Trichome micromorphology in drupe of Amygdalus L. (Rosaceae) from Iran

Abstract

For delimitation of species and systematic resolution, pericarp indumentum in drupe of 17 species and two hybrids of the genus Amygdalus L. representing two subgenera and two sections distributed in Iran were studied using scanning electron microscopy (SEM) in order to assess whether in this genus, pericarp micromorphological characters are of taxonomic value. The pericarp indumentum type is velutinous with different density of trichomes. Glabrous pericarp was observed in A. reticulata Runemark ex Khatamsaz solely. All trichomes are simple. Two basic types of trichomes were distinguished on the surface of peicarp: tubular and flattened. Among those, tubular trichomes are more frequent than other trichome in most species except for A. kotschyi Boiss. & Hohen., A. eburnea Spach, A. spinosissima Bge. subsp. spinosissima and A. lycioides Spach var. lycioides. Density of trichomes was variable among the studied taxa. In the first subgenus (subgen. Amygdalus) with two sections, there was enough difference between sections. While density of trichomes in sect. Spartioides Spach was very low, most of species in the another section, sect. Amygdalus showed dense pericarp indumentum. Regarding density, the second subgenus, subgen. Dodecandra (Spach) Browicz showed dense indumentum. Two studied hybrids, A.×keredjensis Browicz and A.×kamiaranensis Khatamsaz & Assadi showed different pericarp indumentum, dense and sparse one, respectively. In conclusion, micromorphological investigation of pericarp indumentum in drupe is a useful tool for separating of taxa in some cases especially of the two sections in the first subgenus in Amygdalus.