海棠叶脉网络结构及其输水特性研究

Network Structure and Water Transport Characteristics in Begonia Leaf Vein

摘要

叶脉在植物与外界环境之间的物质和能量交换中发挥着至关重要的作用，叶脉输运网络不仅有极高的效率，而且具有均匀化运输的特点．在换热器、燃料电池等装置的流道设计中，依据叶脉结构进行仿生学设计，可以有效提高流道网络的效率和均匀性．为此，需要对叶脉的结构特点、生长过程和水分在其中的流动过程与规律建立准确的认识．本文以海棠叶片为研究对象，对其叶脉结构、形状特性及叶脉内水分输运的流动特性进行了研究．测量各级叶脉长度、直径及各级分支间距和夹角等参数，并进行统计学分析，总结叶脉网络的结构特征；使用荧光染 料处理叶脉，观察水在各级叶脉中的运输过程．结果表明：海棠叶片的中脉可近似看作一细长圆锥体，其基部直径 约为1.18 mm，且不随叶片生长而加粗；次脉的长度和基部直径分别与其基部距离叶基的距离呈线性负相关，基部直径仅在叶片生长的前半阶段有所加粗，次脉的分支角、同侧前间距与其基部距离叶基的距离之间也存在一定关系；中脉及次脉中某一点处的水分流速与该点距离该条叶脉基部的距离呈线性负相关，该线性关系的斜率在同一叶片上的不同叶脉间基本相等；中脉及次脉中的水分输运具有同步性，微脉中的水分运输则表现出不同于中脉、次脉的分级性．

Abstract

Leaf veins are vital for the exchange of matter and energy between plants and the environment. The leaf vein transport network is not only extremely efficient but also has the characteristics of homogeneous transportation. While designing the flow channels of heat exchangers, fuel cells and other devices, a biomimetic design based on the leaf vein structure can effectively improve the efficiency and uniformity of the flow channel network. Therefore, it is necessary to understand the structural characteristics, growth and flow processes and law of leaf veins. This paper studied the structure and shape characteristics of leaf veins and the flow characteristics of water transport within them. Parameters such as the length and diameter of the veins and the spacing and angles of their branches at all levels were measured. Statistical analysis summarized the structural characteristics of the leaf vein network. Fluorescent dyes were used to observe water transport through the veins at all levels. The results show that the midvein of the begonia leaf can be regarded as an elongated cone, with a diameter of approximately 1.18mm at the base, which do not thicken with leaf growth. The length and diameter of the secondary vein are linearly negatively correlated with the base leaf base distance, respectively, and the base only thickened during the first half of leaf growth. There is also a relation ship between the branch angle of the secondary vein, the anterior distance of the ipsilateral vein and the distance from the leaf base. The water flow velocity at a point in the midvein and secondary vein is linearly negatively correlated with the distance between the point and the vein base, and the linear relationship slope is similar between the various veins on the same leaf. The water transport in the midvein and the secondary vein is synchronous, while that in the microvein varied from the midvein and secondary veins.

关键词

叶脉 / 结构参数 / 水分运输 / 结构优化

Key words

leaf vein / structural parameter / water transport / structural optimization

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基金资助

天津市自然科学基金资助项目(21JCQNJC01660)