Pollen viability of Polygala paniculata L. (Polygalaceae) using different staining methods

Polygala paniculata L. is a medicinal plant that grows in the Brazilian Atlantic coast, known as 'barba-de-Sao-Joao', 'barba-de-bode', 'vassourinha branca', and 'mimosa'. In this study, pollen viability was estimated by three different staining methods: 2% acetic orcein, 2% acetic carmine, and Alexander's stain. The young inflorescences of twenty accessions were collected and fixed in a solution of ethanol: acetic acid (3:1) for 24 hours, then stored in ethanol 70% under refrigeration. Six slides per plant, two for each stain, were prepared by squashing, and 300 pollen grains per slide were analyzed. Pollen viability was high (> 70%) for most accessions of P. paniculata using the Alexander's stain, which proved the most adequate method to estimate pollen viability.