构树叶性状分化的生态功能初步研究

Ecological function of leaf trait differentiation in Broussonetia papyifera

叶性状分化在自然界中较为普遍,不同的叶性状特征与植物对资源获得及利用效率密切关联,反映了植物适应特定环境所形成的生存对策。叶性状分化的生态功能一直以来备受生态学家和进化生物学家的广泛关注。自然界构树(Broussonetia papyifera)在个体发育过程中出现全缘叶和裂缺叶的分化,但其生态功能尚不清楚,推测两者的叶型分化是构树对虫害规避的结果。为了探讨构树叶性状分化对应的可能生态功能,该研究采用野外监测和室内分析的方法,对构树全缘叶和裂缺叶的虫害发生率、叶面积、与抗虫有关的酚类物质(总酚、缩合单宁、黄酮)含量进行了比较。结果表明:(1)相对于裂缺叶,全缘叶虫害发生率显著增加,全缘叶虫害发生率是裂缺叶的两倍。(2)自然条件下,全缘叶叶面积显著高于裂缺叶,增加了约44个百分点。(3)自然条件下,裂缺叶中总酚、缩合单宁、黄酮含量均显著高于全缘叶,分别提高了6.0%、4.2%和16.2%。(4)除黄酮外,虫害处理下裂缺叶中总酚、缩合单宁含量显著高于全缘叶,均提高了约5.0%。(5)人为移除部分叶片,裂缺叶中总酚、缩合单宁、黄酮含量均显著高于全缘叶,分别提高8.0%、1.6%和25.4%。这说明构树全缘叶和裂缺叶中酚类物质含量对外来损伤响应不一致,裂缺叶虫害发生率较全缘叶低可能由于两种类型叶片中酚类物质含量存在差异所引起。

Leaf trait differentiation is common in the nature.Different leaf traits have close relationship with resources access and utilization efficiency of plants,and reflect the survival strategies of plants to certain environments.Their ecological function have been focused by ecologists and evolutionists.Dozens of studies have shown that the diversity of leaf traits reflected to the differential adaptive strategy of plant.There are two types of leaf traits（ entire leaf and cleft leaf） of Broussonetia papyifera.However,we are still unknown about the ecological function of these two types of leaves.We hypothesized that the entire leaf and the cleft leaf had differential function for adaptting to herbivory disturbance.We conducted to the field and laboratory experiment for examining the incidence of pest,leaf area,total phenol,condensed tannins and flavonoid contents between the entire leaves and the crack leaves.The results were as follows：（ 1） Incidence of pest in the entire leaves was higher than that in the crack leaves,and it was increased averagely by 100%.（ 2） The entire leaf area was dramatically higher than that the crack leaves under natural conditions,and it was increased averagely by 44%.（ 3） There were the significant differences in total phenol,condensed tannins and flavonoid contents between the entire leaves and the cleft leaves under natural conditions.On average,total phenol,condensed tannins and flavonoid contents were increased by 6.0%,4.2% and 16.2% in the crack leaves than those in the entire leaves,respectively.（ 4） Similarly,total phenol and condensed tannins content were increased averagely by 5.0% in the cleft leaves than those in the entire leaves under the pest damage leaf treatments.（ 5） In addition,there were significant differences in total phenol,condensed tannins and flavonoids content between the entire leaves and the cleft leaves under artificial remove leaf treatments.On average,total phenol,condensed tannins and flavonoids content were increased by 8.0%,1.6% and 25.4% in the crack leaves than those in the entire leaves,respectively.The results suggested that the phenol content of the entire leaves and the cleft leaves divergently respond to the pest damage leaf and artificial remove leaf treatment.We speculate that the variation in peat damage rate between the entire leaves and the cleft leaves may result from the divergence of the phenol contents in leaves.The result offer the case study of leaf function to respond to herbivory disturbance.