Response of Job’s tears Cultivars to Short-Term Water Stress Using Comparative Phenomics

Abstract

　Water stress is a major limitation in Job’s tears’ cultivation. We evaluated morpho-physiological characteristics under normal and restricted irrigation conditions using twelve Job’s tears cultivars in pot experiment. Irrigation treatments of 100% (control) and 50% (water stress) were applied and irrigation was controlled based on evapotranspiration. Water stress reduced the relative growth rate (RGR) during the treatment period, significantly decreasing total biomass. Because leaf area (LA) and the net assimilation rate (NAR) were also reduced by water stress and positively correlated with RGR, the reduction in RGR involves a reduction in both LA and dry matter production per unit leaf area. Additionally, LA negatively correlated with dead leaves, and NAR positively correlated with net photosynthetic rate (Pn), suggesting that an increase in dead leaves and decrease in photosynthetic capacity significantly affect dry matter production under water stress. Pn decreased under stress with the reduction in water potential, and the relative value of Pn under the stress compared with control differed markedly from 6.3 to 95.7% among the cultivars. Given that stomatal conductance and Rubisco activity showed a positive correlation with Pn, stomatal regulation and carbon fixation via Rubisco would be attributed to photosynthetic variation in Job’s tears under water stress.