The accumulation and properties of starch are associated with the development of nutrient transport tissues at grain positions in the spikelet of wheat.

Abstract

A wheat spikelet accumulates several grains, which show significant positional effects in terms of size, weight, and material accumulation. However, few studies have investigated whether starch accumulation in these grains is related to the development of vascular bundles. This study analyzed the correlation between the morphology of vascular bundles and starch accumulation. The area of nutrient transport tissues in G1 and G2 was greater than that in G3 and G4. The proportion of A-type starch granules in G3 and G4 was significantly greater than that in G1 and G2, with the greatest proportion of C-type starch granules occurring in G2. The short-order structure of the starch granules in G1 was more developed than that in the other samples, and the crystalline region in G2 was the greatest. The area of the nucellar projection and vascular bundle was positively correlated with C- or B-type starch granules but negatively correlated with A-type starch granules and swelling power. The area of wall ingrowth was positively correlated with the proportion of branch chains (DP 25-36 and DP 37-100), and negatively correlated with the starch content. The above results indicate that the developmental status of the vascular bundles in the wheat grains controls the accumulation, composition, and characteristics of starch in the endosperm. The novelty of this study lies in elucidating the grain position effect on starch accumulation in wheat grains. This provides a new perspective for agricultural production, aiming to enhance the accumulation of carbohydrates in inferior grains, thereby facilitating their transformation into superior grains.