Leaf Traits and Histochemistry of Trichomes of Conocarpus lancifolius a Combretaceae in Semi-Arid Conditions

Leaf traits, structure and water status of Conocarpus lancifolius, a Combretaceae were investigated under semi-arid conditions. The leaf traits examined included leaf area and thickness, stomatal distribution, sclerophylly, succulence and relative water content. Additionally, the types of secretory structures, histochemistry of trichomes, and chemical nature of the cuticlular waxes were evaluated. Leaves showed xerophytic characteristics including a high degree of sclerophylly, thick cuticle and outer epidermal cell wall, low relative water content and high trichome density on younger leaves. The species has two types of trichomes; a secretory, short-stalked capitate trichome and a non-secretory trichome with a bulbous base and a pointed tip. The leaves also have a pair of extrafloral nectaries on both sides of the distal end of the petiole, 3 4 pairs near the leaf apex and two secretory ducts or cavities on mature leaves that secreted polysaccharides, epicuticlar waxes and polyphenols. Compared to young leaves mature leaves had almost 3 times total cuticular wax deposit or load. The most abundant fatty acids were palmitic, stearic, nondecanoic, behenic and arachidic acids. The leaf traits and structures are discussed in relation to semi-arid habitat.