Male and female booths with separate entrances in the tiny flowers of Guazuma ulmifolia (Malvaceae–Byttnerioideae). I. Structural integration

Abstract

In spite of their tiny dimensions (3×5 mm 2), the strongly honey-scented flowers of Guazuma ulmifolia (Malvaceae–Byttnerioideae) provide six sexual chambers. A central female unit is surrounded by five interconnected male compartments. At the onset of anthesis the strap-shaped odoriferous petal appendages form an open star with the female chamber in the centre. Hereafter, they wilt, intermingle and finally lock access to the stigma. Meanwhile, wilting sepals liberate new entrances from the back between the petal claws. They give way to nectar-offering male chambers. In each of them a well-lit (but closed) window lures the visitor into a standard position for passive pollen uptake. Finally, the insects have to back out of one of the rear entrances. It remains unknown how the minute visitors (maximum height ca. 0.5 mm) – if ever – overcome the distance to another Guazuma tree.