Deciphering the response of medicinal plants to abiotic stressors: A focus on drought and salinity

Both salinity and drought stand as significant abiotic stresses that adversely affect crop production worldwide. While medicinal plants offer substantial economic and social benefits, their productivity faces challenges globally due to abiotic stresses. The distinctive quality of medicinal plants stems from their active ingredients. However, these abiotic stresses can compromise the potency of active and herbal ingredients in medicinal plants. Both drought and salinity result in osmotic stress and Na+ toxicity, leading to a myriad of morphological, physiological, biochemical, and metabolic changes in plants. Such changes encompass alterations in water relationships, water use efficiency (WUE), relative growth rate (RGR), nutrient balance, transpiration rate, stomatal conductivity, CO2 uptake and diffusion, photosynthesis potential, and overall productivity. Being a pivotal physiological process crucial for plant survival, photosynthesis becomes one of the earliest processes to be affected under abiotic stress. Specifically, drought and salinity diminish the photosynthesis rate by disrupting chlorophyll metabolism, inducing oxidative stress, and prompting plastid degradation. This decline can be attributed to the adverse effects of ion absorption disturbances on chloroplast development and the protein translation machinery within plastids. Interestingly, plant responses to both salinity and drought often mirror each other. To combat these challenges, medicinal plants employ a range of protective mechanisms. These include preserving cell wall architecture, accumulating osmolytes, generating antioxidants, initiating stomatal closure, and boosting secondary metabolite levels. This review delves into the growth, development, and photosynthesis of various medicinal plants under the duress of salinity and drought.