Nectar Production inAnagyris foetida(Fabaceae): Two Types of Concentration in Flowers with Hanging Droplet

Abstract

In Anagyris foetida, a shrubby legume with autumn–winter flowering, the flowers produce great amounts of very dilute nectar during the first half of their life, consonant with their pollination by passeriforms. With advancing age, the volume of nectar diminishes and the concentration increases to values characteristic of bee‐pollinated flowers. The daily nectar secretion is greatest in volume early in the morning, damping during the day, whereas the concentration usually undergoes a gradual rise from morning to evening. The flowers visited for the first time in any day in the first half of anthesis have greater accumulated final nectar volumes than those first visited in the second half of anthesis. The accumulated nectar per flower is less in flowers that receive one visit per day than in those that receive three visits per day and is less in shrubby plants than in arboreal plants. In unvisited flowers, the rate of production of nectar depends on the environmental conditions, and at the end of their life there is a major loss of volume due to evaporation and of solutes possibly due to reabsorption. These flowers usually present a large hanging droplet of nectar that has a greater concentration and sugar content than does the nectar inside the calyx. The sugar, hexose dominant, is homogeneous in both locations.