镉处理后两种景天的光合相关参数变化

超积累植物是一种绿色、经济、环保的土壤重金属污染修复材料.本研究以超积累型(hyperaccumulating ecotype,HE)东南景天(Sedum plumbizincicola)和非积累型(non-hyperaccumulating ecotype,NHE)东南景天为试验材料,在水培条件下,测定镉处理不同时间两种东南景天叶片中叶绿素含量、光合参数及叶绿素荧光参数的变化,分析镉胁迫对两种东南景天光合能力的影响.结果表明,在胁迫7d时,HE的叶绿素a(Chla)、叶绿素b(Chlb)较未胁迫时分别显著(P＜0.5)下降了46.91％和43.09％,而NHE则分别显著下降了50.9％和49.98％;在镉胁迫过程中,HE的Pn下降幅度小于NHE,HE的Pn在胁迫7d时较对照显著下降了31.97％,NHE显著下降了50.69％;HE的Tr在胁迫4d时下降了50.58％,然后呈上升趋势,而NHE则在胁迫1d时就下降了60.47％,然后上升;随着镉胁迫时间延长,HE初始荧光强度(F0)先升后降,NHE的F0胁迫前4 d一直上升;HE最大荧光强度(Fm)始终大于NHE;HE实际光化学效率(ΦPSⅡ)、光化学猝灭系数(qP)、表观光合电子传递速率(ETR)均先降后升,NHE的ΦPSⅡ和ETR下降后趋于稳定;HE的非光化学淬灭系数(NPQ)一直处于上升趋势,NHE的NPQ和qP一直趋于稳定状态.由此认为,两种东南景天对于镉胁迫的响应不同,本研究进一步完善了两种景天应对镉胁迫时的生理响应,这为超积累型东南景天用于镉污染土壤的修复提供更多依据.

Variation in photosynthesis related parameters in two kinds of Sedum after cadmium treatment

Hyperaccumulator plants are recognized as promising phytoremediation candidates owing to their ability to accumulate substantial heavy metal ions without obvious signs of poisoning.Two ecotypes of Sedum alfredii (hyperaccumulating,HE and non-hyperaccumulating,NHE) were employed for hydroponic experi ments with a modified culture solution.The chlorophyll content,photosynthetic parameters,and chlorophyll fluorescence characteristics were analysed.The results indicated that the chlorophyll a (Chla) and chlorophyll b (Chlb) content of the HE plants significantly decreased (P＜0.05) by 46.91％ and 43.09％,respectively,compared with non-Cd treated samples after stress for 7 days,whereas the Chla and Chlb contents of NHE were significantly decreased by 50.9％ and 49.98％,respectively.Under the stress,the decrease in net photosynthetic rate (Pn) in HE was less than that in NHE.The Pn of HE was 31.97％ less than that of the control and 50.69％ less in NHE;both changes were statistically significant.The transpiration rate (Tr) of HE decreased by 50.58％ after stress for 4 days and then increased,whereas the Tr of NHE decreased by 60.47％ after stress for 1 day and then increased.The initial fluorescence (F0) of HE increased promptly and then decreased,whereas the F0 of NHE gradually increased during stress for 4 days.The maximum fluorescence (Fm) in HE was always higher than NHE.The actual photochemical efficiency (ΦPSⅡ),photochemical quenching coefficient (qP),and apparent photosynthetic electron transport rate (ETR) of HE firstly decreased and then increased,whereas the ΦPSⅡ and ETR of NHE were stable after a decrease.The non-photochemical quenching coefficient (NPQ) of HE gradually increased,whereas NPQ and qP tended to be stable.Thus,the response of the two ecotypes of Sedum to cadmium treatment was completely different.This study also investigated the physiological responses of the two S.alfredii ecotypes to cadmium stress,which would provide further evidence for the HE S.alfredii restoration of soil cadmium pollution.