Effect of Exogenous Application of Nicotinic Acid on Morpho-Physiological Characteristics of <i>Hordeum vulgare</i> L. under Water Stress

Abiotic stresses, such as high temperature and drought conditions, greatly influence the development of plants and the quality and quantity of products. Barley (<i>Hordeum vulgare</i> L.) crop production is largely impacted by drought, affecting growth, yield, and ultimately the productivity of the crop in hot arid/semi-arid conditions. The current pot experiment was directed to observe the outcome of nicotinic acid (NA) treatments on barley’s physiological, biochemical, and production attributes at two capacity levels, i.e., 100% normal range and withholding water stress. Randomized complete block design (RCBD) was used during the experimentation with the two-factor factorial arrangement. NA was applied exogenously by two different methods, i.e., foliar and soil application (fertigation). NA solution contained various application levels, such as T1 = control, foliar applications (T2 = 0.7368 gL⁻¹, T3 = 1.477 gL⁻¹, T4 = 2.2159 gL⁻¹), and soil applications (T5 = 0.4924 gL⁻¹, T6 = 0.9848 gL⁻¹, and T7 = 1.4773 gL⁻¹). Results depicted that, overall, foliar treatments showed better effects than control and soil treatments. Plant growth was preeminent under T4 treatment, such as plant height (71.07 cm), relative water content (84.0%), leaf water potential (39.73-MPa), leaf area index (36.53 cm²), biological yield (15.10 kgha⁻¹), grain yield (14.40 kgha⁻¹), harvest index (57.70%), catalase (1.54 mmolg⁻¹FW⁻¹), peroxidase (1.90 g⁻¹FWmin⁻¹), and superoxide dismutase (52.60 µgFW⁻¹) were superior under T4 treatment. Soil plant analysis development (54.13 µgcm⁻²) value was also higher under T4 treatment and lowest under T7 treatment. In conclusion, NA-treated plants were more successful in maintaining growth attributes than non-treated plants; therefore, the NA foliar treatment at the rate of 2.2159 gL⁻¹ is suggested to find economical crop yield under drought conditions. The present study would contribute significantly to improving the drought tolerance potential of barley through exogenous NA supply in water deficit areas.