Hydroscapes: A Useful Metric for Distinguishing Iso-/Anisohydric Behavior in Almond Cultivars

Abstract

As a consequence of climate change, water scarcity has increased the use of the iso-/anisohydric concept with the aim of identifying anisohydric or drought-tolerant genotypes. Recently, Meinzer and colleagues developed a metric for discriminating between iso- and anisohydric behavior called the hydroscape, which describes a range in which stomata control leaf water potential (Ψ) with decreasing water availability, and it is linked to several water-regulation and drought-tolerance traits. Thus, our objective was to test the usefulness of the hydroscape in discriminating between iso- and anisohydric Prunus dulcis cultivars, a species that is widely cultivated in Mediterranean central Chile due to its ability to withstand water stress. Through a pot desiccation experiment, we determined that the hydroscape was able to discriminate between two contrasting Prunus cultivars; the more anisohydric cultivar had a hydroscape 4.5 times greater than that of the other cultivar, and the hydroscape correlated with other metrics of plant water-use strategies, such as the maximum range of daily Ψ variation and the Ψ at stomatal closure. Moreover, the photosynthesis rates were also differently affected between cultivars. The more isohydric cultivar, which had a smaller hydroscape, displayed a steeper photosynthesis reduction at progressively lower midday Ψ. This methodology could be further used to identify drought-tolerant anisohydric Prunus cultivars.

Examining physiological, water relations, and hydraulic vulnerability traits to determine anisohydric and isohydric behavior in almond (Prunus dulcis) cultivars: Implications for selecting agronomic cultivars under changing climate

“…Second, the hydroscape area (hereafter, hydroscape) was measured following methodology described in Meinzer et al (2016) and Álvarez-Maldini et al (2021) . In brief, the hydroscape is the area comprising the Ψ pd vs. Ψ min regression line and a 1:1 line, which is calculated according to Equation 3:…”

“…To assess the relationship between Ψ pd and Ψ min , a first-order kinetic model was fitted using PROC REG procedure (SAS Institute Inc., Cary, NC, United States) ( Álvarez-Maldini et al, 2021 ).…”

“…Thus, larger hydroscapes are indicative of a higher degree of anisohydry. This methodology has been previously assessed in almond rendering consistent results with other traits related to stomatal stringency during water stress ( Álvarez-Maldini et al, 2021 ).…”

“…The first irrigation treatment, wellwatered (WW), maintained plants at container capacity for the remainder of the experiment. For the second irrigation treatment, pot desiccation (PD), irrigation ceased allowing for a progressive decrease in substrate water content due to plant transpiration (Álvarez-Maldini et al, 2021). To ensure that water losses corresponded to plant transpiration only and 10.3389/fpls.2022.974050 not to evaporation from the substrate, the surface of each pot was covered with a plastic film, allowing only the plant stem to emerge.…”

Using δ¹³C and hydroscapes for discriminating cultivar specific drought responses

“…Conversely, a small hydroscape indicates a genotype with more strict stomatal control (i.e., more isohydric). This methodology has shown to be effective in classifying drought-responses of different species (Li et al, 2019, Meinzer et al, 2016, Álvarez-Maldini et al, 2021. Hydroscapes, however, are time-consuming to produce, requiring multiple measurements of Ψ PD and Ψ L over a wide range of water deficits.…”