Water availability influences thermal safety margins for leaves
Water availability influences thermal safety margins for leaves
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DOI：
10.1111/1365-2435.13868
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发表时间：
2021-07-08
影响因子：
5.2
通讯作者：
Leigh, Andrea
中科院分区：
文献类型：
--
作者：
Cook, Alicia M.;Berry, Neil;Leigh, Andrea
1.植物生理耐热性测量的一个应用是评估气候变化下对环境温度升高的脆弱性。热安全裕度（TSM）是植物生理耐受性与环境温度之差，是评价植物热脆弱性的常用指标。然而，在评价热脆弱性时，需要考虑生物和方法方面的问题，这些问题有可能大大改变评估结果。其中两个方面包括叶片与气温的关系和气温数据收集的尺度。我们生长的植物的沙漠物种，Myoporum montanum，在原位水分胁迫和良好的浇水条件下，并测量其叶片温度和光合耐热性（T-50阈值），每三天超过12天在夏季。根据叶片温度计算热安全裕度，并与当地和区域气温计算的热安全裕度进行比较.结果表明，植物的耐热性和热脆弱性评价随水分状况的变化而变化。当水是现成的，植物保持广泛的叶温安全裕度和显示部分恒温。当蒸腾降温受限时，叶片温度升高对应于叶片变温和高温现象的发生、较高的耐热性和较窄的安全裕度.我们的研究表明，高生理热阈值不一定反映了广泛的安全裕度，而是可以表明更大的脆弱性和热应激暴露的风险增加。使用空气温度计算TSM也可以大大改变边距宽度。在可能的情况下，在评估热脆弱性时使用叶片温度将导致更有意义的脆弱性评估。我们建议在测量和解释植物TSM时，考虑温度测量的来源和时间配对以及植物水分状况。
1. One application of plant physiological heat tolerance measurements is the assessment of vulnerability to increasing environmental temperatures under climatic change. A thermal safety margin (TSM), the difference between physiological tolerance and environmental temperature, is a common metric for the assessment of plant thermal vulnerability. However, there are biological and methodological aspects to consider when evaluating thermal vulnerability that have the potential to substantially alter the assessments. Two such aspects include the leaf to air temperature relationship and the scale at which air temperature data are collected.2. We grew plants of a desert species, Myoporum montanum, in situ under water-stressed and well-watered conditions, and measured their leaf temperatures and photosynthetic heat tolerance (T-50 threshold) every third day over 12 days in summer. Thermal safety margins were calculated based on leaf temperatures and compared to those calculated with local and regional air temperatures.3. We found that heat tolerance and the thermal vulnerability assessment of a plant changed with water status. When water was readily available, plants maintained wide leaf temperature safety margins and displayed partial homeothermy. When cooling via transpiration was limited, increasing leaf temperature corresponded with occurrences of leaf poikilo-and megathermy, higher heat tolerance and narrower safety margins.4. Our study shows high physiological heat thresholds are not necessarily reflective of wide safety margins, but instead can indicate a greater vulnerability and increased risk of heat stress exposure. Calculating TSMs using air temperatures can also substantially alter margin widths. Where possible, the use of leaf temperatures in assessments of thermal vulnerability will lead to more meaningful vulnerability assessments. We recommend considering the source and temporal pairing of temperature measurements as well as plant water status, when measuring and interpreting plant TSMs.