Temperature dependent chlorophylls accumulation and photosystem II assembly during etioplast to chloroplast transition in sunflower cotyledons

Abstract

Functional changes during biogensis of photosynthetic membranes in higher plants still remained insufficiently understood and thus became hot topics in plant biochemistry. The dynamics of chlorophylls a and b (Chl a and Chl b) accumulation as well as photosystem II (PSII) efficiency  during 24 h of greening in etiolated sunflower cotyledons (Helianthus annuus L.) exposed to the three different temperatures (10, 20 and 30 ^oC, respectively), were investigated. The main goal of our study was to emphasize how would chosen temperatures influence chlorophylls accumulation and the maximum quantum yield of PSII (Fv/Fm). We also aimed to evaluate combined effects of different temperatures (20 and 30 ^oC) and short-term application of increased irradiation (800 ?mol m^-2 s^-1) on effective quantum yield of PSII (?F/F’_m) and non photochemical quenching (NPQ) in cotyledons with fully developed PSII. Our results showed reduced chlorophylls accumulation and the total arrest of PSII assembly at 10 ^oC in comparison with 20 and 30 ^oC. Further, the increased irradiance induced equal down regulation of effective quantum yield of PSII at 20 and 30 ^oC, with significantly higher capability of heat dissipation at 30 ^oC.