Optimal leaf water status regulation of plants in drylands

Abstract

Leaf water potential regulation is a key process in whole plant and ecosystem functioning. While low water potentials induced by open stomata may initially be associated with greater CO 2 supply and a higher water flux from the rhizosphere to the canopy, they also inhibit cell growth, photosynthesis and ultimately water supply. Here, we show that plants regulate their leaf water potential in an optimal manner under given constraints using a simple leaf water status regulation model and data from a global dryland leaf water potential database. Model predictions agree strongly with observations across locations and species and are further supported by experimental data. Leaf water potentials non-linearly decline with soil water potential, underlining the shift from maximizing water supply to avoiding stress with declining water availability. Our results suggest that optimal regulation of the leaf water status under varying water supply and stress tolerance is a ubiquitous property of plants in drylands. The proposed model moreover provides a novel quantitative framework describing how plants respond to short- and long-term changes in water availability and may help elaborating models of plant and ecosystem functioning.

Severe drought limits trees in a semi‐arid savanna

“…, Ratzmann et al. ), and most of these traits are as‐yet poorly known among savanna trees, particularly in African species. Characterizing this variability across species should be a priority, especially for predicting compositional and functional shifts under future increases in drought frequency and severity.…”

Convergent Variations in the Leaf Traits of Desert Plants

“…The LWP plays an important role in stomatal conductance, CO 2 uptake, xylem functioning, water supply and the growth of cells. When plants uptake CO 2 , then they drop their LWP through transpiration to avoid a reduction in growth [ 61 ]. However, the LWP mean value ( Table 2 ) was found significantly lower than all plant types of the USA [ 62 ].…”

“…For plant life forms, desert shrubs accrued more C, N and K and showed more LWP than the herbs and subshrubs; and subshrubs showed higher concentration of P than the herbs and shrubs; while, the value of δ 13 C was found roughly similar for all life forms, such as herbs, shrubs and subshrubs ( Table 2 ). Leaves C, N and K are tightly coupled with main biological functions, like photosynthesis, respiration and water use [ 38 , 64 ]; while, leaf water potential depict the water status of the plant [ 65 ], the key process for ecosystem functioning [ 61 ], influenced plant productivity, photosynthesis and growth [ 66 ]; so, desert plants regulate optimal leaf water status for their survival which is a basic constituent of plant functioning [ 61 ]. This is the reason shrubs dominate most of the desert lands [ 67 ].…”

“…LWP mean value ( Table 2 ) was found significantly lower than all plant types of the USA [ 62 ]. Low LWP is common in arid areas [ 61 ] and in these areas, WUE can be enhanced by reducing H 2 O and CO 2 balance [ 63 ].…”

“…The elements of the first PCA axis were primarily necessary for plant structure, photosynthesis and protein synthesis [ 19 , 32 ]. The elements associated with the second and third PCA axis were essential for enzyme activity, stomatal conductance, regulation of transpiration and plant water supply [ 53 , 61 ].…”