Structure of leaves and localization of secretory ducts in Sphaerosciadium denaense (Apiaceae)
Abstract
A leaf morphological and anatomical structure of the Sphaerosciadium denaense (Schischk.) Pimenov et Kljuykov is described. The species belongs to the Central Asia relics. It is a narrow endemic of the Sangardak river valley (Gissar range) and it is listed in the Red Data Book of Uzbekistan. The study of the leaf structure revealed the following mesomorphic features: wide leaf segments, well-developed leaf vagina the ear-shaped form, light petiole lignification, dorsiventral type of mesophyll. The unloading (unsubmerged) stomata are predominant at the abaxial side. The anticlinal walls at the abaxial epidermis are undulate. The species xeromorphism is expressed by outer wall thickening in the leaf -blade (sheet) epidermis and by cells elongation in the palisade tissue. The diagnostic leaf-blade features are: biconvex central part, marginal parts wrapped to adaxial side; 2(3) secretory ducts above the main bundle at the abaxial side, and one larger at the adaxial side. Above and below lateral bundles they locate one by one. Also, there is a single duct at the adaxial part of the leaf top. The petiole diagnostic features are a cross-sectional shape, widened to the sides at the basal part, directed upwards at the middle part and curved into the winged outgrowths abaxial side at the leaf-blade (sheet) top; the presence of central conducting bundles and localization the secretory ducts at the phloem close part of the peripheral conducting bundles. The revealed features in the anatomy structure of the leaf-blade and petiole, as well as the localization of secretory ducts are species-specific. It can be used for systematics problems solvation of the Apiaceae Lindl. family.