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低磷胁迫下杉木根系对硝态氮的响应
Response of Chinese fir roots to nitrate addition under phosphorus starvation
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摘要: 以不同杉木半同胞家系幼苗为研究材料,采用水培控制试验,设计正常供磷和低磷胁迫处理15 d后,分别在2种供磷水平下进行0.5倍、1倍、1.5倍、2倍供氮处理培养15 d,测定正常供磷和低磷胁迫下杉木幼苗响应不同强度硝态氮添加的根系形态、根系分泌、保护酶活性、氮代谢相关酶活性和氮磷代谢相关基因表达的变化,研究杉木幼苗根系对正常供磷和低磷胁迫下杉木幼苗响应不同强度硝态氮添加的适应性机制。结果表明:10号杉木家系的根系形态响应最为敏感,低磷胁迫下的高强度硝态氮添加处理显著促进了其根系增生和侧根增多。硝态氮添加能够显著缓解10号家系由于缺磷胁迫导致的根系P含量减少,显著增加根系酸性磷酸酶和有机酸的分泌,且根系超氧化物歧化酶、过氧化氢酶和过氧化物酶活性及丙二醛含量显著降低。此外,硝态氮添加并不能有效缓解低磷带来的氮代谢活动的减弱,低磷胁迫下,10号家系根系NR活性和NiR活性显著降低,而硝态氮添加处理的根系NR和NiR活性依旧低于正常供磷处理。qPCR分析表明,正常供磷下硝态氮添加会诱导10号家系根系ClNRT1.1、ClNIR1和ClCPR2显著下调表达来降低氮吸收和代谢,而低磷胁迫下硝态氮添加会诱导ClNIR1和ClCPR2显著上调表达来增加对硝态氮还原能力,从而提高对高氮低磷环境的适应能力。Abstract: The coordinated utilization of nitrogen and phosphorus is the key to maintaining the best plant growth and achieving maximum yield.For a long time, the research on the phosphorus nutrition efficiency of Chinese fir mainly focused on the effect of single phosphorus deficiency but ignored the possible interaction between nitrogen and phosphorus. In this study, the changes in root morphology, root secretion, protective enzyme activity, nitrogen metabolism related enzyme activity, and nitrogen and phosphorus metabolism related gene expression of Chinese fir seedlings under normal phosphorus supply and low phosphorus stress were analyzed. It was found that the root morphological response of Chinese fir family 10 was the most sensitive, and the high intensity nitrate treatment under low phosphorus stress significantly promoted root proliferation and lateral root growth. The addition of nitrate nitrogen could significantly alleviate the decrease of phosphorus content in roots of family 10 due to phosphorus deficiency stress and significantly increase the secretion of acid phosphatase and organic acids in roots. the activities of superoxide dismutase, catalase and peroxidase, and the content of malondialdehyde in roots decreased significantly. In addition, nitrate nitrogen addition could not effectively alleviate the weakening of nitrogen metabolism activity caused by low phosphorus stress. Under low phosphorus stress, nitrate reductase(NR) activity and nitrite reductase(NiR) activity decreased significantly in family 10, while NR and NiR activities in roots of nitrate nitrogen treatment were still lower than those of normal phosphorus treatment. The results of quantitative PCR analysis showed that the addition of nitrate nitrogen under normal phosphorus supply could significantly down-regulate the expression of ClNRT1.1, ClNIR1 and ClCPR2 to reduce nitrogen uptake and metabolism, while under low phosphorus stress, nitrate nitrogen addition could significantly up-regulate the expression of ClNIR1 and ClCPR2 to increase the ability of nitrate nitrogen reduction, thus improving the ability to adapt to high nitrogen and low phosphorus environment.