Syvertsen J P
University of Florida-IFAS, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL 33850-2299, USA.
Tree Physiol. 1994 May;14(5):497-508. doi: 10.1093/treephys/14.5.497.
Effects of defoliation on partial shoot removal by decapitation on seedling growth, water use and net gas exchange of remaining basal leaves, were examined in Citrus spp. Shoot and root growth rates were manipulated to test for effects of growth demands on net gas exchange. Partially defoliated plants had higher leaf pressure potentials, root conductivities and rates of water use than intact control plants. Shoot regrowth occurred at the expense of root loss. Basal leaves on defoliated plants consistently had higher rates of CO(2) assimilation (A) than leaves on intact plants. Stomatal conductance (g(s)) changed little after defoliation so the higher A of leaves on defoliated plants lowered the ratio of intercellular to ambient CO(2) concentration (C(i)/C(a)) in the mesophyll. In some cases, g(s) increased with A in defoliated plants but C(i)/C(a) was not affected. Stomatal conductance only limited A when intact seedlings were stressed by root confinement in small pots or when leaves were exposed to high vapor pressure deficits during gas exchange measurements. Increased carbon demand for shoot regrowth increased photosynthetic capacity and was more important than stomatal responses in determining A after partial shoot loss.
在柑橘属植物中，研究了去叶处理对通过摘心去除部分枝条后幼苗生长、水分利用以及剩余基部叶片净气体交换的影响。对地上部和根系生长速率进行调控，以测试生长需求对净气体交换的影响。部分去叶的植株比完整的对照植株具有更高的叶片压力势、根系导水率和水分利用速率。地上部的重新生长是以根系损失为代价的。去叶植株的基部叶片始终比完整植株的叶片具有更高的二氧化碳同化速率（A）。去叶后气孔导度（g(s)）变化不大，因此去叶植株叶片较高的A值降低了叶肉细胞间与外界二氧化碳浓度之比（C(i)/C(a)）。在某些情况下，去叶植株中g(s)随A增加，但C(i)/C(a)不受影响。仅当完整幼苗因种植在小盆中根系受限，或在气体交换测量期间叶片暴露于高蒸汽压亏缺时，气孔导度才会限制A。地上部重新生长对碳需求的增加提高了光合能力，并且在部分枝条损失后决定A时，比气孔反应更重要。
