黑青杂交杨‘中金杨7号’局部遮阴对新生叶光合特性的影响

Effects of partial shading on photosynthetic characteristics of newly developed leaves in Populus×euramericana’Zhongjin7’

森林内部不仅存在弱光,而且冠层与中下层的光强条件差异较大。为了探究这种不均一光强环境对杨树光合作用光适应的影响,本文选用黑青杂交杨‘中金杨7号’(Populus×euramericana ‘Zhongjin7’)为实验材料,在林地条件下研究了叶片性状、光合色素、气体交换和叶绿素荧光等对光强差异的响应变化。结果表明:成熟叶遮阴不但降低了自身的比叶重、气孔面积、光合色素含量、净光合速率(P_(n))和光系统Ⅱ最大光化学效率(F_(v)/F_(m)),而且还显著降低了处于曝光环境中新生叶的相同指标。进一步分析表明,成熟叶遮阴影响了冠层顶端新生叶的形态结构与光合功能,同时还增强了新生叶的强光敏感性。因此,‘中金杨7号’成熟叶在适应周围弱光环境的过程中会对冠层新生叶的生长发育产生影响,而且新生叶的光合功能受到了系统调控。

Light intensity increases gradually with leaf position from bottom to top of trees in forest.The effects of heterogeneous light intensity on light adaptation of photosynthesis were studied in poplar,a poplar variety Populus×euramericana’Zhongjin7’.Changes of leaf characteristics,photosynthetic pigment,gas exchange and chlorophyll a fluorescence were carefully investigated in woodland-grown poplar.Results showed that stomatal area,specific leaf weight,photosynthetic pigment content,net photosynthetic rate(P_(n))and maximum quantum yield of photosystem II photochemistry(F_(v)/F_(m))decreased significantly in newly developing leaves and mature leaves due to the shading of mature leaves.Further,newly developed leaves exposed to high light intensity in the upper canopy also exhibited a large change in leaf characteristics,photosynthesis and high-light tolerance when light intensity decreased for mature leaves.The weak-light environment around the lower mature leaves had a strong impact on the photosynthetic performance not only in themselves but also in newly developed leaves.Accordingly,we suggest that morphological structure and photosynthetic function in newly developed poplar leaves were regulated by a systemic irradiance signalling from mature leaves under woodland conditions.