Comparison of photosynthetic activity of <Emphasis Type="Italic">Orychophragmus violaceus</Emphasis> and oil-seed rape

Orychophragmus violaceus, Brassica campestris cv. Chuanyou No.8, and Brassica juncea cv. Luzhousileng diurnal changes of net photosynthetic rate (P _N) and activities of carbonic anhydrase (CA) of leaves were studied. One uni-modal curve occurred at the diurnal changes of P _N in O. violaceus, but bimodal curves were found in B. campestris and B. juncea. Thus photosynthetic midday depression was not found in O. violaceus but in both Brassica species. Midday depression of P _N in O. violaceus was not related to high temperature or low humidity at midday but to the activity of CA.