Effects of weak-light stress during grain filling on the physicochemical properties of normal maize starch.

The grain development of normal maize in Southern China is affected by decreases in sunlight intensity over the period of mid-June to mid-July. This study examined the starch structure and function of four normal maize varieties that had been exposed to weak-light stress (50% light deprivation; ambient light conditions served as the control) during grain filling. In all tested varieties, light deprivation decreased the contents of starch and amylose, and increased the size of starch granules and the proportion of long chains in amylopectin. Shading increased the relative crystallinity and ordered-to-amorphous ratio of starch. Shading decreased the gelatinization and retrogradation enthalpies and pasting and gelatinization temperatures of starches but increased retrogradation percentage and pasting viscosities. In conclusion, weak-light stress during grain filling increases starch viscosity and retrogradation tendency and decreases thermal stability by reducing amylose content, increasing the sizes of starch granules and the proportion of long chains in amylopectin, and improving the relative crystallinity.