Effects of Temperature, Light Intensity and Nitrogen Application on the Recovery of Photosynthesis in the Senescent Primary Leaves by the Removal of Foliage Leaves in Snap Bean

The effects of three environmental factors on the recovery of net photosynthetic rate (Pn) in the senescent primary leaves by the removal of foliage leaves in snap bean plants (Phaseolus vulgaris L.) were examined. Effects of temperature were examined under three different conditions : 23/18, 25/20, and 28/23°C (day/night) . Under these conditions, Pn at 25°C were not affected. Effects of light intensity were examined by covering the primary leaves with 1-3 layers of black cheesecloth. The recovery of Pn on a fresh weight basis decreased with increasing shade level. However, any difference was not observed in Pn on a dry weight basis. Since shading with black cheesecloth increased leaf extension and decreased leaf thickness, the effect of light intensity appeared to be through the effect on leaf morphology. Effects of nitrogen were examined by applying three different levels of nitrogen during the different experimental period. It became evident that the nitrogen level in the nutrient solution applied to plants is an important environmental factor affecting the recovery of Pn.