Histological-functional analysis of xerophytic plants of zaporizhzya region

Pyurko Olga Yevgenivna
Candidate of Biological Sciences, Associate Professor
Bogdan Khmelnytsky Melitopol State Pedagogical University
ECOLOGY (Global and regional environmental issues)

Histological-functional analysis of xerophytic plants of zaporizhzya region
In Ukraine, out of 35 million hectares of arable land, about 15 million hectares are in the zone of low-income agriculture due to the lack of moisture. These are mainly the territories of the southern regions, where the coefficient of humidity is less than one and per year per square meter of area is on average only: in Kherson - 4.9* 102, Odessa - 10.5*102, Zaporozhye - 22.8*102, Nikolaev - 23,2*102 km3 of fresh water that makes accordingly 0,79; 1.69; 3.70 and 3.75% of the same indicator in the Transcarpathian region - 618.7*102 km3 area [4]. The low level of water supply and various types of drought that occur during the growing season or in certain periods, cause the formation of an appropriate histological and physiological response in plant organisms. Climate aridization and significant expansion of arid areas due to global temperature increase while reducing precipitation and reducing soil moisture attracts the attention of many researchers [1-10]. In such conditions, the study of adaptive rearrangements in xerophytic plants, which form natural and cultural phytocenoses, is of great theoretical and practical importance. The results of quantitative anatomical studies can be used in taxonomy, histology and ecology of plants [2,5,9], as they allow to establish the main adaptive features that are characteristic of this particular group, and this is important for establishing the evolution of the plant world as a whole. Steppe phytocenoses of Zaporizhia region, especially Melitopol district, are represented by xerophytic associations. Most of them are herbaceous plants, which, depending on the degree of dryness of the area, are divided into main groups: succulents, eukserophytes, hemixerophytes, poikiloxerophytes, ephemerals. The main indicators of adaptation to the conditions of minimum water supply are as follows: reduced, and sometimes completely reduced leaf blade or leaves fall during the greatest drought; leaves and stem covered with epidermis with a well-developed cuticle, leathery, often with hair or wax; small epidermal and mesophilic cells, and therefore more of them per unit area, including more stomata; significant development of conductive and mechanical elements, and in this regard, the high density of veins on the leaves; high concentration of cell juice [8,10].
Typical xerophytes of our region are members of the genus Elytrígia, in particular Elytrigia repens L. - a medicinal plant, the drugs of which are used in metabolic disorders, as a diuretic, diaphoretic, expectorant and laxative, which regulates salt metabolism. The main area of Elytrigia repens L. application is blood purification, when slags are released with increasing water outflow from the body, which is primarily reflected in the reduction of skin rashes. Fatigue and brokenness are removed. In this case, all components act together, both vitamins and minerals [1,7]. Elytrigia repens L. as a food plant has repeatedly helped people in difficult times. Rhizome is used for food, which is ground, flour is obtained that is not inferior to wheat in terms of nutrition, and bread, cakes, gingerbread and other flour products are baked [3,6]. Due to the fact that the study of structural and physiological features of the genus Elytrigia repens L. in the scientific literature is insufficiently covered, we chose it as the topic of our study.
Our study of morpho-anatomical parameters of vegetative organs of plants of the genus Elytrígia répens L. in the Zaporozhye region showed that the leaf of this plant is covered with simple, unicellular hairs; the epidermis is formed by the main cells of three types, which differ from each other in shape, projection, angles, size and number per unit surface, with the upper epidermis of the leaf is 4.53% of the total thickness, the lower epidermis - 3.83%; respiratory complexes of anocytic type, their number - 245-250 pcs / cm2, location only on the underside of the leaf, the leaf is hypostomatic, mesophile has an isolateral structure, conductive bundles collateral, located in the middle layers of the leaf blade, mesophile is 62.72% of the total thickness, and the leading beam - 28.92%. Histological analysis of the Elytrígia répens L. stem showed that it has a mixed type of structure, consists of primary bark, which is 26.3%, interbeam and bundle cambium - 0.12%, xylem, represented by tracheas of three orders - 19.31% and core, which occupies 54.28% of the total thickness of the stem.
Elucidation of functional disorders in the leaf under the influence of drought, in particular the intensity of photosynthesis and the specificity of the pigment composition of the experimental plant proved that mainly experimental plants under normal conditions have a parabola-like curve of photosynthesis, and under atmospheric drought these indicators dynamics of photosynthesis found that the most intense photosynthesis occurs in plants under normal conditions, and when exposed to drought in plants there is a decrease in the process of photosynthesis by 10-12%. During the study of the pigments specificity of Elytrígia répens L., it was found that they have 1.5 - 2 times more chlorophyll than carotenoids, which indicates their high photosynthetic activity.
Thus, we proved that the adaptation of xerophytic plants of the genus Elytrígia L. to arid habitats is characterized by the presence of unicellular trichomes, which reduces transpiration; increasing the share of storage tissues in the leaf and conductive and mechanical elements in the stem, as well as reducing the intensity of photosynthesis under conditions of unforeseen prolonged drought. Violation of the physiological functions of plants in drought conditions is the first appropriate response of the body to water deficiency. Changes in the microstructure are usually the result of functional disorders. Adaptation of plants to extreme conditions includes both nonspecific (independent of the nature of stressors) and specific (dependent on the nature of the adverse factor) mechanisms.
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