XVI International Botanical Congess

Two South American species, M. gilliesii and M. potentilloides and also a putative hybrid were studied in the Andes of Mendoza at 2,800-m sm. M. gilliesii had the smallest flowers, M. potentilloides the largest, and the hybrid showed intermediate characters. Flowers were protandrous, with the stigma becoming receptive the second day after opening. Open, natural-self, manual-self (MS), and cross-pollination (CP) were evaluated. Pollen viability was over 90% in all cases. The pollen tube reached the micropile 2-3 hours after pollination in MS and CP flowers. All the species showed self-compatibility, although a temporal differentiation in male and female phases tended to favor CP. A balance of selfing and crossing seems to be advantageous for these Andean plants.