Way Danielle A, Sage Rowan F
Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada.
Plant Cell Environ. 2008 Sep;31(9):1250-62. doi: 10.1111/j.1365-3040.2008.01842.x. Epub 2008 Jun 4.
We investigated the thermal acclimation of photosynthesis and respiration in black spruce seedlings [Picea mariana (Mill.) B.S.P.] grown at 22/14 degrees C [low temperature (LT)] or 30/22 degrees C [high temperature (HT)] day/night temperatures. Net CO(2) assimilation rates (A(net)) were greater in LT than in HT seedlings below 30 degrees C, but were greater in HT seedlings above 30 degrees C. Dark and day respiration rates were similar between treatments at the respective growth temperatures. When respiration was factored out of the photosynthesis response to temperature, the resulting gross CO(2) assimilation rates (A(gross)) was lower in HT than in LT seedlings below 30 degrees C, but was similar above 30 degrees C. The reduced A(gross) of HT seedlings was associated with lower needle nitrogen content, lower ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) maximum carboxylation rates (V(cmax)) and lower maximum electron transport rates (J(max)). Growth treatment did not affect V(cmax) : J(max). Modelling of the CO(2) response of photosynthesis indicated that LT seedlings at 40 degrees C might have been limited by heat lability of Rubisco activase, but that in HT seedlings, Rubisco capacity was limiting. In sum, thermal acclimation of A(net) was largely caused by reduced respiration and lower nitrogen investments in needles from HT seedlings. At 40 degrees C, photosynthesis in LT seedlings might be limited by Rubisco activase capacity, while in HT seedlings, acclimation removed this limitation.
我们研究了在日/夜温度为22/14摄氏度[低温（LT）]或30/22摄氏度[高温（HT）]条件下生长的黑云杉幼苗[白云杉（Picea mariana (Mill.) B.S.P.）]光合作用和呼吸作用的热适应性。在30摄氏度以下，LT幼苗的净CO₂同化率（A(net)）高于HT幼苗，但在30摄氏度以上则是HT幼苗的A(net)更高。在各自的生长温度下，处理间的暗呼吸速率和日呼吸速率相似。当从光合作用对温度的响应中扣除呼吸作用后，在30摄氏度以下，HT幼苗的所得总CO₂同化率（A(gross)）低于LT幼苗，但在30摄氏度以上则相似。HT幼苗较低的A(gross)与较低的针叶氮含量、较低的1,5-二磷酸核酮糖羧化酶/加氧酶（Rubisco）最大羧化速率（V(cmax)）以及较低的最大电子传递速率（J(max)）有关。生长处理不影响V(cmax) : J(max)。光合作用对CO₂响应的模型表明，40摄氏度时LT幼苗可能受到Rubisco活化酶热不稳定性的限制，但在HT幼苗中，Rubisco容量是限制因素。总之，A(net)的热适应性很大程度上是由于HT幼苗呼吸作用降低以及针叶中氮投资减少所致。在40摄氏度时，LT幼苗的光合作用可能受到Rubisco活化酶容量的限制，而在HT幼苗中，适应性消除了这一限制。
