The effect of additional red irradiation on the photosynthetic apparatus of Pisum sativum

Pisum sativum (L.) plants were grown under "white" luminescent lamps, W [45 mu mol(quantum) m(-2)s(-1)] or under the same irradiation supplemented with narrow spectrum red light-emitting diodes (LEDs), RE [lambda(max) = 660 nm, Delta lambda = 20 nm, 40 mu mol(quantum) m(-2) s(-1)]. Significant differences in the chlorophyll (Ch1) a fluorescence parameters, degree of State 1-State 2 transition, and the pigment-protein contents were found in plants grown under differing spectral composition. Addition of red LEDs to the "white light" resulted in higher effective quantum yield of photosystem 2 (PS2), i.e. F'(v)/F'(m), linear electron transport (phi(PS2)), photochemical quenching (q(P)), and lower non-photochemical quenching (q(N) as well as NPQ). The RE plants were characterised by higher degree State I-State 2 transition, i.e. they were more effective in radiant energy utilisation. Judging from the data of "green" electrophoresis of Ch1 containing pigment-protein complexes of plants grown under various irradiation qualities, the percentage of Ch1 in photosystem 2 (PS2) reaction centre complexes in RE plants was higher and there was no difference in the total Ch1 bound with Ch1-proteins of light-harvesting complexes (LHC2). Because the ratio between oligomeric and monomeric LHC2 forms was higher in RE plants, we suggest higher LHC2 stability in these ones.