ЭлБиб

XI Съезд Русского ботанического общества

sclerification o f coatings (78% of species), mixospermy (53%) and the hydrocytous tissue (62%) are the main

features that provide the protection o f embryo in these habitat. Sclerification o f fruit covers is the most widespread

universal sign o f plants with different phenorhythm and biomorphs, but it prevailes in annuals. The development

o f mixospermy and hydrocytous cells in seeds is in reverse correlation, because of functional similarity. The

whole diversity in the fruits and seeds o f desert plants is provided by different combination of these features

and depends considerably on phenorhythmical type of plant. Anatomical structure o f the assimilating organs

was ananysed at 93 species o f Kyzylkum dicotyledon plants from 58 genera and 17 families most of them are

the edificators and dominants o f vegetation: 18 species o f the woody biomorph (tree, shrub, shrublet), 17

species o f semiwoody (semishrub, semishrub let), 12 perennial grasses (geoephemeroides), 16 long time

vegetating annual grasses and 30 species o f epfemers (Begbaeva, 1995). The structure o f assimilating organs

(cotyledons and leaves) o f desert plants is various even in individual highspecialized genera (for example,

Sasola

L.). All mesophyll types are classified into 2 groups on the base of presence or absence of specialized

kranz-sheath bundles: non-kranz (NK) and kranz (K) group. Kranz group of mesophyll types is more young

evolutionally and is connected with the transition to more economical photosynthetic types permit plants to

photo-synthesize in more wide ecological range: temperature, water, ligth, low level of CO (Piankov et al.,

1992). The cotyledon of desert plants are mainly xeromorphic. The mesomorphic isolateral-spongy mesophyll

type was found only in woody and ephemer biomorphs. 3 types o f mesophyll predominate in leaves of desert

biomorphs: non-kranz dorsiventral and isolateral types in ephemers and geoephemeroides and kranz-centric

type in the leaves of plants with prolonged phenorhythms (woody, semiwoody and long vegetating annual

grasses). If the biomorphs are considered as the community of branching architectural model and definite

biorytgm, then the structural type of leaf is more connected with the second component. The prolongation of

short life cycle (spring-summer-autumn phenorythm) correlates with the highering specialization and xeromorphity

at all ontogenic stages of plants. In spite of abundance of structural version in xerophytes we distinguish 4 main

adaptive strategies: picnophyll, sclerophyll, succulent, aphyll. Certain general peculiarities are typical for generative

organs of desert plants. These are small flowers sexual polymorphism of flowers, lability of polination, fast rate

o f pollen germination on stigma, entering additional pollen tubes into the embryo sack and its subsequent

absorbtion by developing embryo, formation of haustorium like cells o f suspendors and endospermal

haustoriums, high potential and low real seeds production (Tursunov et al., 1966). The polymorphysm of

investigated species of flowers is expressed by the following way. In species of genera

Acanthophyllum

C.A.

Mey. (

Caryophyllaceae

) on one and the same plant and the same time the hermaphroditic the functional female

and intermedial types of flower are observed. The hermaphroditic homogamic flowers with large stigma and

germaphroditic proterandrous ones with small stigma in species of genus

Calligonum

(Polygonaceae

Juss.),

hermaphroditic, functional male and intermedial flowers in species of

Ferula

L. (

Apiaceae

), homogamous,

proteandrous, protegynous hermaphroditic flowers and also functionally female flowers in

Haloxylon

aphyllum

(Minkw.) Iljin and

Kochia prostrata

(L.) Schrad. (

Chenopodiaceae

) were revealed. The ratio o f various sexual

forms of flowers depends on different periods of flowering and the climate. Polymorphism o f flowers promotes

realization of the different types of pollination: autogamous, xenogamous, geitonogamus. This gives the possibility

for selected fertilization of ovule and formation of seeds with different hereditary sings. We regard peculiarities

as one of adaptation to extreme desert conditions. Thus, some specific peculiarities of generative prosses

passing are typical for different species of desert plants. Flowering of species o f genera

Acanthophyllm

Calligonum

and

Ferula

flowering occurs at mesothermal period o f a year, in spring. Flowering and fruit

formation finishs during 1,5-2 months. For all investigated plants the time interval between pollen catch on

stigma and its germination is very short and it takes 3-10 minutes. Double fertilization is observed in 5-10

hours after the catching of pollen tubes into embryo sack. For

H. aphyllum

there is a long time interval between

flowering and formation of seeds. It is about 6-7 months. The embryo sack is ready for realization of double

fertilization in 30-40 days after pollination. In this case the pollen tubus penetrate into ovary cavity full of

viscous liquid and its content with sperms remains there about 30-40 days until the embryo sack becomes

riped. This method unknown earlier is undoubtedly unique and represents the original example of high-specified

adaptation to xerothermic conditions of desert. Above mentioned adaptibe peculiarites of generative organs of

desert plant are directed to development of great potential possibility for successful pollination and fecundation

as it is these stages, that are the most critical in the process of seed formation.

Wide adaptive radion of stuctures and functijns o f desert plants is the leading vector o f its evolution. It

provides the plants with high effeciency use of microfaktors of the mosaical arid environment and different

ecological niches. Each ontogenical stage has the difinite ratio of structures and functions for preservation of

organism as a whole. It shows the multyregularity of the structures and functions and at the same time their

integrity that is organism as system. Full realization of all ontogenic stages that are over fruiting is the index of

reaction norm o f the plants on the ecological environment. The difinion of ontogenical types, the characterization

184

Электронная Научная СельскоХозяйственная Библиотека