Annual Research & Review in Biology

Aims: Water deficiency causes an enhanced generation of reactive oxygen species (ROS) by mitochondria, leading to oxidative stress. It is known that plant growth regulators (PGRs) increase the resistance of plants to stresses and, evidently, to a water stress. Such PGRs are melaphen – a melamine salt of bis(oxymethyl)phosphinic acid and a pyraphen salt of bis(oxymethyl) phosphinic acid 2,4,6- triaminopyrimidine. The aim of this work was to elucidate the effects of insufficient watering and treatment of seeds of pea (Pisum sativum L) with PGRs melaphen or pyraphen on the fatty acid composition of the lipid fraction membranes and bioenergetic functions of mitochondrial in etiolated 6-day pea seedlings.
Place and Duration of Investigation: Emanuel Institute of Biochemical Physics Russian Academy of Sciences, Moscow, Russia and Timiryazev Institute of Plant Physiology Russian Academy of Sciences, Moscow, Russia, between April 2010 and October 2011.
Methodology: Functional state of mitochondria was researched by rate of mitochondria respiration, by the level of lipid peroxidation and study of fatty acid composition of mitochondrial membranes by chromatography.
Results: A water deficiency has caused changes in the fatty acid (FA) composition which manifested themselves in increasing the content of saturated FAs and decreasing the content of unsaturated FAs containing 18 and 20 carbon atoms. The treatment of the seeds with melaphen (2 × 10⁻¹² Ðœ) has prevented the transformation of pool of fatty acids in lipid fraction of mitochondrial membranes. Pyraphen (10^-14 Ðœ) has prevented the changes only in the content of FAs containing 20 carbon atoms. Changes in the FA compositions of membrane lipids were correlated with changes in the maximum rates of oxidation of NAD-dependent substrates (r =0.765 for С₁₈).
Conclusion: It is suggested that tolerance to water stress is determined by the antioxidant system protecting the unsaturated C₁₈ and C₂₀ fatty acids from changes caused by oxidative stress, i.e., of activation of free radical processes.