低温胁迫下外源硝态氮对黄瓜生长和氮吸收的影响OA

[Objective]The effects of exogenous nitrate nitrogen(NO3--N)with different concentrations on growth and nitrogen absorption and utilization of cucumber seedlings were investigated under different low temperature stress to provide a reference for scientific nitrogen application in cucumber cultivation under abiotic stress.[Method]The seedlings at four leaves with one bud stage of Xintai Mici cucumber variety cultured by a hydroponics were used as the tested materials.Four exogenous NO3--N concentration treatments of N0(0 mmol/L),N6(6 mmol/L),N12(12 mmol/L)and N24(24 mmol/L)were designed.The effects of 4 exogenous NO3--N concentrations on dry seedling weight,NO3--N content,plasma membrane H+-ATPase activity,expression level of related genes,nitrogen accumulation,nitrogen utilization efficiency,nitrogen physiological efficiency and nitrogen absorption rate of cucumber seedlings were determined under low temperature stress for 4 d and 12 d.[Result]The dry seedling weight of N6 treatment under low temperature stress for 4 d reached the maximum value and increased by 57.81%compared with N0 treatment.The roots,stems,leaves and dry seedling weight of N24 treatment under low temperature stress for 12 d reached the maximum value and increased by 218.73%,68.16%,82.81%and 95.59%compared with N0 treatment,respectively.The N utilization efficiency of cucumber seedlings of N6 treatment under low temperature stress for 4 d and 12 d was the highest.The N physiological efficiency of cucumber seedlings of N24 treatment under low temperature stress for 4 d and 12 d was the lowest.The NO3--N content in roots,N content,N accumulation and N absorption rate of cucumber seedlings of N24 treatment under low temperature stress for 4 d and 12 d all were the highest.The expression of NRT1 gene family of four treatments was N24＞N6＞N12＞N0,and the expression of NRT1.5,NRT1.8 and NRT1.10 was higher in roots of cucumber seedlings.The root plasma membrane H+-ATPase activity of N24 treatment was the highest.The expression of CsHA2 gene in CsHA gene family was relatively higher in roots of cucumber seedlings.The CsHA2 gene expression of N24 treatment was the highest,and the NO3--N content in roots,N utilization efficiency,N absorption rate,N content,N accumulation,root plasma membrane H+-ATPase activity and expression of CsHA2 gene and NRT1 gene family of N24 treatment all increased with prolongation of low temperature stress time.There were significant positive and very significant positive correlations between indexes of dry seedling weight,NO3--N content,N content,N accumulation,N absorption rate and H+-ATPase activity.The N physiological efficiency was negatively related to other indexes very significantly.The exogenous NO3--N concentration was positively related to other indexes significantly or very significantly except for N utilization efficiency and N physiological efficiency.[Conclusion]Under short-term low-temperature stress,the 6 mmol/L of exogenous NO3--N treatment can improve growth and N utilization efficiency of cucumber seedlings under short-term low temperature stress.With extension of low temperature stress,the 24 mmol/L of exogenous NO3--N treatment is more beneficial to maintain growth of cucumber seedlings and promote N absorption and accumulation,but is not beneficial to N utilization efficiency.