Analysis of climate adaptability in four tropical fruit trees:  Longan (Dimocarpus longan Lour.), Lychee (Litchi chinensis Sonn.), Pulasan (Nephelium ramboutan-ake (Labill.) Leenh.) and Rambutan (Nephelium lappaceum L.) through leaf anatomy evaluation

Abstract

The tropical fruit species Dimocarpus longan (Longan), Litchi chinensis (Lychee), Nephelium lappaceum (Rambutan), and Nephelium ramboutan-ake (Pulasan) demonstrate significant ecological adaptability, enabling their cultivation under diverse tropical conditions.  This study uses light and scanning electron microscopy to investigate the adaptive significance of leaf micromorphological, anatomical, and histochemical traits in these species. Fresh leaf samples were collected from cultivated habitats in Kerala, India, a tropical monsoon zone. Microscopic evaluations revealed a unique combination of evergreen and xerophytic traits. Evergreen features, including robust internal anatomy, extensive photosynthetic area, and well-developed vein vasculature, support adaptation to high light intensity and fluctuating humidity. Xerophytic characteristics, such as thick abaxial and adaxial cuticles, stomatal index of less than three, and compartmentalised photosynthetic areas, enhance drought resilience. Defensive adaptations like papillated cuticles, trichomes, crystals, phenolic compounds, mucilage, and domatia mitigate herbivory, UV stress, and thermal load. These traits collectively ensure survival in challenging tropical environments. The findings underline the critical role of leaf anatomy in the ecological adaptability and economic viability of these species, providing valuable insights for crop selection and cultivation strategies. Promoting such adaptive traits in tropical horticulture can enhance productivity while minimising environmental impact, contributing to sustainable agriculture and ecosystem stability.