Ellsworth D S, Tyree M T, Parker B L, Skinner M
Department of Botany, University of Vermont, Burlington, VT 05405, USA.
Tree Physiol. 1994 Jun;14(6):619-32. doi: 10.1093/treephys/14.6.619.
An experimental introduction of pear thrips (Taeniothrips inconsequens Uzel), a major defoliator in sugar maple (Acer saccharum Marsh.) forests in northeastern North America, was conducted in a field plantation to determine if compensatory gas exchange occurs in response to feeding damage by this piercing-sucking insect. Sugar maple trees were enclosed in netting (167 micro m mesh) and pear thrips adults were introduced before leaf expansion in the spring. Pear thrips reduced whole-tree leaf area by approximately 23% and reduced leaf size (both mass and area) by 20% in the upper crown. Measurements of net CO(2) assimilation rate (A(net)) and stomatal conductance (g(s)) were made on tagged foliage that was later analyzed for stable carbon isotope composition (delta(13)C) to provide estimates of short- and long-term leaf water use efficiency (WUE). Pear thrips feeding reduced A(net) for fully expanded leaves by approximately 20%, although leaf chlorophyll content and leaf mass per unit area were apparently not affected. Comparison of A(net), g(s), instantaneous WUE and leaf delta(13)C between damaged and control trees as well as visibly undamaged versus moderately damaged foliage on pear thrips-infested trees indicated that there were no effects of pear thrips feeding damage on WUE or leaf delta(13)C. Long-term WUE among sugar maple trees in the field plantation, indicated by leaf delta(13)C analysis, was related to shorter-term estimates of leaf gas exchange behavior such as g(s) and calculated leaf intercellular CO(2) concentration (C(i)). We conclude that pear thrips feeding has no effect on leaf WUE, but at the defoliation levels in our experiment, it may reduce leaf A(net), as a result of direct tissue damage or through reduced g(s). Therefore, even small reductions in leaf A(net) by pear thrips feeding damage may have an important effect on the seasonal carbon balance of sugar maple when integrated over the entire growing season.
北美东北部糖枫林（糖槭，Acer saccharum Marsh.）中的主要食叶害虫梨蓟马（Taeniothrips inconsequens Uzel）被引入一片人工林进行实验，以确定这种刺吸式口器昆虫取食造成的损害是否会引发糖槭树的补偿性气体交换。糖槭树被罩在网中（网眼为167微米），春季叶片展开前引入梨蓟马成虫。梨蓟马使整树叶片面积减少了约23%，树冠上部叶片大小（质量和面积）减少了20%。对标记叶片进行净二氧化碳同化率（A(net)）和气孔导度（g(s)）的测量，随后分析其稳定碳同位素组成（δ(13)C），以估算短期和长期的叶片水分利用效率（WUE）。梨蓟马取食使完全展开叶片的A(net)降低了约20%，尽管叶片叶绿素含量和单位面积叶片质量显然未受影响。比较受害树与对照树之间以及梨蓟马侵害树上明显未受害与中度受害叶片之间的A(net)、g(s)、瞬时WUE和叶片δ(13)C，结果表明梨蓟马取食损害对WUE或叶片δ(13)C没有影响。通过叶片δ(13)C分析表明，人工林中糖槭树的长期WUE与叶片气体交换行为的短期估算值有关，如g(s)和计算得出的叶片细胞间二氧化碳浓度（C(i)）。我们得出结论，梨蓟马取食对叶片WUE没有影响，但在我们实验的落叶水平下，由于直接的组织损伤或g(s)降低，可能会降低叶片A(net)。因此，在整个生长季节综合来看，即使梨蓟马取食损害使叶片A(net)有小幅降低，也可能对糖槭树的季节性碳平衡产生重要影响。
