SEQUENTIAL YIELD COMPONENT ANALYSIS AND MODELS OF GROWTH IN BUSH BEAN (PHASEOLUS VULGARIS L.)

We describe the effect of repeated fruit harvest on yield and components of yield in bush bean, and we construct several growth models. Multiple-regression analysis was used to estimate the relative contributions of individual components to overall yield, and a technique comparing ‘backward’ and ‘forward’ multiple regressions was used to identify points of direct and indirect influence on the ontogenetic series contributing to yield. By testing alternative models we were able to identify components which did not contribute significantly to yield. Plant height was an important direct and indirect determinant of yield in both treated and untreated plants. There were more compensation effects between components in plants which were continuously harvested, perhaps because pods no longer contributed photosynthate, or because harvested plants were ‘rejuvenated’ through bud release, thus more resource sinks were competing actively for limited resources. Competition between resource sinks apparently occurs earlier in the model sequence where pods are harvested continuously, and becomes important later, as pods mature, in plants left intact to the end of the experiment. The reciprocal of leaf area ratio was another major component of yield. In both treated plants and controls, this ratio of leaf area to total plant dry weight behaved indirectly, apparently influencing yield through other components.