Abstract: Water scarcity is becoming one of those most critical threats to global agricultural systems, with over 4 billion people experiencing severe water shortage for at least one month per year. Root crops grown for medicinal reasons—think licorice (Glycyrrhizauralensis), ashwagandha (Withaniasomnifera), turmeric (Curcuma longa), ginger (Zingiber officinale), and valerian (Valeriana officinalis) — are now seeing more frequent exposure to drought stress, linked to climate change, plus unsustainable irrigation behaviors. What’s a bit paradoxical is how drought affects these plants: it reliably cuts down plant biomass and root yield, yet at the same time it can stimulate the production of secondary metabolites, the same kind of compounds that form the core medicinal value. Depending on how intense the drought is, the particular species involved, and where the plant is in its growth phase, bioactive substances like glycyrrhizin, withanolides, curcuminoids, gingerols, and valerenic acid may either build up noticeably or drop off under water-limiting conditions. This article kinda explores the physiological and biochemical routes behind those responses, it also brings together species focused experimental results from peer-reviewed studies available through 2018, and then it talks about what this means for cultivating medicinal plants, as well as for securing pharmaceutical raw materials in a water scarce world.

Keywords: secondary metabolites, phytochemicals, plant quality, medicinal root crops, drought stress, water scarcity.