Physiological and anatomical changes in tomato roots in response to low water stress

Abstract

Low water availability is one of the most severe environmental stresses to agricultural systems. Therefore, understanding how plants respond to low water conditions is essential to develop and implement new management strategies. We evaluated the effects of water deficit on the water relations of tomato plants. Plants were grown under frequent watering or prolonged and repeated drying cycles (‘wet’ and ‘dry’ treatments, respectively). We measured root hydrostatic and osmotic hydraulic conductivity (Lp*hyd and Lp*os, respectively) of intact root systems, diameter of xylem elements, stem water potential, leaf abscisic acid (ABA) concentration, and stomatal conductance (gs). Plants in the ‘dry’ treatment had 36 % and 65 % lower Lp*hyd and Lp*os, respectively, 27 % smaller xylem elements, and 57 % less total xylem area than in the ‘wet’ treatment. The number of xylem vessels was similar between both treatments. Low soil water content (11 % SWC) increased leaf ABA by at least 65 % even in plants exposed to a single dry down. The ‘dry’ treatment had consistently lower gs even after plants were fully watered, which may have compromised carbon assimilation and reduced shoot biomass. In response to water deficit, tomato plants exhibited decreased root hydraulic conductivity and long-lasting root anatomical changes. As we aim for effective water use, the root traits studied here can be used to evaluate cultivar performance under novel water management strategies and as criteria for breeding selection.