Impacts of soil water stress on the acclimated stomatal limitation of photosynthesis: Insights from stable carbon isotope data,Global Change Biology

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Impacts of soil water stress on the acclimated stomatal limitation of photosynthesis: Insights from stable carbon isotope data
Global Change Biology ( IF 10.8 ) Pub Date : 2020-09-24 , DOI: 10.1111/gcb.15364
Aliénor Lavergne ₁ , David Sandoval ₂ , Vincent John Hare _{1,

3} , Heather Graven _{1,

4} , Iain Colin Prentice _{2,

4,

5,

6}

Affiliation

Atmospheric aridity and drought both influence physiological function in plant leaves, but their relative contributions to changes in the ratio of leaf internal to ambient partial pressure of CO₂ (χ) – an index of adjustments in both stomatal conductance and photosynthetic rate to environmental conditions – are difficult to disentangle. Many stomatal models predicting χ include the influence of only one of these drivers. In particular, the least‐cost optimality hypothesis considers the effect of atmospheric demand for water on χ but does not predict how soils with reduced water further influence χ, potentially leading to an overestimation of χ under dry conditions. Here, we use a large network of stable carbon isotope measurements in C₃ woody plants to examine the acclimated response of χ to soil water stress. We estimate the ratio of cost factors for carboxylation and transpiration (β) expected from the theory to explain the variance in the data, and investigate the responses of β (and thus χ) to soil water content and suction across seed plant groups, leaf phenological types and regions. Overall, β decreases linearly with soil drying, implying that the cost of water transport along the soil–plant–atmosphere continuum increases as water available in the soil decreases. However, despite contrasting hydraulic strategies, the stomatal responses of angiosperms and gymnosperms to soil water tend to converge, consistent with the optimality theory. The prediction of β as a simple, empirical function of soil water significantly improves χ predictions by up to 6.3 ± 2.3% (mean ± SD of adjusted‐R²) over 1980–2018 and results in a reduction of around 2% of mean χ values across the globe. Our results highlight the importance of soil water status on stomatal functions and plant water‐use efficiency, and suggest the implementation of trait‐based hydraulic functions into the model to account for soil water stress.

中文翻译：

土壤水分胁迫对光合作用适应气孔限制的影响：来自稳定碳同位素数据的见解

大气干旱和干旱都会影响植物叶片的生理功能，但是它们对叶片内部与环境中CO ₂分压比（χ）的变化的相对贡献–是环境条件下气孔导度和光合速率调节的指标–很难解开。许多预测χ的气孔模型仅包括这些驱动因素之一的影响。特别是，最小成本最优假设考虑了大气对水的需求对χ的影响，但并未预测含水量减少的土壤如何进一步影响χ，可能导致对χ的高估在干燥条件下。在这里，我们使用C ₃木本植物中稳定碳同位素测量的大型网络来检查χ对土壤水分胁迫的适应性响应。我们估计了从理论上预期的用于解释数据差异的理论预期的羧化和蒸腾作用成本因子的比率（β），并研究了种子植物群中β（以及χ）对土壤水分和吸力的响应，叶片物候类型和地区。总体而言，β随土壤干燥呈线性下降，这意味着随着土壤中可用水的减少，沿土壤－植物－大气连续体的水运输成本增加。但是，尽管采取了不同的水力策略，但被子植物和裸子植物对土壤水分的气孔反应趋于收敛，这与最优理论是一致的。的预测β作为一个简单的，土壤水分的经验函数显著提高χ预测达6.3±2.3％（平均值± SD adjusted-的[R ²中的减少的2％左右的平均的在1980至2018年）和结果χ全球价值观。我们的结果突出了土壤水分状况对气孔功能和植物水分利用效率的重要性，并建议在模型中实施基于特征的水力函数以解决土壤水分胁迫。

更新日期：2020-11-22

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