中文摘要：

用PAM-2100叶绿素荧光仪测定了沙地与黄土丘陵区生物结皮层双色真藓（Bryum dichotomum）、真藓（Bryum argenteum）、土生对齿藓（Didymodon vinealis）、小扭口藓（Barbula indica）和小石藓（Weissia cont-roversa）的叶绿素荧光参数日变化,结果表明：（1）5种藓类植物的初始荧光（F0）、最大荧光（Fm）、ΦPSⅡ最大光化学效率（Fv/Fm）、ΦPSⅡ的有效量子产量（Yeild）及叶绿素荧光的光化学淬灭系数（qP）值的变化都呈现先下降后上升的趋势,而非光化学淬灭系数qN值则相反;（2）随着光照强度的变化,土生对齿藓和真藓的最大荧光、ΦPSⅡ最大光化学效率、ΦPSⅡ的有效量子产量的变化幅度明显小于其他3种藓类,其中土生对齿藓的自我保护热耗散能力又明显强于其他物种;（3）小扭口藓和双色真藓的ΦPSⅡ最大光化学效率和ΦPSⅡ的有效量子产量值的降低幅度明显大于其他物种,而小扭口藓的光化学淬灭系数的降低幅度显著高于双色真藓和其他物种;（4）小石藓对光照的敏感程度低于小扭口藓,但是在一天之中其热耗散能力又显著低于其他物种.

英文摘要：

Diurnal change of chlorophyll parameters of 5 mosses were measured by using Pulse-Amplitude-Modulation,PAM-2100,which contains Bryum dichotomum,Bryum argenteum,Didymodon vinealis,Barbula indica and Weissia controversa distributed in Sandland and loess hilly region.The conclusions as followed：（1）The value of F0,Fm,Fv/Fm,Yeild and qP of mosses all showed descended and then ascended;（2） The changes of value of Fm,Fv/Fm and Yield of Bryum argenteum and Didymodon vinealis are obviously less than the others.Among of them,heat dissem ability of Didymodon vinealis is obviously stronger than the other species;（3） The descended value of Fv/Fm and Yield of Barbula indica and Bryum dichotomum are obviously more than others.While the descended value of qP on Barbula indica is obviously more than other species;（4）The light sensitive of Weissia controversa is less than Barbula indica,but the heat dissem is less than the other species during a day.The research provided importance physiology evidence for the nature distribute reason of different species and the formation mechanism of soil crust.