Nymphaea Revisited: A preliminary communication: A preliminary communication

A number of pollination syndromes within the genus Nymphaea are examined. Adaptive radiation has created a wide range, from beetle-pollination with production of solid food bodies for the visitors to pollination by small Hymenoptera and syrphid flies with production of a pool of stigmatic fluid in which, on the first day of anthesis when the flower is functionally pistillate, pollinators drown. In the latter category, there is striking sophistication in the features that ensure proper deposition and germination of the pollen grains. In the tropical water lilies examined, the sugar level of the stigmatic fluid was 1%—1.5% which is well below the threshold of perception for honeybees regardless of the nature of the sugar; fructose and glucose were present in roughly equal concentrations. In Nymphaea odorata, a temperate zone water lily, the sugar concentration was about 3%, a considerable part of which was sucrose; glucose and fructose were again present in almost equal concentrations. No obvious biological reasons for the difference in sugar composition and concentration can at present be identified. The ability of Nymphaea pollen to germinate in a fluid so close to pure water in composition must be considered exceptional. The high boron level in the stigmatic fluid, as well as the amounts of calcium, potassium and magnesium ions, are close to optimal for pollen germination. Chloride, present at a concentration several times higher than that of the surrounding pond water, is the most important anion. A number of free amino acids are present in very low concentration. The diurnal taxa examined opened and closed on at least three successive days. On the second and third days, the stamens form a protective cone over the central pool of stigmatic fluid, while the flowers are functionally staminate, shedding their pollen. Insect visitors collecting the latter can now come and go with impunity. However, on the basis of their first-day activities, the flowers must still be considered exploitative, rather than as partners in a mutually beneficial relationship with insects. © 1979 Taylor and Francis Group, LLC.