engleski

Chlorophylls content and photochemistry of thylakoid membranes in two pea cultivars with different leaf colouration

Photochemical features of thylakoid membranes and chlorophyll content were investigated in two pea (Pisum sativum L.) cultivars different leaf colouration: Assas (red leaves) and Arvika (green leaves). Particularity of Arvika cultivar is the appearance of red leaves in juvenile developmental stages (2-3 leaves), in the part of year when low temperatures in the morning are combined with medium irradiation. In vivo measured fast transients of chlorophyll fluorescence (OJIP) was used to evaluate overall photosynthetic efficiency (expressed as performance index - PIABS) as well as for advanced analysis of main photochemical processes per active reaction centre (RC) of photosystem II (PSII), such as absorption of light energy (ABS), trapping of exciton (TR0), excess energy dissipation (DI0) and electron transport (ET0) beyond primary acceptor (QA-). Further, we challenged investigated plants with short-term high light conditions and evaluated response of photosystem II driven linear electron transport (relETR) and non-photochemical quenching (NPQ). It was revealed that in spite of prevailing red colour, Arvika leaves had identical levels of chlorophylls a and b. Field measurements of OJIP transients showed that red leaves grown at incident irradiation (500-800 µmol m-2s-1) had decreased PIABS and ET0 per RC, while other fluxes per RC showed no significant differences in comparison with green leaves. Experiment with high light (~2000 µmol m-2s-1) in laboratory conditions also revealed impaired relETR accompanied with increased NPQ values in red leaves. In summary, here we demonstrated that red colour that emanates from anthocyanins located in epidermal cells does not affect neither chlorophylls levels neither the light capture features of PSII. In spite of equal levels of chlorophylls and PSII photochemistry upstream of QA- in red and green leaves, red leaves had reduced overall photosynthetic efficiency due to impaired linear electron transport in thylakoid membranes.

chlorophyll fluorescence; photosystem II; Pisum sativum

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