Marks Rose A, Burton James F, McLetchie D Nicholas
Department of Biology, University of Kentucky, 101 Thomas Hunt Morgan Building, Lexington, KY 40506, USA
Department of Biology, University of Kentucky, 101 Thomas Hunt Morgan Building, Lexington, KY 40506, USA.
Ann Bot. 2016 Aug;118(2):347-56. doi: 10.1093/aob/mcw102. Epub 2016 Jun 20.
Adaptations allowing plants to cope with drying are particularly relevant in the light of predicted climate change. Dehydration tolerance (DhT, also dehydration-tolerant) is one such adaptation enabling tissue to survive substantial drying. A great deal of work has been conducted on highly DhT species. However, bryophytes showing less intense and variable DhT are understudied, despite the potential for these species to provide an informative link between highly tolerant and sensitive species. In this study, we tested the degree to which DhT varies across populations and the sexes of a species expected to exhibit a moderate DhT phenotype.
To test predicted patterns of tolerance we assessed DhT in males and females of Marchantia inflexa from two distinct habitat types that differ in water availability. Both common garden and field-collected tissue was subjected to drying assays at multiple intensities and recovery was monitored by chlorophyll florescence. Verification studies were conducted to confirm the level of dehydration, the rate of drying and the associated changes in photosynthetic physiology.
We confirmed our expectation that M. inflexa is able to tolerate moderate dehydration. We also found that females exhibited higher DhT than males, but populations did not differ in DhT when cultured in a common garden. However, field-collected samples exhibited differences in DhT corresponding to environmental dryness, suggesting plasticity in DhT.
By studying a less extreme DhT phenotype we gained insight into how more sensitive (yet still tolerant) organisms cope with dehydration. Additionally, the identified sex-specific variation in DhT may explain ecological patterns such as female-biased sex ratios. Furthermore, plasticity in DhT has the potential to inform management practices aimed at increasing tolerance to drought conditions.
鉴于预测的气候变化，使植物能够应对干旱的适应性尤为重要。脱水耐受性（DhT，也称为耐旱性）就是这样一种适应性，使组织能够在大量干燥的情况下存活。已经对高度耐旱的物种进行了大量研究。然而，尽管这些物种有可能在高度耐受和敏感物种之间提供有价值的联系，但对表现出较弱且可变的脱水耐受性的苔藓植物的研究却很少。在本研究中，我们测试了一种预计表现出中等脱水耐受性表型的物种在不同种群和性别之间脱水耐受性的变化程度。
为了测试预测的耐受性模式，我们评估了来自两种不同生境类型（水分可利用性不同）的弯叶地钱的雄性和雌性的脱水耐受性。对温室栽培和野外采集的组织都进行了多种强度的干燥试验，并通过叶绿素荧光监测恢复情况。进行了验证研究以确认脱水水平、干燥速率以及光合生理的相关变化。
我们证实了我们的预期，即弯叶地钱能够耐受中等程度的脱水。我们还发现雌性表现出比雄性更高的脱水耐受性，但在温室栽培时不同种群的脱水耐受性没有差异。然而，野外采集的样本在脱水耐受性方面表现出与环境干燥程度相对应的差异，这表明脱水耐受性具有可塑性。
通过研究一种不太极端的脱水耐受性表型，我们深入了解了更敏感（但仍具耐受性）的生物体如何应对脱水。此外，所确定的脱水耐受性的性别特异性差异可能解释了诸如雌性偏向的性别比例等生态模式。此外，脱水耐受性的可塑性有可能为旨在提高对干旱条件耐受性的管理实践提供参考。
