Effect Of Applying Zinc And Silicon Fertilizer On The Physiological Characters Of Flag Leaves And The Yield Of Winter Wheat Under Drought Stress

Pot experiments of were carried out at Henan Agricultural University Research Station to study the effect of applying exogenous zinc(Zn+) and silicon fertilizer(Si+) on the physiological characters of the flag leaves and the yield of winter wheat cultivar Yumai 49-198 under different drought stress(normal water content: NW, mild drought stress: MD, severe drought stress: SD), in wheat growing-season of 2013-2014. The main results were as follows:1 Effect of applying exogenous zinc and silicon fertilizer on the yield of wheat under drought stressThe results showed that, compared to the control of none silicon and zinc applied, applying zinc and silicon fertilizer significantly increased the grain weight under NW. Under mild and severe drought stress, applying silicon fertilizer increased the grain weight by 1.85% and 4.00%, respectively; increased the yield by 29.24% and 33.33%, respectively. At the same time, applying zinc fertilizer increased the yield by 22.45% and 28.23% under mild and severe drought stress, respectively. It indicated that applying exogenous zinc and silicon fertilizer can improve the ability of defending drought stresss of wheat and finally increase the yield.2 Effect of applying exogenous zinc and silicon fertilizer on the photosynthetic characteristics of wheat flag leaves under drought stressSPAD value of wheat flag leaves were reduced under drought stress and were increased in the treatment by applying zinc and silicon fertilizer. If the comparison was made with CK, applying zinc and silicon fertilizer increased the average(under stress for 10 days and 20 days) values of SPAD by 7.83% and 11.93% under MD, respectively; and increased SPAD by 7.43% and 17.20% under SD, respectively.The values of Fv/Fm, q P and ΦPSⅡ were reduced under drought stress. Comparing with CK, the MD-Zn+ treatment and SD-Zn+ treatment increased the values of Fv/Fm by 4.46% and 5.49% at 10 days after stress(DAS), respectively. Correspondingly, applying silicon fertilizer increased the values of Fv/Fm by 5.11% and 7.09% at 10 DAS. If the comparison was made with CK at 20 DAS, MD-Zn+ treatment and SD-Zn+ treatment increased the values of ΦPSⅡ by 9.29% and 23.40%, respectively. Similarly, MD-Si+ treatment and SD-Si+ treatment increased the values by 8.23% and 16.99%, respectively. These results indicated that the photosynthetic characteristics of wheat flag leaves can be improved by the application of exogenous zinc and silicon fertilizer under drought stress.3 Effect of applying exogenous zinc and silicon fertilizer on the content of antioxidants and the activity of antioxidant enzymes under drought stressApplying zinc and silicon fertilizer can decrease the content of MDA and H2O2 in wheat flag leaves under drought stress. Compared to CK, applying zinc fertilizer at mild drought decreased the average content of MDA and H2O2 by 11.71% and 8.48%, respectively. Correspondingly, the decrease range in severe drought treatment was 9.11% and 21.15%, respectively. Comparing with CK, MD-Si+ treatment decreased the average content of MDA and H2O2 by 114.09% and 10.50%, respectively. Similarly, SD-Si+ treatment decreased MDA and H2O2 by 9.17%, 12.31%, respectively. Applying zinc and silicon fertilizer increased the enzyme activity of SOD and POD under drought stress. Comparing with CK, the average enzyme activity of SOD and POD of applied zinc fertilizer treatment were increased by 25.03% and 11.60%, respectively. Compared to CK, applying silicon fertilizer increased the average enzyme activity of SOD and POD by 21.03% and 11.53%, respectively.Compared to the CK, applying zinc fertilizer increased the average content of flavonoids, total phenol by 31.02% and 11.28%, respectivley. Applying silicon fertilizer increased the average content of flavonoids, total phenol, ascorbic acid and glutathione in wheat flag leaves under different drought stress. Compared with CK, the content of flavonoids was increased by 30.52%. These results indicated that the application of exogenous zinc and silicon fertilizer could improve antioxidants content in wheat flag leaves under drought stress, which enhaced the wheat’ ability of resistanting drought stress.4 Effect of applying exogenous zinc and silicon fertilizer on the expression of multiple antioxidant system under drought stressCompared to the CK, MD-Zn+ treatment enhanced the average expression level ofTa SOD, Ta CAT genes by 35.60% and 29.06%, while SD-Zn+ treatment increased its expression level by 38.14% and 51.36%, respectively. Correspondingly, MD-Si+ treatment increased the average expression level of these genes by 49.11% and 36.96%, respectively. SD-Si+ treatment increased these gene expression levels by 59.31% and 108.88%, respectively.The results showed that applying zinc fertilizer increased the average expression level of Ta APX, Ta GR, Ta GS, Ta MDAR, Ta DHAR genes which involved in ascorbic acid and glutathione circulatory system. If the comparison was made with CK, MD-Si+ treatment increased the average expression level of these genes by 39.67. Comparing with CK, SD-Zn+ treatment and SD-Si+ treatment increased the relative expression level of Ta APX gene by 30.14% and 87.67% at 10 DAS, respectively. At 20 DAS, SD-Zn+ treatment and SD-Si+ treatment increased the relative expression level of Ta APX gene by 30.14% and 87.67%, respectively. Applying zinc and silicon fertilizer significantly increased the relative expression of Ta GR, Ta GS, Ta MDAR gene under at 20 DAS. Comparing with CK, applying zinc and silicon fertilizer increased the average relative expression of Ta GS genes by 98.14% and 151.51%, respectivley.Ta CHS, Ta F3 H, Ta DFR, Ta ANS were the key genes of flavonoids synthesis pathway. Compared to the CK, applying zinc fertilizer can strengthen the expression level of these genes in flavonoids synthesis pathway under drought stress. Compared with CK, the relative expression level of Ta CHS and Ta ANS genes under MD were increased by 40.66% and 73.94%, respectively. Similarly, silicon fertilizer increased the relative expression levle of Ta DFR by 91.73% and 79.14% under severe drought stress, respectively.This study showed that applying exogenous zinc and silicon fertilizer could improve the ability of wheat plant resistanting drought stress by enhancing the transcriptional level of multiple antioxidant defense system.