Morpho-anatomical Features of the Leaves of the Mediterranean Geophyte Urginea maritima (L.) Baker (Liliaceae)

Abstract

The morpho-anatomy and histochemistry of the hysteranthous leaf of Urginea maritima (L.) Baker and its adaptive strategies to the Mediterranean climate were investigated. The leaf of U. maritima is 714 μm thick and possesses moderate specific leaf mass (8.564 mg cm−2) and low tissue density (136.5 mg cm−3). The epidermal cells are compactly arranged and covered with cuticle. The average density of stomata in lower epidermis is higher than that of the upper one. The mesophyll cells occupy 52.96% of the total volume of the leaf, while the mesophyll intercellular spaces and the air spaces occupy 30.41%. Idioblastic cells containing raphide bundles and different phenotypes of crystalloid inclusions, embedded in polysaccharides, occur in the lower side of the mesophyll. The presence of oil droplets and lipids is evident. Bundle sheath cells are hardly visible with no chloroplasts which are a pronounced C3 plant character. Plastids containing protein crystalloid inclusions are abundant in the protophloem sieve elements. U. maritima, a deciduous plant, possesses leaves with mesophytic characters, in order to optimize its adaptation to the seasonal fluctuation of environmental conditions of the Mediterranean climate.