The Effect Of Different Nitrogen Concentrations On Growth Of Endive And Nitrogen Optimization Simulation Study

Nitrogen is one of the essential nutrient elements, nitrogen nutrition plays an important role in vegetable crop growth, yield and quality formation. Endive is one of the emerging of leafy vegetables, due to its health care function and high nutritional value as a result of the market demand is increasing. But the phenomenon of excessive fertilization in vegetable cultivation due to pursue high yield caused widespread ecological pollution caused by more serious. The experiment with common market of fine leaved endive varieties as materials, the effects of different for nitrogen level endive growth, photosynthetic characteristics, nitrogen assimilation characteristics, active oxygen scavenging capacity and dry matter and nitrogen accumulation. The main results are as follows:1、In the appropriate for nitrogen levels were within the range, the Sonchus oleraceus growth index is better, too low or too high concentration of nitrogen were on lettuce growth adversely affected.2、Moderate N level(8-11 mmol · L-1) could promote the endive’s growth and the accumulation of dry matter by improve the endive leaf area and chlorophyll relative content(SPAD), PSII maximal photochemical quantum yield(Fv/Fm) and PSII actual photochemical efficiency(PSII), and improve the net photosynthetic rate(Pn), stomatal conductance(Gs),photosynthetic pigment to capture light with greater efficiency into chemical energy for photosynthesis, and improve the efficiency of the photochemical reaction.Furthermore, the application of low nitrogen or high nitrogen level decreased the relative content of chlorophyll from leaves(SPAD), net photosynthetic rate(Pn), stomatal conductance(Gs),transpiration rate(E) and the maximal photochemical quantum yield(Fv/Fm), PSII actual photochemical efficiency(PSII)and inhibited the dry matter accumulation of shoots and roots of endive plants in different degree likely due to decrease the photosynthetic pigment content, CO2 transmission capacity and photochemical activity of PSⅡin leaves of endive. when the supply of nutrient solution concentration was 9.557 mmol/L, the maximum amount of accumulation of dry matter. From each period of photosynthetic characteristics and dry matter accumulation was positively correlated. Low and high nitrogen levels will produce unfavorable effects on the photosynthesis.3、The appropriate level of nitrogen supply can significantly improve the nitrate reductase in leaves of lettuce(NR), nitrite reductase(NiR), glutamine synthetase(GS) and glutamate dehydrogenase(GDH) activity, increased soluble protein content and nitrogen accumulation. When the nitrogen concentration was from 8 mmol·L-1 to 11mmol·L-1, the key enzymes of nitrogen metabolism reached highest. The equation fitting of nitrogen supply and total output of endive protein, could be obtained when the supply of nutrient solution concentration of 10.730 mmol·L-1 protein from the highest total yield. Correlation analysis showed that the leaf in different growth periods of nitrogen metabolism key enzyme activity and nitrogen accumulation was positively correlated, indicating that appropriate nitrogen levels could increase the activity of key enzymes from nitrogen metabolism and improvenitrogen accumulation and protein yield in leaves of endlive.4、Proper N level can reduce the leaf MDA and H2O2 accumulation, improve the ability of scavenging active oxygen plant. Furthermore, the application of low nitrogen or high nitrogen level decreased Pn and inhibited the growth of endive plants in different degree likely due to the leaf photosynthetic pigment content and the damage in structure and function of cell membrane caused by the decrease of active oxygen scavenging capacity, which resulted in the accumulation of H2O2 and membrane lipid peroxidation enhancement.resulting in poor plant growth.5、When the nitrogen supply from 9.935 to 11.448 mmol/L, the yield of endlive reached highest in two different experiments by function fitting,...