Pressure-volume curve traits of chia (Salvia hispanica L.): an assessment of water-stress tolerance under field conditions

Chia is a species that has been described as being tolerant to water stress, but its ecological adaptative responses to water deficits are unknown. The effect of water availability on the performance of chia cultivated at three irrigation levels (100%, 70%, and 40% of the reference evapotranspiration) was evaluated under field conditions. The growth and leaf-water relation traits of the plants were measured using pressure-volume curves (PVCs) and vapor pressure osmometry to estimate the water potential at the turgor loss point, relative water content, symplast volume, osmotic potential at maximum turgor, elasticity modulus of cell walls, and the leaf water potential and its components. The results indicated that chia plants adjust their physiological traits under water stress and suggested that they maintain turgor by decreasing both the water potential at the point of turgor loss and the solute potential to maintain functionality. This osmotic adjustment capacity in chia reached a maximum value of 0.5 MPa near the harvest stage. These adjustments allowed Salvia hispanica to maintain its growth and stomatal conductance at a water stress level of 70% of the reference evapotranspiration. Under water stress at 40% of the reference evapotranspiration, independent of these trait adjustments, chia growth virtually stopped, and its stomatal conductance approached zero. Under these conditions, chia experienced stomatal closure at a leaf water potential (- 1.55 MPa) that was higher than the water potential at the point of turgor loss (similar to - 3.0 MPa). It is concluded that chia is able to perform osmotic adjustment and that this process interacts with another series of variables that allow chia to adapt to drought stress.