Scanning electron microscopic observations of degradation of starch granules in germinating kernels of several maize (Zea mays L.) endosperm mutants in four inbred and one hybrid background and their normal counterparts.

Abstract

The objective of this study was to make SEM observations of starch granules of several different maize endosperm mutants following the early germination period and to compare the relative patterns and digestibility by starch-degrading enzymes. Mature kernels of the ae endosperm mutant in four inbred lines and in a single cross hybrid and of five endosperm mutants in an inbred and a single cross hybrid, and their normal counterparts were used. Enzymatic erosion of the starch granules was visible in the disected endosperm of the normal maize following germination 4, 6 and 8 days after planting. The types of the enzymatic erosion were similar to those of the in vitro attack by a-amylase on normal starch granules. Namely, numerous pin holes were visible on the surfaces of the granules and the pores penetrated into the granules and the inner portion, which appeared to be terraced or step-shaped indicative of layered internal structures. Some types of enzymatic erosion suggested the possibility of enzymatic attack other than that of a-amylase. Starch granules of the germinating Oh43, C103, W64A, and Oh43XC103 ae endosperm mutant lines scarcely showed enzymatic erosion on their surfaces. These observations were similar to the in vitro amylase attack of ae starch granules. On the other hand, enzymatic erosion of starch granules of the B37 ae endosperm was similar to the germinating kernels of the normal B37. The types of enzymatic erosion of endosperm starch granules of the germinating su2 su2o2, wx, and 02 mutants were similar to those of their normalcounterparts.