接种土壤微生物对铜胁迫下海州香薷生长及光合生理的影响

采用框栽试验方法,模拟Cu胁迫条件下,探讨接种土壤微生物对海州香薷(Elsholtzia splendens)生长和光合生理的影响。结果表明:(1)在Cu胁迫下,海州香薷株数、株高、基径、生物量、茎重比均显著低于对照;与Cu胁迫相比,接种土壤微生物能显著缓解Cu胁迫对海州香薷生长的抑制作用,使植株的株数、株高、生物量、茎重比显著提高。Cu胁迫下,接种土壤微生物均降低了植株体内不同器官Cu含量,茎和叶Cu的累积量显著减少,但对其它器官的Cu含量影响不显著。(2)秋季,各处理的海州香薷的净光合速率(Pn)日变化均呈"单峰"曲线,接种土壤微生物显著提高了Cu胁迫下海州香薷的日均Pn、日均蒸腾速率(Tr),而日均气孔导度(Gs)、日均胞间CO2浓度(Ci)显著降低。(3)Cu胁迫下,接种土壤微生物显著提高了植株的最大净光合速率(Pnmax)、光饱和点(LSP)、表观量子效率(AQY)、最大羧化速率(Vcmax)、最大电子传递速率(Jmax)、磷酸丙糖利用率(TPU),且使光补偿点(LCP)显著降低。表明接种土壤微生物通过提高光能利用率、利用弱光和碳同化能力来增强光合作用能力及有机物的积累,缓解Cu胁迫对海州香薷的毒害。因此,接种土壤微生物可促进Cu胁迫下海州香薷的生长,在重金属污染土壤的植物修复中具有较好的应用潜力。

Effects of soil microbe inoculation on the growth and photosynthetic physiology of Elsholtzia splendens under copper stress

Phytoremediation, an emerging cost effective and ecologically benign technology for the decontamination of soils, is the use of plants and their associated microbes for environmental cleanup. The efficiency of phytoremediation depends mostly on the establishment of robust plant-microbe interactions. Elsholtzia splendens is a Labiatae plant well known for its high copper tolerance, which is widely distributed on copper deposits as well as non-contaminated areas. It has been considered for the phytoremediation of copper polluted soils; however, little is known about the role of the soil microbe community in the roots of E. splendens in adapting the non-contaminated plants to copper stress. In order to evaluate the effects of inoculation with soil microbes on the copper tolerance of E. splendens, this experiment studied the effect of inoculation with soil microbes on the seedling dry weight, plant morphology, survival rate, copper content and leaf gas exchange parameters of E. splendens under copper stress using a mesocosm system. The experiment included four soil treatments: the addition of copper (copper stress); soil microbe inoculation; addition of copper and soil microbe inoculation; and no additional copper or soil microbe inoculation (control). The results were as follows: (1) The plant number, plant height, basal diameter, biomass, and stem weight ratio of E. splendens under copper stress were lower than in the control. Inoculation with soil microbes significantly increased the plant number, plant height, biomass, and stem weight ratio of E. splendens under copper stress, indicating an alleviation effect on the inhibition of copper on the growth of E. splendens. Compared with the control, the copper content of roots, stems, leaves, inflorescences and seeds were increased under copper stress. Under copper stress, soil microbe inoculation significantly decreased copper content in the stem and leaf organs of E. splendens, but did not markedly affect copper content in the other organs. (2) In autumn, the diurnal variation in net photosynthetic rate (P_n) in the leaves of E. splendens under all treatments took on a one-peak curve. Inoculation with soil microbes significantly increased the daily mean P_n and daily mean transpiration rate (T_r), and significantly decreased the daily mean stomatal conductance and daily mean intercellular CO₂ concentration (C_i) of E. splendens under copper stress. (3) Under copper stress, the maximum net photosynthetic rate (P_nmax), light saturation point (LSP), apparent quantum yield (AQY), maximum rate of carboxylation (V_cmax), maximum rate of electron transport (J_max) and the triose phosphate use rate (TPU) of E. splendens significantly decreased, while the light compensation point (LCP) significantly increased. Inoculation with soil microbes significantly increased the P_nmax, LSP, AQY, V_cmax, J_max and TPU, but decreased the LCP. In conclusion, inoculation with soil microbes can effectively alleviate the damage of copper stress to E. splendens by increasing the photosynthetic ability, enhancing the light energy utilization and carbon assimilation and promoting the accumulation of organic matter. Inoculation with soil microbes can increase the growth of plants under copper stress, which could have potential applications in the phytoremediation of soils contaminated with heavy metals.