In situ variation in leaf anatomy and morphology of Andira legalis (Leguminosae) in two neighbouring but contrasting light environments in a Brazilian sandy coastal plain

Andira legalis (Vell.) Toledo is a legume shrub widespread along the sandy plains of the Brazilian coast. It occurs both shaded, in forest habitats, or exposed to full sunlight, in the vegetation islands growing on sand deposits. Previous studies reported a high range of morpho-physiological variation for this species along a geographical gradient. This study compared leaf morphology and anatomy of A. legalis in two distinct but adjacent light environments: a dense forest (shaded) and a scrub of Palmae (exposed). We studied the amplitude of variation for these traits within a small (0.5 ha) geographical area. Leaf anatomy parameters were measured for five leaves collected from five plants in each habitat. The parameters measured were leaf and mesophyll thickness, thickness of the outer periclinal cell wall, thickness of the adaxial and abaxial epidermis and vascular bundle transversal section area, and also common epidermal cells, stomata and trichome density. Leaf morphology parameters were obtained from five leaves of each of 20 plants in each site. Dry and fresh weights were measured to obtain leaf specific mass and succulence. All anatomy and morphology parameters, except trichome density, were significantly higher for the sun-exposed plants. Less expected, however, was the marked qualitative difference between exposed and shaded plants: in the former the mesophyll had a unilateral symmetry (i.e., the whole mesophyll occupied by photosynthetic tissue), whereas in the latter there was a dorsiventral symmetry (i.e., partly palisade and partly spongy parenchyma). Such amplitude of variation shows that even within a small geographic area A. legalis has a broad ecological plasticity