Activity of photosystem II in spring barley leaves under the action of manganese ions

Abstract

The influence of manganese ions (30, 60 and 90 mg/l) on the functioning of the photosystem II (PSII) in leaves was assessed on plants of six spring barley cultivars (Belgorodsky 100, st.). The plants were grown on a complete Knop medium without (control) and with the addition of manganese ions (experiment) under natural light conditions. On 14-day-old leaves, parameters of chlorophyll's rapid fluorescence were recorded using a Fluor Pen FP 110/S fluorometer. The sensitivity of the different structural parts of PSII was found to vary depending on the concentration of Mn ions and the genotype used. Thus, absorbed energy flows increased in the cv. Boyarin at 30 and 60 mg/l Mn (by 7.9 and 14.1 %), in cv. Farmer at 60 and 90 mg/l  (by 15.8 and 16.1 %), but decreased in cv. Dobryak at 30 and 90 mg/l (by 9.7 and 9.0 %), Farmer at 30 mg/l (by 15.8 %) and Bionic at 60 and 90 mg/l (by 8.0 and 6.8 %). The flow of energy stored in primary photochemical reactions in the cv. Bionic increased at 30 mg/l of manganese (by 6.3 %), but decreased at 60 (by 6.8 %) and 90 mg/l (by 5.3 %); increased in the cv. Boyarin at 30 mg/l of Mn (by 6.4 %), but decreased in the cv. Forward (by 11.7 %). Electronic transport leading to CO2 fixation increased in cv. Farmer at all Mn concentrations (by 8.1...12.6 %), and in cv. Bionic it increased at 30 mg/l (by 7.2 %), but decreased at  90 mg/l (by 7.4 %). The electron flux leading to the oxidation of the finile acceptor of PSI in the studied cultivars did not change under the influence of the stressor. However, the integral parameters of PSII activity (PIABS and PIABS_total indices) under stressful conditions were determined by the plant genotype. This indicates, firstly, the need for targeted selection (to a specific level of the stress factor); secondly, on the possibility of pyramidation of the integral level of resistance to the stressor by selecting parents who differ in the level of change in individual functional reactions of photosynthesis.