Abstract
Plant hydraulic conductivity (K) refers to the rate of water flow (kg s−1) per unit pressure drop (MPa), which drives flow through the plant organ system. It is an important eco-physiology index for measuring plant water absorption and transport capacity. A field study was conducted in the arid region of the Heihe River Basin in northwestern China, plant hydraulic conductivity was measured by high-pressure flowmeter (HPFM) to investigate the characteristics of hydraulic conductivity of typical dominant desert plants (Reaumuria soongarica M., Nitraria sphaerocarpa M., and Sympegma regelii B.) and their relationship with functional traits of leaves, stems, and roots, and explaining their adaptation strategies to desert environment from the perspective of plant organs hydraulic conductivity. The results showed that the hydraulic conductivity of the leaves and stems of R. soongarica and N. sphaerocarpa (KLA, leaf hydraulic conductivity per unit leaf area; KLW, leaf hydraulic conductivity per unit leaf weight; KSLA, stem hydraulic conductivity per unit leaf area; KSLW, stem hydraulic conductivity per unit leaf weight) were significantly lower than those of S. regelii, while their fine root (KRL, root hydraulic conductivity per unit leaf length; KRSA, root hydraulic conductivity per unit root surface area) and whole root (KTRW, whole root hydraulic conductivity per unit root weight) of hydraulic conductivity were significantly higher than those of S. regelii. In addition, KLA and KLW, KSLA and KSLW, and KRL and KRSA in three desert plants all exhibited consistent trends. Correlation analysis illustrated that the hydraulic conductivity of leaves and stems had a significantly positive correlation, but they had no significant negative correlation with the specific leaf weight (SLW, specific leaf weight). The hydraulic conductivity of fine root weight (KRW, root hydraulic conductivity per unit root weight) and specific root surface area (SRSA, specific root surface area) showed significantly positive correlation (r = 0.727, P < 0.05). The results demonstrated that the R. soongarica and N. sphaerocarpa preserved their water content through the strong leaf absorption capacity of soil water and the low water dispersion rates of leaves to adapt to the harsher arid habitat, which is more drought tolerant than S. regelii.
Highlights
IntroductionTo adapt to the arid environment, plants formed multiple morphologic and physiologic adaptation strategies to resist the drought stress environment of the outside world, including plant morphology and structure, growth rate, water use efficiency, antioxidant system, and developed root system [3]
Water is a limiting factor for survival and growth of desert plants [1]
Previous research regarding plant hydraulic architecture has mainly concentrated on trees and crops [5,8,9], the economic importance of trees and crops had an impact on the number of studies addressing their hydraulic architecture; the water transport distance of shrubs is shorter than that of the trees and crops, and the branching system of shrubs is more complex, the hydraulic architecture of shrubs is of less concern
Summary
To adapt to the arid environment, plants formed multiple morphologic and physiologic adaptation strategies to resist the drought stress environment of the outside world, including plant morphology and structure, growth rate, water use efficiency, antioxidant system, and developed root system [3]. Hydraulic architecture involves different morphologies, structures, and water transport and supply strategies formed by plants for adaption to survival and competition requirement in a particular environment. Research hydraulic architecture of plants can help us understand the characteristics of water physiological ecology and clarify the mechanism of drought resistance of plants. Studies have shown that the roots and leaves hydraulic conductivity of wheat and soybean were decreased or lost under water stress, and Pinus tabulaeformis and Platycladus orientalis showed the same trend [5,6,7]. Zheng et al [12]
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