Endorsperm Development of Maize Defective Kernel (dek) Mutants. Auxin and Cytokinin Levels

To provide insight into the regulatory roles of auxin and cytokinin in endosperm development, defective kernel ( dek ) mutants of maize ( Zea mays L.) were examined. The mutants dek 6, dek 18 and dek 26 had substantially lower indole-3-acetic acid (IAA) levels than wild-type counterparts while dek 8, dek 12 dek 24 had higher IAA levels than wild-type counterparts. The mutant dek 6 had a somewhat lower zeatin level than its wild-type counterpart. The mutation-induced changes in IAA levels and effects of exogenously-applied auxin were not consistently related to changes in numbers of nuclei per endorsperm; however, there was a correspondence between auxin level in endosperm and nuclear diameter, which is proportional to the extent of post-mitotic DNA synthesis (endoreduplication). We conclude that auxin may be involved in stimulating endoreduplication.