The generally accepted assumption that CAM is an important adaptation to the drought conditions in arid deserts is mainly based on studies in controlled environments comparing the respective photosynthetic pathways in plants of different morphology. Comparative long-term field studies on the ecophysiology of C₃- and CAM succulents co-occurring in the same desert habitat are too rare to satisfactorily answer the old question whether the metabolic pathway or the succulence is more important to guarantee survival in such a harsh habitat. Thus, relevant ecophysiological parameters were repeatedly monitored on plants of the leaf succulents Augea capensis (C₃) and Malephora purpureo-crocea (CAM), which commonly dominate a habitat in the Knersvlakte, Namaqualand, South Africa. Under identical conditions in the same habitat, carbon gain of the C₃ species was higher than that of the CAM plant, but their WUE lower and maximum photosynthetic activity nearly the same. In M. purpureo-crocea, irrigation induced rapid whole day stomatal opening at drastically increased daytime but decreased night-time CO₂-uptake, while respective responses of the C₃ species were delayed. These different response dynamics were due to different rooting depth, root morphology and water acquisition strategy of the flat rooting CAM and the deep-rooting C₃ species. This, however, may not explain the highly similar growth success. Anyway, the results verify that CAM provides no advantage over C₃ for long-term survival in the same desert environment in morphologically similar succulents.

CAM是对干旱沙漠干旱条件的重要适应的普遍公认的假设主要是基于在受控环境中进行的研究，比较了不同形态植物中各自的光合作用途径。在同一沙漠生境中同时存在的C ₃和CAM多肉植物的生态生理学的长期比较研究太少，无法令人满意地回答这个古老的问题，即代谢途径或多肉植物对于保证在如此恶劣的条件下的生存更为重要。栖息地。因此，在叶片多肉植物Augea capensis（C ₃）和Malephora purpureo-crocea的植物上反复监测了相关的生理生态参数。（CAM），通常在南非Namaqualand的Knersvlakte栖息。在相同的条件下，在相同的生境中，C ₃物种的碳吸收高于CAM植物，但其WUE降低和最大光合活性几乎相同。在紫斑紫罗兰花中，灌溉导致白天气孔快速开放，白天急剧增加，但夜间CO ₂吸收却减少，而C ₃物种的相应反应却被延迟了。这些不同的响应动力学是由于平生根CAM和深生根C _3的生根深度，根系形态和水分获取策略不同而引起的物种。但是，这可能无法解释高度相似的增长成功。无论如何，结果证明，在形态相似的多肉植物中，在相同的沙漠环境中，CAM不能提供优于C ₃的长期生存能力。