离体饲养下HgCl_(2)影响水稻叶片光合特性及其生理机制研究

Effects of HgCl_(2) on photosynthetic characteristics and its physiological mecha-nism of rice leaves in vitro feeding

HgCl_(2)作为水通道蛋白专用抑制剂,可有效量化水通道蛋白和叶片结构对光合作用的贡献度,对认识提高作物光合作用的潜在途径具有重要意义。然而,有关抑制叶片水通道蛋白的HgCl_(2)浓度和时长尚不清楚。本研究以水稻品种Y两优900和徽两优898为试材,采用HgCl_(2)溶液离体饲养水稻叶片(叶龄余数为2),设置不同处理浓度:0、100、200、300和500μmol L^(-1)及不同处理时间:0、0.5、1、1.5、2、2.5、3、3.5、4和4.5 h。研究表明,不同浓度和处理时长对叶片相对含水量无显著影响(P>0.05)。随着浓度增加,叶片SPAD值、净光合速率和气孔导度呈明显降低趋势。与对照相比,浓度为100μmol L^(-1)时长2 h时的净光合速率降低至最低值(62.33%),随着处理时间延长,光合速率趋于稳定。当浓度>100μmol L^(-1)时,随着处理时长增加,净光合速率持续降低,且超氧化物歧化酶(SOD)和过氧化物酶(POD)活性及丙二醛(MDA)含量均显著增加(P<0.05),表明浓度>100μmol L^(-1),处理时间较长时,HgCl_(2)溶液能对叶片活体造成伤害。与活体测量相比,叶片净光合速率离体稳定数值降幅约15%~20%,因而离体叶片测量光合速率乘以1.25~1.33的矫正系数,可能较准确反映水稻叶片活体原位测定的光合指标。此外,100μmol L^(-1) HgCl_(2)显著降低水稻叶片水通道蛋白基因表达。这些结果表明,HgCl_(2)高效安全抑制水稻水通道蛋白的最佳组合为100μmol L^(-1)下饲养2 h。

As a special inhibitor of aquaporin,HgCl_(2) can effectively quantify the contribution of aquaporin and leaf structure to photosynthesis,which is of great significance for understanding the potential ways to improve crop photosynthesis.However,the concentration and duration of HgCl_(2) inhibiting aquaporin in leaves are still unclear.In this study,rice varieties Y liangyou 900 and Huiliangyou 898 were used as materials to feed rice leaves in vitro with HgCl_(2) solution(the remainder of leaf age was 2),and different treatment concentrations(0,100,200,300,and 500μmol L^(-1)),and different treatment times(0,0.5,1,1.5,2,2.5,3,3.5,4,and 4.5 h)were set.The results showed that different concentrations and treatment times had no significant effect on the relative water content of leaves(P>0.05).With the increase of concentration,the SPAD value,net photosynthetic rate,and stomatal con-ductance of leaves decreased obviously.Compared with the control,the net photosynthetic rate decreased to the lowest value(62.33%)when the concentration was 100μmol L-1 for 2 h,and the net photosynthetic rate tended to be stable with the extension of treatment time.When the concentration was less than 100μmol L^(-1),the net photosynthetic rate decreased continuously with the increase of treatment time,and the activities of superoxide dismutase(SOD),peroxidase(POD),and malondialdehyde content increased significantly(P<0.05),indicating that HgCl_(2) solution could damage the living leaves when the concentration was less than 100μmol L^(-1) and the treatment time was longer.Compared with in vivo measurement,the steady value of net photosynthetic rate of leaves in vitro decreased by about 15%-20%,so the correction coefficient of measured net photosynthetic rate of leaves in vitro multiplied by 1.25-1.33 might accurately reflect the photosynthetic index of rice leaves in vivo measurement.In addition,100μmol L^(-1) HgCl_(2) significantly reduced the expression of aquaporin gene in rice leaves.Therefore,the optimal combination of HgCl_(2) to effectively and safely inhibit aquaporin in rice was 100μmol L^(-1) for 2 h.