Abstract
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.
Highlights
Most plants in arid and semi-arid conditions survive extreme environmental conditions by developing structures to tolerate their habitats
Leaves were amphistomatous with relatively same number of stomata on both adaxial and abaxial surfaces (Table 1)
The stomata complex was anomocytic, with guard cells embedded in crypts formed by deposits of cuticular wax
Summary
Most plants in arid and semi-arid conditions survive extreme environmental conditions by developing structures to tolerate their habitats. These plants commonly referred to as xerophytes have common features which include: small ratio of leaf area to volume [1,2], a reduction in leaf cell size and number [3], thick cuticle and epidermal cell walls [2] and increased density in vascular tissues and sclerenchyma, which contribute to sclerophylly [4,5]. Some plants that grow well in wet conditions have xeromorphic leaf features while others in dry habitats have mesomorphic characters [6]. Leaf features partially explain how xerophytes thrive in arid habitats
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