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首页> 外文期刊>Journal of Experimental Botany >On the nature of facultative and constitutive CAM: environmental and developmental control of CAM expression during early growth of Clusia, Kalanchoë, and Opuntia
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On the nature of facultative and constitutive CAM: environmental and developmental control of CAM expression during early growth of Clusia, Kalanchoë, and Opuntia

机译：关于兼性和构成性CAM的性质：Clusia，Kalanchoë和Opuntia早期生长期间CAM表达的环境和发育控制

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摘要

The capacity to induce crassulacean acid metabolism developmentally (constitutive CAM) and to up-regulate CAM expression in response to drought stress (facultative CAM) was studied in whole shoots of seven species by measuring net CO2 gas exchange for up to 120 day–night cycles during early growth. In Clusia rosea, CAM was largely induced developmentally. Well-watered seedlings began their life cycle as C3 plants and developed net dark CO2 fixation indicative of CAM after the initiation of the fourth leaf pair following the cotyledons. Thereafter, CAM activity increased progressively and drought stress led to only small additional, reversible increases in dark CO2 fixation. In contrast, CAM expression was overwhelmingly under environmental control in seedlings and mature plants of Clusia pratensis. C3-type CO2 exchange was maintained under well-watered conditions, but upon drought stress, CO2 exchange shifted, in a fully reversible manner, to a CAM-type pattern. Clusia minor showed CO2 exchange reponses intermediate to those of C. rosea and C. pratensis. Clusia cretosa operated in the C3 mode at all times. Notably, reversible stress-induced increases of dark CO2 fixation were also observed during the developmental progression to pronounced CAM in young Kalanchoë daigremontiana and Kalanchoë pinnata, two species considered constitutive CAM species. Drought-induced up-regulation of CAM was even detected in young cladodes of a cactus, Opuntia ficus-indica, an archetypal constitutive CAM species. Evidently, the defining characteristics of constitutive and facultative CAM are shared, to variable degrees, by all CAM species.
机译：通过测量净CO 2 气体交换量，研究了七个物种全芽中的发育诱导草甘膦酸代谢的能力（组成型CAM）和响应干旱胁迫上调CAM表达的能力（兼性CAM）。在早期生长过程中，长达120个昼夜周期。在玫瑰丛（Clusia rosea）中，CAM主要是发育诱导的。水分充足的幼苗从C 3 植物开始其生命周期，并在子叶的第四个叶片对开始萌发后，发展出表明CAM的净暗CO 2 固定。此后，CAM活性逐渐增加，干旱胁迫仅导致黑暗的CO 2 固定中额外的可逆增加。相反，在环境控制下，Clusia pratensis的幼苗和成熟植物中的CAM表达绝大多数。 C 3 型CO 2 交换在充分灌溉的条件下得以维持，但在干旱胁迫下，CO 2 交换以完全可逆的方式转移。方式，以CAM型模式。较小的Clusia显示出CO 2 交换反应，介于中间的玫瑰和C. rosea。 Cluosa cretosa始终以C 3 模式运行。值得注意的是，在年轻的Kalanchoëdaigremontiana和Kalanchoëpinnata这两个被认为是组成型CAM物种的发育过程中，在向明显CAM的发展过程中也观察到了可逆的应力诱导的暗CO 2 固定的增加。甚至在干旱的仙人掌仙人掌丛中也发现了干旱引起的CAM上调，仙人掌是典型的组成型CAM物种。显然，所有CAM物种在不同程度上都共享本构和兼性CAM的定义特征。

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