The Effect of Light on the Accumulation of Lipids in Seeds

To investigate the effects of light on the accumulation of lipids in seeds, fruits of both peanut and soybean plants were allowed to grow under different types of light conditions (natural, red, blue, green, or far-red light) and in darkness. Irradiation with each type of light from the 20th or 30th day, except for green light from the 30th day, resulted in lower dry weight of peanut seeds. The peanut seeds irradiated with natural, blue or far-red light from the 30th day onward contained a smaller amount of lipids, lower levels of triacylglycerides (TG), and higher levels of total sugar and diacylglycerides (DG), than the seeds grown in darkness. In the case of soybean seeds grown in darkness, the lipid content increased, but the total sugar and protein contents decreased. Exposure of soybean seeds to far-red light did not result in an increase in the lipid content. In vitro, ¹⁴C-glycerol-3-phosphate was converted to DG rather than to TG under irradiation with light compared with dark conditions. In contrast, the effect of light on the incorporation of ¹⁴C-oleoyl-CoA into TG was not appreciable. These findings suggest that the accumulation of lipid in the seeds of leguminous plants is depressed by light, with far-red light affecting most the accumulation of lipids, which may regulate the synthesis of TG via DG from glycerol-3-phosphate.