Maintaining photosynthetic integrity over carbon gain is a key adaptive mechanism among plant species in the trans-Himalayan region.

The cold desert ecosystem of the trans-Himalayan Ladakh region presents extreme micro-environmental challenges that shape plant physiological responses and ecological distribution. This study examined the photosynthetic performance and photoprotective mechanisms of four co-occurring plant species, viz. Christolea crassifolia, Nepeta floccosa, Rheum australe, Tanacetum gracile, and their comparison with a widely adapted native species, Lepidium latifolium to study the adaptive strategies supporting their ecological amplitude. L. latifolium exhibited significantly (p ≤ 0.05) lower PN rates compared to the other plants, which may be a trade-off mechanism between carbon assimilation and photoprotection, thereby prioritizing tolerant mechanisms over maximizing photosynthesis. Despite its reduced carbon assimilation, it maintained a stable photochemical efficiency, indicating active photoprotective responses, including regulated energy dissipation (NPQ mediated by zeaxanthin, HY5, and PsbS), high water use efficiency (iWUE & eWUE), and sustained photosystem integrity at high altitudes. The decrease in various physiological processes including Fv/Fm, PIABS and electron transport (ETo/RC), suggested a conservative resource-use strategy that minimises photodamage and enhances physiological adaptation under fluctuating intense-radiation, low-temperature photo-oxidative environments. Our results suggested that the wide ecological amplitude of L. latifolium in Ladakh might be due to its capacity to promote resilience and adaptability in a variety of microhabitats by prioritizing photosystem protection above productivity. This study emphasizes the importance of photoprotective physiology in determining the plant spread at high altitudes.