The occurrence and significance of amino acids in floral nectar

Abstract

Approximately 1 500 angiosperm species, in previous papers, have been sampled for the assessment of the amino acids (a. a.) in their nectar. We reaffirm that the findings provide statistically significant data linking differences in the concentration with pollinator type. Flowers that are pollinated by animals that have alternative sources of protein-building a. a.’s show lower a. a. concentration than those that are not. There is a tendency for woody plant nectar a. a.’s to be less concentrated than those of herbaceous plants, but there can be “phylogenetic constraints” which may reduce the correlations of a. a. concentration with pollinator type and with life form. The individual a. a.’s form complements which are qualitatively extremely constant within species. Proline is a normal constituent of many nectars and does not necessarily indicate contamination of the nectar by pollen. Criticism of our findings byGottsberger & al. (1984) is answered by reference to our previous publications and those of other workers, and to the presentation of data from California native species, not published previously. All previous postulates are borne out by these new data with the exception of positive correlations of a. a. concentration with “primitive” and “advanced” floral characteristics taken one at a time, which appear to be inconsistent and are affected strongly by the nature of the family in which they occur. Summary data are provided for families and genera which indicate that high or low a. a. concentration can typify certain families and genera of both relatively “primitive” and relatively “advanced” nature. Needs for future research on an ecosystem basis are quoted.