High temperature-induced changes in the photosystem II (PSII) activity of thylakoid membranes isolated from pea (Pisum sativum L. ‘Ran’) plants treated with low (10–8 M) and high (10–7 M) concentrations of fluridone were investigated. | Turkish Journal of Botany Turk J Bot (2015) 39: 420-428 © TÜBİTAK doi: Research Article Temperature sensitivity of photosystem II in isolated thylakoid membranes from fluridone-treated pea leaves 1 1 2 1, Kolyo DANKOV , Georgi RASHKOV , Amarendra N. MISRA , Emilia L. APOSTOLOVA * Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria 2 Centre for Life Sciences, School of Natural Sciences, Central University of Jharkhand, Ranchi, India 1 Received: Accepted: Published Online: Printed: Abstract: High temperature-induced changes in the photosystem II (PSII) activity of thylakoid membranes isolated from pea (Pisum sativum L. ‘Ran’) plants treated with low (10–8 M) and high (10–7 M) concentrations of fluridone were investigated. Pulse amplitude modulated (PAM) chlorophyll fluorescence and photosynthetic oxygen evolution (measured by polarographic oxygen rate electrode) were used to estimate the effect of high temperature on the functional activity of PSII. Higher temperature treatments lead to stronger inhibition of the flash oxygen evolution than the primary photochemistry of PSII (Fv/Fm). The inhibitory effect of higher temperature on the PSIIα centers is stronger than on the PSIIβ centers. The heat-induced damage in the PSIIα centers as well as in the donor side of all PSII centers (PSIIα and PSIIβ) is accentuated by fluridone. Key words: Fluridone, PAM chlorophyll fluorescence, photosynthetic oxygen evolution, PSIIα centers, PSIIβ centers, carotenoids 1. Introduction The photosynthetic apparatus in the thylakoid membranes of green plants is one of the main targets of heat stress in plants (Misra et al., 2001a, 2001b; Ducruet et al., 2007). The extent of damage to the photosynthetic apparatus caused by high temperature varies depending on plant species and ecotypes, growth and development of the plant, the .
