Structural Aspects of Protein Accumulation in Developing Pea Cotyledons. Iv. Effects of Preparative Procedures on Ultrastructural Integrity.

Abstract

The pea storage proteins legumin and vicilin have previously been shown to be deposited in the vacuoles of cells of young developing cotyledons. By electron microscopy, the appearance of vacuole contents, and in particular of the peripheral protein deposits, are known to vary even in controlled and reproducible conditions of plant growth. This observation suggests an influence of specimen preparation on appearance. Different fixative solutions used on developing pea-seed cotyledons affected the appearance of the cytoplasm and its contents only slightly. The appearance of vacuole contents was greatly modified by the type of buffer used as a fixative vehicle and by osmotic conditions induced by added sucrose, and less by the primary fixative used. From a comparison with living protoplasts from cotyledon cells, it was concluded that the non-membrane-bound peripheral protein deposits are not artefacts of preparation. It is suggested that sucrose may play a role in the transition of vacuoles to protein bodies.