Study Of Silicon On Physiological Mechanism Of Formation For Yield And Quality In Chinese Spring Onion

As an accepted and beneficial element, silicon plays an important role in improving crop yield and quality, but the response of Chinese spring onion to silicon had not been reported. Therefore, Under the condition of Na2 Si O3·9H2O as utilized silicon source, two varieties of Chinese spring onion, ‘Tianguang’ and ‘Zhangqiu’, were taken as materials to investigate the effects of different silicon levels of nutrient solution(0,0.6,1.2,1.8 mmol/L) and soil silicon fertilizers(0,10,20,30 kg/667m2 Si O2) respectively, on plant growth, yield and quality, and other physiological characteristics by combining pot Hoagland nutrient solution culture and field cultivation.in this experime nt. The chief results are showed as follows:1. The results showed that plant height, cauloid length, cauloid diameter, dry weight of the two varieties firstly increased and then decreased in the range of 1.8 mmol/L silicon. Among all treatments, 1.2 mmol/L silicon was the best, and the single plant yields of the two varieties were improved by 19.41% and 30.85% respectively compared with the control and in the treatment of 1.8 mmol/L, the two varieties were improved by 12.31% and 22.79%. In the field experiment, at the treatment of supplying 20 kg/667m2 silicon(Si O2), the yields of ‘Tianguang’ and ‘Zhangqiu’ were the highest and increased by 15.43% and 25.69% compared with the control. Moreover, appropriate silicon also significantly increased the contents of free amino acids, soluble sugar, pyruvic acid of C hinese spring onion, which indicated that Chinese spring onion quality could be enhanced by applying silicon.2. Applying silicon can increase chlorophyll and carotenoid conrent of C hinese spring onion and enhance light utilization efficiency of plant. Among all treatments, 1.2 mmol/L silicon was the best, the photosynthetic rate of ‘Zhangqiu’ variety was higher than that of ‘Tianguang’. Moreover, appropriate silicon also significantly decreased the transpiration rate of the two varieties and 1.8 mmol/L silicon was the lowest, were decreased by 23.45% and 25.86%. Under high temperature of summer, the two varieties had showed noon break, but utilized silicon improved Fv/Fm、φpsⅡ of C hinese spring onion leaves and decrease NPQ so that reduced noon break phenomenon and promote the production and accumulation of assimilation.3. With the increase of silicon levels, silicon contents in different organs of two varieties increased dramatically, then reached the highest values at 1.8 mmol/L silicon concentration, but conversely potassium contents always fell down. N itrogen, phosphorus contents increased firstly and then decreased, and their maximums occurred at 1.2 mmol/L silicon level. Because applying silicon promoted the growth of C hinese spring onion, the uptake amounts of silicon, nitrogen, phosphorus and potassium were raised with the increase of silicon levels.4. Appropriate silicon also significantly increased the nitrogen use efficiency of Chinese spring onion. At vigorus growth stage, adding silicon could significantly increase the NR, GS, GOGAT and GDH activity of the leaves and roots of the two varieties. Moreover, silicon also increased the content of free amino acids and soluble protein. Among all treatments, 1.2 mmol/L silicon was the best and the effect of ‘Zhangqiu’ was significantly higher than that of ‘Tianguang’ so that showed the effect of silicon to ‘Zhangqiu’ was more pronounced5. A siginificant increase of accumulation of H2O2 and MDA were observed in drought stressed ‘Tianguang’ onion leaves. Additionally, SOD, POD and CAT activities were enhanced at the early stage of drought sress, which were then sharply inhibit with stress time prolonging and blocked As A-GSH cycle. Compared with the control, application of 1.2mmol/L silicon significantly enhanced activities of antioxidant enzymes as well as palingenesis of As A-GSH cycle that significantely decreased levels of reactive oxygen species and membrane lipid peroxidation. Therefo re, silicon could enhanced drought resistance of C hinese spring onion.