Persistence of Non-Crease Protophloem Strands in the Developing Wheat Grain

The two protophloem strands in the lateral ovary walls of the developing wheat grain, previously reported to be obliterated during grain elongation, are shown to persist through about half, or somewhat longer, of the grain filling period. During the latter part of their functional life, they appear to be involved in the absorption of solutes produced during degeneration of the middle pericarp. During the final stages of pericarp degeneration, the protophloem strands show a basipetal progression of degeneration and adherence to the remaining inner and outer pericarp layers.