Adaptation, Stress Tolerance and Climate Resilience in Gulmohar (Delonix regia): A Review

Abstract

Delonix regia (Gulmohar) is a widely cultivated ornamental and multipurpose tree in tropical and subtropical landscapes, valued for its rapid growth, broad canopy, seasonal flowering, and ability to persist under warm and seasonally dry conditions. This review synthesises information presented in the manuscript on the adaptation, stress tolerance, and climate-resilience potential of D. regia, with emphasis on drought, heat, salinity, oxidative stress, and urban environmental constraints. The species exhibits several morphological traits associated with stress avoidance and tolerance, including an extensive rooting habit, semi-deciduous leaf shedding during dry periods, bipinnate leaves, and an umbrella-shaped canopy that provides shade and moderates the surrounding microclimate. Physiological responses discussed include stomatal regulation, photosynthetic adjustment, improved water-use efficiency, and osmotic adjustment under water-deficit and saline conditions. Biochemical responses include the accumulation of compatible solutes, such as proline, soluble sugars, and amino acids, together with the activation of antioxidant enzymes, including superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase, which help reduce oxidative injury caused by reactive oxygen species. The manuscript also highlights the ecological role of D. regia in urban forestry through shade provision, microclimate regulation, particulate interception, soil stabilisation, biodiversity support, and carbon storage through biomass accumulation. However, the evidence base remains fragmented, and several stress-tolerance mechanisms require stronger species-specific validation. Overall, D. regia appears to have useful traits for climate-resilient landscaping, provided its use is supported by site-specific evaluation and further physiological, biochemical, molecular, and field-based research.