Hogewoning Sander W, van den Boogaart Stefan A J, van Tongerlo Evelien, Trouwborst Govert
Plant Lighting B.V., Bunnik, The Netherlands.
Horticulture and Product Physiology, Department of Plant Sciences, Wageningen University & Research, Wageningen, The Netherlands.
Plant Cell Environ. 2021 Mar;44(3):762-774. doi: 10.1111/pce.13960. Epub 2020 Dec 16.
The regulation of photosynthesis and carbon gain of crassulacean acid metabolism (CAM) plants has not yet been disclosed to the extent of C3-plants. In this study, the tropical epiphyte Phalaenopsis cv. "Sacramento" was subjected to different lighting regimes. Photosynthesis and biochemical measuring techniques were used to address four specific questions: (1) the response of malate decarboxylation to light intensity, (2) the malate carboxylation pathway in phase IV, (3) the response of diel carbon gain to the light integral and (4) the response of diel carbon gain to CO . The four CAM-phases were clearly discernable. The length of phase III and the malate decarboxylation rate responded directly to light intensity. In phase IV, CO was initially mainly carboxylated via Rubisco. However, at daylength of 16 h, specifically beyond ±12 h, it was mainly phosphoenolpyruvate carboxylase (PEP-C) carboxylating CO . Diel carbon gain appeared to be controlled by the light integral during phase III rather than the total daily light integral. Elevated CO further enhanced carbon gain both in phase IV and phase I. This establishes that neither malate storage capacity, nor availability of PEP as substrate for nocturnal CO carboxylation were limiting factors for carbon gain enhancement. These results advance our understanding of CAM-plants and are also of practical importance for growers.
景天酸代谢（CAM）植物光合作用和碳同化的调控尚未像C3植物那样得到充分揭示。在本研究中，对热带附生植物蝴蝶兰品种“萨克拉门托”进行了不同的光照处理。采用光合作用和生化测量技术来解决四个具体问题：（1）苹果酸脱羧对光强的响应；（2）第四阶段的苹果酸羧化途径；（3）日碳同化对光积分的响应；（4）日碳同化对CO₂的响应。四个CAM阶段清晰可辨。第三阶段的时长和苹果酸脱羧速率直接响应光强。在第四阶段，CO₂最初主要通过核酮糖-1,5-二磷酸羧化酶（Rubisco）羧化。然而，在16小时日长时，特别是在±12小时之后，主要是磷酸烯醇式丙酮酸羧化酶（PEP-C）羧化CO₂。日碳同化在第三阶段似乎受光积分而非每日总光积分的控制。在第四阶段和第一阶段，升高的CO₂进一步增强了碳同化。这表明，苹果酸储存能力和作为夜间CO₂羧化底物的PEP可用性都不是碳同化增强的限制因素。这些结果增进了我们对CAM植物的理解，对种植者也具有实际意义。
