镉胁迫对龙葵叶绿素荧光和光合生化特性的影响

Effects of cadmium stress on chlorophyll fluorescence and photosynthetic biochemical characteristics in leaves of Solanum nigrum

超积累植物是重金属污染土壤植物提取修复技术的核心问题,研究镉(Cd)胁迫对超积累植物龙葵光合生化特性的影响,为超积累植物Cd污染生理机制的阐释和Cd污染土壤的生物修复提供理论基础。通过室内水培试验,研究Cd胁迫对龙葵叶片SPAD值、叶绿素荧光参数和光合生化参数的影响,分析Cd胁迫下龙葵光合作用的主要限制因子。结果显示:1)Cd胁迫下龙葵叶片SPAD值、初始荧光(Fo)和PSII最大光化学效率(Fv/Fm)均显著小于对照(CK),但Cd胁迫对叶片光化学淬灭系数(qP)和非光化学淬灭系数(NPQ)没有显著影响;Cd胁迫下龙葵叶片最大净光合速率(Amax)与CK相比减小了24.9%,而光下暗呼吸速率(Rd)显著大于CK;Cd胁迫对表观量子效率(AQY)和光补偿点(LCP)没有显著影响。2)Cd胁迫下,龙葵叶片净光合速率(A)、CO2气孔导度(gsc)、胞间CO2浓度(Ci)、Rubisco酶最大羧化速率(Vcmax)和最大电子传递速率(Jmax)均不同程度小于CK,减小程度在4.6%~51.2%之间,而Rubico酶活性限制阶段与RuBP再生速率限制阶段的临界胞间CO2浓度(CiCJ)显著高于CK;Cd胁迫对光合作用的限制主要来源于非气孔限制(82.14%)。3)Cd胁迫下龙葵单株生物量、地上部分生物量和根系生物量与CK相比分别减小了46.8%、33.3%和49%,而且龙葵单株生物量与SPAD值、Amax、A、Vcmax、Jmax等光合参数呈显著相关。因此,Cd胁迫对龙葵光合作用有限制作用,而且该限制主要来源于非气孔原因。

Hyperaccumulator plants are the core of phytoremediation of Cadmium(Cd) contaminated soil. Studying the effects of Cd on the biochemistry of photosynthesis in leaves of hyperaccumulator plant(Solanum nigrum) can provide a theoretical basis for elucidating the physiological mecahnisum of hyperaccumulator plants under Cd toxicity and bioremediation of Cd contaminated soils. Solanum nigrum was cultured in a solution under Cd stress. The effect of Cd stress on the SPAD values, chlorophyll fluorescence parameters, and photosynthetic biochemical parameters in Solanum nigrum leaves were investigated and the main limitations to photosynthesis in Solanum nigrum leaves under Cd stress were assessed. The important findings are showed as follows: 1) SAPD values, minimal fluorescence(Fo), and PSII maximum efficiency(Fv/Fm) in leaves of Solanum nigrum under Cd stress are significantly lower than those in the control, respectively. Photochemical quenching(qP) and nonphotochemical quenching(NPQ) are not significantly affected by Cd stress. 2) Maximum net photosynthetic rate(Amax) in leaves of Solanum nigrum under Cd stress is 24.9% lower than that in the control, while the dark respiration rate(Rd) under Cd stress is higher than that in the control. Apparent quantum yield(AQY) and light compensation point(LCP) are not significantly affected by Cd stress. 3) Net photosynthetic rate(A), stomatal conductance of CO2(gsc), intercellular CO2 partial pressure(Ci), maximal Rubisco carboxylation rate(Vcmax), and the maximum electron transfer rate(Jmax) in leaves of Solanum nigrum under Cd stress are significantly lower than those in the control and the reduction ratios are between 4.6% and 51.2%. The transition between the Rubisco-and RuBP regeneration-limited states(CiCJ) under Cd stress are higher than that in the control. 4) The reduced photosynthesis observed under Cd stress is mainly due to non-stomatal conductance limitation(82.14%). 5) Dry weight, shoot biomass and root biomass of Solanum nigrum under Cd stress are 46.8%, 33.3%, and 49% lower than those in the control, respectively. The dry weight of Solanum nigrum was significantly correlated with SPAD, Amax, A, Vcmax, and Jmax. In conclusion, the photosynthesis of Solanum nigrum is reduced under Cd toxicity and the limitation is mainly due to the non-stomatal limitation.