Antioxidants as plant growth regulators
Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, street Kosygin, 4, Moscow, 119334 Russia
Stressful effects lead to a shift in the antioxidant / pro-oxidant balance toward an increase in the content of reactive oxygen species (ROS) in the cell, which underlies the disturbance of the physiological functions of plant organisms (reducing growth processes, yields, etc One of the main sources of ROS under stress conditions are mitochondria and chloroplasts [Grabelnykh O.I, Borovik O.A. et al., 2013]. It is known that regulators of plant growth and development (PGR) increase plant resistance to stress factors [Chalova L.I., Ozheretskovskaya O.L., 1984]. In this regard, it was suggested that they may influence the generation of ROS by mitochondria and the role of PGR can execute by antioxidants. The objects of study were selected antioxidants from the class of sterically hindered phenols: sodium anphen (1-carboxy-1-(N-methylamide)-2-(3,5-di-tert-butyl-4-hydroxy-phenyl propionate sodium) and potassium phenosan (3,5-di-tert-butyl-4-hydroxy-phenyl propionate potassium). The effect of these antioxidants on the functional state of mitochondria of pea seedlings (Pisum sativum L.), cv Alpha exposed to a 2-day water deficit was studied. A check of the protector properties of the preparations was carried out using 2 × 10-12 M potassium phensan and 10-13 M sodium anphen (in a concentration in which these antioxidants in the model experiments reduced the intensity of LPO to the control values). Water deficit resulted in a 3-fold increase in the fluorescence intensity of LPO products in mitochondrial membranes of etiolated pea seedlings. Treatment of seeds and sprouts of peas with studied antioxidants prevented the activation of LPO. Changes in the physico-chemical properties of mitochondrial membranes were likely to lead to changes in lipid-protein interactions, and, consequently, the activity of enzymes of the respiratory chain of mitochondria. .Indeed, the water deficit caused a 25% decrease in the maximum oxidation rates of NAD-dependent substrates and a 30% decrease in the efficiency of oxidative phosphorylation. Introduction to the incubation medium of mitochondria 10 µM of vitamin K3 almost restored the electron transport rates in the initial part of the respiratory chain, indicating a decrease in the activity of the I respiratory complex in conditions of water deficiency. Treatment of seeds and sprouts of peas with antioxidants prevented mitochondrial dysfunction. Activation of LPO in conditions of water deficiency, leading to changes in energy metabolism, was reflected in physiological indices, namely, on the growth of seedlings: in conditions the water deficit inhibited the growth of shoots and roots of seedlings 3 and 3.2 times, respectively. Treatment of seedlings with antioxidants prevented inhibition of growth processes. Antioxidants, preventing the activation of LPO, prevented a change in the bioenergetic characteristics of mitochondria. This preserves the high functional activity of mitochondria, likely providing the resistance of seedlings to water deficit.