Photosynthesis and respiration in plants grown under red and white light

Tomato (Lycopersicon esculentum Mill), sunflower (Helianthus annuus L.), and cucumber (Cucumis sativus L.) plants were grown under red or white light at a radiance of 115 W/m(2) under controlled conditions. The red spectra were characterized by either two well-distinguished spectral lines (RL1) or only one (RL2). Apparent photosynthesis (P-a), gross photosynthesis (P-g), dark (R-d) and Light (R-l) respiration, the content of pigments, and the biochemical composition of plants were estimated. Enhancing the destructive red Light influence led to a rise in the P-a/R-l and P-a/P-g ratios and to a decrease in chlorophyll a, nitrate, and reduced nitrogen. RL1 was more inhibitory for plants than RL2. It is concluded that declined energy efficiency of respiration contributes to the destructive effect of RL in sunflower and cucumber plants. The rearrangement of metabolic processes, at which energy efficiency of respiration is maintained, is responsible for adaptation of tomato plants to red Light. The obtained results allow one to outline the ways to study the species-specific mechanisms of plant responses to prolonged RL action.