Ca(NO_3)_2和NaCl胁迫下耐盐砧木嫁接黄瓜光合特性及碳同化关键酶基因表达分析

Analysis of photosynthetic characteristics and key enzyme genes expression of carbon assimilation in cucumber by grafting onto salt-tolerant rootstock under iso-osmotic Ca(NO_3)_2 or NaCl stress

以白籽南瓜‘青砧1号’为砧木,黄瓜作接穗,黄瓜‘津优3号’自根嫁接株为对照,研究耐盐砧木嫁接对Ca(NO3)2和NaCl胁迫下黄瓜幼苗光合特性和CO2同化特征的影响。结果表明:Ca(NO3)2胁迫下黄瓜植株光合色素含量、净光合速率(Pn)、气孔导度(Gs)、水分利用率(WUE)、光系统Ⅱ实际光化学效率(ΦPSⅡ)、光化学猝灭系数(qP)、Rubisco活性和含量、碳同化关键酶基因表达水平均显著高于等渗的NaCl胁迫;Ca(NO3)2胁迫下植株的胞间CO2浓度(Ci)呈下降趋势,而NaCl胁迫下Ci呈上升趋势;Rubisco活性显著下降导致NaCl胁迫下黄瓜幼苗Pn显著下降。不同盐胁迫下,砧木嫁接株光合色素含量、Pn、Gs、Ci、WUE、ΦPSⅡ、Rubisco活性和含量均显著高于自根嫁接株,且可上调RbcL(Rubisco大亚基)、RCA(Rubisco活化酶)和PRK(5-磷酸核酮糖激酶)的基因表达,下调RbcS(Rubisco小亚基)的基因表达。因此认为,等渗Ca(NO3)2和NaCl胁迫下砧木嫁接株能维持较高的光系统Ⅱ活性和碳同化能力。

The effects of grafting on the photosynthesis and CO2 assimilation were studied with salt-tolerant pumpkin（Cucurbita maxima×Cucurbita moschata）＇Qingzhen 1＇as the rootstock and a cultivar cucumber＇Jinyou 3＇as the scion under iso-osmotic Ca（NO3）2 or NaCl stress.Results showed that the photosynthetic pigment content,net photosynthetic rate（Pn）,the stomatal conductance（Gs）,water use efficiency（WUE）,the actual photochemical efficiency of photosystemⅡ（ΦPSⅡ）,the photochemical quenching（qP）,the content and activity of Rubisco,the expression of key genes of carbon assimilation in leaves of both rootstock-grafted and self-grafted seedlings were higher under Ca（NO3）2 stress than those of under NaCl stress.Intercellular CO2 concentration（Ci）was decreased by the Ca（NO3）2 treatment,while was increased by the NaCl treatment.The decline of Pn in seedlings was due to the decreased Rubisco activity under NaCl stress.The photosynthetic pigment content,Pn,Gs,Ci,WUE,ΦPSⅡ,qP,Rubisco activity and content in rootstock-grafted seedlings were more higher than those of self-grafted seedlings under iso-osmotic Ca（NO3）2 or NaCl stress.And the genes of RbcL（Rubisco large subunit）,RCA（Rubisco activase）and PRK（5-phosphoribulokinase）were also up-regulated while RbcS（Rubisco small subunit）was down regulated by rootstock-grafted under salt stress.We concluded that grafting with salt-tolerant pumpkin could maintain higher activity of PSⅡand carbon assimilation capacity.