荒漠区植物光合器官解剖结构对水分利用效率的指示作用

Abstract

植物生理功能的发挥以结构为基础,因此,植物光合器官(叶片或同化枝)解剖结构会对水分利用效率(WUE)有一定的指示作用。通过对黑河流域优势种灌木光合器官的解剖特征和表征WUE的稳定碳同位素比率(<em>δ</em>¹³C)进行分析,试图从解剖结构的角度为荒漠植物WUE寻求一个有效的指示指标。结果显示:(1)除花棒外,轴状光合器官植物的<em>δ</em>¹³C值均高于叶状。(2)不同荒漠植物光合器官及不同组织厚度变化范围较广,叶厚度(<em>Tl</em>)或轴直径(<em>Da</em>)、角质层厚度(<em>Tc</em>)、表皮厚度(<em>Te</em>)、栅栏组织厚度(<em>Tp</em>)、海绵组织厚度(<em>Ts</em>)、贮水组织厚度<em>(Ta)</em>的最大值分别约为最小值的6.9、5.8、11、4、3.5和3.5倍。荒漠区多数轴状光合器官植物的<em>Da</em>以及<em>Te</em>高于叶状。(3)所研究优势种灌木的<em>δ</em>¹³C值与<em>Tl</em>或<em>Da</em>之间存在极显著的正相关关系(<em>r</em>=0.719,<em>P</em><0.01),与不同组织厚度<em>(Tc、Te、Tp、Ts和Ta)</em>之间相关性不显著。由此可知,从植物光合器官的解剖结构来看,荒漠区植物的WUE可以用Tl或Da来表征,叶片越厚,越有利于植物高效利用水分,且轴状光合器官植物的WUE高于叶状。;Affected by the extreme arid environment caused by salinization, high temperature and intensive radiation, desert plants change their structural characteristics, such as fleshy leaf, assimilating shoots, lots of epidermal hairs, thick cuticle and so on, to improve their water use efficiency. Structure being basis of function, the anatomic structure of photosynthetic organ (including leaf and assimilating shoot) of desert plants can indicate their water use efficiency. It has been improved that stable carbon isotope (<em>δ</em>¹³C value), an indicator of long-term water use efficiency (WUE) of desert plants and a comprehensive value reflecting the whole life history of plants, was widely applied to illustrate the response of <em>δ</em>¹³C values in plants to environment factors. Therefore, there must exist an important relevance between plant anatomical structure and <em>δ</em>¹³C value to some degree. However, most of studies on plant anatomical structure have been focused on its relationships with drought resistance, environmental plasticity and plant taxonomy for a long time, little was known about its response to WUE indicated by <em>δ</em>¹³C value. In this paper, the relationship between plant anatomical structure and <em>δ</em>¹³C value was analysed in the middle reaches of Heihe River basin, in order to find an effective indicator for WUE from the point of plant anatomical structure. The results showed that: (1)all the plants with axial photosynthetic organs had higher <em>δ</em>¹³C values that those with leafy organs but <em>Hedysarum scoparium</em>. (2) The variation range of thicknesses of the photosynthetic organs and different tissues among different desert plants was large. The maximum value of the leaf thickness (<em>Tl</em>) or axis diameter (<em>Da</em>) was 6.9 times higher than the minimum, and those of cuticle thickness (<em>Tc</em>), epidermis thickness (<em>Te</em>), palisade tissue thickness (<em>Tp</em>), spongy tissue thickness (<em>Ts</em>) and aqueous tissue thickness (<em>Ta</em>) were 5.8,11,4,3.5 and 3.5 times higher than the corresponding minimum, respectively. <em>Tl</em> or <em>Da</em> and <em>Te</em> of most desert plants with axial photosynthetic organs were higher than those with leafy organs. (3)The correlation analysis between different tissue thicknesses of desert plants and their <em>δ</em>¹³C values indicated that: there was a significantly positive correlation between <em>δ</em>¹³C value and <em>Tl</em> or <em>Da</em>, with the correlation coefficient 0.719 (<em>P</em><0.01), while the correlations of <em>δ</em>¹³C value with other tissue thicknesses were not significant. In conclusion, from the point of the anatomic structure of photosynthetic organs of desert plants, WUE could be indicated by <em>Tl</em> or <em>Da</em>. The higher <em>Tl</em> or <em>Da</em>, the higher WUE desert plant possesses, and WUE of plants with axial photosynthetic organs are higher than those with leafy organs.