Influence of sugars on blue light-induced synthesis of chlorophyll in cultured plant cells

In supension cultured tobacco cells only blue light induces and maintains chlorophyll synthesis if the liquid nutrient medium is supplemented with sucrose. The yield per gram fresh weight is closely correlated with the energy fluence rate of blue light, but not with the initial amount of sucrose added to the medium (3-12 g/l). The uptake of sucrose by the cells proceeds with a constant rate over the growth period independently of the initial amount leading within 10-25 days to sucrose-free media. Under these conditions the cells continue to synthesize chlorophyll for about 10 days. This limitation is overcome by adding sucrose to the medium at equal time intervals thus establishing a constant sugar level beyond the growth period. In contrast, glucose as carbon source cannot adequately replace sucrose in inducing and maintaining blue light-induced chlorophyll synthesis. Depending on the initial amount (3-10 g/l) this sugar is rapidly disappearing from the medium within 1-5 days after inoculation of the cells. It apparently serves as a preferential source of energy and carbon skeletons thus suppressing chlorophyll synthesis. On the other hand, glucose combined with sucrose in the medium brings about the characteristic induction and accumulation of chlorophyll in blue light which is observed with sucrose as the sole carbon source.