is one individual. The offspring is an exact genetic copy of the parent material. 1) The biological role of asexual reproduction Maintaining fitness enhances the importance of stabilizing natural selection; provides fast breeding rates; used in practical breeding. 2) Forms of asexual reproduction The following forms of asexual reproduction are distinguished in unicellular organisms: division, endogony, schizogony and budding, sporulation. Division is typical for amoeba, ciliates, flagellates. First, mitotic division of the nucleus occurs, then the cytoplasm is divided in half by an ever deepening constriction. In this case, daughter cells receive approximately the same amount of cytoplasm and organelles. Endogony (internal budding) is characteristic of Toxoplasma. With the formation of two daughter individuals, the mother gives only two offspring. But there may be internal multiple budding, which will lead to schizogony. Occurs in sporozoa (malarial plasmodium), etc. There is a multiple division of the nucleus without cytokinesis. A lot of daughter cells are formed from one cell. Budding (in bacteria, yeasts, etc.). In this case, a small tubercle containing a daughter nucleus (nucleoid) is initially formed on the mother's cell. The bud grows, reaches the size of the mother, and then separates from her. Spore formation (in higher spore plants: mosses, ferns, moss, horsetails, algae). The daughter organism develops from specialized cells - spores containing a haploid set of chromosomes. 3) Vegetative reproduction Typical for multicellular organisms. In this case, a new organism is formed from a group of cells that are separated from the mother's organism. Plants reproduce by tubers, rhizomes, bulbs, root tubers, root crops, root shoots, layering, cuttings, brood buds, leaves. In animals, vegetative reproduction occurs in the lowest-organized forms. The ciliary worms are divided into two parts, and in each of them the missing organs are restored due to disordered cell division. Ringed worms can regenerate an entire organism from one segment. This type of division underlies regeneration - the restoration of lost tissues and body parts (in annelids, lizards, salamanders)
19 Sexual reproduction - associated with the fusion of specialized germ cells - gametes with the formation of a zygote. Gametes can be the same and different morphologically. Isogamy - the fusion of identical gametes; heterogamy - the fusion of gametes of different sizes; oogamy is the fusion of a motile sperm with a large, immobile egg.
For some groups of plants, alternation of generations is characteristic, in which the sexual generation produces germ cells (gametophyte), and the non-sexual generation produces spores (sporophyte).
Fertilization - this is the union of the nuclei of male and female germ cells - gametes, leading to the formation of a zygote and the subsequent development of a new (daughter) organism from it.
Gamete Is a reproductive cell that has a single (or haploid) set of chromosomes and participates in sexual reproduction. That is, in other words, the egg and sperm are gametes with a set of 23 chromosomes each.
Zygote Is the result of the fusion of two gametes. That is, a zygote is formed as a result of the fusion of a female egg and a male sperm. As a consequence, it develops into an individual (in our case, into a person) with hereditary characteristics of both parental organisms.
Isogamy
If merging gametes do not differ morphologically from each other in size, structure and chromosome set, then they are called isogametes, or asexual gametes. Such gametes are mobile, can carry flagella or be amoeba-like. Isogamy is typical of many algae.