Dipartimento di Biologia Vegetale, Università di Napoli, Via Foria 223, 80139, Napoli, Italy.
Photosynth Res. 1987 Jan;13(2):113-24. doi: 10.1007/BF00035235.
Pattern and magnitude of stem gas exchange were studied under controlled conditions on two CAM species of the genus Cissus differing in morphological features. In the cactus-like liana Cissus quadrangularis, at water vapour deficit of the air (VPD) lower than 400 mPa Pa(-1) during daytime, under 24/16°C and 27/16°C temperature regime, CO2 uptake occurred during daytime and nighttime but night fixation was responsible for 74 and 77% respectively of the CO2 fixed during the whole diurnal cycle; the contribution of night fixation increased up to 84% at VPD of 590 mPa Pa(-1) under 27/15°C. In Cissus sp., a slightly succulent xerophytic liana with mesophytic deciduous leaves, at 27°C day temperature and VPD of 520-540 mPa Pa(-1), under both 12 and 16°C night temperature, CO2 uptake occurred exclusively during the night; however at lower day temperatures (18-20°C) and lower VPD (169-269 mPa Pa(-1)) substantial CO2 uptake was observed in the light. Transpiration was higher in Cissus sp. than in Cissus quadrangularis under all of the conditions applied; moreover night transpiration in Cissus sp. contributed more to total day transpiration as compared with Cissus quadrangularis. The results support the opinion that the nocturnal gas exchange has a preeminent role in Cissus sp. as compared with Cissus quadrangularis. Indeed under conditions which enhance evaporative demand even well-watered plants of Cissus sp. resort totally to night fixation. In contrast Cissus quadrangularis which shows a larger resistance to water loss and possesses an abundant water storing parenchyma as compared with Cissus sp. resorts totally to night CO2 fixation only under drought stress.
在受控条件下，对形态特征不同的两种 Cissus 属 CAM 物种进行了茎气体交换模式和幅度的研究。在仙人掌状的木质藤本植物四方藤 Cissus quadrangularis 中，在白天空气水汽亏缺（VPD）低于 400 mPa Pa(-1)、24/16°C 和 27/16°C 温度条件下，CO2 吸收发生在白天和夜间，但夜间固定分别负责整个昼间周期中固定的 CO2 的 74%和 77%；在 VPD 为 590 mPa Pa(-1)、27/15°C 时，夜间固定的贡献增加到 84%。在 Cissus sp.，一种稍肉质的旱生木质藤本植物，具有中生落叶叶，在 27°C 的日温下，VPD 为 520-540 mPa Pa(-1)，在 12 和 16°C 的夜间温度下，CO2 吸收仅发生在夜间；然而，在较低的日温（18-20°C）和较低的 VPD（169-269 mPa Pa(-1))）下，在光照下观察到大量的 CO2 吸收。在所有应用条件下，Cissus sp. 的蒸腾作用均高于 Cissus quadrangularis；此外，与 Cissus quadrangularis 相比，Cissus sp. 的夜间蒸腾作用对总日蒸腾作用的贡献更大。结果支持了这样的观点，即与 Cissus quadrangularis 相比，夜间气体交换在 Cissus sp. 中具有突出的作用。事实上，在增强蒸发需求的条件下，即使是水分充足的 Cissus sp. 植物也完全依赖夜间固定。相比之下，与 Cissus sp. 相比，四方藤具有更大的抗水分损失能力，并且具有丰富的水储存薄壁组织，仅在干旱胁迫下才完全依赖夜间 CO2 固定。
