Salvi Amanda M, Smith Duncan D, Adams Mark A, McCulloh Katherine A, Givnish Thomas J
Department of Botany, University of Wisconsin-Madison, Madison, WI, 53705, USA.
School of Ecosystem and Forest Sciences, University of Melbourne, Creswick, Vic., 3363, Australia.
New Phytol. 2021 Jun;230(5):1844-1855. doi: 10.1111/nph.17304. Epub 2021 Apr 2.
Photosynthetic sensitivity to drought is a fundamental constraint on land-plant evolution and ecosystem function. However, little is known about how the sensitivity of photosynthesis to nonstomatal limitations varies among species in the context of phylogenetic relationships. Using saplings of 10 Eucalyptus species, we measured maximum CO -saturated photosynthesis using A-c curves at several different leaf water potentials (ψ ) to quantify mesophyll photosynthetic sensitivity to ψ (MPS), a measure of how rapidly nonstomatal limitations to carbon uptake increase with declining ψ . MPS was compared to the macroclimatic moisture availability of the species' native habitats, while accounting for phylogenetic relationships. We found that species native to mesic habitats have greater MPS but higher maximum photosynthetic rates during non-water-stressed conditions, revealing a trade-off between maximum photosynthesis and drought sensitivity. Species with lower turgor loss points have lower MPS, indicating coordination among photosynthetic and water-relations traits. By accounting for phylogenetic relationships among closely related species, we provide the first compelling evidence that MPS in Eucalyptus evolved in an adaptive fashion with climatically determined moisture availability, opening the way for further study of this poorly explored dimension of plant adaptation to drought.
光合作用对干旱的敏感性是陆地植物进化和生态系统功能的一个基本限制因素。然而，在系统发育关系的背景下，对于不同物种光合作用对非气孔限制的敏感性如何变化，我们却知之甚少。我们使用10种桉树苗，在几个不同的叶片水势（ψ）下，通过A - c曲线测量了最大CO₂饱和光合作用，以量化叶肉光合作用对ψ的敏感性（MPS），这是一种衡量碳吸收的非气孔限制随ψ下降而增加的速度的指标。在考虑系统发育关系的同时，将MPS与物种原生栖息地的宏观气候水分可利用性进行了比较。我们发现，中生栖息地的物种具有更高的MPS，但在非水分胁迫条件下具有更高的最大光合速率，这揭示了最大光合作用和干旱敏感性之间的权衡。膨压损失点较低的物种具有较低的MPS，这表明光合和水分关系性状之间存在协调性。通过考虑近缘物种之间的系统发育关系，我们提供了首个令人信服的证据，表明桉属植物的MPS是随着气候决定的水分可利用性以适应性方式进化的，为进一步研究植物适应干旱这一鲜有探索的维度开辟了道路。
