Study of pollen grain morphology in perennial species of sainfoin (Onobrychis) of Khorasan province

Pollen grain morphology of 8 perennial taxa of the genus Onobrychis of Khorassan province was studied-using light and electron microscopy. Major taxonomical attributes of pollen grains were characterized. The pollen grains were 3-colpate, prolate and perprolate. The ectocolpi were elongated, shallow or deep, narrowing at the poles. The colpus membrane was covered by large granules. The ornamentation of axin surface was reticulate, the lumina differed in shape and size. In equatorial view the pollen grains were elongated, elliptic to rectangular-obtuse, and in polar view they were circular, triangular-obtuse or triangular. Based on pollen size and shape in polar and equatorial view as well as ornamentation, two types of pollen graind could be recognized. In the first type pollen grains were circular in polar view with shallow colpi. Lumina of the reticulum sharply decreases in size at the extreme margin of the colpi. O. arnacantha and O. amoena subsp. amoena, O. amoena subsp. meshhedensis, O. cornuta, O. chorassanica and O. ptychophylla belong to this type. In the second type pollen grains were triangular in polar view with deep colpi, and lumina of the reticulum of the same size at the extreme margin of the colpi. The pollen grains of O. lipskyi var. lipskyi and O. lipskyi var. rechingeri belong to this type.The macro-morphological similarity of O. amoena subsp. amoena and O. amoena subsp. meshhedensis could be distinguished by their pollen grain. The similarity of pollen grain morphology of O. lipskyi var. lipskyi and O. lipskyi var. rechingeri suports their close relationship based on the other characteristics and reconfirms the comment by Rechinger that they are synonyms.