Gibberellic Acid Treatment Reduces the Tolerance of Field-Grown Common Bean to Leaf Removal

Abstract.

I studied the influence of gibberellic acid (GA₃) treatment in a field population of common bean on plant tolerance to leaf removal. Individual bean seedlings were treated with a foliar application of 10 μM GA₃ on day 7 and day 14 after emergence, which led to a significant increase in height in GA₃-treated plants. Twenty-eight days after emergence, either zero, one, two, or three leaflets from each trifoliate leaf were removed from each of 20 GA₃-treated and 20 control plants. All pods were harvested from each plant after plants became senescent 6 weeks later. Multivariate analyses revealed that leaf removal produced significant reductions in several yield components in both GA₃-treated and control plants, although the effects were not pronounced until at least two leaflets from each trifoliate leaf (67% of the total leaf area) were removed. However, GA₃-treated plants suffered greater reductions in total pod wall mass and total seed number than control plants after 33 and 67% leaf area removal. These results indicate that GA₃ treatment may have altered the assimilatory capacity or resource allocation pattern of treated plants in such a way as to decrease their ability to tolerate leaf removal, a negative consequence of the hormonal alteration of traits important to plant compensation for biotic stressors.