[Spectrophotometric analysis of phytochrome in the embryo of Cucurbita pepo and Cucurbita maxima].

Phytochrome detection and △ (△O.D.) measurements were made for the first time in a single embryo of pumpkin or gourd thanks to an apparatus adjusted to the differential spectrophotometer constructed by Dr. Spruit (Wageningen). Observed △ (△O.D.) values are comparable with usual values obtained by analysis of several seeds in a cuvette. The differential spectrum obtained has the same characteristics as the spectra of seedlings and seeds which can be found in the present literature. The time course of phytochrome appearance in a single pumpkin embryo showed the different phases previously described in lettuce seeds. Use of masks which delimit different areas on the embryo made it possible to locate changes in phytochrome concentration. Analysis of pieces cut off from embryos and packed into a cuvette showed the existence of a decreasing concentration gradient from the cotyledons to the vegetative axis.