More than iso/anisohydry: Hydroscapes integrate plant water use and drought tolerance traits in 10 eucalypt species from contrasting climates

Abstract

The iso/anisohydric continuum describes how plants regulate leaf water potential and is commonly used to classify species drought response strategies. However, drought response strategies comprise more than just this continuum, incorporating a suite of stomatal and hydraulic traits. Using a common garden experiment, we compared and contrasted four metrics commonly used to describe water use strategy during drought in 10 eucalyptus species comprising four major ecosystems in eastern Australia. We examined the degree to which these metrics were aligned with key stomatal and hydraulic traits related to plant water use and drought tolerance. Species rankings of water use strategy were inconsistent across four metrics. A newer metric (Hydroscape) was strongly linked to various plant traits, including the leaf turgor loss (TLP), water potential at stomatal closure (Pgs90), leaf and stem hydraulic vulnerability to embolism (PL50 and Px50), safety margin of hydraulic segmentation (HSMHS), maximum stomatal conductance (gsmax) and Huber value (HV). In addition, Hydroscape was correlated with climatic variables representing the water availability at the seed source site. Along the continuum of water regulation strategy, species with narrow Hydroscapes tended to occupy mesic regions and exhibit high TLP, PL50 and Px50 values and narrow HSMHS. High gsmax recorded in species with broad hydroscapes was also associated with high HV. Despite a fourfold difference in Hydroscape area, all species closed their stomata prior to the onset of hydraulic dysfunction, suggesting a common stomatal response across species that minimizes embolism risk during drought. Hydroscape area is useful in bridging stomatal regulation, hydraulic architecture and species drought tolerance, thus providing insight into species water use strategies. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13320/suppinfo is available for this article.

Desiccation time during drought is highly predictable across species of Eucalyptus from contrasting climates

“…In the current study, the largest increase in plant desiccation time due to leaf shedding was recorded in the arid‐zone species E. largiflorens , which started to shed leaves at higher water potentials relative to Ψ crit than other species. It is also consistent with large differences between the hydraulic vulnerability of leaves and stems recorded for this and other arid‐zone species in our sample group (Li et al ., ), suggesting that leaves may act as hydraulic fuses in delaying the onset of cavitation in more carbon‐expensive stems (Tyree & Ewers, ; Johnson et al ., ). Interestingly, the onset of leaf shedding tended to occur earlier in species from more mesic environments with lower levels of leaf and stem cavitation resistance (Li et al ., , ).…”

“…It is also consistent with large differences between the hydraulic vulnerability of leaves and stems recorded for this and other arid‐zone species in our sample group (Li et al ., ), suggesting that leaves may act as hydraulic fuses in delaying the onset of cavitation in more carbon‐expensive stems (Tyree & Ewers, ; Johnson et al ., ). Interestingly, the onset of leaf shedding tended to occur earlier in species from more mesic environments with lower levels of leaf and stem cavitation resistance (Li et al ., , ). This suggests a possible causal link between embolism and leaf shedding (Hochberg et al ., ), although there is still some uncertainty regarding the consistency of the shedding response with leaf water status under strongly contrasting conditions.…”

Below‐ground determinants and ecological implications of shrub species' degree of isohydry in subtropical pine plantations

“…Another knowledge gap concerns the associations between below‐ground and above‐ground hydraulic traits that determine a species' degree of iso/anisohydry. Studies have shown that where species operate along the isohydric to anisohydric continuum results from the integration of properties of different plant organs (Fu et al , 2019; Li et al , 2019; Mirfenderesgi et al , 2019). At the leaf level, more isohydric species tend to have less negative turgor loss point (Ψ TLP ), slower kinetics of stomatal opening and activation of photosynthesis, but higher intrinsic water‐use efficiency and are more likely to exhibit drought‐induced leaf shedding (Meinzer et al , 2017; Fu & Meinzer, 2019; Li et al , 2019).…”

“…Studies have shown that where species operate along the isohydric to anisohydric continuum results from the integration of properties of different plant organs (Fu et al , 2019; Li et al , 2019; Mirfenderesgi et al , 2019). At the leaf level, more isohydric species tend to have less negative turgor loss point (Ψ TLP ), slower kinetics of stomatal opening and activation of photosynthesis, but higher intrinsic water‐use efficiency and are more likely to exhibit drought‐induced leaf shedding (Meinzer et al , 2017; Fu & Meinzer, 2019; Li et al , 2019). At the stem level, more isohydric species tend to have higher hydraulic capacitance, conductivity and safety margins, but lower wood density and xylem resistance to embolism (Klein, 2014; Martínez‐Vilalta et al , 2014; Fu et al , 2019; Mirfenderesgi et al , 2019).…”

Corrigendum

“…Li, X, Blackman, C. J., Peters, J. M. R., Choat, B., Rymer, P. D., Medlyn, B. E., Tissue, D. T. (2019). More than iso/anisohydry: Hydroscapes integrate plant water use and drought tolerance traits in 10 eucalypt species from contrasting climates.…”