Effects Of Different Nitrogen Forms On Photosynthetic Characteristics And Root Physiology Of Mini-chinese Cabbage

The objective of this experiment is to investigate the effects of different nitrogen forms and ratios on root physiology and activities of enzymes related to nitrogen metabolism in mini C hinese cabbage(Brassica pekinensis). The treatments include, 10:0,7:3,5:5,3:7,0:10 of nitrate ammonium ratios, 100% urea treatment, local fertilizer and blank as control.TField experiments were conducted and after treatments the photosynthetic pigment content between different growth stages of b aby food, changes of gas exchange parameters of photosynthesis and chlorophyll fluorescence parameters of NO3--N and total nitrogen ratio and photosynthetic parameters were measured. The main results of this research are as follow:1. Growth stage of Mini-Chinese cabbage, the local fertilization is more conducive to an increase in long pieces, cabbage beginning of the period, 10 more than in ammonium nitrate: 0-3: Range 7 in favor of an increase in long pieces.2. Ammonium nitrate and total nitrogen percentage ΦPSII, Pn showed a quadratic dependency relationships, that is, with ammonium nitrate and total nitrogen percentage increases, ΦPSII, Pn rise first and then decline. Ammonium nitrate ratio 7: 3-5: 5 range when baby food is more conducive to the accumulation of chlorophyll, light absorption and transmission, energy transformation and CO2 fixation.3. Total root length, root surface area and root number tips of plants treated with 3:7(nitrate: ammonium) were significantly higher than those of plants under other treatments, supporting that plants when treated with 3:7(nitrate: ammonium) had more lateral root and easily absorbed more water and nutrients. The root volume and average diameter of plants treated with 5:5(nitrate: ammonium) were greater than those of plants under other treatments, although the number of root tip was the minimum under this treatment, the growth of root is rather robust.4.When the ratio of nitrate and ammonium ranged from 10: 0 to 5: 5, free amino acids and activities of key enzyme involved in nitrogen metabolism were higher than other treatments, thus, it is more beneficial for plant nitrogen metabolism. Ammonium nitrate ratio of 3: 7 is more conducive to Mini-C hinese cabbage in advance of entering the cabbage and the rosette stage.