Photodormant lettuce seeds: Phytochrome-induced protein and lipid degradation.

Photodormant lettuce (Lactuca sativa L.) seeds were incubated in mannitol to prevent germination. Under these conditions, red light induced an extensive degradation of protein and a moderate one of lipid in the cortical cells of the radicle 24 h after treatment. It is suggested that the previously reported phytochrome-caused lowering of the water potential in light-treated embryos, which enables these embryos to overcome the resistance of the surrounding layers of the seed, is caused by lowering of the osmotic potential due to degradation of storage compounds in the radicle.