Enhanced drought resistance in tomato via reduced auxin sensitivity: delayed dehydration and improved leaf resistance to embolism

Abstract

AbstractAuxins are master regulators of plant development and auxin perception mutants display smaller leaves, lower transpiration, and narrower xylem vessels than their corresponding wild types. Here, we evaluated whether the leaf embolism resistance and overall plant resistance to drought are altered in the auxin perception mutant diageotropica (dgt). Our assessments demonstrate that the dgt mutants in tomato exhibit considerably smaller xylem vessels in stems (‐24%), leaf petioles (‐43%), and leaf midribs (‐34%) than the wild type. Alongside narrower vessels, dgt mutants exhibited greater xylem cell wall thickness‐to‐conduit diameter and greater leaf embolism resistance than the wild type. The water potential at 50% cumulative leaf embolism (P50) of dgt and wild type was ‐1.39 and ‐1.14 MPa, respectively. Plants of dgt also exhibited higher stomatal safety margin (water potential difference between stomatal closure and P50), needed a longer time to reach their P50 in a dry‐down experiment, and showed a faster recovery in leaf gas exchange upon rehydration than the wild type. The impaired auxin signaling resulted in lower canopy area and stomatal conductance, which likely contributed to delaying the time for plants to reach hydraulic damage during drought. These findings demonstrate a clear association between structural and physiological changes and improved resistance against drought‐induced hydraulic dysfunction in the dgt tomato mutant.