盐胁迫对转AtNHX1基因杨树光合特性与叶绿体超微结构的影响

以欧美107杨(Populus×euramericana ‘Neva',Wt)和转拟南芥液泡膜Na~+/H~+逆向转运蛋白基因AtNHX1的欧美107杨新品系(Tr) 幼苗为材料,研究了高低度盐胁迫对两品系幼苗光合色素含量、光合参数和叶绿体超微结构的影响,以阐明转AtNHX1基因杨树的耐盐性与其光合作用及叶绿体结构之间的关系.结果表明:(1)盐处理后,两品系叶片叶绿素含量、类胡萝卜素含量、净光合速率、蒸腾速率和气孔导度均下降,且高盐度处理下降幅度更大;同等盐度处理下,Tr品系叶片叶绿素含量、净光合速率和气孔导度的下降幅度显著低于Wt品系,且在高盐度处理间差异更大;两品系杨树叶片P_n下降的原因在低盐处理时以气孔限制为主,而在高盐下则是气孔限制和非气孔限制共同作用的结果.(2)盐胁迫对T_r 品系叶片叶绿体超微结构的影响较轻,其在高盐下仍保持了较好的内部结构;盐胁迫Wt品系叶绿体则缩皱成球形,内部结构趋向简单,以至解体,脂质球显著增多.可见,盐胁迫导致杨树叶绿体结构破坏而引起叶绿体色素含量下降,最终降低其光合作用效率;同等盐度胁迫下,转AtNHX1基因品系叶片保持了较完整的叶绿体超微结构、更高的叶绿素含量,能维持较好的光合状态,从而表现出较高的耐盐能力.

Photosynthetic Characteristics and Chloroplast Ultrastructure of Transgenic Poplar under NaCl Stress

Our objective was to reveal the relationship between photosynthetic traits and salt tolerance of the AtNHX1 gene transformation into poplar.In order to investigate the effects of salt stress on photosynthetic pigment contents,photosynthetic parameters and chloroplast transgenic poplar (Tr) were subjected to low salt and high salt treatments.The results showed that,under the salt stress condition,chlorophyll (Chl) contents,Carotenoid (Car) contents,net photosynthetic rate (P_n),transpiration rate (T_r),and stomatal conductance (Gs) of the two strains declined,and all these parameters decreased gradually with the increasing of salt content.However,the decline of Chl,P_n,T_r and G_s was slighter for T_r than for Wt,and the discrepancy was increased with the increasing of salt content.The dynamic changes of Gs,intercellular CO_2 concentration (C_i) and stomatal limiting value (L_s) indicated that the decline of P_n was mainly caused by the stomatal limitation under low salt stress,and by both of stomatal and non-stomatal limitation under high salt stress.Under salt stress,the chloroplasts of Wt were shrunken and became round in shape,the internal structure became simplified or disappeared and the plastoglobuli increased significantly,while the chloroplasts of T_r under low salt stress were no different from the control,and the structure of chloroplasts under high salt were better than that of Wt.These indicated that salt stress wrecked the chloroplast structure and induced the decrease of chloroplast contents,moreover,so as to restrain the photosynthetic activity of poplar.The changes of chlorophyll contents,photosynthetic parameters,stomata characters and the ultrastructure of chloroplast correlated significantly to salt tolerance of poplar.Under the same salinity level,the transgenic poplar can maintain a relative integrated chloroplast,high chlorophyll contents and preferable net photosynthetic rate,so its salt tolerance were improved.