Changes in organization of action of photosystem II in oat leaves under osmotic stress

Abstract

The parameters of chlorophyll a fast fluorescence were estimated with husked oats (A. sativa subsp. sativa) and naked oats (A. sativa subsp. nudisativa). The purpose of the study was to identify differences in the control of primary energy storage processes in two subspecies of oats under the influence of osmotic stress for the subsequent selection of parameters and strategies for oat breeding to increase photosynthetic productivity in early drought conditions. Plants were grown on a complete Knop’s nutrient solution; osmotic stress was created by 10 % polyethylene glycol (PEG-400), osmotic pressure 0.709 mPa. Fluorescence parameters were determined using a Fluor Pen FP 110/S fluorometer (Photon Systems Instruments, Czech Republic). The data was processed by principal component analysis. In husked genotypes, the four main factors were responsible for 94.2 % (control) and 91.4 % (stress) variability of the parameters assessed. In naked oats, three main factors were governed 90.5 % of variability in the absence of stress, four factors (97.1 % variability) - under stress conditions. In naked oats, the flows of trapped energy (TR0/RC) and electronic transport (ET0/ RC) under stress were controlled by the same factor and in the absence of stress - by two different factors; in husked genotypes - on the contrary, by one factor in the absence of stress and by two different factors under stress. Osmotic stress led to the transition of control of absorbed (ABS/RC) and trapped (TR0/RC) energy flows from one factor to two factors in husked oats, but did not affect naked oats. The parameter of efficiency of electron transfer until the primary acceptors of photosystem I (δRE) was controlled by two different factors and enhanced their effect (factor loads from 0.564 to 0.740). Under stress, the δRE parameter reduced the effect of both factors in naked genotypes (factor loads -0.625 and -0.705), decreased the effect of one factor and strengthened the second factor in husked genotypes (factor loads -0.552 and 0.687).