Assessment of the Electrochemical Potential of Thylakoid Membranes in Hordeum vulgare L. Sprouts of Different Ages Under Heat Stress Using Differential Absorption Spectroscopy

Abstract

The electrochemical potential on the thylakoid membrane and its components in cotyledons of 4-, 7- and 11-day-old Hordeum vulgare L. sprouts was studied using differential absorption spectroscopy and the electrochromic shift of pigment absorption. It was found that the proton motive force decreased and the proportion of its electrical component increased during the ontogenesis of the cotyledon. Exposure to elevated temperature (40°C for 3 h) decreased the electrochemical potential, proton gradient, and thylakoid membrane conductivity for protons and increased the electrical potential on the thylakoid membrane in young 4-day-old sprouts. No significant changes in the formation of the electrochemical potential on the thylakoid membrane were detected in 7-day-old leaves, which had a fully formed photosynthetic apparatus, after heat treatment at 40°C for 3 h. A thermally induced decrease in the electrical component of the proton motive force and an increase in the transthylakoid proton gradient were detected in the senescent cotyledon of 11-day-old sprouts. It was concluded that the electrochemical potential of thylakoid membranes reacts differently to heat effects in Hordeum vulgare L. sprouts of different ages.