High Air Humidity Causes Atmospheric Water Absorption via Assimilating Branches in the Deep-Rooted Tree Haloxylon ammodendron in an Arid Desert Region of Northwest China.

Xue-Wei Gong,Xue-Min He,Guang-Hui Lü,Xiao-Dong Yang,Binoy Sarkar

doi:10.3389/fpls.2019.00573

Xue-Wei Gong, Xue-Min He + Show 3 more

Open Access

https://doi.org/10.3389/fpls.2019.00573

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Abstract

Atmospheric water is one of the main water resources for plants in arid ecosystems. However, whether deep-rooted, tomentum-less desert trees can absorb atmospheric water via aerial organs and transport the water into their bodies remains poorly understood. In the present study, a woody, deep-rooted, tomentum-less plant, Haloxylon ammodendron (C.A. Mey.) Bunge, was selected as the experimental object to investigate the preconditions for and consequences of foliar water uptake. Plant water status, gas exchange, and 18O isotopic signatures of the plant were investigated following a typical rainfall pulse and a high-humidity exposure experiment. The results showed that a high content of atmospheric water was the prerequisite for foliar water uptake by H. ammodendron in the arid desert region. After atmospheric water was absorbed via the assimilating branches, which perform the function of leaves due to leaf degeneration, the plant transported the water to the secondary branches and trunk stems, but not to the taproot xylem or the soil, based on the 18O isotopic signatures of the specimen. Foliar water uptake altered the plant water status and gas exchange-related traits, i.e., water potential, stomatal conductance, transpiration rate, and instantaneous water use efficiency. Our results suggest that atmospheric water might be a subsidiary water resource for sustaining the survival and growth of deep-rooted plants in arid desert regions. These findings contribute to the knowledge of plant water physiology and restoration of desert plants in the arid regions of the planet.

Highlights

IntroductionWater is the limiting factor on the ecological performance of plants (Kidron 2010; Yang et al, 2014a; Dai et al, 2015; Yang et al, 2017)
In arid ecosystems, water is the limiting factor on the ecological performance of plants (Kidron 2010; Yang et al, 2014a; Dai et al, 2015; Yang et al, 2017)
Our results showed that the relative humidity (RH) values at any time during the rainfall pulse were significantly higher than those during the three typical sunny days (Figure 2A) (p < 0.01)

Summary

Introduction

Water is the limiting factor on the ecological performance of plants (Kidron 2010; Yang et al, 2014a; Dai et al, 2015; Yang et al, 2017). Atmospheric water is an unstable and scarce water source, while groundwater is a more stable and abundant water source (Dawson and Pate, 1996) Due to their perennial nature, deeprooted woody plants in arid regions must increase carbon investments in their roots to obtain a large amount of groundwater to satisfy a higher water demand (Dai et al, 2015). Because they are annual or ephemeral plants, shallow-rooted herbaceous plants only absorb a small amount of atmospheric water to guarantee their growth (Zhuang and Ratcliffe, 2012; Yang et al, 2017). Whether deep-rooted desert trees can absorb atmospheric water and the assumption that the atmospheric water content is closely related to atmospheric water uptake via the aerial organs of deep-rooted desert plants have not yet been properly assessed in previous studies (Yan et al, 2015; Wang et al, 2016b)

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