SUMMER SQUASH RESPONSE TO ROOT RESTRICTION UNDER DIFFERENT LIGHT REGIMES

Two week-old summer squash (Cucurbita pepo L.) were transplanted to container volumes of 0.35, 2.00, or 7.60 liters and were grown under full light or 47% shaded conditions to determine the growth and development responses of the crop relative to root and shoot stresses. Light regime had no apparent impact on plant leaf area production; however, leaf area of plants grown under both light regimes was reduced similarly by root restriction. Leaf area reductions were largely attributable to smaller individual leaf sizes. Specific leaf area did not respond to root restriction, but shading increased the amount of leaf area produced per unit of leaf dry weight for all soil volumes. Whole-plant dry weight reductions due to root restriction were more pronounced in full light than in the shaded environment. There were no consistent differences in the percent of biomass allocated to roots, shoot, or leaves in response to either soil volume or light regime. Also, there were no effects of root restriction or light regime on timing, duration, and sex of flowers, or on timing of fruit set. Fruit dry weights at final harvest were reduced by increased root restriction under full light conditions; however, there were no differences in fruit dry weight among different container volumes under shaded conditions. The results from this study indicate that root restriction does reduce squash growth and yield; however, the effects of shading may be more important.