Ethylene may be involved in abortion of the maize caryopsis

The involvement of ethylene and 1-aminocyclopropane-1-carboxylic acid (ACC) in shade-induced kernel abortion at an early kernel growth stage was investigated. Changes in levels of glucose, sucrose, starch, ACC and ethylene were measured during the first 6 days after pollination (DAP) at sampling intervals of 12 or 24 h. In response to shading treatment, dry weight accumulation of apical kernels ceased within 96 h after pollination (HAP). Glucose levels in shaded kernels 12 HAP were significantly higher than in control kernels, while sucrose and starch levels were similar until 48 HAP. In the shade treatment ACC and ethylene levels increased rapidly around 24 HAP in both apical and basal kernels. When ACC was applied to ears at 32 HAP and 5 DAP, dry weight accumulation was significantly reduced only in apical kernels of 32 HAP. Significant reduction in endosperm nuclei number was also found in both shaded and ACC-treated kernels. The results of the present study suggest that ethylene may be involved in the processes leading to kernel abortion in maize. Kernels at the very early developmental stages seem to be most sensitive to ethylene.