Effects of some healing agents on sodium bicarbonate (NaHCO3)induced alkaline stress in garnem rootstocks in vitro conditions

Alkaline stress is the main abiotic stress factor limiting plant production in global agriculture. In these stress conditions, high pH disrupts intracellular pH balance in addition to ion toxicity and osmotic stress. This study was conducted to evaluate the physiological, morphological and biochemical responses to NaHCO3 induced alkaline stress in vitro by sodium nitroprusside (SNP) and salicylic acid (SA) applications to improve the negative effects of alkaline stress. In the study, plantlets of Garnem rootstock propagated by micropropagation method in vitro were used. The study was established at the rooting stage of the plantlets. SNP and SA (50, 100, 150 μM) applications were made against alkaline stress caused by NaHCO3 (0%, 20%, 40%) at different concentrations in vitro. In the study, as the severity of alkaline stress increased, survival rate, rooting rate, shoot length, root number, root length, plant fresh weight, plant dry weight, injury index, membrane permeability, leaf relative water content (YOSI), chlorophyll a, chlorophyll b, total chlorophyll, hydrogen peroxide (H2O2) and malondialdehyde (MDA) parameters were negatively affected. SNP and SA applications improved the harmful effects of alkaline stress. As a result of the study, alkaline stress reduced the survival rate of plantlets, rooting rate, shoot length, root number, root length, plant fresh and dry weight. SNP and low concentration SA applications alleviated the effects of alkaline stress in these parameters and provided improvement in these parameters. While membrane permeability increased under high alkaline stress, 100 μM SNP applications reduced this rate and contributed to the protection of cellular structure. All SNP and 50 μM SA applications increased leaf relative water content against alkaline stress. It was determined that chlorophyll a, b and total chlorophyll content decreased significantly under alkaline stress, while SNP applications increased chlorophyll content by alleviating the negative effects of stress. SNP applications significantly reduced H2O2 and MDA levels among biochemical parameters. As a result of the study, it was determined that SNP applications at all concentrations and SA applications especially at low concentrations alleviated the negative effects of alkaline stress and supported plant growth and development. However, it was determined that SA applications at high concentrations (150 μM) caused a toxic effect and significantly suppressed plant development. As a result, although Garnem rootstock showed a certain tolerance to alkaline stress conditions caused by NaHCO3, it was understood that this tolerance could be increased and plant development could be supported sustainably by applying appropriate concentrations of healing agents such as SNP and SA.