Selenium Spinach, Cabbage Growth, Nutrient Uptake And Antioxidant Enzyme Activities

Using spinach (Spinacia oleracea L.) andpakchoi (.Brassica. campestris ssp chinensis L.) as materials, using sodium selenite as selenium source. Effects of different concentrations of selenite on the growth and nutrient absorption were studied in plant cultured by hydroponic solution. Effects of selenite on the activities of antioxidase in plant were studied. The selenium uptake and inversion and effects of selenite and sulphate on the plant growth and contents of nutrient were also studied. The results showed as follows:1. Plant growth was promoted when selenite concentration was low in the solution, however, it was inhibited if selenite concentration was high. Effects of selenite on the contents of carbohydrate were different in spinach and pakchoi. In spinach, contents of soluble sugar and reducing sugar were decreased, but sucrose was increased, while in pakchoi, contents of soluble sugar and reducing sugar were increased, but sucrose was decreased. Contents of total protein were decreased at low selenite concentration, but they were increased with the increasing of selenite concentration in the solution. Total free amino acids were increased in all the treatments. Constituents of mineral elements in plant were changed after selenite was added. In spinach, contents of N, Fe, Cu were depressed, but contents of P, K, Ca, Mg, S, Mn, Zn were increased. In pakchoi, contents of N, Ca, Mg, Mn and Zn were increased, but contents of P, K, S were decreased.2. Effects of selinite concentration gradient on the activities of antioxidase in spinach and pakchoi were different. Activities of SOD, CAT, GSH-PX were enhanced, but Activities of APOD and DHAR were suppressed in spinach. While in pakchoi, activities of GPOD, DHAR, GSH-PX were enhanced. Activity of APOD was enhanced at low slenite concentration, but it was hardly affected at high selenite concentration. Effects of different selenite on the activities of SOD and CAT were hardly affected.3. There was a significant positive relationship between selenium content inplant and selenite concentration of nutrient fluid. The main form of selenium existed in plant was organic selenium, inorganic selenium was occupied a little. Rate of inversion of organic selenium was more than seventy-five percent in spinach, while it was more than eighty percent in pakchoi. There was a great relation between selenium content in shoots of spinach and pakchoi and selenite supplied tune. Selenium content in shoots of spinach reached the peak at twelve days before harvest time, while it was nine days in pakchoi. 4. At the low sulphate level, plant growth was promoted if selenite concentration was low in the solution, but it was inhibited if selenite concentration was high. At the high sulphate level, the plant growth was inhibited in all treatments added selenite.At the same sulphate level, selenium content in plant was increased with the increasing of selenite hi solution. In spinach, contents of P, Mg, Fe, Mn were increased, however, contents of N, Ca, B were decreased in the selenite treatments at low sulphate level. Fe content was markedly increased, however, contents of N, P, Ca, Mg, B were decreased in the seleite treatments at high sulphate lever. At low sulphate level, contents of total protein were decreased at the low selenite concentration, but those were increased with the increaseing of selenite concentration. While at high sulphate level, those were increased in all treatments added selenite. Contents of total free amino acids were decreased either at low sulphate level or at high sulphate level.In pakchoi, at low sulphate level, the uptake of B by pakchoi was enhanced, but the uptake of K, Ca and Mn were depressed. On the contrary, at high sulphate level, uptakes of K, Ca and Mn by plant were enhanced, but B depressed. Contents of total protein in pakchoi were increased, while contents of total free amino acids were decreased in all treatments added selenite either at low sulphate level or at high sulphate level.