骆驼刺叶形态和荧光参数对光照的响应

Responses of leaf morphology and fluorescence parameters of Alhagi sparsifolia in different light environments

以塔克拉玛干沙漠南缘策勒绿洲-荒漠过渡带防护林下的骆驼刺和自然光照下的骆驼刺为研究对象,研究不同光照环境下骆驼刺地上生物量分配、叶片形态特征、叶绿素含量以及叶绿素荧光动力学参数的变化。结果表明:与自然光照下相比,①林下骆驼刺比叶面积较高,而叶片厚度和叶干物质含量较低,地上生物量分配存在显著差异,叶比重升高,同化枝比重降低;②林下骆驼刺的叶绿素a(Chl a)和叶绿素b(Chl b)含量明显较高,叶绿素a/b(Chl a/b)降低;③林下骆驼刺的最大荧光(Fm)、光系统Ⅱ(PSⅡ)潜在活性(Fv/Fo)、PSⅡ最大光化学效率(Fv/Fm)和单位面积反应中心的数量(RC/CSo)均显著升高,而单位反应中心吸收的能量(ABS/RC)、捕获的能量(TRo/RC)和耗散的能量(DIo/RC)低于对照条件下的骆驼刺。在林荫环境下,除了通过改变骆驼刺地上生物量的分配、叶形态特征来响应光照环境的变化外,叶绿素a/b(Chl a/b)比值的变化和PSⅡ光化学效率的提高,反应中心数量的增加也是骆驼刺适应荫蔽环境的重要生理途径。形态和生理上更好的光资源利用和响应特点是骆驼刺适应弱光环境的主要方式。

Characterizing the ecophysiological traits of the desert species Alhagi sparsifolia in response to different growth light environments through aboveground biomass allocation,leaf morphology,leaf chlorophyll content,and leaf chlorophyll rapid fluorescence kinetics was conducted at the southern rim of the Taklimakan Desert. A. sparsifolia plants grown in forest protection systems (understory plants) and those under full sunlight conditions (sunlight plants) were sampled to make comparisons. Our results indicated that compared to sunlight plants,understory plants showed relatively higher specific leaf area (SLA),lower leaf thickness,lower dry matter content,an increasing leaf mass ratio (LMR),and a decreasing assimilation branch mass ratio (ABMR). Understory plants also had profoundly high chlorophyll a (Chl a) and b (Chl b) contents and a reduced ratio of Chl a to Chl b (Chl a/b). In addition,leaf fluorescence kinetics traits,such as the maximum relative fluorescence (Fm),the potential activity of photosystem Ⅱ (PSⅡ,Fv/Fo),the maximum photochemical efficiency of PSⅡ (Fv/Fm) and amounts of active reaction centers per cross-section (RC/CSo) were substantially enhanced in understory plants while,declines in absorption flux per reaction center (ABS/RC),the maximal trapping flux per reaction center (TRo/RC),and flux of dissipated excitation energy per reaction center (DIo/RC) were observed. Besides the morphological adaptations of A. sparsifolia to a shading environment,as observed in the biomass allocation and SLA,shading acclimation through positive changes of physiological traits,such as lower (Chl a/b) and the improvement of Fv/Fm and RC/CSo was crucial to improving light use efficiency. Concurrently adjusting morphological and physiological traits to effectively utilize light resources was the main growth strategy for the desert plant A. sparsifolia grown in a low light environment.