GROWTH OF BROCCOLI AS AFFECTED BY GLOBAL RADIATION AND AIR-TEMPERATURE

In 4 field experiments with broccoli (Brassica oleracea var, italica c v. Emperor) irradiance was varied by shading. Irradiance affected grow th and yield all over the growing time. Reducing irradiance by 1 % res ulted in a 0.9 % decrease of dry matter of plants at harvest and in a 1 % decrease of yield. Leaf area decreased by 0.5 % per 1 % reduction bf irradiance due to a higher specific area of shaded plants. The inte gral of global radiation over the growing time accounted for 50 % of t he variation of yield and dry matter, the global radiation absorbed by the canopy for more than 80 %, respectively. Temperature affected dry matter at harvest and yield mainly during the first half of the growi ng time. Increasing temperature accelerated leaf expansion and thereby increased radiation absorbed by the plants as well as enlarged plant size at the start of head growth finally resulting in increasing poten tial plant and head size at harvest.