不同品种苹果幼树对氮磷亏缺的生理响应

Physiological response of young trees of different apple cultivars to nitrogen and phosphorus deficiency

【目的】探究不同苹果品种对低磷、低氮及低磷低氮胁迫的生理响应,为养分高效利用苹果品种的选育提供理论基础。【方法】采用沙培盆栽试验方法,供试材料为三年生‘嘎拉’/M9T337、‘富士’/M9T337和‘蜜脆’/M9T337矮化自根砧苹果(M9T337为矮化砧木)。以改良1/2Hoagland营养液为基础,设置正常、低氮两个氮水平(NO_(3)^(-)15、1.5 mmol/L)和正常、低磷两个磷水平(H_(2)PO_(4)^(–)1.0、0.1 mmol/L),共配置适氮适磷、适氮低磷、低氮适磷和低氮低磷4个处理。测定了苹果树体生长、叶片光合作用和叶绿素荧光参数,分析了苹果叶片氮、磷代谢相关酶活性,树体氮、磷累积量。【结果】与适氮适磷相比,适氮低磷和低氮适磷条件下,‘嘎拉’和‘蜜脆’的植株总干物质量均显著降低,‘富士’的植株总干物质量有显著增加;适氮低磷条件下的‘嘎拉’、‘富士’和‘蜜脆’叶绿素b含量均显著降低,F呈升高趋势,但‘嘎拉’和‘富士’的F/F显著升高且P未有显著变化,而‘蜜脆’P则降低了65.72%;低氮适磷条件下,‘嘎拉’、‘富士’与‘蜜脆’叶片F均呈升高趋势,F/F降低,降幅分别为7.45%、2.47%和8.59%。与适氮适磷相比,适氮低磷、低氮适磷和低氮低磷条件下,‘富士’的类胡萝卜素含量升高,而‘嘎拉’和‘蜜脆’则均呈下降趋势;‘嘎拉’、‘富士’和‘蜜脆’的叶片亚硝酸还原酶(NiR)活性均显著降低;‘嘎拉’叶片硝酸还原酶(NR)活性显著降低,植株氮累积量降幅最大,而‘富士’叶片NR活性受影响最小,植株氮累积量降幅最小;在适氮低磷条件下,‘嘎拉’、‘富士’和‘蜜脆’的叶片酸性磷酸酶(ACP)活性显著增加,‘富士’的增幅最大,低氮适磷和低氮低磷条件下三者ACP活性与适氮低磷相比均大幅降低;适氮低磷和低氮适磷条件下‘嘎拉’和‘蜜脆’的植株总磷累积量均显著降低。依据雷达图定量综合评价函数值Y可知,3个品种对低磷、低氮以及低磷低氮的适应性排序均为‘富士’>‘蜜脆’>‘嘎拉’。【结论】低磷胁迫、低氮胁迫及低磷低氮胁迫下,抗性品种‘富士’的叶片类胡萝卜素含量显著升高,保护光系统以维持正常光合作用,显著提高叶片酸性磷酸酶活性和硝酸还原酶活性,提高植株对磷和氮的利用率,保证植株生长。与‘富士’相比,‘蜜脆’叶片光合作用受到显著抑制,‘嘎拉’叶片NO_(3)^(-)还原过程明显减弱,植株氮累积量显著降低,二者植株生长均受到显著抑制,抗性较弱。

【Objectives】We studied the physiological response of different apple cultivars to P and N deficiencies,to guide the selection and breeding of nutrient efficient apple cultivars.【Methods】A pot experiment was conducted,using three-year-old‘Regal Gala’/M9T337,‘Fuji’/M9T337 and‘Honeycrisp’/M9T337 as test materials(M9T337 is dwarf rootstock).In the 1/2 Hoagland nutrient solution,normal and low N levels(NO_(3)^(–)15 and 1.5 mmol/L),and normal and low P levels(H_(2)PO_(4)^(–)1.0 and 0.1 mmol/L)were prepared to make four treatments,as normal N and P(NNNP),normal N and low P(NNLP),low N and normal P(LNNP),and low N and P(LNLP).The apple seedlings were subjected to the treatments for total of 120 days.The growth,photosynthesis and chlorophyll fluorescence parameters,the activities of N and P metabolism enzymes,as well as the accumulation of N and P were investigated.【Results】Compared to NNNP treatment,the total plant dry weight of‘Regal Gala’and‘Honeycrisp’reduced significantly,but‘Fuji’increased significantly in NNLP and LNNP treatments;NNLP reduced the chlorophyll b contents of‘Regal Gala’,‘Fuji’and‘Honeycrisp’,increased F_(v)/F_(m) of‘Regal Gala’and‘Fuji’significantly;NNLP decreased the P_(n) of‘Honeycrisp’by 65.72%;LNNP did not increase the F_(0) of‘Regal Gala’,‘Fuji’and‘Honeycrisp’significantly,and decreased the F_(v)/F_(0) of‘Regal Gala’,‘Fuji’and‘Honeycrisp’by 7.45%,2.47%and 8.59%,respectively.The carotenoid content of‘Fuji’was significantly lower under NNNP than under other treatments,while the carotenoid content of‘Regal Gala’or‘Honeycrisp’did not show significant change among the four treatments.Compared to NNNP,the NNLP,LNNP and LNLP treatments significantly reduced the leaf nitrite reductase(NiR)activity in‘Regal Gala’,‘Fuji’and‘Honeycrisp’;decreased the leaf nitrate reductase(NR)activity and plant N accumulation of‘Regal Gala’,but did not affect those of‘Fuji’.NNLP increased the leaf acid phosphatase(ACP)activity of‘Regal Gala’,‘Fuji’and‘Honeycrisp’,with the largest increase in‘Fuji’;LNNP and LNLP markedly decreased the leaf ACP activity of‘Regal Gala’,‘Fuji’and‘Honeycrisp’compared with NNLP.Based on the quantitative evaluation function values Y of the radar plots,the adaptability to low P,low N,and low N and P were ranked in the order of‘Fuji’>‘Honeycrisp’>‘Regal Gala’.【Conclusions】Under P,N and N and P deficiency stress,‘Fuji’has significantly higher leaf carotene content for maintaining normal photosynthesis,has significantly increased leaf ACP and NR activities to improve the uptake and accumulation of P and N to ensure the normal plant growth.While the other two cultivars exhibite less adaptability for the N,P,and N and P deficiencies,of which the leaf photosynthesis of‘Honeycrisp’is significantly inhibited,and the leaf NO_(3)^(–) reduction process in‘Gala’is significantly weaker,and their growth are both significantly inhibited.