作 者 ：黄文娟,李志军*,杨赵平,白冠章
期 刊 ：生态学报 2010年 30卷 17期 页码：4636~4642
Keywords:Populus euphratica Oliv., heteromorphic leaves, structural traits,
摘 要 ：胡杨在个体生长发育过程中，叶形不断发生变化，植株上会逐年依次出现条形、披针形、卵形和阔卵形叶，且在同时具有这4种叶形的植株上，叶片在树冠中分布的顺序自上而下分别是阔卵形、卵形、披针形和条形。通过实验的方法对胡杨4种叶形叶片厚度、叶面积、比叶面积、叶片干重和干物质含量等5个结构型性状指标进行分析，研究不同叶形叶片的结构型性状与叶形（叶长/宽比值）之间的关系，以及各结构型性状指标间的相互关系。结果表明：叶片厚度、叶片干物质含量、叶面积和叶片干重与叶长/宽比值之间均呈明显负相关（P＜0.05）；比叶面积随着叶长/宽比值的减小而逐渐减小，但二者相关性不明显，表明胡杨在个体发育过程中通过增加叶面积、叶厚度，减小比叶面积等方式来提高适应环境的能力。各结构型性状指标间相关性表现为：比叶面积与叶干物质含量和叶干重之间均呈明显负相关（P<0.05），与叶厚度间呈极明显负相关（P＜0.01）；叶片干重与叶厚度间呈明显正相关（P＜0.05）；叶厚度与叶干物质含量之间、叶干重与叶面积之间均呈极明显正相关（P＜0.01），其它指标间无明显相关性。
Abstract:Populus euphratica Oliv., a member in the family Salicaceae, is mainly distributed in central Asia, west Asia and the Mediterranean region, especially in Xinjiang of China and Kazakhstan where it occupies the widest distribution area. P. euphratica poseeses many excellent characteristics such as cold tolerance, high temperature resistant, anti-drought, anti-sand, salt and alkali resistant etc. It plays an active role in climatic regulation, desert extension control, bank protection, channels stabilization and oasis conservation. It has not only protected desert fragile ecological system but also been an irreplaceable natural barrier in the ecological security maintenance and sustainable socio-economic development. During the growth and development of P. euphratica, the leaf morphology changed accordingly. The linear, lanceolate, ovate, or broadly ovate leaves come out in turn. In one plant with four types of leaf shapes at the same time, the heteromorphic leaf distribution in the canopy from top to bottom is broadly ovate, ovate, lanceolate, or linear, respectively. In one growth season, the leaves with small length/wide ratio appears earlier in the plant, which means that broadly ovate leaves at the top of canopy expansion first, and then the ovate leaves, lanceolate leaves, linear leaves at lower layer expansion one by one. Through analysis of five indices of structural traits, e.g. thickness (TH), area (AR), specific leaf area (SLA), dry weight (DW) and dry matter content (DMC) with four leaf shapes (broadly ovate, ovate, lanceolate and linear, respectively) of Populus euphratica, the relationship between structural traits of Populus euphratica heteromorphic leaves and length/width (L/W) and the correlations among five indices would be investigated. The results showed that, the L/W of leaves was significantly negatively correlated with their TH, DMC, AR, DW (P＜0.05), but positively correlated with their SLA. It indicated that the growth and development process of the P. euphratica individual, is also a process of increasing leaf area and leaf thickness, development of xerophytic structure, and increase of photosynthesis rate along with the leaves shape changing. It indicated that it the emerge of different leaf types results in bigger photosynthetic area, higher net photosynthetic rate, more accumulation of photosynthate and excellent guard structure gradually. Thus P. euphratica plant dramatically improve its photosynthetic area by increasing the leaf area and the leaf thickness and forming the developed stockade tissue to meet the demands of plant nutrient. On the other hand, P. euphratica plant improves the diffusion distance or the resistance from the leaf internal to the surface by increasing leaf thickness, cutin layer thickness and cell number of mucous etc., and improved the leaf water retaining capacity. The water dissipation was reduced to be a certain degree. It is also illustrated that the leaf shape changing in the growth process of P. euphratica is an adaptability performance of its survival and growth. Correlations among structural characteristics indices showed that, the SLA of leaves was significantly negatively correlated with DMC and DW (P＜0.05), and more significantly negatively correlated with their TH (P＜0.01), the TH of leaves was more significantly positively correlated with DMC (P＜0.01), and the DW of leaves was more significantly positively correlated with SLA (P＜0.01). There were no significant correlations among other indices.
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