Observation and comparison of structure changes in wheat caryopsis maternal tissues and endosperm

Abstract

During the caryopsis development, maternal tissues provide protection and nutrients for the endosperm. Wheat caryopses were observed using different microscopies to investigate structure characteristics of wheat caryopsis maternal tissues and endosperm. The results were as the following: (1) Maternal tissues, especially nucellar cells and pericarp parenchyma cells, degenerated to supply space to the endosperm growth. A thick cuticle layer adhered to the outer integument existed till the endosperm matured. The thick cuticle layer not only made sure that nutrients from the vascular system got into the endosperm through the chalaza but also was probably the key reason why integuments could affect the endosperm growth. (2) The green pericarp contained chloroplasts and perhaps played an important part in nursing other maternal tissues and limiting nutrients from phloem to be transported toward pericarp parenchyma cells. (3) Sieve tubes of the vascular system increased in response to the enhanced endosperm sink strength. Chalazal cell walls and inclusions probably changed to regulate the flux of nutrients transported into the endosperm. In one word, structure changes of maternal transport tissues had a close relationship with the endosperm development.