Hormonal control of ear abortion in a stress-sensitive maize (Zea mays) inbred

Abstract

A cold-sensitive maize (Zea mays L.) inbred was used as a model for investigating the interactions between growth regulators, reproductive development, and environmental stress. In this genotype, a chilling treatment given just before floral transition caused the topmost ear to abort and be replaced at maturity by a sterile, leaf-like, structure. Exogenous applications of the synthetic auxin 2,4-dichlorophenoxyacetic acid or of the cytokinin benzyladenine respectively mimicked or prevented the abortive response caused by chilling. Chilling also induced a moderate decrease in the content of endogenous indoleacetic acid (IAA) in the apical shoot tissues. By contrast, zeatin-type cytokinins decreased dramatically (5–8 fold), both in the apical shoot tissues and in the xylem exudate of chilled plants. Overall, the ratio of free-IAA to zeatin-cytokinins was increased in the apical shoot of chilled plants. Our results suggest that: (1) ear abortion induced by chilling might be related to an altered cytokinin content; (2) the number of developing ears may be limited by the endogenous levels of cytokinins just before floral transition; and (3) cytokinins may have a potential for increasing yield in maize.