Studies on the leaf epidermal characters and petiole anatomy of four species of Citrus L. viz., C. limon (L.) Burm., C. paradisi Macf., C. reticulata Blanco and C. sinensis (L.) Osbeck were carried out to establish and document their foliar anatomical characters with the aim of separating them from the modified varieties been cultivated globally. Leaf epidermal features that revealed close relationship among these taxa include hypostomatic condition, stomata shape and type, presence of secretory cavity on the adaxial surface, and polygonal shape of epidermal cells. The absence of secretory cavity on the abaxial surface separates C. limon and C. sinensis from others. Petiole anatomy revealed that the outline is flat without ribs in C. sinensis, convex with short ribs in C. reticulata, convex with long ribs in C. paradisi while in C. limon it is circular without ribs. Presence of trichomes and crystals distinguishes C. paradisi from the rest.

The responses of seven selected plant species to gemstone mining activities were investigated based on data obtained from exo-and endo-morphology of the leaves with the aim of establishing the responses of the plant species to gemstone mining pollution and the underlining mechanism which could possibly explain such responses. Both qualitative and quantitative methods, using visual and microscopic assessment were adopted. Results of the foliar morphology showed that most of the plant species had significant increase (p<0.05) in the leaf area and petiole length in polluted sites compared to those from unpolluted site though with noted variations in others. The observed morphological responses are associated with corresponding significant increase (p<0.05) in stomata frequency, epidermal cell number, glandular and non-glandular trichome frequency and length, cuticle thickness, upper and lower epidermis. However, characters such as stomata size and palisade mesophyll tissue were significantly (p<0.05) reduced. We conclude based on the data obtained in this study that plants generally respond differently to pollution due to mining through either increase or reduction in some of their external (leaf area and petiole length) and internal features. These depict adaptive mechanisms employed by the plants in order to cope with polluted environments.