LEAF ANATOMICAL STUDY OF THE GENUS AMYGDALUS L. (ROSACEAE) IN IRAN AND ITS TAXONOMICAL IMPLICATION

In this survey, leaf anatomy (midrib and blade) of 22 species and hybrids of the genus Amygdalus L. (Rosaceae) in Iran is studied. Regarding to vegetative form, the species of Amygdalus are distributed as four forms in Iran: trees, shrubs with brachyblast (short shoots), shrubs without brachyblast and spiny shrubs. Forty-one characters were measured and among them, some characters were variable and taxonomically valuable. The most important characters includes: presence or absence of hair and hair type on midrib and blade, length of adaxial and abaxial epidermal cells in midrib and blade, presence or absence of spongy parenchyma and its thickness, number of palisade parenchyma layers and their thickness, the angle between two halves of blade, midrib shape, ratio of midrib length/width, presence or absence of fiber around phloem in midrib and its thickness, presence or absence of internal phloem in midrib, ratio of xylem length/width and phloem length/width, adxial and abaxial collenchyma thickness in midrib and adaxial and abaxial parenchyma thickness in midrib. One of the special characters in leaf anatomy of Amygdalus is the density of palisade parenchyma layers and the absence of spongy parenchyma in leaf in most species that is related to semi-arid ecological conditions. While leaf anatomical features of the genus Amygdalus are relatively reliable in specific level, they are not useful in subgeneric or sectional level.