THE EFFECTS OF INCREASED ATMOSPHERIC CARBON-DIOXIDE ON GROWTH, CARBOHYDRATES, AND PHOTOSYNTHESIS IN RADISH, RAPHANUS-SATIVUS

The effects of sink capacity on the regulation of the acclimation of p hotosynthetic capacity to elevated levels of carbon dioxide are import ant from a global perspective. We investigated the effeocts of elevate d (750 mu mol mol(-1)) and ambient (350 mu mol mol(-1)) atmospheric CO 2 on growth, carbohydrate levels, and photosynthesis in radish seedlin gs from 15 to 46 d after planting. In radish, a major sink is the stor age root, and its thickening is initiated early. Elevated CO2 increase d the accumulation of dry matter by 111% but had no effect on the accl imation of the rate of photosynthesis or on the levels of carbohydrate s in leaves at dawn, Elevated CO2 increased the dry weight in storage roots by 105% by 46 d after planting, apparently enhancing the sink ca pacity, This enhanced capacity seemed to be responsible for absorption of elevated levels of photosynthate and to result in the absence of a ny over-accumulation of carbohydrates in source leaves and the absence of negative acclimation of photosynthetic capacity at the elevated le vel of CO2.