Morphology, viability, and germinability of pollen from two forms of Nymphaea nouchali var. versicolor, a day-blooming waterlily

Abstract

Pollen morphology, viability, and germinability of two distinct forms (Bua Phan and Bua Phuean) of Nymphaea nouchali var. versicolor, one of the only two naturally occurring native varieties of the day-blooming waterlily in Thailand, were studied. Under a scanning electron microscope, the pollen morphology of the two forms of N. nouchali was very similar. The pollen grains were nearly ellipsoidal, heteropolar, round-shaped from one side and boat-shaped from the other side, and had a smooth surface and a ring-like aperture around the equator. There was no significant difference between the pollen viability (95%) of the Bua Phan and Bua Phuean forms examined after acetocarmine staining. Pollen germinability was evaluated on a medium supplemented with various concentrations of sucrose under different incubation temperatures and illumination conditions. The highest percentages of pollen germination in the Bua Phan (93%) and Bua Phuean (80%) forms took place at 32 °C in the dark on a medium supplemented with 5% sucrose. These germination results were significantly different. The dissimilar germination response is also consistent with the current classification of the versicolor variety into two forms.