Pollen morphology and anatomy of Rubus L. (Rosaceae) in Thailand

Abstract

Pollen morphology and anatomy were investigated in 19 species of the genus Rubus L. from Thailand by observation and analysis under a light microscope and a scanning electron microscope. The pollen grains are monads, with radial symmetry, circular shaped in polar view and isopolar. The sizes of the pollen grains are small and medium. Considering the species studied, the majority have medium sized pollen grains. There were different shapes detected viz., oblate, suboblate, prolate spheroidal, oblate spheroidal and prolate. The pollen grains have various apertures: tricolporate, tricolporate-tetracolporate, tricolpate and tricolpate-tetracolpate. There were five forms of exine sculpturing as follows: rugulate-perforate, striate-perforate, microverrucate-perforate, microverrucate and perforate. In the genus Rubus it is not possible to use the morphology of the pollen for the identification to species level. Eleven species had the morphology of the pollen studied for the first time. The anatomy of the leaf, petiole and stem were observed by transverse section. The anatomy can be used for the identification to species level. The results indicate that the anatomical characteristics used for the identification key are shape of leaf margin, shape of adaxial surface of midrib, pericyclic fibers, idioblast cell, shape of petiole, starch grain, number of vascular bundles, shape of stem and types of trichomes. In this study, the anatomy of 19 species was reported for the first time. The numerical analysis based on the pollen morphology and anatomy data did not support classification of the genus Rubus L.