Changes in the content of malondialdehyde and glycine betaine in plant leaves under the influence of NaCl salinization in combination with different pH levels in the root medium

Background. Salinization of soils can be accompanied by both an increase in the pH level to alkaline values, and a decrease to strongly acidic ones. At the same time, plants experience complex salt and acid-base stress. The aim of the research is to trace the dynamics of the content of malondialdehyde (MDA) and glycine betaine (GB) in soft wheat and oat plants when exposed to NaCl against the background of acidic, neutral and alkaline reactions of the root medium. Materials and methods.Soft wheat Triticum aestivum L. and oat Avena sativa L.. were used as the object of the study. The plants were grown on vermiculite. On the 7th day after the emergence of seedlings, stress factors were added, as which solutions combining NaCl salinity (150 mM) and different pH levels of the medium (pH 3, pH 7, pH 10) were used.. The acidic medium of the solutions (pH 3) was created by an acetate buffer, the alkaline medium (pH 10) by a borate buffer. After stress exposure for 72 hours, the content of malondialdehyde in plant leaves was determined spectrophotometrically by color reaction with thiobarbituric acid, glycine betaine – by the Grieve and Grattan method. Results. The most striking manifestation of oxidative stress in plant leaves was noted against the background of an acidic reaction of the root medium. On an alkaline background, the amount of MDA in oat leaves differed little from the control variant, and in wheat leaves there was a slight increase in MDA in the period 6–48 hours after the onset of stress factors. Salinization on a neutral background did not cause an increase in the level of MDA in both cereals, and salinization on an acidic and alkaline background caused a decrease in the amount of MDA. In wheat leaves, an increased level of GB was noted against the background of acidic and alkaline reactions of the root medium. Salinization against the background of different pH levels practically did not change the number of GB relative to the same pH variants without salinization. According to the content of GB in the leaves of oats, we noted a significant variability in the change of the reaction of the root medium. In conditions of salinization and different pH levels, including on a neutral medium, the change in the content of GB was noted only at certain times, compared with the same pH variants, but without salinization. Conclusions. Against the background of a neutral, alkaline and acidic reaction of the medium, a different degree of stress was noted in both cereals. Increased inhibition and plant responses indicate the most negative effects of the acidic reaction of the environment, both in combination with salinization and without it.