Phenotypic differentiation in the Himalayan medicinal plant Nardostachys jatamansi: morpho-physiological and phytochemical variation across elevation gradients.

Phenotypic variation occurs across heterogeneous habitats. As a medicinally valuable species widely distributed across subalpine to alpine regions of the Himalayas, Nardostachys jatamansi exhibits a remarkable ecological breadth, though the consequences of its geographic variation remain poorly understood. In this study, individuals with spatulate leaves and fibrous leaf sheaths (type I) were predominantly distributed in the southern regions of the Qinghai-Tibetan Plateau, which were characterized by warmer and moister climates. In contrast, those with lanceolate leaves and lamellar sheaths (type II) occupied cooler and drier habitats. Morphological analyses revealed that leaf area, thickness, adaxial epidermis thickness, mesophyll thickness, and stomatal area were significantly greater in type I, whereas stomatal density and vein density were significantly higher in type II. Significantly, under comparable growing conditions, type II displayed greater leaf chlorophyll content and higher gas exchange capacity. Additionally, the roots and rhizomes of type II contained higher levels of nardosinone, while its leaves exhibited lower concentrations of linarin and chlorogenic acid than type I. Type-adjusted analyses identified associations between selected metabolites and composite climate gradients or elevation. Together, these observations document geographically structured morpho-physiological and phytochemical variation in N. jatamansi. They do not establish cold or drought tolerance, genetic differentiation, or causal effects of climatic conditions, but provide a basis for future conservation, cultivation, and breeding research.