STRUCTURAL ASPECTS OF RESERVE PROTEIN ACCUMULATION IN DEVELOPING COTYLEDONS OF PROSOPIS-JULIFLORA (LEGUMINOSAE, MIMOSOIDEAE)

Structural changes during reserve protein deposition in Prosopis julif lora cotyledons were studied using both light and electron microscopy. The large and empty vacuoles in the cotyledonary cells of developing seeds are replaced toward seed maturity by many small bodies that are packed densely with proteinaceous materials. Subdivisions in the vacuo les are followed by concomitant deposition of storage proteins on the vacuolar rim resulting in the formation of protein bodies. The vacuola r protein deposits are apparent as irregular lumps of electron-dense p recipitates which either line the tonoplast or lie free in the vacuole . The protein deposition is accompanied by a massive proliferation of rough endoplasmic reticulum that pinches off vesicles into the cytopla sm. Morphological evidence suggests that ER-bound ribosomes are involv ed in the synthesis of storage proteins and that the transport of stor age proteins from their site of synthesis, the rough endoplasmic retic ulum to their site of deposition, the vacuolar protein bodies, is medi ated via protein vesicles that are derived from ER.