ULTRASTRUCTURAL AND PHYSIOLOGICAL DIFFERENCES IN SOYBEANS WITH GENETICALLY ALTERED LEVELS OF PHOTOSYNTHETIC PIGMENTS

Soybeans displaying incomplete dominance for leaf pigmentation possess chloroplasts with characteristic shape and organization of photosynthetic membranes. The chloroplasts of light green plants lack grana typical of dark green or a field type (Beeson) but normally possess doubled thylakoids. Achlorophyllous lethal yellow plants have thylakoids reduced to single spiralled membranes. The yellow plants lack a waxy cuticle over the leaf surface which is characteristic of all other soybeans examined, and they lack catalase activity in microbodies. Photosynthetic rates in the light green plants are at least as high as in the fully pigmented ones and photorespiration levels are not significantly different. Thus, in light green plants greater efficiency of enzymatic processes in photosynthesis apparently offsets the inhibitory activities associated with photorespiration. Single allele alterations from dark green to light green and light green to lethal yellow appear to alter a variety of structures and functions.