The sago palm is a guest from the Mesozoic era in your home. Cycas home care watering transplantation and reproduction See what "cycads" are in other dictionaries
The cycad family consists of 130 plant species resembling palm trees and ferns. All of them live within the tropics and subtropics. They are found mainly singly or in small scattered groups, occasionally forming extensive thickets. Cycads grow very slowly. For example, the trunk of a cicada grows by only 2-3 cm per year.
All cycads have a semblance of cones - strobili, resembling pineapple. They grow on top of trunks. Moreover, the trees make their further growth bypassing the strobilus due to the formation of a branch below, bending around it and continuing to grow upwards.
Cycad class.
Class cycads - dioecious plants, on some of which female strobili with ovules grow, and on others - male, with pollen. This pollen is transferred by air from male representatives to female representatives, and thus the process of fertilization is carried out. Until their seed germinates, it takes several months, or even up to two months.
Oppressive
Department oppressive(Gnetophyta) contains three peculiar families of gymnosperms with unclear evolutionary relationships. Plants of the genus gnetum- tropical creepers. Ephedra(conifers) - desert shrubs with scaly leaves. Velvichia- the only representative of the Velvichiaceae family - has a stem immersed in sand, from which two huge ribbon-like leaves extend.
Gnetovye are similar to, but differ from them in a more perfect shape of a cone, similar to a flower.
Cycads
Cycads are bizarre plants that appeared no later than 285 million years ago, somewhere at the beginning of the Permian period. They were so numerous in the Mesozoic that this time was figuratively called "the time of cycads and dinosaurs." Now only 10 genera of this department have survived, including about 100 species. Most of them are large plants; some reach a height of more than 18m. Their trunk is densely covered with the bases of fallen leaves, and the functioning leaves are collected in a bunch at the top. In this way, cycads resemble palm trees (not without reason some of them are called so - sago palms). However, unlike palms, cycads have a real, albeit slow, secondary growth as a result of the activity of the cambium. The reproductive organs of the cycads consist of more or less reduced leaves with sporangia attached to them, where the spores mature. Sporangia are loosely or heaped together in cone-like formations at the top of the plant. Male and female "bumps" are on different individuals
A typical representative is the drooping cycad (Cycas revolute). This plant is used by gardeners of all countries as an ornamental plant. He comes from southern Japan, sometimes grown on our Black Sea coast.
Of the other cycads, one can name the dwarf zamia (Zamia pumila), Encephalartos altensbinii.
The bark and core of the cycads are rich in starch and were formerly used to produce the starchy food product, sago. The seeds of most cycads are also edible and are still eaten in some countries.
CONIFEROUS- a group of seed vascular plants. Modern representatives of Conifers are evergreen, less often deciduous trees and shrubs.
According to one of the classification systems, this group is combined into the class Coniferous or Pinopsida (Pinopsida) of the department of gymnosperms (Gymnospermae). This class is divided into two subclasses: the extinct subclass Cordaites (Cordaitidae) and the modern subclass Conifers (Pinidae or Coniferae).
According to another classification system, all modern conifers are combined in the order Conifers (Coniferales), which is part of the coniferous class (Coniferopsida) of the department of gymnosperms. Another system classifies modern conifers as an independent division of Coniferophyta.
The Russian name "coniferous" comes from the word "needles", which refers to the needle-shaped leaves of some of their representatives (for example, spruce, fir, pine). However, not all Coniferous leaves are "needles". The name "cone-bearing" is equally inaccurate, which is a translation of the second Latin name Coniferae (from Latin conus - cone and ferro - to wear), since not all representatives of this group have cones.
Spreading. Conifers - plants of a predominantly warm temperate climate, for the existence of which, first of all, sufficient moisture is necessary. Therefore, they mainly grow in the temperate climate zone. The northern border of the distribution of arboreal conifers (as well as all tree species in general) coincides with the July isotherm +10 ° С. thawing, which prevents the roots of trees from getting enough moisture and nutrients from the soil. However, along the valleys of rivers and streams, where the layer of seasonal thawing increases due to the warming effect of water, coniferous forests move north a little further. In subtropical and tropical climates, the growth of conifers is hindered by insufficient atmospheric moisture, therefore, in these climatic zones, they grow mainly in the mountains at altitudes at which the climate corresponds to the climate of the temperate climate zone.
The currently existing Conifers are the largest and most widespread group among modern gymnosperms. The largest number of species and genera of Conifers is found in the northern hemisphere. Some of them, such as pines, spruces, larches, fir, form here extensive coniferous forests, sometimes consisting of one or a few species. In the southern hemisphere, conifers are most abundant in the temperate regions of New Zealand, Australia, and South America.
Most of the endemic genera of Conifers (genera whose distribution is limited to a very small area) and all ancient relict genera (genera that in this territory are a relic of the flora of past eras, their presence may be in some discrepancy with modern conditions of existence in this territory) are concentrated along the basin Pacific Ocean, especially in Southeast and Central China, Taiwan, Japan, New Caledonia, Tasmania, the Pacific coast of North America, Southern Chile, New Zealand, Eastern Australia and New Guinea. This is due to the fact that the climatic conditions in the Pacific Ocean have undergone the least changes since the Mesozoic, the era in which this group reached its maximum development. Not only the number of genera, but also the number of species of Conifers increases towards the Pacific Ocean.
In terms of their importance both in nature and in human life, conifers take second place after flowering plants, far surpassing all other groups of higher plants.
History of development. Conifers appeared in the Carboniferous period (about 370 million years ago), and at that time they grew mainly in the northern hemisphere. They outlived their cordaite relatives and already from the Triassic period (about 235-185 million years ago) began to play a significant role in the vegetation cover of the northern hemisphere. In the Jurassic and especially the Cretaceous periods of the Mesozoic era (about 185-66 million years ago), Conifers reached their greatest diversity and maximum distribution. At this time, most of the modern genera appeared, with the Pine (Pinaceae), Yew (Taxaceae), Taxodiaceae (Taxodiaceae) and Cypress (Cupressaceae) families concentrated in the northern hemisphere, and the Araucariaceae (Araucariaceae) and Podocarp (Podocarpaceae) families in the southern hemisphere.
In the Tertiary period of the Cenozoic era (about 66-2.5 million years ago), conifers were widespread throughout the Earth, they were not as noticeably concentrated around the Pacific Ocean as they are now. They grew then even in the polar regions, in territories that now lie outside the boundaries of the distribution of woody vegetation (Svalbard, West Greenland, Antarctica). Interestingly, conifers grew in Antarctica as early as the Quaternary (2.5 million years ago and later).
Conifers are older than all currently existing groups of seed plants, including even Ginkgoaceae, quite reliable remains of which have been known since the Permian period (this period began 280 million years ago and lasted 45 million years). But while only one species of the Ginkgo class has survived, the Ginkgo (essentially a genuine "living fossil"), the Conifers are a thriving group. Among modern conifers, the most ancient families are the Araucariaceae, Podocarps and Pine families. More or less reliable remains of representatives of these three families are already known from the deposits of the end of the Permian period (about 250 million years ago), and Pine, apparently, appear somewhat earlier than the other two. Ancient age not only in families, but also in some genera. Thus, plant remains more or less confidently attributed to the genus Pine (Pinus) are known from deposits of the Jurassic period (their age is from 185 to 132 million years), and pollen grains of the genus Cedar (Cedrus) are known from deposits of the late Permian period (their age about 250 million years). This suggests that some modern genera of Conifers existed even before the Cretaceous period, i.e. before the emergence of flowering plants.
Dimensions. Modern representatives of Conifers are evergreen, less often deciduous trees and shrubs. The sizes of Conifers are very different - there are all transitions from dwarf forms to real giants.
In terms of gigantic size, the first place belongs to the evergreen sequoia (Sequoia sempervirens), which belongs to the Taxodiev family. This is the tallest tree in the world. Its average height is over 90 m, and its record height is 117 m; the diameter of the trunk can reach 11 m. In terms of trunk thickness, the sequoia is second only to the Mexican marsh cypress (Taxodium mucronatum), whose trunk thickness can reach 16 m, and the mammoth tree (Sequoiadendron giganteum), the most powerful specimens of which are up to 12 m thick.
Among the dwarf conifers, the championship belongs to the New Zealand dacridium loose-leaved (Dacrydium laxifolium) from the Podocarp family, whose height is less than 1 meter. This tiny conifer with thin creeping stems forms thickets, mainly on mountainous and subalpine peatlands in areas with a humid climate.
Lifetime. Some species of Conifers are among the longest-lived plants in the world. For example, a mammoth tree is such a long-liver, the age of some of its specimens is more than 3000 years, but another species breaks the record of longevity, namely, the North American long-lived pine (Pinus longaeva). In Eastern Nevada, a specimen of this species was found, the age of which is estimated at about 4900 years, that is, almost five thousand years. This means that already during the construction of the Cheops pyramid, this plant was already quite old (it was more than 200 years old).
Structure.
Run away. Most conifers have two types of shoots: long shoots that are unlimited in growth (auxiblasts) and shortened shoots that are limited in growth (brachyblasts).
The branching of shoots in Conifers is monopodial. With this type of branching, the main stem (monopodium) developing from the seed has unlimited apical growth, due to which the plant grows in height. Lateral shoots of the first, second, etc. depart from the monopodium. orders. Shoots extending from the main trunk are arranged in a spiral, but they often come together so close that they turn into whorls (rings of shoots around the main trunk), and no more than one such ring of branches is formed annually. By counting the whorls, you can determine the age of the tree by adding 2 years to the figure obtained, since the first 2 years of life in coniferous trees do not form whorls. However, this method is applicable to relatively young (up to 50 years old) plantations, in which the lower whorls on the trunks have not yet had time to completely tighten due to the secondary growth of the trunk.
The branches of such false whorls gradually shorten upwards, which gives the tree a characteristic pyramidal shape. At the same time, the lateral branches of the second and subsequent orders are bilaterally symmetrical, sometimes becoming completely flat, which gives the tree a longline character. If the apical shoot is damaged, then one of the branches of the youngest whorl of lateral branches may begin to grow upward and take on the role of the main one. In old trees, a wide spreading crown is usually formed, consisting no longer of one, but of several main branches, which is clearly visible, for example, in old pines.
As the tree ages, in the open, its lower branches may persist, reaching almost to the ground (running crown), but in dense forest they usually die off quite quickly due to lack of light. As a result, the long lower part of the trunk is exposed and remains practically free of branches, which is very much appreciated when harvesting wood.
In most conifers growing in cold areas, the tip of the shoot is protected by tightly fitting thin scales that form a well-defined bud at the end of the growing season. Kidney scales are covered with a protective layer of resin or densely covered with thick hair. In other cases, such as araucaria and most cypresses, bud scales do not develop.
Stem. The anatomical structure of coniferous stems is relatively uniform. They have a fairly thin bark and a massive wood cylinder, inside of which is a core, barely visible in older trunks. Both in the bark and in the wood itself there are many resin passages (channels), consisting of elongated intercellular spaces. The resin canals are filled with resin, which is secreted by the lining cells.
Most conifers have well-defined growth rings in the trunk, the formation of which is associated with a slowdown in tree growth during the annual periods of winter cold or summer drought. Each ring corresponds to the growth of wood in one growing season. These rings are distinguishable on transverse sections of the trunk, branches and roots. They are best expressed in coniferous temperate and cold latitudes. By the number of annual rings on the cut of the trunk, carried out at the height of the neck of the root, one can fairly accurately determine the age of the tree. Moreover, based on a number of signs of the structure of the growth ring, certain conclusions can be drawn about the climatic conditions of the past. The study of the growth rings of Conifers (as well as tree Tsvetkovy) is used to date archaeological remains and natural phenomena (this method is called dendrochronology), as well as to study the ancient climate (dendroclimatology).
Root. The primary root in many conifers persists throughout life and develops in the form of a powerful tap root, from which lateral roots extend. Less commonly, for example, in some pines, the primary root is underdeveloped and is replaced by lateral ones. In addition to long roots (main and lateral), Conifers also have short, often highly branched roots, which are the main absorptive organs of the plant. Such roots may contain mycorrhiza - a symbiosis of the mycelium of the fungus and the roots of the plant. Mycorrhiza-forming fungi decompose some organic soil compounds inaccessible to the plant, promote the absorption of phosphates, nitrogen compounds and produce substances such as vitamins, while they themselves use the substances they extract from the roots of the plant.
On the roots of Conifers there are root hairs near the narrow zone of the root apex, which easily fall off when the root is washed.
The leaves of most Conifers are narrow and needle-shaped, such leaves are called needles, but in older genera (for example, in some species of Araucariaceae and Podocarps), the leaves are lanceolate and even broadly lanceolate. So, in the largest podocarp (Podocarpus maximus), the largest leaves reach 35 cm in length and 9 cm in width.
The green leaves of Conifers are most often sessile, but sometimes with a short petiole. Almost always they are whole, and only in some species of fir the leaves at the top are more or less notched. Their length is from 1-2 to 30-40 cm. The longest leaves among modern conifers are in the North American swamp pine(Pinus palustris), the needles of which reach 45 cm in length. With the exception of a few deciduous or branch-falling genera (araucaria, agathis, taxodium, metasequoia and cunningamia), the leaves of Conifers are evergreen, dense, more or less stiff and leathery. The leaf arrangement is usually spiral or alternate, rarely whorled or opposite. Narrow leaves (needles) have one vein, wide - many parallel veins. In section, the leaves are flat, tetrahedral or rounded.
In addition to green photosynthetic leaves, some conifers have brown scale-like leaves.
Reproduction. The reproductive organs of Conifers are strobili - modified shortened shoots that carry special leaves - sporophylls, on which spore-forming organs - sporangia are formed. There are male strobiles (they are called microstrobils) and female strobiles (megastrobils). Megastrobils tend to grow in compact collections, very rarely they grow alone. Gatherings of megastrobils and single megastrobils are called female cones.
Microstrobili in most conifers grow singly, and, very rarely, in some primitive forms of Conifers, in compact collections. Collections of microstrobils and single microstrobils are called male cones.
Usually Conifers are monoecious plants (male and female cones develop on the same tree), less often they are dioecious (female and male cones develop on different trees).
Male cones are most often collected in groups and are usually located in the axils of the leaves, less often on the tops of lateral shoots. At the base of the cones, there are often scales that play a protective role. Microsporophylls are very reduced, scaly or corymbose. Each microsporophyll produces from 2 to 15 microsporangia. In the microsporangium, a sporogenic tissue is formed, surrounded on all sides by a tapetum - a layer of cells that deliver nutrient material for developing microspores. The number of microspores produced in the microsporangia is usually very large, they are very light, which helps them to be dispersed by the wind.
From each microspore, a male gametophyte develops - the sexual generation of plants, the life cycle of which passes with the alternation of sexual and asexual generations. In almost all higher plants (with the exception of mosses), the gametophyte is poorly developed and short-lived.
In most conifers, the development of the male gametophyte begins even before the dispersal of microspores, i.e. even when they are inside the microsporangium. In the rest of the Conifers (most of the Yew and Cypress) the development of the male gametophyte begins only after the microspores are carried by the wind to the ovules in the female cones.
Each female cone, as a rule, consists of a central axis on which cover scales sit, in the axil of each of which there is a seed scale, which is a megastrobil modified in the process of evolution. In various lines of evolution of Conifers, a process of gradual fusion of the covering and seed scales (i.e., scaly megastrobilus) occurs, which, in the end, leads to the formation of a simple, fused scale, often called the fertile complex.
On the upper side of these scaly megastrobils are the ovules. The ovule is a megasporangium (here called nucellus) surrounded by a special protective substance - the integument. Each nucellus develops 3-4 potential megaspores, of which only one is capable of development. Inside the megasporangium, as a result of repeated division, a female gametophyte, called the endosperm, develops from a functioning megaspore.
Pollen from the male cones is transferred to the ovules with the help of air sacs. Pollination occurs and the scales of the female cone close. The male gametophyte continues its development on the megasporangium. After a certain period of time after pollination, the process of fertilization begins, which usually occurs during the same season. This period of time is unusually long in pine species, in which 12 to 14 months pass between pollination and fertilization. After fertilization, a zygote is formed (a cell resulting from the fusion of male and female germ cells), from which the embryonic embryo (pre-embryo) immediately begins to develop, and then the real embryo. The development of the embryo occurs due to the reserve substances of the endosperm.
The formed embryo consists of a root, a stalk, several cotyledons (embryonic leaves) and a kidney. The embryo is surrounded by endosperm, which is used during germination. The integument forms the hard seed coat. The ovule tightly adheres to the seed scale, from the tissue of which a pterygoid film is formed, which contributes to the spread of seeds by the wind. Thus, a mature seed contains a sporophyte embryo, supplied with reserve substances and protected by a peel. Sporophyte - asexual generation of plants, the life cycle of which passes with the alternation of sexual and asexual generations. All higher plants (with the exception of bryophytes) are represented by sporophytes.
Coniferous seeds vary greatly in size, shape and color. The seed coat may be woody, leathery, or membranous. Seeds adapted for wind dispersal are equipped with one large wing-like appendage or 2-3 small wings. Seeds distributed by animals often have a juicy and brightly colored coat.
Quite a lot of time passes between pollination and seed maturation. For example, in Scots pine (Pinus sylvestris), seed ripening occurs in autumn, in the second year after pollination. Cones by this time reach a length of 4-6 cm, their scales become lignified and turn from green to gray. The next winter, the cones droop, the scales diverge and the seeds spill out. Separated from the mother plant, the seed can be dormant for a long time and only with the onset of favorable conditions starts to grow.
Characteristics of families. Currently, there are 7 families, about 55 genera and at least 560 species of Conifers.
The Araucariaceae family is a very ancient group of conifers, their geological history is known from the end of the Permian period, although they may have an even more ancient origin. These are tall trees growing in the tropical and subtropical zones of the southern hemisphere. The leaves are usually large, broadly lanceolate or ovate, and sometimes almost round; less often they are small, needle-shaped. In some species, green leaves grow not only on the shoots, but also on the trunk. The features of Araucariaceae include twigfall - the property of completely shedding leafy lateral shoots or even shoots with leaves.
Plants are often dioecious. Microstrobili are large, bearing numerous spirally arranged microsporophylls. The female cone consists of a large number of scales, which are the result of complete or almost complete fusion of seed and cover scales.
The family includes 2 genera: araucaria (Araucaria) and agatis (Agatis).
The genus Araucaria has 15 species growing in South America (Chile, Patagonia, Tierra del Fuego) and Australia. Araucaria species often form extensive forests.
The genus Agatis has about 20 species distributed in New Zealand, Northern Australia and Oceania. Some species are forest-forming species.
Araucariaceae are of great practical importance. Most of the species provide valuable wood, the seeds are edible (they are the food product of the Chilean population). Resin is extracted from agathis species. Outside their natural range, they are often bred as ornamental breeds.
Family Podocarp or Nogoplodnikovyh (Podocarpaceae)
The history of the development of the family begins at the end of the Permian period. The family includes 130 species distributed in the extratropical regions of the southern hemisphere, where they are the main forest-forming species. In the tropical zone, they are found in the mountains of India and East Asia.
These are powerful erect trees or creeping shrubs. The leaves are often small, broadly lanceolate, lanceolate, needle-shaped or scaly, sometimes large and wide, with several veins.
Plants are usually dioecious. Microstrobili are small, consist of numerous small microsporophylls arranged in a spiral order, each bearing 2 microsporangia. There is usually no typical female cone. Megastrobil is very reduced, consists of one ovule, surrounded by a highly modified seed scale, which either completely envelops the ovule, or is reduced to a small vaginal appendage at the base, sometimes the seed scale is completely absent.
The wood of Podocarps is very dense and is widely used for various crafts.
Yew family (Taxaceae). With the exception of two species, Yews are common in the northern hemisphere, where the family has an extensive but fragmented range. They are found in North America, Europe and Asia. The geological history of the family begins with the Jurassic period.
Yew - evergreen trees or shrubs. In wood, annual growth layers are more or less clearly expressed. Leaves lanceolate or linear, sometimes on short (1-2 mm) petioles.
Yew trees are dioecious, rarely monoecious. Microstrobili in most yew trees are solitary, but there are also their catkin-shaped, spike-shaped or spherical collections located in the axils of the leaves. Microsporophylls have a different structure, most often they are corymbose, each of them bears from 2 to 9 microsporangia. Megastrobils are united into collections that look like small cones with opposite pairs of megastrobils. However, usually these collections are greatly reduced and reduced to single megastrobiles. They consist of one ovule, surrounded at the base by a collar-shaped roof (it is called aryllus) of red, yellow or white. Morphologically, the aryllus corresponds to the seed scale. Roofing completely covers mature seeds, over time it becomes juicy and brightly colored, which is an adaptation for seed dispersal by birds.
Among the yew there are real centenarians. Thus, the life expectancy of the common yew (Taxus baccata) is up to 1500 years, and sometimes, apparently, up to 3-4 thousand years.
There are 5 genera in the family. These are yew (Taxus), torreya (Torrea), pseudotiss, or pseudotaxus (Pseudotaxus), austrotaxus (Austrotaxus) and amentotaxus (Amentotaxus).
Family of head tyss (Cephalotaxaceae). The family is represented by one genus - the capitate (Cephalotaxus), consisting of only 6 species. In ancient geological times, the head yews were widespread in the northern hemisphere, but now they are found only in Asia, where they grow mainly in mixed mountain forests at an altitude of 300-3300 m above sea level.
These are evergreen, dioecious, rarely monoecious trees of small height (10-15 m) or shrubs. Leaves are leathery, narrow-linear.
A feature of the family is the presence of spherical assemblies of microstrobils. These globular male cones are borne on short stalks on last year's shoots. Megastrobili are collected in small cones, each of which develops from one to three drupe-like seeds.
In Japan, from the seeds of one of the species of the family, a waxy substance suitable for technical purposes (for example, for candle production) is obtained, and the seed oil is used for the production of paints and varnishes. Sometimes capitate is used for decorative purposes.
The Taxodiaceae family. Modern Taxodiaceae are real "living fossils", the remains of a once flourishing family that arose more than 140 million years ago (the oldest remains of Taxodiaceae date back to the end of the Jurassic period). They reached their greatest prosperity in the Tertiary period, when its numerous representatives were widespread throughout the northern hemisphere. Taxodiaceae were important components of the forests that stretched across the vast territories of North America and Eurasia, reaching as far as Svalbard and Greenland, now only small islands in North America and East Asia remain of them.
Now this family is represented by 10 genera and 14 species. Due to their decorative appearance and beautiful durable wood, most of the genera of this family are cultivated in many countries of the globe.
Modern taxodiaceae are mostly large, often gigantic trees with shoots of the same or different lengths. The leaves are linear-lanceolate, needle-shaped or scaly, spirally arranged on the shoot. Some species are deciduous, and in some genera that have shoots of two types (elongated and shortened), the phenomenon of branch fall is observed - in autumn, shortened shoots fall off along with the leaves.
Microstrobili are solitary, only in one species they are collected in a primitive capitate assembly. Female cones are small, solitary, apical, with flat or shield-like scales.
Modern Taxodiaceae include a number of interesting plants. The first of them should be called - sequoiadendron or mammoth tree (Sequoiadendron giganteum) and evergreen sequoia (Sequoia sempervirens) - one of the largest and longest-lived plants in the world.
Cypress family (Cupressaceae). The family includes 19 genera and about 130 species, widely distributed in both the southern and northern hemispheres. Of the 19 genera, only three include many species (from 15 to 55) - these are cypress, callitris and juniper.
Cypress - evergreen trees and shrubs. The trees are most often of medium size and stunted, although some can be very tall, up to 70 m tall, with a trunk sometimes reaching 6 m in diameter. Among shrub cypress, creeping forms are also found. The leaves are small, scaly or needle-shaped. Microstrobiles are usually solitary. The female cones consist of several woody, leathery, or succulent scales.
Pine family (Pinaceae). It is difficult to name such a family, even among flowering plants, which, in terms of its developed territory and accumulated biomass, could compete with pines. With the exception of one species, the entire family is distributed in the northern hemisphere, mainly in the temperate and subtropical zones (in the latter, mainly in the mountains). Some species of pine, spruce, fir and larch climb high into the mountains and go beyond the Arctic Circle.
This extensive family contains 10 or 11 genera and about 250 species. There are 4 largest genera - fir (Abies), larch (Larix), spruce (Picea) and pine (Pinus), each of which has several dozen, or even a hundred (pine) species. Other genera (cedar, hemlock, pseudo-hemlock, keteleeria, kataya, false larch) contain one or more species.
Pines are evergreen or, more rarely, deciduous trees, sometimes creeping shrubs. Needle-shaped, scaly, less often narrow-lanceolate leaves can be of different sizes from tiny to strongly elongated, reaching a length of 45 cm (marsh pine - P. palustris). The leaves stay on the tree from 2 to 7 years, and only larch and false larch fall annually for the winter.
Some genera (for example, pine, larch, cedar) have two types of shoots - long (unlimited in growth) and shortened. Long shoots are covered with numerous, quickly drying scaly leaves. In larch, cedar and false larch, they also bear green leaves. Short shoots arise in the axils of scaly leaves on elongated shoots, often they fall off along with the leaves growing on them.
In pine trees growing in the harsh conditions of the North, the buds are protected by thin scales tightly adjacent to each other, covered with a protective layer of resin.
Microstrobiles are solitary, rarely collected in groups, consist of numerous microsporophylls. Megastrobili are collected in complex formations - cones, the shape and size of which are different for each genus. The size of the cones is from 2.5-3 cm in length in the Lyell larch (Larix lyallii) to 50 cm in length in the American Lambert pine (Pinus lambertiana).
Most pine trees have a powerful root system, on which mycorrhiza is often found (symbiosis of the mycelium of the fungus and the roots of the plant). Mushrooms that enter into symbiosis with forest trees most often belong to the group of cap mushrooms. Mushrooms that are harvested in the forest are nothing more than the fruiting bodies of mushrooms associated with the roots of various trees.
Pine tree forms are large trees, reaching 40-50 m in height and 0.5-1.2 m in diameter. However, in unfavorable conditions of existence for themselves (far in the North, high in the mountains, in swamps), they can turn into undersized dwarfs, but it is in such places that the oldest centenarians of the Earth can be found. Thus, the longest-lived plant on Earth (namely, the already mentioned copy of the long-lived pine, whose age was about 4900 years old) grew on a mountain peak and was in a very depressed state.
Pine wood is diverse in texture and physical properties. It has long been used in Eurasia, North America and partly in Africa, where it has always been the main material from which dwellings, outbuildings, religious and public buildings were built.
Now the importance of this wood has increased even more. As before, it is used in carpentry and construction, but it has acquired the greatest importance in the pulp and paper industry. To use this wood in many countries of the world, various species of this family are artificially bred.
Class Cycads (Cycadopsida). The class includes one order Cycads and one family Cycads, uniting about 130 species of tropical and subtropical evergreen low trees, sometimes bushy or epiphytic forms of Southeast Asia, Central America. Modern species of cycads are the remains of the once lush cycad flora of the Mesozoic Yar. They appeared in the Permian period of the Paleozoic. They are directly related to seed ferns, which gave rise to two lines of evolution - micro- and megaphilic groups of gymnosperms.
Outwardly, they resemble tree ferns or palm trees. They are characterized by the presence of a taproot, a typical stem eustela, and a cambial ring with secondary cambial elements of the cortex. However, like ferns, cycads have a highly developed large-celled core rich in starch. The leaves of the cycads are large, pinnatipartite, rigid.
One of the typical representatives of cycads - drooping cycad (Cycas revoluta). It is a dioecious plant with a short trunk, covered with a shell of brown hard remnants of the bases of the leaves.
Due to dioeciousness, microstrobiles are formed on some trees, on others - megastrobiles located at the top of the trunk. Microstrobili consist of a rod and numerous microsporangia. Megastrobil does not have a typical shape, it is leaf-shaped, pinnate, and two or more pairs of large megasporangia develop in its lower part and on the sides, i.e. ovules.
The ovule is two-covered, as it consists of two integuments (from lat. integumentus- cover). Under the integument is the main part of the ovule - nucellus, formed by parenchymal diploid cells. At the top of the ovule, a small hole is preserved in the integuments - the pollen inlet (micropyle). The pollen-entrance channel approaches the nucellus, and in this place a small cavity is formed, called pollen chamber.
In the nucellus, one large archesporial cell separates against the pollen inlet. It divides reductively, forming a tetrad megaspore; of the four, only one remains, the remaining three degenerate. Thus, the ovule is megasporangium, in which megaspores arise.
The megaspore in cycads grows inside the megasporangium into a female gametophyte, which is called haploid endosperm, arose by repeated mitotic division of the only surviving megaspore. The development of the endosperm occurs due to the degeneration of the nucellus cells, from which, by the end of the formation of the female gametophyte, only the peripheral layer of cells is preserved. From the endosperm cells closest to the micropyle, two (or more) archegonia arise. The cells covering them dissolve, forming archegonial chamber, filled with sugary liquid. The tubular cells of the archegonium become mucilaginous, which facilitates the easy penetration of spermatozoa to the egg.
In microsporangia, numerous haploid microspores (pollen cells) develop from diploid mother cells by meiosis. While still in the microsporangium, a mature mononuclear microspore (pollen) germinates into a male gametophyte, consisting of one vegetative, larger oval in outline, and a smaller spindle-shaped cell, called antheridial. The vegetative cell develops into a pollen tube that penetrates through the micropyle of the ovule into the nucellus and then to the egg. The anteridial is preliminarily divided into a stalk cell and a generative cell, from which two sperm are formed - male gametes that penetrate with the current of the cytoplasm through the pollen tube to the egg. After the fusion of one of the sperm with the egg, a zygote is formed, which develops into a seed embryo. The embryo is surrounded on all sides by the endosperm. The integuments of the ovule turn into the seed coat, and the entire ovule into the seed.
Seeds of cycads are large (from 3-4 to 8 cm in length), with a juicy red or orange cover. The seeds are edible for many animal species (monkeys, bears, wild pigs, rodents). Among the classes of gymnosperms, cycads have the most primitive seeds in structure. This is expressed in the formation of a powerful differentiated seed coat, abundant endosperm, and underdevelopment of the embryo in a morphologically and physiologically mature seed.
From the middle of the trunk, bark and endosperm of seeds, starch is extracted - sago. Cycads are decorative and valued in landscaping.
Ginkgo class (Ginkgoopsida). The class is monotypic and is represented by the Ginkgo family with a single species - ginkgo biloba (Ginkgo biloba). This species differs sharply from other gymnosperms. The origin of the genus dates back to the Triassic of the Mesozoic. The natural focus of modern growth of ginkgo is located in a small area in East China, where ginkgo is found together with conifers and broadleaf species.
Outside of its natural range, ginkgo biloba is widely distributed in Japan, Korea, it can be found in botanical gardens and parks in the subtropics and temperate zone of Europe and North America. On the territory of Russia in the open pound grows in Krasnodar (in the arboretum).
Ginkgo biloba is a tall (up to 30 m) tree with a thick (up to 1.5 m in diameter) trunk and spreading crown. The bark is gray rough, in old trees with longitudinal cracks (Fig. 2). The main mass of the trunk is formed by wood. The core is poorly developed, the bark is thin. Ginkgo has two types of shoots - elongated with spirally arranged leaves and shortened - with a bunch of 5-7 leaves at the top of the shoot. Leaf blade with more or less deep median lobe.
Ginkgo is one of the few deciduous gymnosperms. Before falling, the leaves turn golden yellow. The plant is dioecious. Strobili are formed on shortened shoots. Megastrobili bear two ovules on a long stalk. Ginkgo microstrobili are catkin-shaped and consist of an axis and microsporophylls spirally sitting on it with two, less often 3-4 hanging microsporangia. Of the two ovules, as a rule, only one develops. After pollination and fertilization, a seed is formed from the ovule, surrounded by a juicy shell formed from the outer layer of the integument - sarcotesta. Sarcotesta of mature seed turns into a beautiful amber-yellow color.
Ginkgo is a very long-lived plant, the age of individual trees reaches 1,000 years. Propagated by seeds, cuttings. It tolerates urban and industrial environments well.
Class Gnetovye (Gnetopsida). The class includes 3 families and over 70 species. There are about 30 species in the Gnetovye family, more than 40 in the Ephedra family, and one single species in the Velvichiaceae family.
The species included in these families differ quite sharply from each other at the generic level. Most of the oppressive ones are large trees, climbing, clinging, climbing vines. Velvichia amazing (Welwitschia mirabilis) not at all like any of the plants known to us - it is a dwarf tree with a stump-like trunk, more than half submerged in the soil, and two belt-like leathery leaves that grow throughout the life of the individual (up to 2,000 years or more).
Ephedra - in most cases, low, strongly branched shrubs that look like horsetails.
Cycas flower (cycad) is another bright representative of domestic palms, successfully cultivated in winter gardens and indoor greenhouses. If you grow cycas in the way experienced flower growers advise, this plant will decorate the interior for more than a dozen years. If the conditions of keeping cycads are fully consistent with their needs, then the life of plants can be extended up to two decades.
cicadas (Cycas) or the cycad belongs to the Cycadidae family (Cycadoideae). Homeland - Southeast Asia.
This is a small isolated group of tropical and subtropical gymnosperms. We learn about them from the reports of the first European explorers of distant overseas countries on the eve of the Renaissance. In those days, as well as much earlier, starting with the “father of botany” Theophrastus, cycads were mistaken for palm trees by their purely external resemblance.
The generic name of the Asian representatives of plants cycad or cycas (Cycas) comes from the Greek word kykas - palm tree.
A decisive role in determining the position of cycads in the phylogenetic system of higher plants was played by the classic work of the outstanding German botanist Wilhelm Hofmeister (1851). The chamberlain carefully studied the cycles of development ("from spore to spore") in higher plants from bryophytes to conifers. He established that the so-called "corpuscles" of gymnosperms correspond to the archegoniums of bryophytes, ferns and other non-family higher plants, and the endosperm of seeds corresponds to the female gametophyte. Thus, the idea of an impassable abyss between "spore" and seed plants was destroyed.
Not only that, the Hofmeister essentially predicted the discovery in cycad spermatozoa. This prediction was brilliantly confirmed when, half a century later, in 1896, almost simultaneously, the Japanese botanists S. Hiraze and then S. Ikeno discovered polyflagellated spermatozoa, respectively, in Ginkgo and in the drooping cycad (Cycas revoluta). These discoveries determined the place of the cycads among higher plants, as one of the oldest groups of gymnosperms.
The total number of cycad species, united by ten genera, according to the latest data, is close to 120-130. Thus, in terms of species richness among gymnosperms, cycad palms rank second after conifers.
Distribution of plants of the Cycad family
Cycads live in all parts of the world except Europe and Antarctica. The American cycad group includes the genera:
Zamia
ceratosamia (Ceratosamia)
Dion (Dioon)
microtsikas (Microcycas).
African cycads are represented by genera:
Encephalartos (Encephalartos)
stangeria (Stangeria).
Finally, the most extensive area (Australia, South and Southeast Asia, the islands of the Indian and Pacific Oceans) is inhabited by species of the genera cycads:
Macrosamia (Macrozamia)
Lepidosamia (Lepidozamia)
Bovenia (Bowenia).
Of the latter, only the cycad is distributed west to Africa, occurring in Madagascar. The cycad grows, however, on the east coast of Africa, in the delta of the Zambezi River, however, it is believed that it was brought here in the relatively recent past.
A notable feature of the distribution of most of the species of cycads is their confinement to the oceanic territories of the continents.
Cycads in most cases do not form continuous thickets: they are found scattered, singly or in small groups. Only a few species are found, and then in places, in great abundance, giving a specific look to plant communities. This applies, for example, to the drooping cycad. On the Ryukyu Islands (Japan), it forms, usually near the sea coast, extensive, almost continuous thickets, becoming a background plant. In Eastern Australia, some types of macrosamia have a significant abundance in communities.
Cycads are more common in low-growing evergreen sclerophyllous forests and shrubs, similar in different areas physiognomically, but differing in composition: with the dominance of eucalyptus trees in Australia, evergreen oaks in America, various sclerophyllous plants in Africa.
On sea coasts, cycads are found not only on rocky cliffs, like the drooping cycad in Japan, but also in typical coastal plant communities.
So, Madagascar cycad Tuara (Cycas thouarsii) It is part of the typically coastal Barringtonia Formation.
Cycad Rumpha (C. rumphii) confined to the littoral zone of the islands of the Indian Ocean.
zamia florida (Zamia floridana) found on coral reefs.
Description of cicada leaves and photos of palm trees at the time of flowering
Cycas, cycad (Cycas), a genus of gymnosperms from the class of cycads. About 20 species distributed from Madagascar and the Comoros to the south and southeast. Asia, Australia and Polynesia. The most famous are 2 species, originally from Southeast Asia:
Cycas swirling, or cochlear (C. circinalis), sometimes also called the sago palm.
Cycas drooping, or bent (C. revoluta), cultivated in the USSR as an ornamental plant on the Black Sea coast of the Caucasus.
The cycad, or tsikas (Cycas), is the only genus of the subfamily. Of all ten genera of the family, it has the most extensive range, being represented by various species on two continents (in Asia, Australia), as well as on numerous islands in the Indian and Pacific Oceans. The center of the greatest diversity of the genus is Southeast Asia, where 11 of its species are concentrated.
Cycads are usually low palm-like plants, although some of them sometimes reach 10 or even 15 meters in height. The trunk of the cycad, covered with a shell of the bases of dead leaves, is crowned with a bunch of pinnate (in rare cases, double-pinnate) leaves, in the middle of the segments, which are always one powerful unbranched vein. And one more distinctive feature of the leaves of the cycad is that their segments are cochlearly folded in the kidney and at the first stages of development.
In males, microstrobili are formed, as in other cycads, but in females, compact strobili are not formed. At the top of their trunk, a beautiful "collar" of spirally arranged and brightly colored leaf-shaped megasporophylls unfolds.
Cycas, or cycad, boxwood, buxus - the oldest plant on the planet. Outwardly, it resembles a short-stemmed palm tree. Perennial ornamental evergreen slow growing dioecious plant. The trunk looks like a big bump. Several leaves grow throughout the year.
As you can see in the photo, indoor cycas leaves reach a length of 50 cm:
Leaves remain for several years.
It is used as an ornamental plant, has a beautiful crown, shiny foliage. When sheared, it is given various shapes that last a long time.
In indoor floriculture, evergreen boxwood is mainly found, which reaches up to 50 cm in height. Grows very slowly. Shoots are straight, sticking out. Leaves are glossy dark green, light green underneath.
At home, it blooms very rarely. At the time of flowering, cicas gives small flowers, greenish, which are collected in compact inflorescences.
These photos show cycas flowers:
The fruit is small, in the form of a spherical box. As the seeds ripen, the valves open. The plant is resistant to diseases and pests.
Types of cicas (cycad)
The genus cycad is still poorly understood, there are from 8 to 20 of its species (the last number is probably closer to the truth).
The most popular types of cycads are:
Cycad curled, or cochlear (C. circinnalis)
New Caledonian cycad (C. neocaledonica)
drooping cycad (C. revoluta).
The drooping cycad is best known outside the area of natural growth. In the USSR, it is cultivated in gardens and parks of the Black Sea coast of the Caucasus (to a lesser extent, Crimea). Here it can be seen as single plants or in small groups on lawns, as well as in alleys. From Gagra to Batumi, it is grown outdoors without special protection for the winter, and in Batumi conditions it is able to produce mature and viable seeds. To the north of Gagra, this subtropical plant suffers from temperature drops: the leaves are damaged already at -4 °C.
drooping cycad- a small graceful, like a palm tree, plant up to 2, rarely 3 m high (very old specimens up to 8 m), but with a thick stem, sometimes about 1 m thick and with a rather miniature crown of shiny dark green leaves compared to other cycads , against which yellow megasporophylls with bright red ovules stand out effectively.
The birthplace of this wonderful plant is subtropical southern Japan (Kyushu and Ryukyu islands), where it often forms large thickets, which are still the object of widespread exploitation.
Unlike the drooping cycad, which is so narrowly localized in natural conditions, cycad curled (C. circinalis)- the most common species among all cycads in general: it has the largest range, stretching from east to west from the Pacific Islands to the Mascarene Islands, lying near Madagascar.
Curly cycad is a very beautiful and ornamental plant, reaching up to 8 m in height. Differs in long, dense, dark green leathery leaves. Only young leaves remain on the tree. This cycad is a valuable crop of the tropics and subtropics, where it is grown in parks and botanical gardens. The plant is propagated only vegetatively, namely by rooting shoots (bulbs), which are formed in large quantities on the tree. Curly cycad seeds are not propagated due to the unpleasant smell of male cones, which are necessary for pollination.
Among the most closely related species to the cycad is cycad Tuara (C.thouarsii).
The same western representative of the genus lives in abundance in Madagascar in coastal forests under the canopy of a beautiful slender barringtonia (Barringtonia speciosa) from myrtle. The columnar, often forked trunk of the Tuara cycad reaches a height of 10 m, and the seeds are said to reach the size of a goose egg. Next to this cycad, in a plant community called “barringtonia”, on the coastal dunes you can see the famous “traveler tree” - the Madagascar equal, pandanus, coconut palm, and an orchid often settles on its trunk - Madagascar vanilla, which finds a place in the cracks between the leaf bases for your attachment.
Cycad species are well distinguished by the shape of megasporophylls.
This applies in particular to Cycas pectinata, which got its name from the comb-shaped cycad - due to the specific dissection of the megasporophylls plate, which makes it look like a rooster's comb.
Native to the hills and plains of India, Bangladesh, Burma, and South Vietnam, this small tree hides old, dying leaves hanging along its trunk under its crown.
One of the tallest members of the genus is cycad Rumpha (C. rumphii).
In some places of growth, it reaches about 15 m in height. The Rumfa cycad lives in the lowlands of Sri Lanka, along the shores of the Andaman and Nicobar Islands, on the islands of Sulawesi, Java and New Guinea and is a common culture of tropical Asia.
Cycad non-thorny (C. inermis) belong to one of the representatives of the Vietnamese species of the genus.
This type of cycad was first described in 1793 by the Portuguese botanist Loureiro. This cycad differs from its other relatives in the absence of thorns on the leaf petiole. Under the lush crown of female plants, a so-called “collar” is formed, dotted with bright yellow seeds, which is very similar to grape clusters.
This plant can be found in Vietnam, its coastal areas. It mainly settles on the slopes of mountains, high cliffs and among thickets of bushes.
Of the four Australian species of cicada, the cycad medium (C. media).
How common it is in a number of areas of its range on the northern and northeastern coast of Australia is shown by reports that the seeds of this cycad were the main food of local residents in the last century. The harvest of its seeds only on the Arnhemland peninsula (northern Australia) reached many tons. It was this rather tall (reaching 7 m) palm-like plant that attracted the attention of the participants in the first round-the-world voyage of James Cook.
The following describes how to care for cicas at home.
How to grow cycas and how to care for a palm tree at home: watering and feeding
Indoor cicada palm is an unpretentious plant. The most important thing for him is temperature. In summer, the air temperature is 18–30 degrees, in winter it should not be lower than 10–12 degrees. In winter, when caring for a drooping cicada palm tree, a temperature of 10-12 ° C is needed, while caring for curled cicada -16-18 ° C.
The cycad is undemanding to lighting. To properly care for cicas, as experienced gardeners advise, plants should be placed in bright, well-ventilated areas.
In summer, the plant needs abundant watering; in winter, watering the cicada should be more moderate. Does not tolerate the dryness of indoor areas, constantly needs to be sprayed.
For successful care of the cicada palm at home, you need to make a substrate of clay-turf and leaf soil, peat, humus and sand (2: 1: 1: 1: 1). Cycas lives very long, but grows extremely slowly.
Attention! When caring for a cycas houseplant, do not forget that all parts of the palm tree are poisonous!
Needs top dressing with organic fertilizers, during the period of intensive growth 2 times a month.
In winter, indoor flower cicadas are limited. The cycad is transplanted up to 5 years annually; in adult specimens, the top layer of the earth is replaced. The plant should be transplanted in the spring, adult plants once every 3-5 years.
When planting and transplanting, you need to make sure that the "bump" of the cycad is on the surface of the soil.
Cycas care and palm propagation at home (with video)
In summer, the domestic cicada palm tree can be put on the balcony. If the leaves of the plant dry out, then the air is too dry. Yellowing of the leaves, especially in winter, is a sign of waterlogging the soil.
Great harm is done to the plant, especially the mealybug and scale insect.
"Cones" (young shoots), which appear only in an adult plant. Seeds. They germinate quickly - in a month or two.
When seed propagation of cycas at home, fresh seeds should be soaked for 2 days in warm water. You can plant indoor cicadas in a pot with moist soil. Seeds are planted to a depth of 1 cm, covered with glass on top. For germination, a pot of seeds needs to be placed in a warm place. In order to take care of home cycas as carefully as possible, the glass needs to be gently lifted from time to time so that the ground is ventilated. When the first shoots appear, the glass is removed and placed in a brighter place. After a year, the plant can be transplanted.
Basically, as a medicine, boxwood is used in folk medicine as an anticancer agent, also for hematomas.
The leaves are astringent and diuretic. Used for gastrointestinal disorders, jaundice, dropsy. From the stem of the plant, sago is made, which has a rejuvenating effect and helps prolong life. The seeds are also used for medicinal purposes, but their recipe is not given due to the poisonousness of the plant.
The video “Care for cicas shows all the main agricultural practices:
seed plants.
The main differences between seed plants from higher spores are as follows:
o Seed plants produce seeds for distribution. They are divided into two departments. Gymnosperms are plants that spread by seed but do not produce fruit. Angiosperms are plants that produce seeds enclosed in fruits.
o In seed plants, there is a further improvement in the life cycle and an even greater dominance of the sporophyte and a further reduction of the gametophyte. The existence of the gametophyte in them is completely dependent on the sporophyte.
o The sexual process is not associated with a drop-liquid medium, and gametophytes develop and go through a full cycle of their development on a sporophyte. In connection with the independence of the process of fertilization from water, immobile male reproductive cells arose - sperm, which reach the female reproductive cells - eggs - with the help of a special formation - a pollen tube.
In seed plants, the only mature megaspore remains permanently enclosed within the megasporangium, and here, inside the megasporangium, the development of the female gametophyte and the process of fertilization take place.
Megasporangium in seed plants is surrounded by a special protective cover called the integument. The megasporangium with its surrounding integument is called the ovule. This is really the germ of the seed (ovule), from which, after fertilization, the seed develops.
Inside the ovule, the process of fertilization and development of the embryo takes place. This ensures the independence of fertilization from water, its autonomy.
In the process of development of the embryo, the ovule turns into a seed - the main unit of seed plant dispersal. In the vast majority of seed plants, this transformation of the ovule into a mature seed ready for germination takes place on the mother plant itself.
Primitive seeds, such as cycads, are characterized by the absence of a dormant period. For most seed plants, a more or less long dormant period is characteristic. The dormant period is of great biological importance, because. it makes it possible to survive the unfavorable season, and also contributes to a more distant settlement.
Internal fertilization, the development of the embryo inside the ovule, and the appearance of a new, extremely effective unit of settlement - the seed - are the main biological advantages of seed plants, which made it possible for them to more fully adapt to terrestrial conditions and achieve a higher development, higher spore plants.
Seeds, unlike spores, have not only a fully formed embryo of the future sporophyte, but also reserve nutrients necessary at the first stages of its development. Dense shells protect the seed from adverse natural factors that are detrimental to most spores.
Thus, seed plants acquired serious advantages in the struggle for existence, which determined their flourishing during the drying up of the climate. It is currently the dominant group of plants.
Class Cycads - Cycadopsida.
The leaves are large, pinnate, rarely entire, lanceolate. The stem (trunk) has a powerful pith and bark and relatively small wood. The ovules are located on leaf-shaped or more or less metamorphosed megasporophylls, which are arranged singly or collected in cones. They represent a large-leaved line of evolution. The class is divided into three orders: Seed Ferns, Cycads, Bennettites.
Order Seed Ferns - Pteri dospermales.
The most ancient and primitive gymnosperms, completely extinct.
This is a transitional group from ferns to gymnosperms. They are united with the former by the structure and appearance of the leaves, the structure of microsporophylls and microsporangia; with the second - the secondary growth of the stem in thickness, the presence of ovules and seeds.
Order Cycads - Cycadales.
It unites about 100 living species. They are common in tropical and subtropical regions of East Asia, Australia, Africa and America. Cycads are slow growing trees reaching a height of 20 m and living up to 1 thousand years. Dioecious. The stem is unbranched or slightly branched, columnar or tuberous thickened, sometimes partially hidden in the soil (geophilia). Starch accumulates in the core. The top of the stem ends with a vegetative bud surrounded by a bunch of evergreen leaves. The leaves in the bud are twisted in a cochlear-like manner, as in ferns, large, pinnate, up to 2 m long. The archegonia are located in the deepening of the endosperm - the archegonial chamber. When pollen germinates from a spermagen cell, 2-4 or more large spermatozoa with numerous flagella are formed. They enter the fluid of the archegonial chamber, swim for a while, and then one of them fertilizes the egg. The practical significance of cycads is small. From the core of some species, especially the drooping cycad (Cycas revoluta), sago groats are made. Cycads are excellent ornamental plants, they are bred in greenhouses, as well as in open ground.
Bennettita order - Bennettitales.
Completely died out. Unlike all other gymnosperms, they had bisexual cones. In terms of the structure of the vegetative organs, they are similar to cycads, but there were also herbaceous plants among them.
Bibliography:
Abstract of lectures of the candidate of biological sciences Surkov Viktor Aleksandrovich
Related Articles
