Changes in Seed Structure and Composition during Development and Their Effects on Leakage in Two Endosperm Mutants of Sweet Corn

Field- and greenhouse-grown seeds of 2 sweet corn ( Zea mays L.) endosperm mutants— shrunken-2 ( sh2 ) and sugary ( su )—were harvested 18 to 46 days postpollination (dpp). Mature sh2 seeds had a greater imbibition and leakage rate than did su . Leachate conductivity was greater from field-grown sh2 seeds than greenhouse-grown sh2 at maturity. No difference in carbohydrate leakage was observed between genotypes at maturity. Leakage generally decreased in all seed types with increasing maturity. Cracking of the pericarp was not noticeable in either sh2 or su during development. In mature seeds of both genotypes, the pericarp appeared to be thicker and adhered more tightly to the aleurone layer than in immature seeds. Dry seeds of sh2 contained considerably less total carbohydrates and starch than su 18 to 46 dpp. Field-grown su seeds accumulated more total carbohydrates during development than greenhouse-grown su or sh2 . The lowest amounts of sugars in dry seeds occurred at maturity with no difference noted between field- and greenhouse-grown sh2 and field-grown su . Immature fresh kernels (freeze-dried) of su and sh2 contained 2 to 3 times, respectively, more sugars than immature dry kernels. At maturity, fresh and dry kernels of either genotype had equal amounts of sugars, but fresh kernels contained more starch.