Water Deficit Modulates the CO2 Fertilization Effect on Plant Gas Exchange and Leaf-Level Water Use Efficiency: A Meta-Analysis

Abstract

Elevated atmospheric CO2 concentrations ([eCO2]) and soil water deficits significantly influence gas exchange in plant leaves, affecting the carbon-water cycle in terrestrial ecosystems. However, it remains unclear how the soil water deficit modulates the plant CO2 fertilization effect, especially for gas exchange and leaf-level water use efficiency (WUE). Here, we synthesized a comprehensive dataset including 554 observations from 54 individual studies and quantified the responses for leaf gas exchange induced by e[CO2] under water deficit. Moreover, we investigated the contribution of plant net photosynthesis rate (Pn) and transpiration rates (Tr) toward WUE in water deficit conditions and e[CO2] using graphical vector analysis (GVA). In summary, e[CO2] significantly increased Pn and WUE by 11.9 and 29.3% under well-watered conditions, respectively, whereas the interaction of water deficit and e[CO2] slightly decreased Pn by 8.3%. Plants grown under light in an open environment were stimulated to a greater degree compared with plants grown under a lamp in a closed environment. Meanwhile, water deficit reduced Pn by 40.5 and 37.8%, while increasing WUE by 24.5 and 21.5% under ambient CO2 concentration (a[CO2]) and e[CO2], respectively. The e[CO2]-induced stimulation of WUE was attributed to the common effect of Pn and Tr, whereas a water deficit induced increase in WUE was linked to the decrease in Tr. These results suggested that water deficit lowered the stimulation of e[CO2] induced in plants. Therefore, fumigation conditions that closely mimic field conditions and multi-factorial experiments such as water availability are needed to predict the response of plants to future climate change.

Effects of elevated CO2 concentration and experimental warming on morphological, physiological, and biochemical responses of winter wheat under soil water deficiency

“…The micrographs characterizing the distribution of stomata on the leaves were digitized in the same coordinate system by Arc GIS 10.0 software to obtain the spatial coordinate values of each stoma. Next, the point pattern analysis was estimated with Ripley's K-function, a cumulative density function using the second moment of all point-to-point distances to evaluate twodimensional distribution patterns at different scales (Xu, 2015;Zheng et al, 2020;Li et al, 2021). The results were plotted as Lhat(d) values, calculated as:…”

“…As a result, the increased atmospheric [CO 2 ] has resulted in a rapid rise in global surface temperature over the past decades (Barlow et al, 2015;Jin et al, 2017), even the average global temperature is predicted to rise 2 to 6 °C depending on the concentrations of greenhouse gases such as CO 2 in the atmosphere (IPCC, 2021). It has been estimated that global precipitation may decline under future climatic warming, and meanwhile the spatial and temporal patterns of global/regional precipitation distribution may also become uneven (Chun et al, 2011;Zhang et al, 2020), thus drought and elevated temperature may constrain plant growth and crop yield alone or in combination (Yu et al, 2012), although elevated [CO 2 ] generally facilitates plant growth and promotes plant adaptation to climate change (Kirkham, 2011;Xu, 2015;Li et al, 2021). Unfortunately, simultaneous drought stress, elevated [CO 2 ] and elevated temperature has already occurred in summer in many regions throughout the world, which is even more detrimental to plant growth than either stress alone.…”

“…It has been well demonstrated that various physiological, biochemical, and molecular processes of plants are sensitive to water deficiency, elevated [CO 2 ], and elevated temperature alone or the combination (Mirwais et al, 2006;Yu et al, 2012;Bencze et al, 2014;Xu, 2015;Zheng et al, 2018;Duan et al, 2019a;Zheng et al, 2020;Li et al, 2021). Elevated [CO 2 ] generally promotes leaf photosynthesis, plant growth, and crop yield through the "CO 2 fertilization" effect with enhancing the ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) carboxylation efficiency (Arndal et al, 2014;Niaz et al, 2020) and inhibiting leaf respiration rates (Yu et al, 2012;Xu, 2015).…”

A global meta-analysis of woody plant responses to elevated CO2: implications on biomass, growth, leaf N content, photosynthesis and water relations

“…9a, d and g). This response is surprising given that stomatal closure limits water loss (Zhang et al 2021;Li et al 2021). It is, however, worthy to postulate that higher reduction in g s exhibited by leguminous trees increased leaf temperature, which probably amplified diffusion out of water in the leaves (Kerstiens et al 1995).…”

“…Atmospheric CO 2 (atCO 2 ) have increased globally since the industrial revolution, owing to fossil fuel combustion and land cover changes due to increasing human population and the need for rapid economic growth (Jayawardena et al 2021). Over the past decade, atCO 2 has been increasing at an alarming rate of 2.4 μmol mol −1 year −1 (Li et al 2021) and it is currently 50% higher than pre-industrial levels (Ebi et al 2021). It is predicted that atCO 2 may rise as high as 936 μmol mol −1 by the year 2100 if greenhouse gas emissions are not mitigated (Hu et al 2018).…”