Flora 201 (2006) 102–107 Leaf and green stem anatomy of the drought deciduous Mediterranean shrub Calicotome villosa (Poiret) Link. (Leguminosae) Charilaos Yiotis, Yiannis Manetas, George K. Psaras à Section of Plant Biology, Department of Biology, University of Patras, GR 265 00, Patras, Greece Received 7 March 2005; accepted 28 April 2005 Abstract Light and scanning electron microscopy were used to study leaf and stem fine structure of the drought deciduous green-stemmed Mediterranean shrub Calicotome villosa (Poiret) Link. (Leguminosae). Each leaf consists of three small obovate leaflets with abundant but small (16 mm length) anomocytic stomata on both surfaces. Adaxial surface exhibits more than double stomatal density (44078 mm 2 ) than the abaxial one (18574 mm 2 ). T-shaped trichomes (3673 mm 2 ) are present only on the abaxial leaf surface. Leaves are unifacial, furnished with palisade parenchyma on both sides. The stem is characterized by raised ridges and grooves. Beneath the one-cell-layered epidermis sclerenchyma is found on ridges, whereas stomata and palisade chlorenchyma are found in grooves. Hairs are abundant, especially in grooves. Stem and leaf palisade chlorenchymas are structurally similar. According to these data, photosynthesis could be efficiently supported by the stem. r 2005 Elsevier GmbH. All rights reserved. Keywords: Calicotome villosa; Leaf anatomy; Mediterranean species; Stem anatomy; Stem photosynthesis Introduction Dominant perennial plant species native in the Mediterranean-climate areas belong to xerophytes (Fahn and Cutler, 1992) and may be classified as evergreen sclerophylls and drought deciduous shrubs (Margaris, 1981). Structural features of the drought- adapted leaf of xerophytes have been related to the whole plant physiology and adaptability (Shields, 1950). Small and thick leaves with multilayered mesophyll are considered to characterize evergreen sclerophylls (Fahn and Cutler, 1992) and sun species (Terashima et al., 2001, 2005). Drought deciduous species possess leaves that undergo senescence and desiccation during the period of dryness (Orshan, 1963). Amphistomaty and leaf compartmentation have been repeatedly evaluated concerning leaf xeromorphy. Amphistomaty, which is more common in xeric habitats (Fahn and Cutler, 1992; Parkhurst, 1978), shortens the distance of CO 2 diffusion to mesophyll cells (Parkhurst et al., 1988; Terashima et al., 2005). Small but abundant stomata are also believed to lower the CO 2 diffusion resistance toward the photosynthesizing tissue; thus, non-succulent species show increased stomatal density (Sundberg, 1986). Mesophyll compartmentalization is supposed to protect the leaf against water stress (Terashima, 1992), but, unavoidably, increases the CO 2 diffusion resistance of the tissue (Miyazawa and Terashima, 2001). Abundant palisade tissue is also believed to increase the CO 2 absorbing surface of the mesophyll (Rhizopoulou and ARTICLE IN PRESS www.elsevier.de/flora 0367-2530/$ - see front matter r 2005 Elsevier GmbH. All rights reserved. doi:10.1016/j.flora.2005.04.007 à Corresponding author. Tel.: +30 2610 996254; fax: +30 2610 997411. E-mail address: g.k.psaras@upatras.gr (G.K. Psaras).