Buwalda J G, Green T G, Curtis J P
MAF Technology, Ruakura Agricultural Centre, Private Bag, Hamilton, New Zealand.
Tree Physiol. 1992 Jun;10(4):327-41. doi: 10.1093/treephys/10.4.327.
Net CO(2) assimilation (A) for canopies of kiwifruit (Actinidia deliciosa var. deliciosa) vines enclosed in a whole-canopy cuvette was measured continuously for three periods of 15-20 days during late summer, near Hamilton, New Zealand (latitude 38.2 degrees S). Canopy A showed an asymptotic response to incident radiation (PAR), saturating at about 1300 micromol m(-2) s(-1) for one vine and about 800 micromol m(-2) s(-1) for two other vines. Radiation interception at low solar angles and low leaf area apparently limited the response of A to PAR. Radiation saturated rates of A were 25-30 micromol CO(2) m(-2) s(-1) for one vine, and 12-18 micromol CO(2) m(-2) s(-1) for two other vines. At any PAR, canopy A was often lower in the afternoon than in the morning. Canopy respiration averaged 8.9 micromol CO(2) m(-2) s(-1) at 12 degrees C, but increased only 24-34% over the range 7-17 degrees C. Net daily C gains for the whole canopy, calculated as the temporal integral of A, ranged from -0.8 g C m(-2) for a cloudy day (PAR </= 450 micromol m(-2) s(-1)) to 6.2 g C m(-2) for a day with intermittent cloud. Measurements of gas exchange for single leaves in a leaf cuvette were used to examine the basis of the whole-canopy responses to environmental variables. Partial stomatal closure due to water stress apparently contributed to the afternoon depressions in A, although non-stomatal limitations may also have been involved.
在新西兰哈密尔顿附近（南纬38.2度）夏末期间，对置于全冠层比色皿中的奇异果（美味猕猴桃变种美味猕猴桃）藤蔓冠层的净二氧化碳同化量（A）进行了连续三个15 - 20天的测量。冠层A对入射辐射（光合有效辐射，PAR）呈现渐近响应，一株藤蔓在约1300微摩尔·米⁻²·秒⁻¹时达到饱和，另外两株藤蔓在约800微摩尔·米⁻²·秒⁻¹时达到饱和。低太阳角度和低叶面积时的辐射截获显然限制了A对PAR的响应。一株藤蔓的A的辐射饱和速率为25 - 30微摩尔二氧化碳·米⁻²·秒⁻¹，另外两株藤蔓为12 - 18微摩尔二氧化碳·米⁻²·秒⁻¹。在任何PAR下，冠层A通常在下午低于上午。冠层呼吸在12℃时平均为8.9微摩尔二氧化碳·米⁻²·秒⁻¹，但在7 - 17℃范围内仅增加24 - 34%。整个冠层的净日碳增益，计算为A的时间积分，范围从阴天（PAR≤450微摩尔·米⁻²·秒⁻¹）时的 - 0.8克碳·米⁻²到间歇性多云天的6.2克碳·米⁻²。在叶比色皿中对单叶气体交换的测量用于研究整个冠层对环境变量响应的基础。水分胁迫导致的部分气孔关闭显然是下午A降低的原因，尽管可能也涉及非气孔限制。
