Pollen Morphology of Helicteres (Malvaceae s.l.) from Thailand

Abstract

The pollen morphology of seven species (eight samples of each) of Thai Helicteres (Malvaceae s.l.) was determined based on observations using light microscopy and scanning electron microscopy. The pollen morphology of all species has bilateral symmetry, with isopolar and triporate apertures. There are two pollen shapes: semi-trilobate and semi-triangular. The mean±SD size on the polar view was 21.97±1.47 μm to 34.63±3.24 μm and the mean±SD equatorial view pollen size range was 19.87±0.76 μm to 34.10±2.98 μm. The largest pollen was observed in H. hirsuta (purple flower) and the smallest pollen one in H. lanceolata. Pollen grains from this study can be divided into two groups based on size following Walker and Doyle (1975), being small sized and medium sized. The sculpture of the exine varies from perforate, verrucate, verrucate-perforate, verrucate-sparsely perforate, slightly verrucate-scabrate to slightly verrucate-sparsely perforate. The pollen morphology of H. lanceolata is similar to the pollen of H. hirsuta (pale pink flower). The pollen morphology of H. hirsuta (purple flower) is not different from the pollen of H. hirsuta (pale pink flower) in shape but differs in size and exine sculpturing. The pollen morphology of H. lanceolata was studied for the first time globally.