This invention relates generally to the field of plant molecular biology. More specifically, this invention relates to methods and reagents for the temporal and/or spatial expression of genes that affect metabolically effective levels of cytokinins in plant seeds and related maternal tissue. This invention further relates to transgenic plants having enhanced levels of cytokinin expression wherein the transgenic plant exhibits useful characteristics, including: improved seed size, decreased tip kernel abortion, increased seed set during unfavorable environmental conditions, and stability of yield.