Nectar secretion pattern and removal effects in Lycium (Solanaceae)

Abstract

Nectar secretion pattern and effects of nectar removal were comparedin five Argentine species of Lycium (Solanaceae) from several phytogeographical regions with different floral morphologies and floral visitors. The studied species produced small amounts of nectar volume (< 5 mL). Nectar had a low sugar concentration when the flowers first opened (9–22%, except for the PatagonianL. chilense var. filifolium with 50%), but concentration quickly reached higher values (27.7–75.8%). In none of the species did the buds produce nectar. Nectar wasmainly secreted during the first day of anthesis. An active nectar resorption period can be inferred during the last hours of the flower lifetime in L. americanum,L. elongatum, and L. gilliesianum due to a decrease in the content of the nectarsugars. Lycium chilense var. filifolium seems to follow the same trend, but this was difficult to confirm due to the small amount of nectar per flower. Lycium vimineum had an increase in the nectar sugar content at the end of the flower lifetime.All species continued to secrete nectar after removal. In L. gilliesianum,L. elongatum, and L. americanum the total amount of nectar secreted by flower sets subjected to removals was lower than control sets. The earlier the removal,the lower the total nectar secreted by a flower. On the other hand, there was an increase in nectar production in L. vimineum and L. chilense var. filifolium, but there were no significant differences between experimental and control sets.These results, together with data on two other species previously studied, indicated that nectar secretion pattern is conservative for the genus, but several patterns were detected as a result of removal on nectar production. None of them could, however, be drawn to particular habitats, flower structures, or pollinator guilds of the involved Lycium species.