Indicator signs of the adaptation of subtropical wood plants based on complex researches
For the Lower Volga region with difficult soil and climatic conditions, forecasts bear an increase in the length of the growing season, an increase in heat, and a softer winters. This indicates the need for studies of subtropical plants for an objective assessment of the identification of mechanisms for their adaptation and prospects for creating protective forest plantations in sparsely wooded regions. Theoretical and practical interest for the Volgograd region is a valuable fruit, medicinal, forest reclamation and ornamental shrub (unabi) plant Zizyphus jujuba Mill. (family Rhamnaceae). The purpose of the research is to study the ecological and physiological features of subtropical woody plants of Zizyphus jujuba and to identify indicator signs of their adaptation in the Volgograd region. The objects of research were the varietal plants of the unabi (Tayangzao, Southerner largefruited, Druzhba, Phenicia mediumfruited, Sochi, Temryuk smallfruited). They are tested in the Volgograd region for the first time, obtained from the FSBI (city of Sochi) and are cultivated in FSBI FNTS Agroecology RAS (Volgograd region, Russia). The soils of the experimental plot (50 450 5N and 45 2245 23E) are characterized by a low humus content (from 0.57 to 1.15). It was revealed that the study area (Volgograd region) is characterized by a small amount of precipitation, low temperatures in winter, high temperatures in summer, droughts of high and medium intensity. The amplitude of the absolute maxima and minima varies from seventyeight (dry steppe) to ninety degrees Celsius (semidesert). It has been established that the agroclimatic resources of natural distribution areas differ from the introduction points of Zizyphus jujuba Mill. to culture. Different levels of morphological variability, as well as water availability, lead to a change in the ability to expend and retain water, to a lack of moisture in the leaves of Z.jujuba. The insignificant effect of drought on the state of the aboveground plant organs during the arid periods was observed in mediumsized and largefruited varieties. Young, nonlignified shoots are damaged (at an air temperature of about 40 C and a decrease in air humidity of up to 10). A decrease in leaf turgor was observed with water deficit indicators of 28.335.8. Water deficiency decreases by 610 with increasing age, which is due to increased adaptation and regulation of water balance. According to the indicators of the relative electrolyte yield, groups were determined according to the degree of drought resistance: low Southerner, TaYanZao (4.234.71), medium Finik, Friendship (3.103.61) and high Temryuk, Sochi (1.641.99). Ecological tolerance of various organisms to low temperatures is quite specific. Evaluation of different varieties of Zizyphus jujuba under lightbrown soils showed that the adaptation of plants to low temperatures increases with increasing age. In small varieties with an increase in age, the damage is minor. Based on the vegetation experience, the limits of ecological tolerance of smallfruited forms of Zizyphus jujuba to chloride salinity were established, which makes it possible to predict their successful cultivation on soils with a chlorine ion content of 0.1. Thus, complex ecological and physiological studies of the adaptive capacity of subtropical plants Zizyphus jujuba revealed indicator signs that allow to evaluate and predict the degree of adaptation depending on the variety and the response to stress factors specific to the conditions of the Lower Volga region.