Эффект действия засухи на синтез нуклеиновых кислот и фракционный состав ДНК у сортов хлопчатника, характеризующихся различной степенью стресс устойчивости

Abstract

Aims. As cotton has the highest sensitivity during seed germination we held intra- and interspecific assessment of the resistance degree of cotton accessions according to germinating ability of seeds in some selected by us resistant and susceptible cotton accessions, the changes in the nucleic acid synthesis and fractional composition of DNA under drought stress was studied as well. Methods. Physiological evaluation of stress resistance of cotton accessions to drought has been carried out according to the stress-depression of germination of seeds in a solution of sucrose. The amount of nucleic acids and fractional composition of DNA were determined by V.G. Alekseev (1973). To study the fractional composition of DNA stepwise impact on chromatin with solutions of different ionic strength and its deproteinization were implemented which allowed to split the cellular DNA to free or weakly bound, functionally active (DNA labile); completely blocked with histones (stable DNA); firmly linked (residual DNA) DNA. Results. In drought conditions the activity of RNA synthesis in experimental samples of cotton 9732Э, 5010-V, S-6022 selected for physiological parameters as drought-resistant plants, exceeds the control by 10.0, 12.3 and 35.6 %, respectively in variety 9732I the increase of the proportion of labile DNA was 9.2 %, and the percentage of stable DNA decreases at the same level – 8.9 %. In 5010-V variety these indicators were 11.1 and 8.0 % and in S-6022 variety 34.9 and 1.4 %, respectively. Conclusions. It was found that because of the stress in drought resistant varieties activation of RNA synthesis, increase of labile and decrease of stable DNA was observed which indicates an increase of the physiological liability and functional activity of the genetic apparatus. In susceptible varieties a reduction in the synthesis of RNA and DNA and displacement of DNA fraction ratio towards the stable were noted.