Chastain Daryl R, Snider John L, Choinski John S, Collins Guy D, Perry Calvin D, Whitaker Jared, Grey Timothy L, Sorensen Ronald B, van Iersel Marc, Byrd Seth A, Porter Wesley
Delta Research and Extension Center, Plant and Soil Sciences, Mississippi State University, P.O. Box 197, Stoneville, MS 38776, USA.
Department of Crop and Soil Sciences, University of Georgia, 115 Coastal Way, Tifton, GA 31794, USA.
J Plant Physiol. 2016 Jul 20;199:18-28. doi: 10.1016/j.jplph.2016.05.003. Epub 2016 May 12.
Temperature and drought are major abiotic limitations to crop productivity worldwide. While abiotic stress physiology research has focused primarily on fully expanded leaves, no studies have investigated photosynthetic tolerance to concurrent drought and high temperature during leaf ontogeny. To address this, Gossypium hirsutum plants were exposed to five irrigation treatments, and two different leaf stages were sampled on three dates during an abnormally dry summer. Early in the growing season, ontogenic PSII heat tolerance differences were observed. Photosystem II was more thermotolerant in young leaves than mature leaves. Later in the growing season, no decline in young leaf net photosynthesis (P) was observed as leaf temperature increased from 31 to 37°C, as average midday leaf water potential (Ψ) declined from -1.25 to -2.03MPa. In contrast, mature leaf P declined 66% under the same conditions. Stomatal conductance (g) accounted for 84-98% of variability in leaf temperature, and g was strongly associated with Ψ in mature leaves but not in young leaves. We conclude that young leaves are more photosynthetically tolerant to heat and drought than mature leaves. Elucidating the mechanisms causing these ontogenic differences will likely help mitigate the negative impacts of abiotic stress in the future.
温度和干旱是全球范围内影响作物生产力的主要非生物限制因素。虽然非生物胁迫生理学研究主要集中在完全展开的叶片上，但尚无研究调查叶片发育过程中对干旱和高温同时胁迫的光合耐受性。为解决这一问题，在一个异常干旱的夏季，对陆地棉植株进行了五种灌溉处理，并在三个日期采集了两个不同叶龄阶段的样本。在生长季节早期，观察到了发育阶段的PSII耐热性差异。幼叶中的光系统II比成熟叶更耐热。在生长季节后期，随着叶片温度从31°C升高到37°C，平均午间叶片水势（Ψ）从-1.25MPa下降到-2.03MPa，幼叶的净光合速率（P）并未下降。相比之下，在相同条件下，成熟叶的P下降了66%。气孔导度（g）占叶片温度变化的84%-98%，并且g在成熟叶中与Ψ密切相关，而在幼叶中则不然。我们得出结论，幼叶比成熟叶对高温和干旱具有更强的光合耐受性。阐明导致这些发育阶段差异的机制可能有助于减轻未来非生物胁迫的负面影响。
