Secretion and use of nectar across floral longevity of the protandrous Tropaeolum pentaphyllum Lam. (Tropaeolaceae)

The herbaceous vine Tropaeolum pentaphyllum Lam. is a geophyte. The species presents potential use as an ornamental, food and medicinal plant. In this study, we aim to understand the reproductive biology of T. pentaphyllum in Brazilian Mixed Ombrophilous Forest, Southern Brazil. Floral structures, duration of the staminate and pistillate phases, interval between phases, overlapping of phases, breeding system were studied. Nectar volume and sugar concentration were evaluated throughout floral longevity. The floral visitor’s behaviour was observed for four years, 6 am to 8 pm, totalling 100 hours of observation each year. Tropaeolum pentaphyllum is protandrous. The mean floral longevity was of 13.6 days. The duration of the staminate (\(\overline{x}\) = 6.7 days) and pistillate (\(\overline{x}\) = 6.1 days) phases did not differ. However, all flowers produced nectar in the staminate phase while just 23.3% produced in the pistillate phase. Sugar concentration remained constant over the floral longevity. Tropaeolum pentaphyllum presents mixed pollination by hummingbirds, bees and ants. Protandry, floral longevity and nectar production for up to ten days are strategies to obtain pollination and promote cross-pollination in T. pentaphyllum. The overlapping of phases (21.4%) also allows self-fertilization if cross-fertilization does not occur. These strategies can be advantageous to obtain crossbreeding and success in sexual reproduction. The longevity of flowers and standing crop of nectar show real food availability for pollinators.