Küppers M, Wheeler A M, Küppers B I L, Kirschbaum M U F, Farquhar G D
Research School of Biological Sciences, Australian National University, GPO Box 475, 2601, Canberra City, ACT, Australia.
Division of Forest Research, CSIRO, GPO Box 4008, 2600, Canberra City, ACT, Australia.
Oecologia. 1986 Sep;70(2):273-282. doi: 10.1007/BF00379251.
The rate of CO assimilation at light saturation and an intercellular CO concentration of 350 μl l (photosynthetic capacity), measured in leaves of Eucalyptus pauciflora, E. behriana, E. delegatensis and Acacia melanoxylon, declined over the course of cloudless days under naturally varying environmental conditions as well as under constant optimal conditions for high CO uptake. Since the capacity did not recover during the light period, it was different from the "midday depression" of gas exchange. The change appeared to be caused neither by the diurnal variation of total leaf water potential, by photoinhibition of redox-reaction centres in photosystems nor by changes in the intrinsic properties of Ribulose-bisphosphate carboxylase-oxygenase. The decline was more pronounced in winter than in summer. It was related to the duration of illumination or the cumulative carbon gain. It was reversible in the following dark phase, and it did not occur on changeable days with short peaks of high light.Despite the decline in photosynthetic capacity, the initial slope of the CO response of net photosynthesis, as obtained at low intercellular CO concentrations, remained constant during the day, but declined at night when photosynthetic capacity recovered. In all cases stomatal conductance varied in parallel with photosynthetic capacity. The relevance of changes in photosynthetic capacity for the intercellular CO concentration is discussed.
在自然变化的环境条件下以及在有利于高二氧化碳吸收的恒定最佳条件下，对多花桉、贝氏桉、德氏桉和黑木相思叶片进行测量，结果显示，在光饱和且细胞间二氧化碳浓度为350 μl l时（光合能力），二氧化碳同化率在无云日期间下降。由于该能力在光照期间未恢复，因此与气体交换的“中午降低”不同。这种变化似乎既不是由叶片总水势的昼夜变化、光合系统中氧化还原反应中心的光抑制，也不是由核酮糖-1,5-二磷酸羧化酶加氧酶的内在特性变化引起的。冬季的下降比夏季更明显。它与光照持续时间或累积碳增益有关。在随后的黑暗阶段它是可逆的，并且在高光短峰值的多变天气中不会发生。尽管光合能力下降，但在低细胞间二氧化碳浓度下获得的净光合作用二氧化碳响应的初始斜率在白天保持恒定，但在夜间光合能力恢复时下降。在所有情况下，气孔导度与光合能力平行变化。文中讨论了光合能力变化对细胞间二氧化碳浓度的相关性。
