Asian Journal of Research in Botany

C4 photosynthesis represents a key adaptive strategy that enhances plant productivity and water-use efficiency under conditions of high temperature and aridity. This study investigated the anatomical characteristics associated with the C4 pathway in ten plant species (monocotyledonous and dicotyledonous) collected from Al-Madinah Al-Munawwarah, Saudi Arabia, a region characterized by extreme environmental conditions. Transverse leaf sections were prepared manually, stained with toluidine blue, and examined using light microscopy. Quantitative anatomical measurements, including leaf thickness, bundle sheath size, mesophyll area, and interveinal distance, were obtained using ImageJ software. In addition, the proportion of bundle sheath tissue relative to total photosynthetic tissue and the bundle sheath-to-mesophyll ratio (BS/M) were calculated to assess structural coordination.Comparative analysis revealed that monocot species exhibited more pronounced C4 anatomical features, including well-developed bundle sheath tissues, reduced interveinal distances, and relatively thicker leaves. In contrast, dicot species showed greater variability and less consistent structural specialization. A positive relationship between bundle sheath and mesophyll areas was observed across all species, with stronger and more coordinated patterns in monocots. These results suggest a higher degree of anatomical optimization in monocots for efficient carbon fixation under arid conditions. Overall, the findings highlight the importance of structural traits in enhancing photosynthetic performance and plant adaptation to environmental stress. This study provides valuable quantitative insights into the anatomical basis of C4 photosynthesis in desert environments and contributes to a better understanding of plant adaptive strategies under extreme climatic conditions.