【摘要】 为了探讨干旱胁迫对吉首蒲儿根光合机构的影响,通过大棚盆栽实验于7月测量了阴生环境中吉首蒲儿根的叶片相对含水量(RWC)、净光合速率(Pn)等光合作用气体交换参数及初始荧光(F0)等叶绿素荧光参数在土壤自然干旱过程中的变化。结果显示:(1)随着干旱处理时间的延长,吉首蒲儿根叶片相对含水量持续下降;于干旱处理第12天时,叶片相对含水量低于15%,且吉首蒲儿根植株已经死亡。(2)自然干旱处理下,吉首蒲儿根叶片Pn、气孔导度(Gs)、蒸腾速率(Tr)大幅降低,胞间CO2浓度(Ci)增加或与对照接近;非气孔因素是导致其Pn下降的主要原因。(3)停止灌水第9~12天时,吉首蒲儿根叶片PSⅡ的最大光化学效率(Fv/Fm)、PSⅡ实际光量子效率[Y(Ⅱ)]显著降低,PSⅡ非调节性能量耗散[Y(NO)]显著增加,PSⅡ已损伤严重,叶片吸收的光能逐渐向非光化学途径分配增加。研究表明,在夏秋高温季节,吉首蒲儿根对土壤干旱较为敏感,其PSⅡ受到了一定的伤害,光能分配发生改变,严重影响其光合作用和生长发育,这可能是其分布受到限制的重要原因。更多还原

【Abstract】 Sinosenecio jishouensis D.G.Zhang,Y.Liu & Q.E.as a new species belongings to Asteraceae,is considered to be a severely endanger species,whose natural populations were only discovered in Dehang canyon in Hunan Province,so far,our previous studies had indicated that low light intensity and high relative humidity are not the restricting factors to their distribution.Here,we further investigated impacts of drought stress on photosynthetic apparatus including the leaf relative water content(RWC),photosynthesis parameters and chlorophyll fluorescence parameters by using the plants of S.jishouensis which lives in shade.Results showed that:(1)RWC of S.jishouensis decreased continuously with the drought stress proceeding.When no watering sustained for 12 days,the RWC was less than 15% and plants could not survive.(2)Net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)had decreased dramatically,while intercellular CO2concentration(Ci)had increased or no significantly change under drought.The results suggested the main reason for Pndecreasing was non-stomatal restriction.(3)When no watering sustained for 9~12days,the value of the maximum efficiency of PSⅡ(Fv/Fm),effective quantum yield of PSⅡphotochemistry[Y(Ⅱ)]had decreased significantly and quantum yield of nonregulated energydissipation in PSⅡ[Y(NO)]had increased obviously.These mean the PSⅡ were serious damaged and the non-photochemical quenching increased significantly.Conclusively,these results proved that S.jishouensis is sensitive to drought stress,which is probably the key cause for its distributing limit.更多还原