Biological Sciences Center, Desert Research Institute, University of Nevada, P.O. Box 60220, Reno, Nevada 89506.
Plant Physiol. 1987 Jan;83(1):213-8. doi: 10.1104/pp.83.1.213.
Two CAM species, Kalanchoë daigremontiana Hamet et Perrier and Hoya carnosa (L.) R. Br., were grown under a range of five photon flux area densitites (PFD) and then characterized. Significant acclimation to shade was indicated by progressive decreases in leaf thickness, rates of respiratory O(2) uptake, light compensation point, maximum rates of photosynthetic O(2) evolution, nocturnal acid accumulation, and delta(13)C values, and increases in chlorophyll concentration and absolute levels of room temperature (25 degrees C) and 77K fluorescence. Quantum yields (as measured by O(2) exchange) and the ratio of variable 77K fluorescence over the maximum yield (F(v)/F(m)) were relatively constant across the treatments. The only significant deviation from the above characteristics was in H. carnosa grown under full glasshouse PFD, where it apparently experienced photoinhibition. Following a photoinhibitory treatment, K. daigremontiana exhibited increases in the light compensation point and progressively greater reductions in the quantum yield, maximum photosynthetic rate, F(v)/F(m), and the variable component of room temperature fluorescence with increasing shade during growth. Thus although Crassulacean acid metabolism plants can adjust to shaded conditions, they are susceptible to photoinhibition when exposed to higher PFD than that experienced during growth.
两种 CAM 植物，大戟科的大戟属和萝藦科的球兰，在五种不同的光量子通量密度（PFD）下生长，然后进行特征描述。对荫蔽环境的显著适应表现为叶片厚度逐渐变薄、呼吸 O(2)摄取速率、光补偿点、最大光合 O(2)释放速率、夜间酸积累和 δ(13)C 值降低，同时叶绿素浓度和室温（25°C）和 77K 荧光的绝对水平增加。量子产率（通过 O(2)交换测量）和可变 77K 荧光与最大产量的比值（F(v)/F(m)）在整个处理过程中相对稳定。唯一与上述特征显著不同的是在全温室 PFD 下生长的球兰，它显然经历了光抑制。在光抑制处理后，大戟属的光补偿点增加，随着生长过程中荫蔽程度的增加，量子产率、最大光合速率、F(v)/F(m)和室温荧光的可变成分逐渐降低。因此，虽然景天酸代谢植物可以适应荫蔽条件，但当它们暴露在高于生长过程中经历的 PFD 时，它们容易受到光抑制。
