Responses of transpiration and photosynthesis to reversible changes in photosynthetic foliage area in western red cedar (Thuja plicata) seedlings.
Responses of transpiration and photosynthesis to reversible changes in photosynthetic foliage area in western red cedar (Thuja plicata) seedlings.
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蒸腾作用和光合作用对西部红柏（Thuja plicata）幼苗光合叶子面积可逆变化的响应。
DOI：
10.1093/treephys/22.6.363
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发表时间：
2002
期刊：
影响因子：
4
通讯作者：
D. Whitehead
中科院分区：
文献类型：
--
作者：
S. Pepin;N. Livingston;D. Whitehead
以1年生西部红杉（Thuja plicata Donn.）幼苗为试验对象，研究光照下叶片对总光合叶面积（L(A)）可逆变化的响应。L(A)的减少是通过遮蔽下部叶片或降低幼苗下部周围空气的环境CO2浓度（c(A)）来实现的。在后一种情况下，蒸汽压也被改变，这样蒸腾速率(E)就可以独立于光合速率(A)来控制。我们假设，在这些处理之后，剩余叶片的气孔导度（g(s)）和气孔导度(A)会发生短期代偿性变化。这些变化可能是对水势梯度变化产生的水力信号的响应，而不是对幼苗体内碳源汇分布的响应。当部分叶片被遮蔽时，整个幼苗的E值立即降低，而其余被遮蔽叶片的g(s)、a和E值随之增加。细胞间CO2浓度变化不大。这些补偿效应在移除遮阳物后被完全逆转。当遮荫或降低c(A)使下层叶片A < 0 micromol m-2 s-1，而E保持不变或增加（通过调节蒸汽压亏缺）时，其余叶片的g(s)和A没有显著增加。我们得出结论，只有当L(A)的减少伴随着全株E的减少时，才会发生补偿反应。全苗E的减少和A的增加之间的关系是高度线性的（r2 = 0.68），这证实了我们的假设，即幼苗内产生的水力信号对g(s)有很强的调节作用。我们认为，补偿效应的机制是由于g(s)的增加而增加的CO2供应和羧基化速率的响应的结合，可能与Rubisco的活性有关。
Experiments were conducted on 1-year-old western red cedar (Thuja plicata Donn.) seedlings to determine the response of illuminated foliage to reversible changes in total photosynthetic foliage area (L(A)). Reductions in L(A) were brought about by either shading the lower foliage or by reducing the ambient CO2 concentration (c(a)) of the air surrounding the lower part of the seedling. In the latter case, the vapor pressure was also changed so that transpiration rates (E) could be manipulated independently of photosynthetic rates (A). We hypothesized that following such treatments, short-term compensatory changes would occur in stomatal conductance (g(s)) and A of the remaining foliage. These changes would occur in response to hydraulic signals generated by changes in the water potential gradient rather than changes in the distribution of sources and sinks of carbon within the seedling. When a portion of the foliage was shaded, there was an immediate reduction in whole-seedling E and a concomitant increase in g(s), A and E in the remaining illuminated foliage. However, the intercellular CO2 concentration did not change. These compensatory effects were fully reversed after the shade was removed. When the lower foliage A was reduced to < 0 micromol m-2 s-1, by shading or lowering c(a), and E was either unchanged or increased (by adjusting the vapor pressure deficit), there was no significant increase in g(s) and A in the remaining foliage. We conclude that compensatory responses in illuminated foliage occur only when reductions in L(A) are accompanied by a reduction in whole-plant E. The relationship between the reduction in whole-seedling E and the increase in A is highly linear (r2 = 0.68) and confirms our hypothesis of the strong regulation of g(s) by hydraulic signals generated within the seedling. We suggest that the mechanism of the compensatory effects is a combination of both increased CO2 supply, resulting from increased g(s), and a response of the rate of carboxylation, possibly related to the activity of Rubisco.