Density of Microbodies on Sucrose Gradients during Phytochrome-mediated Glyoxysome Peroxisome Transformation in Cotyledons of Mustard Seedlings.

The microbodies extracted from the cotyledons of mustard seedlings (Sinapis alba L.) form two bands (at 1.18 kilograms per liter together with the mitochondria, and at 1.24 kilograms per liter) on conventional isopycnic sedimentation density gradients. The artifactual co-banding of part of the microbodies with the mitochondria can be prevented by using flotation gradients. Using this procedure, a systematic investigation revealed no effect of seedling age and irradiation (far red or white light) on the density of the microbody population (1.242 +/- 0.002 kilograms per liter). Thus, although light, through phytochrome, induces conspicuous changes in their enzyme composition the microbodies appear as a homogeneous population of constant density on a sucrose gradient.