Partial root-zone drying enhances antioxidant signaling and physiological resilience in psyllium ( <i>Plantago ovata</i> ) under arid conditions

Drought-induced reduction in crop yield is becoming a serious threat worldwide, especially in arid to semiarid regions. The introduction of medicinal plants into cropping patterns in arid regions is a suitable alternative to conventional crops because of their high demand and market value. Keeping in view the situation, an experiment was planned under natural arid conditions to screen out the best psyllium varieties in less time for cultivation in arid regions. The experiment included three psyllium varieties (V1 = Gujrat isabgol-2, V2 = Vallabh isabgol and V3 = Jawahar isabgol-4) and three irrigation regimes (control = CK, partial rootzone drying = PRD and deficit irrigation = DI) and was carried out in a completely randomized design with eight replications. The results of our experiment revealed that although cell stress indicators (electrolyte leakage, relative cell injury, methylglyoxal, malondialdehyde, and hydrogen peroxide contents) were less and photosynthesis, water relationships, and membrane stability were greater in the control irrigation, the activities of enzymatic and nonenzymatic antioxidants were greater in the PRD and DI regimes. Among the water deficit treatments, more water potential, proline contents, ascorbic acid contents, membrane stability index, and yield were recorded in the PRD than in the DI. Among the varieties, V3 performed the best under water deficit conditions, whereas variety V2 presented the lowest values. It was concluded that under less water availability, the combination of the PRD with the variety V3 optimized physiological and yield outcomes by sustained higher relative water contents (77.10%), mesophyll conductance (0.67 mol CO2 m−2 s−1 bar−1), photosynthesis (15.10 µmol of CO2 m−2s−1), and membrane stability index (78.80%). Consequently, maximized water use efficiency (0.21 g L−1) and antioxidant activities, leading to higher yield (0.76 g plant−1). Future research should focus on integrating PRD with other water management techniques like mulching, osmoprotectants spray to enhance its efficacy under water deficit conditions.

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