氮形态对小白菜根系生长、根区pH及细胞壁组分的影响OA北大核心CSTPCD

[Objective]Nitrogen(N)is a critical factor in regulating the growth of vegetable crops.The purpose of this study was to explore how different N forms affect root growth and cell wall components in pakchoi,and to identify the relationship between root zone pH changes and PM H+-ATPase,so as to provide a theoretical basis for further research on nitrogen regulation of plant root growth and development.[Method]Pakchoi(Brassica campestris ssp.Chinensis L.)was used as the test material.Three N forms,including nitrate nitrogen(NO3-N),ammonium nitrogen(NH4+-N),and glycine nitrogen(Gly-N),were utilized in a hydroponic nutrient solution experiment.The intrinsic mechanisms by which inorganic and organic nitrogen regulate the pH in the root zone and the cell wall components on the root growth of pakchoi were explored,and the effects of nitrogen nutrition on root auxin(IAA)and plasma membrane(PM)H+-ATPase were investigated.The root scanning and physiological experiments were used to determine the root morphology indicators,including total root length,volume,surface area,and tip number;along with physiological indicators including medium pH,PM H+-ATPase activity,IAA content,the main components content of cell wall,pectin methylesterase(PME)and vasodilator(EXP)content,and finally the correlation between root morphology and various physiological indicators were analyzed.[Result]Both Gly-N and NO3-N treatments increased the medium pH,and even Gly-N showed a greater capacity for alkalization than the NO3-N treatment,while NH4+-N acidified the medium pH.Compared with NO3-N treatment,Gly-N treatment significantly decreased the dry matter content in shoots and roots,primary root length,total root length,surface area,tip number,root forks,number of internal,and external links of pakchoi by 40.23％,21.74％,55.15％,58.63％,53.12％,73.07％,65.39％,40.91％,and 73.94％,respectively,and increased the root cell wall extraction rate,pectin,cellulose,EXP content,PM H+-ATPase activity,root/shoot ratio,topological index,and fractal dimension by 22.00％,47.74％,25.30％,109.53％,15.42％,30.33％,11.43％,and 4.32％,respectively.Compared with NO3--N treatment,NH4+-N treatment significantly reduced the plant's shoot dry matter content,primary root length,root forks,number of internal and external links,root PME activity,and IAA content by 22.98％,34.30％,35.32％,26.22％,29.02％,36.38％,and 8.74％,respectively,while enhancing root PM H+-ATPase activity,cell wall extraction rate,pectin,and hemicellulose content by 14.60％,19.38％,22.98％,and 74.33％,respectively.The correlation analysis between root morphology indicators and physiological indicators revealed that total root surface area was highly significantly positively correlated with total root length,the total number of root tips and root forks(P＜0.01),and also positively with primary root length,and negatively correlated with root diameter,expansin,and topological index(P＜0.01),as well as with pectin,cellulose,and fractal dimension(P＜0.05).The root diameter showed a strongly significant positive correlation with expansin,cellulose,fractal dimension,and topological index(P＜0.01),while significantly positively correlated with pectin(P＜0.05).[Conclusion]Both Gly-N and NH4+-N treatments enhanced cell wall content of the root system,thereby inhibited the elongation and growth of pakchoi roots.Among them,Gly-N facilitated the accumulation of pectin and cellulose,and NH4+-N promoted the accumulation of hemicellulose.