Studies on gas exchange of Tamarix ramosissima Lbd.
Studies on gas exchange of Tamarix ramosissima Lbd.
复制标题
作者：
D. Xiong
柽柳（Tamarix Lbd），俗名盐雪松（Saltcedar），是美国十大有害入侵杂草之一，在中国被列为濒危植物。研究了多枝赤杨的气体交换特性，分析了叶水势、气孔导度、水汽压亏缺与水分利用效率的关系。结果表明，盐柏既能在沙漠中生存，又能在美国滨水区大肆蔓延的原因可能在于：①盐柏是一种潜水植物，其根系可达地下深层水; ②盐柏对不同生态位具有良好的适应性。盐柏是一种抗旱性较好的阳生植物，在极低的光强（-4.59MPa）下就能进行气体交换，从其低的光补偿点（LCP）和暗呼吸（Rd）推测其能适应潮湿和阴生环境，并且具有耐盐性。③对气孔有敏感的调节作用。气孔导度与叶片至空气VPD呈显著负相关（P≤0.05）。在干旱和湿润季节，gs对VPD的敏感性随叶片水分状况的不同而不同，并调节叶片的蒸腾作用，从而影响WUE。Gs与蒸腾速率呈显著正相关，与水分利用效率呈显著正相关（P≤ 0.0 5），当Gs即将下降时，水分利用效率达到最大值，光合和蒸腾作用受VPD的限制较小。所有这些适应性的规则可能有助于解释盐雪松在美国河岸地区的猖獗蔓延。传统上人们认为干旱的自然条件是威胁盐柏生存的根本原因，而我们的研究结果表明，主要原因是人为因素，包括过度使用水分导致地下水下降和过度采伐。
Tamarix Lbd, common name Saltcedar, one of the ten worst noxious invading weeds in USA, is classified as an endangered plant in China. We studied the gas exchange of T.ramosissima, and analysed the relationships among its leaf water potential (ψ), stomatal conductance (g s),vapor pressure deficit(VPD) and water use efficiency(WUE). The results showed, the reasons that saltcedar can both exist in the desert and spread rampantly in the riparian area in America may be:①Saltcedar is a phreatophyte, whose roots can reach the deep groundwater.②It has a good adaptability to different niches. Saltcedar is a heliophyte plant with good drought resistance, able to perform gas exchange at very lowψ(-4.59MPa).We inferred that it can adapt itself to wet and shade environments from its low light compensation point(LCP) and dark respiration(R d).Also it is salt-tolerant. ③It has a sensitive regulation of stomatal. Gs had a significant negative correlation(P≤0.05) with from leaf to air VPD. The sensitivity of g s to VPD varied with the water condition of the leaves in dry or wet seasons, and regulated its transpiration, which affected WUE. G s had a significant positive correlation withψ, and was significantly related to WUE(P≤0.05), When g s was about to decline, maximum WUE occurred and photosynthesis and transpiration were being limited slightly by VPD. All these adaptive regulations probably help to explain the rampant spread of saltcedar in the riparian region in America. Traditionally, people have thought the dry natural conditions are the ultimate reason that endanger the existance of saltcedar in the desert, while our results suggest the main reason are artificial factors including over-us of water causing a lowing of groundwater and excessive harvest.