[Effects of Cd stress on photosynthetic characteristics and nutrient uptake of cabbages with different Cd-tolerance].

With solution culture, this paper studied the plant growth, photosynthetic characteristics and nutrient uptake of two cabbage (Brassica oleracea L.) cultivars with different Cd-tolerance under treatments of 0, 20, 50 and 100 micromol Cd x L(-1). The results showed that the growth of Cd-sensitive cultivar Qiufeng was inhibited obviously even under low Cd concentration (20 micromol x L(-1)) stress. The net photosynthetic rate (P9, stomata1 conductance (Gs), photochemical efficiency of PS II (Fv/Fm) and quantum yield of electron flow through PS II (phi (PS II)) in its leaves and the dry weight of its shoots and roots declined sharply. However, negative impact on the growth and photosynthetic characteristics of Cd-tolerant cultivar Beinongzaosheng was only observed under high Cd concentration (50 and 100 micromol x L(-1)) stress. Cd stress decreased the contents of chlorophyll a and b, especially of chlorophyll b, which could be an important factor of photosynthesis inhibition. Under Cd stress, the Mn uptake by plant decreased significantly, and the transportation of Fe and Mg from roots to shoots was restrained, which were more obvious in Cd-sensitive than in Cd-tolerant cultivar. Cd stress promoted the P and S uptake by Cd-tolerant cultivar, but opposite results were observed in Cd-sensitive cultivar. Therefore, physiologically, the decrease of Mn, Fe, Mg, S and P concentrations in Cd-sensitive cultivar's leaves under Cd stress was the key reason for the restraint of leaf photosynthesis, and the decrease of plant growth.