Photochemistry of thylakoid membranes in two pea cultivars with different leaf colouration
Theoretical and Experimental Plant Physiology
Photochemical features of thylakoid membranes and chlorophyll content were investigated in two pea (Pisum sativum L.) cultivars with different leaf colouration: 'Assas' (red leaves) and 'Arvika' (green leaves). In vivo measured chlorophyll fluorescence (OJIP) was used to evaluate overall photosynthetic efficiency (expressed as performance index, PI ABS ) as well as for advanced analysis of main photochemical processes per active reaction centre (RC) of photosystem II (PSII). To evaluate the
... onse of PSII driven linear electron transport (relETR) and non-photochemical quenching (NPQ), the plants were challenged with short-term high light (*2000 lmol m -2 s -1 ). In spite of prevailing red colour, leaves of 'Assas' had identical concentrations of chlorophylls a and b as green ones. The OJIP transients showed that red leaves grown in field (500-800 lmol m -2 s -1 ) had decreased PI ABS and electron transport per RC beyond primary acceptor (Q A -) compared to green leaves. After high light exposure red leaves revealed impaired relETR accompanied with increased NPQ values. Anthocyanins located in epidermal cells affected neither chlorophylls concentrations nor the light capture features of PSII. Despite equal concentrations of chlorophylls and PSII photochemistry further than Q A in both leaf types, red leaves reduced overall photosynthetic efficiency due to impaired relETR in thylakoid membranes.