© 2004 Heron Publishing—Victoria, Canada
Sclerophylly and leaf anatomical traits of five field-grown olive cultivars growing under drought conditions
Eunice A. Bacelar (1, 2), Carlos M. Correia (1), José M. Moutinho-Pereira (1), Berta C. Gonçalves (1), João I. Lopes (3) and José M. G. Torres-Pereira (1)
1. Department of Biological and Environmental Engineering/CETAV, University of Trás-os-Montes e Alto Douro, Apartado 1013, 5001-911
Vila Real, Portugal / 2. Author to whom correspondence should be addressed (areale@utad.pt) / 3. Direcção Regional de Agricultura de Trás-os-Montes, Quinta do Valongo, 5370 Mirandela, Portugal / Received April 30, 2003; accepted July 20, 2003; published online December 15, 2003
Summary
Leaf-level morphological and structural adaptations to reduce water loss were examined in five olive (Olea europaea L.) tree cultivars (Arbequina, Blanqueta, Cobrançosa, Manzanilla and Negrinha) growing under field conditions with low water
availability. Leaf measurements included leaf tissue thickness, stomatal density, leaf area, leaf mass per unit area, density
of leaf tissue, relative water content, succulence, water saturation deficit, water content at saturation and cuticular transpiration
rate. We found considerable genotypic differences among the cultivars. Negrinha, Manzanilla and Cobrançosa had more morphological
and structural leaf adaptations to protect against water loss than the other cultivars. Manzanilla and Negrinha enhanced their
sclerophylly by building parenchyma tissues and increasing protective structures like the upper cuticle and both the upper
and lower epidermis. Cobrançosa exhibited good protection against water loss through high density of foliar tissue and by
thick cuticle and trichome layers. Compared with the Negrinha, Manzanilla and Cobrançosa cultivars, Arbequina leaves had a
thinner trichome layer, implying that the leaves were less protected against water loss; however, the development of smaller
leaves may reduce water loss at the whole-plant level. Among cultivars, Blanqueta had the largest leaves and some anatomical
traits that may lead to high water loss, especially from the adaxial surface. The mechanisms employed by the cultivars to
cope with summer stress are discussed at the morpho-structural level.
Keywords:
cuticle thickness, leaf morphology, LMA, Olea europaea, stem water potential, stomatal density, succulence, summer stress, trichomes.
