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Leaf hydraulic parameters are more plastic in species that experience a wider range of leaf water potentials
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International audience. 1. Many plant species experience large differences in soil moisture availability within a season, potentially leading to a wide range of leaf water potentials (Psi(LEAF)). In order to decrease the risk of leaf dehydration, among species, there is a continuum ranging from strict control (isohydry) to little control (anisohydry) of minimum Psi(LEAF). 2. In central Texas USA, species are exposed to a range of soil moisture from wet springs to hot, dry summers. There are diverging water management strategies among the four dominant woody species in this system; two of these species are more isohydric (Prosopis glandulosa, Quercus fusiformis) while two others are more anisohydric (Diospyros texana, Juniperus asheii). 3. To maintain leaf turgor and photosynthesis during periods of limited soil moisture, anisohydric species may adjust leaf hydraulic parameters more than isohydric species. To test this hypothesis, we quantified iso/anisohydry from 3 years of Psi(LEAF) predawn and midday measurements, and we measured the changes in turgor loss points (Psi(TLP)), osmotic potential at full hydration (Psi(pi 100)), and resistance to leaf hydraulic dysfunction (leaf P-50) throughout the spring and summer of 2016. 4. Diospyros and Juniperus experienced more negative Psi(LEAF) and adjusted Psi(TLP) and Psi(pi 100) in response to both drying soils during the summer also in response to rainfall events during September. In contrast, the more isohydric species (Quercus and Prosopis) did not appear to adjust Psi(TLP) or Psi(pi 100) in response to soil moisture. The more anisohydric species also adjusted leaf P-50 during periods of reduced soil moisture. 5. Our results suggest that species that experience wider ranges of Psi(LEAF) have a greater ability to alter leaf hydraulic properties. This provides insight on how species with different strategies for water potential regulation may modify properties to mitigate drought effects in the future.
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