镉胁迫对豨莶生长及光合作用相关参数的影响

为进一步揭示超积累植物豨莶(Sigesbeckia orientalis L.)对镉(Cd)的耐受机制,本文通过土壤盆栽试验,研究了豨莶在Cd胁迫下生长及光合作用相关参数的变化规律。结果表明,当Cd浓度为10 mg·kg-1时,豨莶生长、光合色素与对照相比无显著性差异(P0.05),表明豨莶在低浓度Cd处理下具有较强的生长适应性。高浓度Cd胁迫下豨莶能维持较高的叶绿素a/叶绿素b比值,有助于豨莶对Cd的耐受。Cd胁迫使叶片净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和气孔限制值(Ls)逐渐降低,但胞间二氧化碳浓度(Ci)随着Cd浓度的升高而逐渐增大,表明豨莶光合速率的下降是由非气孔限制因素引起的。植株叶片最大光化学量子产率(Fv/Fm)、电子传递的量子产率(ΦPSⅡ)、表观光合电子传递速率(ETR)和光化学淬灭系数(q P)随Cd浓度的升高而逐渐降低,而非光化学淬灭系数(NPQ)则呈现先升高后降低的趋势,表明豨莶光合机构对Cd胁迫有一定的耐受能力。上述结果表明,豨莶叶绿素a/叶绿素b、Fv/Fm比值以及NPQ数值的变化与豨莶对Cd的光合适应性有关,在Cd耐受中有一定的作用。

Effects of cadmium stress on growth and photosynthetic parameters of Sigesbeckia orientalis L.

The aim of this study is to examine the change of growth and photosynthetic parameters of Sigesbeckia orientalis L. under cadmi-um(Cd)stress through a soil pot experiment, and to analyze their roles in Cd tolerance. The results showed that the root length, plant length, biomass and chlorophyll contents have no significant change compared with the control at 10 mg·kg-1 Cd treatment, indicating a relatively high growth adaptation of S. orientalis. The ratio of chlorophyll a to chlorophyll b under Cd stress was not significantly different from that of the control, which contributed to the Cd tolerance of S. orientalis. With increasing Cd concentration, net photosynthesis rate(Pn), stomatal conductance(Gs), and transpiration rate(Tr)decreased, while intercellular CO2 concentration(Ci)increased 2.28%~7.83%, which sug-gested that the dominant reason for the decline of Pn was non-stomatal limitation. Moreover, the maximal photochemical of photosystemⅡ(Fv/Fm), ratio of photochemical quantum yield of photochemical of photosystemⅡ(ΦPSⅡ), rate of electronic transmission of photosynthe-sis(ETR)and photochemical quenching coefficient(qP)gradually decreased, but non-photochemical quenching coefficient(NPQ)in-creased compared with the control. Taken together, the results uncover that the change of Chl a/Chl b, Fv/Fm and NPQ might play important roles in photosynthetic adaptive ability and Cd tolerance.