铜胁迫对高丹草和紫花苜蓿生长和光合特性的影响

以高丹草（Sorghum×S.sudanes）和紫花苜蓿（Medicago sativa L.）为试验材料,通过水培试验,研究了不同浓度Cu处理对两种牧草生长及光合特性的影响。试验结果显示,随着Cu处理浓度增加,两种牧草叶、茎、根生物量逐渐下降,并在100μmol.L-1 Cu2＋处理后达到显著水平。Cu胁迫导致两种牧草气孔导度、RuBP羧化酶的最大羧化效率、最大电子传递速率调控的RuBP再生的潜在速率和磷酸丙糖利用中有机磷的释放速率、以及叶绿素质量分数降低,最终导致净光合速率降低。Cu胁迫下,两种牧草二氧化碳饱和点和二氧化碳饱和点净光合速率降低,而二氧化碳补偿点却升高。另外,Cu处理还降低了两种牧草的蒸腾速率和日间呼吸速率。且在光合、蒸腾和呼吸作用参数的变化幅度上高丹草要大于紫花苜蓿。这些结果表明Cu胁迫抑制了两种牧草的生长、光合作用、蒸腾作用和呼吸作用,而且对高丹草的抑制作用要强于紫花苜蓿;Cu胁迫下光合作用的下降不仅与气孔导度的下降相关,而且与光反应和暗反应的受阻有关。这些研究结果可为筛选和培育耐Cu和富集Cu的牧草品种和用牧草修复铜污染水体及土壤提供依据。

Effect of copper stress on growth and photosynthesis in Sorghum×S.sudanes and Medicago sativa L.

A hydroponic experiment was carried out to investigate the effect of different Cu levels on growth and leaf photosynthesis in Sorghum×S.sudanes and Medicago sativa L..Our results showed that with an increase in Cu concentration in solution culture,leaf,stem and root biomasses of the two grass species decreased gradually,and were up to a significant extent at the 100 μmol·L-1 Cu level.Cu stress resulted in decreases in stomatal conductance,maximum rate of carboxylation,the potential rate of RuBP regeneration mediated by maximum electron transport rate,the rate of phosphate release in triose phosphate utilization and chlorophyll content,which led to a decrease in the net photosynthetic rate ultimately.CO2 saturation point and CO2 saturated net photosynthetic rate in two grass species declined,and CO2 compensation point rose under Cu stress.In addition,Cu stress also decreased transpiration rate and daytime respiration rate.The stronger magnitude in variations of photosynthesis,transpiration and respiration parameters in Sorghum×S.sudanes than Medicago sativa L.was observed.The results indicated that Cu stress inhibited growth,photosynthesis,transpiration and respiration in two grass species,and Cu tolerance of Medicago sativa L.was stronger than that of Sorghum×S.sudanes.A decrease in photosynthesis was related to not only a decrease in stomatal conductance,but also inhibition of light reaction and dark reaction.The results of this experiment could provide lines of evidence for selecting and cultivating Cu tolerant and accumulator species as well as using grasses to remediate Cu contaminated water and soil.