Heichel G H, Turner N C
The Connecticut Agricultural Experiment Station, 06504, New Haven, CT, USA.
Oecologia. 1983 Mar;57(1-2):14-19. doi: 10.1007/BF00379555.
The CO assimilation of primary foliage of red maple (Acer rubrum L.) and red oak (Quercus rubra L.), and of regrowth foliage produced in response to simulated insect defoliation, was measured throughout the season by infrared gas analysis: parallel measurements of leaf conductance were obtained by ventilated diffusion porometry. The rate of net photosynthesis, measured at a quantum flux density of 1,150 μmol ms, of primary foliage of both species increased from slightly negative values to about 5 μmol ms by early June. Thereafter the rate of photosynthesis of maple slowly declined to about 4 μmol ms before onset of a senescent decline in early September, while that of oak slowly increased to about 8 μmol ms before onset of senescence. Manual defoliation to simulate insect attack in mid-June elicited refoliation proportional to the severity of defoliation in early July. After 100% defoliation, fully expanded regrowth foliage of maple, but not of oak, had a rate of net photosynthesis from mid-July through September that was about 50% higher than in the primary foliage of undefoliated trees. A 30 to 60% enhancement of photosynthesis of residual primary foliage remaining on 50 and 75% defoliated trees during July was also observed. The seasonal patterns of CO exchange of primary and regrowth foliage, and the enhancement of CO assimilation in residual foliage, was paralleled by similar changes in leaf conductance to water vapour.Carbon budgets of leaf canopies of each species showed that the net assimilation of the leaf canopy of both species ranged from 19 to 67% more than what would have been expected solely from replacement of leaf area. This response was greater in maple than in oak, presumably a reflection of the high rate of CO assimilation of regrowth maple foliage compared with that of the undefoliated control in maple.The increased CO assimilation of regrowth maple foliage and the increases in CO assimilation of residual primary foliage after defoliation offer evidence that heretofore unanticipated physiological mechanisms may be important to perennial species coping with herbivory.
通过红外气体分析法在整个季节测量了红枫（Acer rubrum L.）和红栎（Quercus rubra L.）初生叶以及模拟昆虫落叶后再生叶的一氧化碳同化情况：通过通气扩散气孔计同步测量了叶片导度。在量子通量密度为1150 μmol m⁻² s⁻¹ 时测量的两种植物初生叶的净光合速率，到6月初从略为负值增加到约5 μmol m⁻² s⁻¹ 。此后，枫树叶的光合速率在9月初衰老衰退开始前缓慢下降到约4 μmol m⁻² s⁻¹ ，而栎树叶的光合速率在衰老开始前缓慢增加到约8 μmol m⁻² s⁻¹ 。6月中旬进行人工落叶以模拟昆虫攻击，7月初引起的重新发叶与落叶严重程度成比例。100%落叶后，从7月中旬到9月，枫树叶完全展开的再生叶的净光合速率比未落叶树木的初生叶高约50%，而栎树则没有这种情况。在7月期间，还观察到50%和75%落叶树木上残留的初生叶的光合作用增强了30%至60%。初生叶和再生叶的一氧化碳交换的季节模式以及残留叶中一氧化碳同化的增强，与叶片对水蒸气的导度的类似变化平行。每个物种叶冠层的碳预算表明，两个物种叶冠层的净同化量比仅根据叶面积替换所预期的多19%至67%。这种反应在枫树中比在栎树中更大，大概反映了与枫树未落叶对照相比，再生枫树叶的一氧化碳同化率较高。再生枫树叶一氧化碳同化的增加以及落叶后残留初生叶一氧化碳同化的增加提供了证据，表明迄今为止未预料到的生理机制可能对多年生植物应对食草作用很重要。
