毛乌素沙地2种蒿属植物光合作用特征

摘要

In order to study the photosynthetic adaptation and acclimation to Mu Us sandy land in Artemisia ordosica and A.sphaerocephala,we measured the diurnal dynamics of gas exchange and chlorophyll (Chl) fluorescence parameters of these two species by using LI-6400 portable gas exchange system and PAM-2100 portable pulse-amplitude modulated chlorophyll fluorometer.A midday depression of net photosynthesis (Pn) was observed in both these two Artemisia species.Pn declination in A.ordosica was controlled by non-stomatal factors while the declination in A.sphaerocephala was controlled by stomatal factors base on the tendency of changes in Pn,stomatal conductance (Gs),intercellular CO2 concentration (Ci),and stomatal limitation (Ls).The values of maximum photochemical efficiency (Fv/Fm) in these two Artemisia species typically decreased during the midday hours,indicating in particular the phenomenon of photoinhibition.The midday depression of effective photochemical efficiency (ΦⅡ) along with the increase of regulated non-photochemical quenching of excitation energy (ΦN,o) indicates that regulated (ΦN,P,Q) thermal energy dissipation may be one of the photoprotection mechanisms in these two Artemisia species.Therefore,the photosynthesis adaptation mechanisms of Artemisia species to midday high irradiance stress vary among species.%用LI-6400光合仪和PAM-2100荧光仪测定了油蒿(Artemisia ordosica)和籽蒿(A.sphaerocephala)的气体交换及叶绿素荧光参数日变化规律,探讨了2种蒿属植物光合作用对沙地强光环境的适应机制.结果表明:2种蒿属植物净光合速率(Pn)均出现“午休”现象,根据Pn、气孔导度(Gs)、胞间CO2摩尔分数(Ci)、气孔限制值(Ls)的变化方向,推测油蒿叶片午间光合下调主要是由非气孔因素引起的,籽蒿则主要是由气孔因素引起的;2种蒿属植物午间最大光化学效率(Fv/Fm)均显著降低,说明2种蒿属植物可能受到光抑制;随着午间实际光化学效率(ΦⅡ)的下降,2种蒿属植物调节性能量耗散量子产量(ΦN,P,o和ΦN.O)均上升,暗示调节性热耗散可能是其光保护途径之一.从而说明蒿属植物光合作用对午间环境的适应机制存在种间差异.