| Heilongjiang Province is the largest corn producing and exporting province in China.The form of corn production in Heilongjiang is not only related to the economic and social development of the province,but also to the national food security.In the seedling stage of maize production,low temperature and chilling damage is one of the main limiting factors affecting the high and stable yield of maize.In recent years,some studies have shown that the proper application of organic nitrogen fertilizer in the maize seedling stage can improve a series of physiological responses of maize seedlings under low temperature stress,and at the same time can promote maize development and growth.However,it is difficult to compare the results of different studies due to the different cultivars and culture conditions.At the same time,there are few reports on the physiological and biochemical reactions of different nitrogen utilization genotypes in maize under low temperature stress.Therefore,in this study,two maize varieties with different nitrogen utilization genotypes were used as test materials,Xianyu335(nitrogen-inefficient type)and Liaodan565(nitrogen-efficient type),and were cultured under hydroponic conditions at a day and night temperature of 18℃/9℃,irradiation intensity of 4000 lx,equal nitrogen content and different ratios of glycine to replace ammonium nitrogen design,two genotypes were set with 4 treatments,respectively control CK;(glycine0%+ammonium nitrogen 100%);T1(Glycine 20% ammonium nitrogen 80%);T2(40%glycine+60% ammonium nitrogen);T3(60%glycine+40%ammonium nitrogen);T4(80%glycine+20% ammonium nitrogen),the morphological characteristics of maize seedlings,the physiological characteristics of root system were measured respectively Characteristics,root carbon and nitrogen metabolism and fluorescence parameters,the main research results are as follows:1.T2 treatment group(40% glycine+60% ammonium nitrogen)in the root system of low nitrogen utilization type maize Xianyu335 had the best root shape,root length,surface area,volume,root tip number,root Compared with the CK group,the dry weight was increased by5.40%,7.43%,20.73%,46.84% and 30.07%,respectively.The T2 treatment group(40% glycine+60% ammonium nitrogen)significantly decreased the root length and the number of root tips,but increased the average root diameter and root dry weight.T4treatment(80% glycine+20%ammonium nitrogen)had the most significant effect on the growth of maize shoots.In Xianyu335,the leaf length,leaf width,leaf area,leaf dry weight and leaf fresh weight of maize seedlings in T4 treatment were 94.38%,66.95%,32.68%,8.86% and 86.18% higher than those in CK treatment,respectively.In Liaodan565,the leaf length,leaf width,leaf area,leaf dry weight and leaf fresh weight of maize seedlings in T4 treatment were 170.37%,176.18%,57.63%,35.00% and 31.95% higher than those in CK treatment,respectively.Under the condition of low temperature stress,the high nitrogen utilization type of maize and the lower nitrogen utilization type of maize had better growth and development.2.Under the condition of low temperature stress,the T2 treatment group(40% glycine +60% ammonium nitrogen)had a significant effect on promoting the physiological characteristics of the root system,and the effect was better in the high nitrogen utilization type.In Xianyu335,T2 treatment group was 104.61%,18.88%,26.80% and 24.76% higher than CK treatment,respectively.In Liaodan565,the root damage flow rate,root activity,total root absorption area,and root active absorption area were 6.54%,136.66%,16.85%,and 188.59%higher than those in CK treatment,respectively.Replacing inorganic nitrogen with glycine in two genotypes of maize can promote photosynthesis and various metabolic processes in leaves.In Xianyu335,T1 treatment group(20% glycine + 80% ammonium nitrogen)had higher fluorescence parameter values q L,q P and ΦPSⅡ than CK group by 57.33%,38.60% and 32.61%.In Liaodan565 T2 treatment group(40% glycine + 60 % ammonium nitrogen),the values of q L,q P and ΦPSⅡ were 56.55%,30.13% and 30.24% higher than those in CK group.3.T2 treatment group(40% glycine+60% ammonium nitrogen)and T4(80% glycine+20%ammonium nitrogen)treatment group can alleviate the damage caused by low temperature to maize,significantly affect the process of carbon and nitrogen metabolism in maize,and in The promotion effect was stronger in high nitrogen utilization type corn.The contents of ammonium nitrogen,total nitrogen,soluble sugar,alanine aminotransferase and total phosphorus in the roots of maize seedlings treated with Xianyu335 T2 were 551.46%,25.74%,21.39%,35.32%and 10.99% higher than those of CK.The contents of ammonium nitrogen,total nitrogen,soluble sugar,alanine aminotransferase and total phosphorus in the shoots were 281.43%,38.15%,31.45%,115.76% and 55.82% higher than those of CK.The contents of ammonium nitrogen,total nitrogen,soluble sugar,alanine aminotransferase and total phosphorus in the roots of maize seedlings treated with Liaodan565 T2 were 74.31%,37.41%,33.48%,103.60%and 18.66% higher than those of CK.The contents of ammonium nitrogen,total nitrogen,soluble sugar,alanine aminotransferase and total phosphorus in the shoots were 551.46%,46.20%,5.30%,154.21% and 44.23% higher than those of CK.The root aspartate aminotransferase,soluble protein and reducing sugar of Xianyu 335 T4 treatment group were563.05%,93.27% and 142.38% higher than CK.Aspartate aminotransferase,glutamine synthase and reducing sugar were 233.68%,346.34%,and 165.90% higher than CK.Liaodan565 T4 treatment group had higher aspartate aminotransferase,soluble protein,reducing sugar,total phosphorus and total potassium than CK by 1186.81%,112.87%,392.75%,52.23% and 52.43%.Liaodan565 T4 treatment group had higher aspartate aminotransferase,reducing sugar,total phosphorus and total potassium than CK by 563.57%,269.64%,62.96% and 44.61%.In the shoots of maize,NR and GS activities were significantly negatively correlated,GS and nitrate nitrogen content were significantly negatively correlated,and ammonium nitrogen content was significantly positively correlated.The contents of ammonium nitrogen and nitrate nitrogen were significantly negatively correlated.In maize roots,the activities of GS and GPT were significantly positively correlated,the activity of NR was significantly positively correlated with nitrate nitrogen content,and NR was negatively correlated with ammonium nitrogen content,GS and nitrate nitrogen content.There was a very significant positive correlation between dry weight and soluble protein content in maize shoots.There was a significant positive correlation between root dry weight and reducing sugar content,and a significant positive correlation between soluble protein and reducing sugar content.Therefore,adding part of glycine can promote carbon and nitrogen metabolism in maize,promote the accumulation of ammonium nitrogen,reduce the accumulation of nitrate nitrogen,increase the content of soluble sugar and soluble protein in maize,and improve the quality of maize.4.In the T2 treatment group(40%glycine+60% ammonium nitrogen),it can promote the content of total nitrogen and total phosphorus,and the promotion effect is stronger in high nitrogen utilization type corn.In contrast,T4(80% glycine+20% ammonium nitrogen)treatment group increased the contents of total phosphorus and total potassium in high nitrogen utilization type maize.The root total nitrogen and total phosphorus content of maize seedlings treated with Xianyu335 T2 were 25.74% and 10.99% higher than those of CK.The contents of total nitrogen and total phosphorus in the shoots were 38.15% and 55.82% higher than those of CK.The total nitrogen and total phosphorus contents in the roots of maize seedlings treated with Liaodan565 T2 were 37.41% and 18.66% higher than those of CK.The contents of total nitrogen and total phosphorus in the shoots were 46.20% and 44.23% higher than those of CK.The Liaodan565 T4 treatment group could increase the content of total phosphorus and total potassium in high nitrogen utilization type maize.The total phosphorus and total potassium of the roots were 52.23% and 52.43% higher than that of CK.The total phosphorus and total potassium in the shoots of Liaodan565 T4 treatment group were 62.96% and 44.61% higher than those of CK.Therefore,the replacement of inorganic nitrogen by glycine can promote the content of nitrogen,phosphorus and potassium in maize under low temperature stress.To sum up,the research conditions of this experiment showed that under the condition of low temperature stress,the T2 treatment group(40% glycine + 60% ammonium nitrogen)had a promoting effect on the root vigor,carbon and nitrogen metabolism and photosynthesis of maize seedlings,and it was beneficial to the growth and development of maize absorb a lot of nutrients.The T4(glycine 80% + ammonium nitrogen 20%)treatment group improved the crop quality on the shoot development and soluble protein accumulation of maize seedlings.Therefore,an appropriate amount of glycine to replace inorganic nitrogen can alleviate the damage caused by low temperature stress to maize in agricultural production,improve the morphological characteristics of maize seedlings,thereby promoting the metabolic process of nutrients in maize and providing a basis for the later stage of maize production.Different maize genotypes have different degrees of remission. |
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