Where conifers grow. Conifers
This subclass is the most numerous of all gymnosperms (it includes 7 families, 55 genera, and about 600 species), the most widely distributed practically throughout the globe, except for the Arctic and Antarctica. In the history of the Earth, conifers appeared in the second half of the Paleozoic - representatives of the Lebachiaceae family (Lebachiaceae) are described from the Upper Carboniferous. They originated in the Northern Hemisphere, apparently in a temperate climate; There is an assumption that local continental glaciation caused an increase in climate dryness. Therefore, the first conifers possessed the features of a xeromorphic structure and were characterized by the presence of tree rings in wood. At the border of Perm and Triassic, there was an increase in climate continentality; therefore, the number of conifers sharply increased in the Northern Hemisphere. The most ancient of the living ones appear - Araucariaceae, Podocarpaceae and Pine. However, there was no clear distinction between families; Thus, the species of araucaria described from the Jurassic combined the features of pine, cypress and araucaria. At the end of Perm, conifers began to penetrate into the Southern Hemisphere, and from the Triassic they are widespread throughout the globe.
Coniferous heyday reached in the Jurassic and Cretaceous periods; the time of the appearance of all the remaining living families dates back to this time. At the beginning of the Cenozoic era, the separation of climatic zones and the formation of plant ranges begins. In the first half of the Tertiary period - in the Eocene, the climate was still warm and humid and conifers were distributed from the Arctic (they are noted on Svalbard, in Greenland, in Scotland) to Antarctica. In the subsequent period, in the Oligocene, the area of \u200b\u200bconifers begins to decline, but pine forests with a large participation of thuja, palm trees, chestnuts, magnolias, and other heat-loving species grew in Europe, North America, and East Asia. Oligocene deposits include the famous amber deposits; brown coals of Germany are formed by bog cypress. At that time, it, along with sequoia, still reached Svalbard, and now grows mainly in the mouth of the Mississippi River. Conifers in the Oligocene were also found in Antarctica.
The Quaternary with a series of glaciations turned out to be a turning point in the history of conifers. In Europe and Asia, when a glacier sets in, all thermophilic coniferous species became extinct. Only young cold-resistant species have survived, which, after the retreat of the glacier, spread widely within temperate and moderately cold regions. The exception was Southeast Asia, which was not subjected to glaciation and preserved many ancient thermophilic species. In North America, the mountains are located mainly in the meridional direction, so heat-loving species migrated south during glaciation. After the melting of the glacier, some of them partially regained their positions, although the leading role in North America now belongs to young cold-resistant species. In the southern hemisphere, many ancient coniferous species have survived, but they are distributed mainly in areas with a temperate climate. In the tropics, conifers are found mainly in the mountains, i.e. also in temperate climates, although some species of pine and podocarpus grow in subtropical forests.
Modern conifers are represented mainly by trees, less often shrubs or a special shrubbery - creeping form. However, among the ancient extinct conifers, even herbaceous plants were found. Coniferous shoots are either only elongated, or of two types - elongated and shortened.
Despite the name, conifer leaves do not always have the shape of needles. Conifers with an ovoid, lanceolate leaf form are found, but more often they have a needle-shaped or scaly shape. Judging by the meager paleobotanical data of Permian Lebachian, it can be concluded that they have syntelome origin, since their leaves dichotomously branched or were forked at the apex. Accordingly, their veins also dichotomously branched.
The vast majority of conifers are evergreens; the life span of leaves is determined by both the biological characteristics of the rocks and the environmental conditions of their life. In light-loving breeds, leaves live from 2 to 5 years, in shade-hardy species up to 10-15 years, and in high mountain conditions - even up to 25-30 years. All evergreen breeds have hard, heavily cutinized and scleroficiated leaves; their stomata are located on the lower side in the recesses, which significantly reduces the evaporation of water in the winter. In deciduous species - in larch (Larix) and false larch (Pseudolarix), the needles are soft, soft, like ordinary leaves, for which they got their name. For some conifers, for example, for a taxium (Taxodium), metasequoia (Metasequoia), pine (Pinus), a branch is characteristic, in which not individual leaves fall, but whole shortened branches.
The root system is usually pivotal, but in some species, such as spruce, the main root freezes quite quickly and a superficial root system is formed. In other cases, such as
CLASS CONIFEROUS - PINOPSIDA
This class includes 2 subclasses - cordaity ( Cordaitidae) and conifers ( Pinidae).
CORDITA SUB-CLASS - CORDAITIDAE
Subclass of Cordaita ( Cordaitidae) contains a single order - cordaite ( Cordaitales), which includes one family - Cordaitaceae. Cordaite - long extinct plants. From the beginning of the Carboniferous period to the beginning of the Mesozoic era, like gigantic plaiform and seed ferns, cordaites made up a significant part of the swampy coastal forests. The Kordait thickets were reminiscent of modern coniferous forests, the height of the trees reached 30 m, the trunk thickness 1 m. The length of the linear leaves was 1 m with a width of up to 20 cm.
It is believed that cordaites evolved from seed ferns and their oldest forms gave rise to conifers.
CONIFEROUS SUBCLASS - PINIDAE
Along with angiosperms, conifers are among the most famous and economically significant plants. Both in nature and in human life, conifers in their importance take second place after flowering plants, far surpassing all other groups of higher plants.
This is the best preserved and largest group of gymnosperms. Having arisen at the end of the Carboniferous period, conifers, like other gymnosperms, reached their greatest prosperity in the Mesozoic. Currently, they number at least 560 species, combined in 55 genera and 7 families. Many conifers still play a significant role in the vegetation of the globe. In the vast expanses of Northern Eurasia and North America, they form forests, often representing almost pure plantations of only one species. The largest number of species of pine ( Piniis), fir ( Abies), ate ( Picea) and larch ( Larix) concentrated near the Pacific coast, especially in China. In the southern hemisphere, conifers are most abundant in the temperate regions of New Zealand, Australia, and South America.
All conifers are trees or shrubs with needle or scaly leaves, but a number of representatives have lanceolate or broad lanceolate leaves (araucaria - Araucaria, podocarpus - Podocarpus).
Among conifers there are giants of the plant world. Such, for example, sequoia is evergreen ( Sequoia sempervirens), reaching 100 m in height with a barrel thickness of 10 m; mammoth tree ( Sequoiadendron giganteum), specimens of which have a trunk thickness of up to 12 m and an age of up to 4000 years; bog cypress ( Taxodium mucronatum), growing in southern Mexico, with a trunk thickness of up to 16 m. A longevity record was established by one of the species of pine - the age of the pine is long-lived ( P. longaeva), found in East Nevada (USA), is determined at about 4900 years, i.e., almost five millennia. Most conifers are evergreens, but deciduous, such as larch, are also found.
The anatomical structure of coniferous stems is pretty monotonous. It is characterized by more developed wood and less developed bark and core. Coniferous xylem 90-95% in volume consists of tracheids. Unlike most dicotyledons, coniferous parenchyma in wood has very little or no wood.
Most conifers do not have normal resin passages in the wood; they occur with traumatic damage to the trunk. Resin (non-traumatic) passages in secondary wood are characteristic only of the pine family.
Coniferous leaves are sessile or sometimes with a short petiole. Usually they are dense, more or less stiff and leathery. The leaf arrangement is spiral (regular), less often opposite or whorled. In most cases, coniferous leaves have a pronounced xeromorphic structure: they are covered with a thick layer of cuticle; epidermal cells are small with very thickened walls; stomata are immersed in recesses filled with wax grains that reduce evaporation. Under the epidermis of the leaf of many conifers, a peculiar mechanical tissue of hypodermis is usually developed, consisting of 1-3 layers of elongated thick-walled cells, due to which the leaves acquire a solid outer skeleton, which gives them characteristic rigidity. Many conifers have large resin channels in the mesophyll.
Conifer strobiles are exclusively dioecious; plants are monoecious, rarely dioecious. Strobiles are very variable in shape and size.
Male strobiles are usually formed by microsporophylls, on the lower side of which there are two microsporrangia — pollen sacs, in which pollen forms. Pollen grains are carried by the wind. They are often equipped with two protrusions - air bags, which reduces their relative specific gravity.
Megastrobils of the most primitive, now extinct conifers were collected at the tops of shoots and were located in the axils of vegetative leaves. Subsequently, during evolution, they underwent a significant reduction and in most cases retained only one scale, called the seed, the upper surface of which carries two ovules. These scales remain lying in the bosom of the rudiment of the shoot sheet. The scaly-like rudiment of the leaf is called hiding scales. Seed and hiding scales can be isolated, but sometimes they grow together.
In most conifers, fused scales form more or less dense collections, which are often called a female cone or just a cone. Cones arise at the ends of the shoots, one or more. Young cones are brightly colored, usually in reddish tones.
In other coniferous evolutionary lines, the reduction of the strobil assembly goes even further. And in some cases, for example in yew family (Tahaseae), the formation of single megastrobils is observed, occupying a terminal position on shortened axillary shoots and bearing only one ovule. And hiding, and seed scales at the same time completely disappear.
The process of conifer cones development from the beginning of formation to seed formation takes up to two years. Ovules by the time of pollen maturation produce a small drop of sticky liquid, the surface of which captures pollen grains carried by the wind. Then the fluid is absorbed by the ovule and the pollen enters the micropilar chamber, continuing its development. Fertilization, however, occurs much later. The cone at this time continues to grow, and its scales are partially lignified, reliably protecting ripening seeds. In most cases, ripening seeds are ready to leave already dry, expanding, but still hanging cones on the branches only for the next year.
The coniferous embryo develops from the zygote in a rather complicated way. In parallel with the development of the embryo, a haploid endosperm is formed from the tissue of the female gametophyte, and from the cover of the ovum - the skin of the seed, and thus the entire ovum turns into a seed.
The coniferous subclass includes 7 orders, of which 2 have by now completely died out and are not considered here.
Araucariaceae order - Araucariales
Only one family of the same name belongs to the Araucariids ( Araucariaceae), including 2 genera - araucaria ( Araucaria) and agatis ( Agathis) with 35 species. For araucariaceae
large microstrobiles from numerous microsporophylls are characteristic, bearing 5–20 free microsporangia on the underside and often large cones, whose scales are formed by the complete intergrowth of the hiding and seed scales. Species of araucaria, very similar to modern forms, as an element of the Mesozoic flora, already existed in the Triassic, i.e. 200-240 million years ago. Currently, these large majestic trees of archaic appearance have been preserved only in some tropical areas of the Southern Hemisphere. Many araucariaceae live up to 2000 years or more. The area of \u200b\u200bforests from araucaria and agathis has decreased significantly due to cutting down for their valuable beautiful wood. Particularly high-quality wood, which was widely used earlier in shipbuilding, is given by agatis. Giant specimens of southern agatis ( A. australis), or kauri, composed the previously vast virgin forests of New Zealand. The rather large oily seeds of many Araucariaceae are edible, and their resin is used in the manufacture of natural varnishes.
Order Pine-Pinales
The order includes a single pine family ( Pinasee), numbering 10 genera and at least 250 species, distributed mainly in the Northern Hemisphere. Some species of pine, spruce, fir and larch rise high in the mountains and enter the Arctic. The only species that crosses the equator and enters the Southern Hemisphere is the Merkuse pine ( Pinus merkusii).
The pine family includes 4 large genera - fir, pine, spruce and larch, numbering several dozen, or even a hundred (pine) species.
Pine - evergreen, rarely deciduous plants, sometimes creeping shrubs. Most members of the family develop a powerful root system. On the roots of many forest-forming species of pine, spruce, fir and other pine trees there is mycorrhiza. With rare exceptions, pine trees are represented by large trees, reaching in some cases 40-50 m in height and 0.5-1.2 m in diameter. The real giant of the plant kingdom is Western larch ( Larix occidentalis), reaching 80 m in height with a trunk diameter of 1.5 m.
Pine wood is quite diverse in color, texture and physical properties. For the peoples of the vast regions of Eurasia, North America and partly Africa, it has long been the main building material. Legends of the magnificent palaces of David and Solomon, many of the architectural details of which were made of cedar of Lebanon, have survived to this day ( Cedrus libani) Wooden structures in Kizhi, erected from ordinary pine ( Pinus sylvestris) and ate
european ( Picea abies), existed for several centuries. Due to the long fibers (in the botanical sense these are tracheids), pine wood is of great importance in the pulp and paper industry.
Genus pine ( Pinus) - the largest in the pine family - includes about 100 species. Usually these are slender evergreen trees reaching a height of 30-45 m and a diameter of 1.2 m. The elongated shoots of pine trees are covered with brown scales, in the axils of which are strongly shortened shoots carrying bunches of 2, 3, 5 (less often 4 and 8) needles. For our country, ordinary pine is of greatest economic interest. Pine forests in Russia occupy a huge area, second only to larch forests. Pine grows on diverse, mainly sandy soils. In poor light lands, this light-loving tree species has virtually no competitors. Buds and needles, essential oil, turpentine, turpentine, rosin, tar and charcoal, obtained from various types of pine by processing wood and other parts of plants, are widely used in industry and medicine.
Siberian pine, or cedar ( P. sibirica), outwardly differs from the ordinary pine primarily in the fact that on a shortened shoots it carries a bunch of 5 leaves. In addition to valuable wood, it gives large edible seeds - pine nuts, from which cedar oil is used, which is used in technology.
Species of the genus spruce ( Picea) - tall slender trees, characterized by shade tolerance and reaching heights of 50-60 m and 1.5-2 m in diameter. Many of them live to 500-600 years. Fir trees have a characteristic pyramidal crown shape. They have no shortened shoots. Four-sided or flat, at the end pointed leaves-needles are arranged spirally, sitting on oblong cushions (folds of bark), remaining on the tree up to 7 years. Cones are leathery, dangling (Fig. 28). White or slightly yellow spruce wood is more valuable than pine. European spruce is the most widespread in Russia ( P. abies) and Siberian spruce ( P. obovata) On moist clay soils, spruce usually crowds out other conifers. Spruce wood is used in the woodworking industry, but it is especially valuable for the manufacture of musical instruments (violins, piano, violas and double basses). Blue and silver Canadian spruce ( P. canadensis), Engelmann ( P. engelmannii) and prickly ( P. pungens) are often grown as ornamental trees resistant to the smoky air of cities. The homeland of these fir trees is North America.
Species of the genus fir ( Abies) - large, sometimes huge trees reaching a height of 60-80 m and 2 m in diameter. Their flat soft leaves-needles with a width of 1.5-3 mm make it easy to distinguish fir from other conifers with needle and scaly
Fig. 28. Pine:
european spruce ( Picea abies): 1 - a branch with young female and male cones, 2 - a mature female cone, 3 - seed scales with two seeds; Siberian fir ( Abies sibirica): 4 - a branch with ripened female cones, 5 - seed scales with two seeds; 6 - a branch with old and young female cones of Siberian larch ( Larix sibiriica)
leaves. Cones are erect, ripen in the first year in late autumn or winter, after which they break up into separate scales (Fig. 28).
Most species of firs have a beautiful decorative dark green or bluish conical crown, so they can often be seen not only in the arboretums and botanical gardens, but also in park and alley plantings.
Siberian fir is common in the southern regions of Western Siberia and in the northeast of European Russia ( A. sibirica) Fir wood is less valuable than pine and spruce, and is used mainly in paper production. Essential oil is obtained from fir shoots, individual fractions of which are used for semisynthesis of camphor.
Larch ( Larix) differs from other pine trees in that it discards leaves for the winter. Larch leaves are soft, flat, with whitish rows of stomata visible from below. They are located in bunches on shortened shoots (Fig. 28). In the Urals
and Siberian larch is widespread in Western Siberia ( L. sibirica), in Eastern Siberia and the Far East - larch Gmelin, or daurian ( L. gmelinii) Among Russian forest species, larch trees occupy the largest area. Their wood is heavy, durable, strong, with excellent mechanical properties. In Europe, since ancient times, the wood of European larch, or deciduous ( L. decidua), widely used for construction purposes. Amphitheaters of ancient Rome, piles of buildings of Venice are constructed of the wood of this larch, as it is highly durable and resistant to decay. Larch was considered the best material in shipbuilding. Its wood is valued today.
Kind of cedar ( Cedrus) four types. Three of them are found in the Mediterranean countries, and one species lives in the Himalayas. All cedars have especially valuable wood, which has a beautiful color and a pleasant aroma. Lebanese decorative cedars are grown on the Black Sea coast ( C. libani), Atlas ( C. atlantica) and Himalayan ( C. deodara).
In addition to these genera, the pine family includes small genera - keteleeria ( Keteleeria), tsuga ( Tsuga), pseudo-service ( Pseudotsuga), kataya ( Cathaya), false larch ( Pseudolarix) and ducampopinus ( Ducampopinus) Almost all representatives of these genera have very small ranges. Of the greatest importance are the types of pseudo-suds, forming vast majestic forests in the western United States and Canada. Individual trees in them reach 100 m in height. A prominent place in the composition of forests in North America are also some species of the Tsuga genus.
The geological history of pine trees begins from the Jurassic, and some of them, for example, false larch, having arisen approximately in the Cretaceous, have survived to the present day, having hardly undergone major changes for more than 130 million years.
Cypress Order - Cupressales
2 families belong to the order of cypress.
Taxodium family (Taxodiaceae) with 10 genera and 14 species is a miserable remnant of a huge, once prosperous group of plants, representatives of which in the Paleogene - Neogene formed vast forests on vast tracts of land in the Northern Hemisphere. Now almost all of them have very small areas, and some are sometimes represented in nature by only a few specimens and have survived to this day mainly due to the centuries-old culture. The taxodians include real giants of the plant world. This is a giant sequoiadendron, or mammoth tree ( Sequoiadendron giganteum), sequoia is evergreen ( Sequoia sempervirens)
and Mexican Taxodium ( Taxodium tnucronatum), reaching a height of 100 or more meters with a trunk diameter of more than 10 m. The age of such giants is estimated at 3-4 thousand years. Almost all species of taxodia have beautiful wood that does not rot. Many of them are cultivated as ornamental landscape plants, mainly of a temperate climate.
Cypress family (Cupressaceae) includes 19 genera and about 130 species found in both the Southern and Northern Hemispheres. All of them are represented by trees or shrubs, mostly dioecious, rarely monoecious. Small single cypress microstrobils are located on the tops of shoots or in the axils of their leaves. The microsporophylls in the strobiles are collected opposite or in whorls of 3 and each bear 2-6 microsporangia. Megasporophylls have 1-3, occasionally up to 12 ovules. Usually they are collected in small cones, which become juicy in junipers, resembling externally berries (Fig. 29). Needle cypress leaves
Fig. 29. Cypress: cypress evergreen ( Cupressus sempervirens):
1 - shoot with male cones, 2 - shoot with female cones, 3 - seed scales with ovules, 4 - sectional microsporophyll; juniper ordinary ( Juniperus communis): 5 - shoot with female cones, 6 - shoot with male cones, 7 - microsporophyllum, 8 - young female cone with micropilar tubes at the apex, 9 - ripe juicy cone, 10 - cross section
or scaly, closely adjacent to the axis of the shoot. Junipers are well known to the inhabitants of our country from cypress ( Juniperus), the most numerous in Russia in the south of Siberia. Common juniper almost throughout the temperate and boreal forests of Eurasia is juniper ( Juniperus communis) When the seeds mature, the juniper megasporophylls completely grow together, become juicy and turn blue or black. In mature form, such “fruits”, called cone berries, have a sugary pulp in which several seeds are immersed. Juicy cones of junipers are sometimes used for food, mostly as a flavoring seasoning, including for preparing bitter tinctures and gin. They are part of a number of medicinal fees.
In the Far East, mainly in the Sikhote-Alin mountains, the narrowly endemic monotypic genus microbiota is widespread ( Microbiota) with a single view - cross-linked microbiota ( M. decussata) This is a characteristic dwarf shrub of mountain screes, severely affected by fires. Microbiota belongs to the protected plants of our flora.
Many cypress species are quite decorative and widely cultivated. The unique appearance of the southern cities of Russia, especially on the Black Sea coast, is created by the pyramidal forms of evergreen cypress ( Cupressus semperuirens) originating from Asia Minor and the Eastern Mediterranean. In more northern areas, thuja species are often found in culture ( Thuja), especially thuja western ( T. occidentalis) native to North America and thuja eastern ( T. orientalis), who came to us from China. Tui, like many other representatives of cypress, have fragrant needles that secrete bactericidal essential oils. Therefore, in the plantings of these plants, the air always has a pleasant smell and freshness. The beautiful cypress wood is also distinguished by its special aroma, the natural reserves of which, unfortunately, are very small.
Yew Order - Taxates
The order includes 2 families.
Yew family (Tahaseae) has 5 genera and 20 species, distributed almost exclusively in tropical and warm temperate regions of the Northern Hemisphere. Their indisputable representatives are known since the Jurassic. All yew trees are evergreen shrubs or trees with two rows of lanceolate or linear leaves. Microsporophylls are solitary or collected in capitate or scapular formations. Megastrobils are most often reduced to one direct ovule, which is surrounded by a goblet -
Fig. 30. Yew berry ( Taxus baccata):
1 - a branch with microstrobils, 2 - a microstrobil, 3 - microsporophyll, 4 - a branch with megastrobiles, 5 - a female shoot with a megastrobil, in which the seed begins to develop, 6 - a female shoot with a mature seed wearing a roof (aryllus), 7 - section aryllus
a roof, or, as it is also called, an aryllus. When ripening, the roof usually becomes juicy and fleshy and surrounds (below and from the sides) a mature seed in the form of a bright red or yellow collar. In some cases, for example, in species of the genus Torreya ( Torreua), the juicy roof completely surrounds the ripened seed, which is why such a “fruit” resembles a flower drupe.
Of the yew trees, the best known is yew berry ( Taxus baccdta), widespread in Europe and found in our Caucasus (Fig. 30). This shade-tolerant, slow-growing tree, according to some reports, can survive up to 3-4 thousand years, reaching 35 m in height and over 2 m in diameter. In less favorable conditions, the yew berry takes the form of a squat shrub. The yew wood is very dense, beautiful and virtually indestructible. Due to uncontrolled felling, this plant has significantly reduced its area. Yew berry is quite decorative and easily withstands molding; it is often bred in gardens and parks to the latitude of St. Petersburg. In autumn, it is decorated with bright red "berries". The wood, bark, needles and seeds of this plant are poisonous. A closely related species is spiky yew ( T. cuspidata) is found in our Far East. Its seeds, unlike the previous species, are edible. Tisza spiky also has very valuable wood, but its reserves are extremely limited. The remaining yew trees have very small ranges and are little known.
Capitate family (Cephalotaxaceae) includes one genus and six species common in southeast Asia and Japan. The headache is distinguished by the fact that their microstrobiles are assembled into compact spherical heads. As with some yew trees, the seeds in the capitate are overgrown with a juicy cover, resembling drupes. According to a number of signs, representatives of this family occupy an intermediate position between the yew and podocarp ones.
The most extensive order of conifers (Coniferales) includes families of yew, cypress, pine, etc. In total, more than 400 species of conifers are found.
The order of conifers includes shrubs and trees, sometimes reaching enormous sizes, for example, a mammoth tree (Sequoia) up to 20 m thick and 150 m high. The conifer trunk is thickened due to cambium. The bulk of the wood consists of tracheids with bordered pores. Leaves - needles; it has a needle-shaped or scaly shape. Conifers are monoecious or rarely dioecious plants. Female cones (with the exception of yew) are composed of hiding and seed scales sitting spirally on the axis. On seed scales are macroporangia (ovules), sitting openly, like all gymnosperms. Male flowers contain many light pollen grains that are carried by the wind. Conifers do not have sperm; fertilization is accomplished with the help of a pollen tube, along which male germ cells - sperm - are advancing.
The Cypress family (Cupressaceae) includes common juniper (Juniperus communis), a shrub of the northern forests with needle-shaped leaves collected three in a whorl, with black fleshy cones - “berries” (Fig. 1), Cossack juniper (Juniperus sabina), cypress, thuja and others
Fig. 1. Conifers.
I - spruce branch with cones. II - fir branch with cones. III - pine branch: 1 - female cones of the first year; 2 - last year's female cone; 3 - the opened (old) bump; 4 - "spikelet" with male cones; 5 - male cone, consisting of sporolorists and sporangia; 6 - female. cone; 7 - seed scales and two ovules; 8 - hiding and seed scales; 9 - seed scales and two seeds with pterygoid appendages; 10 - pollen. IV - larch branch in summer. V - juniper branch with berry cones.
Conifers belong to the family of spruce, or pine (Pinaceae): common spruce, Siberian fir, European larch, common pine, etc.
Common forest pine (Pinus silvestris) - photophilous plant, grows under a variety of conditions that leave an imprint on its appearance. In a pine tree growing in the open, the crown is spreading, thick branches grow in all directions. In the pine forest, pine is a slender tree, its lateral branches dry out, and only the top has a green crown, in the swamp it is stunted, “clumsy,” sometimes reaching 100 meters in height. Pine has a monopodial branching method; its age is easily determined by the number of whorls of branches. On a stump cut, the age of the pine can be determined by the number of annual layers. Pine trees live up to 500 years.
Young, long, juicy pine shoots at the top of the trunk and branches are covered with scaly brown leaves. In the sinus of these leaves, shortened shoots (up to 2-3 mm) grow with small scales and with two green needle-shaped leaves (needles). The arrangement of shoots on the branches is spiral. Pine needles live for about three years and gradually fall.
Pine is a monoecious plant. In spring, at the ends of the “flowering” branches, annually formed female reddish cones are noticeable, below last year's green cones are visible at the base of the shoots, and even lower are the old, opened cones, from which the seeds have already spilled out. On other shoots, male yellow cones are visible, consisting of many small cones in which pollen develops in sporangia.
Pollination occurs by the wind in a cross way. A lot of pollen is worn in the air, and part of it falls on the female cones. Female cones consist of hiding scales and seed scales. In the bosom of each seminal scales, two ovules sit openly. The ovule consists of a cover, a nucleus, an endosperm and two archegonia, inside of which one egg cell develops (Fig. 2).
Fig. 2. Pine ovule (macroporangia) in a longitudinal section (in the second year of life):
a - the cover of the ovule; b - the core of the ovule; in - primary endosperm; g - archegonium e by the egg cell; d - pollen tube; e - sperm; W - pollen feeder.
The pollen that fell on the female pine cones remains between the scales on the ovules until next year and, germinating in the spring, gives a tube at the end of which two sperm are developing by this time. The tube grows through the pollen into the ovule, its end dissolves, and one of the sperm penetrates the archegon and fertilizes the egg cell.
Unlike angiosperms in pine and other gymnosperms, double fertilization does not occur, and the role of the second sperm remains unclear. The second distinctive feature of gymnosperms (in comparison with angiosperms) is that they have an endosperm before fertilization and archegonia are formed in the endosperm at the time of fertilization, which brings the gymnosperms closer to the fern-like ones. The endosperm can be compared with the overgrowth of the latter.
After fertilization, the ovules turn into seeds equipped with pterygoid appendages. The ripened cone opens in the winter in the second year, and the seeds are carried by the wind.
Pine seeds have a peel, endosperm (reserve nutrient tissue) and the germ.
Siberian cedar (Pinus sibirica) also belongs to the genus pine. The needles of this pine are long, collected in bunches of 5 pieces. Cones are large, spherical, hard-shelled seeds, rich in oil. They are called "pine nuts".
European spruce (Picea exelsa) differs from a pine in its pyramidal shape, shade tolerance. The needles ate short, tetrahedral, prickly, lives 7-9 years and more. Female “inflorescences” are reddish, larger than pine, male are smaller. Cones elongated, hanging down, not breaking up when ripe (Fig. 1, I).
Siberian fir (Abies sibirica) has needles flatter, with two white stripes, more blunt than spruce. Fir cones stand vertically on the branches and decay when ripe. The lower branches of the fir root easily,
European larch (Larix europaea) is a photophilous plant, with an annual, thin, soft, deciduous needles, collected in bunches (10-12 each), sitting on shortened branches. In spring, on young shoots, you can see single specimens of needles, in the sinuses of which buds develop, which turn into shortened shoots with bundles of leaves next spring. Larch cones are smaller than spruce (Fig. 1).
In the botanical gardens in the south of our country, Lebanese cedar and Himalayan cedar (Cedrus Libani and C. deodara) grow - large trees covered with bunches of perennial needles.
In our country, coniferous plants - pine, spruce, etc. - occupy vast areas. The planned exploitation of forests makes it possible to benefit from poor soils. Coniferous wood is used for construction, various crafts, and firewood. Resin, var, turpentine, rosin and other valuable substances are also extracted from conifers.
