AOBPreview published online on May 28, 2009
Annals of Botany, doi:10.1093/aob/mcp124
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
INVITED REVIEW |
Nectar and pollination drops: how different are they?
1 Department of Environmental Sciences ‘G. Sarfatti’, University of Siena, Via Mattioli 4, 53100 Siena, Italy
2 Graduate Centre for Forest Biology, Department of Biology, University of Victoria, V8W 3N5 Victoria, BC, Canada
* For correspondence. E-mail massimo.nepi{at}unisi.it
Received: 9 January 2009 Returned for revision: 5 March 2009 Accepted: 21 April 2009
Background: Pollination drops and nectars (floral nectars) are secretions related to plant reproduction. The pollination drop is the landing site for the majority of gymnosperm pollen, whereas nectar of angiosperm flowers represents a common nutritional resource for a large variety of pollinators. Extrafloral nectars also are known from all vascular plants, although among the gymnosperms they are restricted to the Gnetales. Extrafloral nectars are not generally involved in reproduction but serve as ‘reward’ for ants defending plants against herbivores (indirect defence).
Scope: Although very different in their task, nectars and pollination drops share some features, e.g. basic chemical composition and eventual consumption by animals. This has led some authors to call these secretions collectively nectar. Modern techniques that permit chemical analysis and protein characterization have very recently added important information about these sugary secretions that appear to be much more than a ‘reward’ for pollinating (floral nectar) and defending animals (extrafloral nectar) or a landing site for pollen (pollination drop).
Conclusions: Nectar and pollination drops contain sugars as the main components, but the total concentration and the relative proportions are different. They also contain amino acids, of which proline is frequently the most abundant. Proteomic studies have revealed the presence of common functional classes of proteins such as invertases and defence-related proteins in nectar (floral and extrafloral) and pollination drops. Invertases allow for dynamic rearrangement of sugar composition following secretion. Defence-related proteins provide protection from invasion by fungi and bacteria. Currently, only few species have been studied in any depth. The chemical composition of the pollination drop must be investigated in a larger number of species if eventual phylogenetic relationships are to be revealed. Much more information can be provided from further proteomic studies of both nectar and pollination drop that will contribute to the study of plant reproduction and evolution.
Key words: Nectar, pollination drop, ovular secretion, plant reproduction, proteins, sugars, gymnosperms, angiosperms, plant–animal interaction
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  J. Ollerton and E. Coulthard Evolution of Animal Pollination Science, November 6, 2009; 326(5954): 808 - 809. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Ren, C. C. Labandeira, J. A. Santiago-Blay, A. Rasnitsyn, C. Shih, A. Bashkuev, M. A. V. Logan, C. L. Hotton, and D. Dilcher A Probable Pollination Mode Before Angiosperms: Eurasian, Long-Proboscid Scorpionflies Science, November 6, 2009; 326(5954): 840 - 847. [Abstract] [Full Text] [PDF]
|
|