Tomato Yields: Harnessing the “Golden Hour”

Traditional static measurements often fall short when predicting crop yields and drought tolerance. Because single-point readings capture only a moment in time, they miss how plants dynamically adjust their water use to changing sun, heat, and moisture levels throughout the day. A breakthrough study led by researchers at The Hebrew University of Jerusalem demonstrates that tracking the continuous, whole-plant water-loss dynamics of young tomato plants can unlock key secrets to breeding higher-yielding and more resilient crops.

By pairing multi-year field data of Solanum pennellii introgression lines with continuous gravimetric phenotyping on the automated PlantArray platform, the researchers uncovered a critical physiological strategy: high-yielding “ideotype” (i.e. ideal plant model) lines optimize their water use early in the day. Under water-deficit conditions, top-performing varieties like IL5-2 and IL11-4 exhibit a distinct peak in canopy conductance during the early morning hours, a phenomenon dubbed the “golden hour”. During this window, when photosynthetically active radiation is plentiful but vapor pressure deficit remains low, the plants open their stomata to maximize carbon intake while minimizing wasteful water loss.

As environmental conditions heat up toward midday, these ideotype plants rapidly downregulate stomatal conductance, conserving critical soil moisture before atmospheric demand reaches its peak. In contrast, lower-performing lines open their stomata later in the day and maintain wide apertures longer into the afternoon, losing significantly more water for every unit of carbon fixed.

Beyond daily water management, the study highlights a counterintuitive finding regarding drought recovery. Varieties with higher overall transpiration rates under well-irrigated conditions were previously assumed to be more vulnerable to drought damage. However, the ideotype lines demonstrated remarkable physiological resilience, bouncing back to their pre-stress transpiration levels faster than conservative water users once irrigation resumed. Cumulative transpiration during the growing period was strongly correlated with final shoot biomass and recovery capacity.

Anatomically, these dynamic responses are tied to specific stomatal traits, including higher ratios of microscopic pores on the lower (abaxial) relative to the upper (adaxial) leaf surface, alongside rapid diurnal aperture adjustments. By screening young plants for these early-stage dynamic traits, breeders can identify high-yielding, drought-tolerant crop candidates far earlier in the breeding process, saving vital time and resources in the race to adapt agriculture to a changing climate.

Source : Science Direct/Plant Science

Reference : https://doi.org/10.1016/j.plantsci.2026.113170