Biology Reference
In-Depth Information
Chapter 5
NECTAR CHEMISTRY
SUSAN W. NICOLSON
1
and ROBERT W. THORNBURG
2
1
Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
2
Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University,
Ames, Iowa 50011, USA
1
INTRODUCTION
Nectar properties tend to be similar for plants visited by the same kinds of
pollinators, and much of the available information on nectar chemistry has
been collected in the context of pollination syndromes. These are defined as
broad associations between floral features and types of animal pollinators
(Faegri & van der Pijl, 1979; Proctor et al., 1996) and are discussed further
by Nicolson (2007, Chapter 7 in this volume). Faegri and van der Pijl in-
cluded nectar volume in their classic descriptions of the various syndromes.
The concept was extended to include nectar chemistry (specifically sugar
and amino acid content and composition) in the influential reviews of Baker
and Baker (1982a 1983b). Herbert and Irene Baker analysed many different
substances in nectar and were largely responsible for drawing attention to its
chemical complexity. However, the adaptive significance of nectar compo-
nents has perhaps been overemphasized and is now being examined more
critically.
The techniques used in nectar analysis have always been constrained by
small fluid volumes, but advances over the years have enabled quantification
of different substances rather than mere identification. This particularly ap-
plies to chromatographic techniques for sugars and amino acids—formerly
measured with paper and thin-layer chromatography, now with gas chromato-
graphy (GC) and high-performance liquid chromatography (HPLC) (Kearns &
Inouye, 1993). The significance of the sugar and amino acid composition
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