nectar

Nectar of camellia

An Australian painted lady feeding on a flower's nectar

Nectar is a sugar-rich liquid produced by plants. It is produced in glands called nectaries, either within the flowers, in which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, which in turn provide anti-herbivore protection. Common nectar-consuming pollinators include bees, butterflies and moths, hummingbirds and bats.

Nectar is an ecologically important item, the sugar source for honey. It is also useful in agriculture and horticulture because the adult stages of some predatory insects feed on nectar.^{[examples needed]}

Nectar secretion increases as the flower is visited by pollinators. After pollination, the nectar is frequently reabsorbed into the plant.^[1]

Etymology

Nectar is derived from Latin nectar, the favored drink of the gods, which in turn is the Latinized version of Greek νέκταρ, néktar, presumed to be a compound of the PIE roots *nek-, "death", and -*tar, "overcoming", i.e. has a similar etymology to ambrosia, the immortality-conferring food of the gods. The earliest recorded use of its current meaning, "sweet liquid in flowers," is 1609 C.E.^[2]

Floral nectaries

Floral nectaries are generally located at the base of the perianth, so that pollinators are made to brush the flower's reproductive structures, the anthers and pistil, while accessing the nectar.

Extrafloral nectaries

Nectar produced outside the flower is generally made to attract predatory insects. These predatory insects will eat both the nectar and any plant-eating insects around, thus functioning as 'bodyguards'.^[3] Extrafloral nectaries are generally located on the leaf petioles, mid-rib or leaf margin. They are thought to be modified trichomes and exude nectar from phloem sap. Extrafloral nectaries can be found on species belonging to (amongst others) the genera Salix, Prunus and Gossypium. In passion flower Passiflora extrafloral nectaries prevent herbivores by attracting ants and deterring two species of butterflies from laying eggs. ^[4] In many carnivorous plants, nectar serves to attract insect prey.^[5]

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  Extrafloral nectaries on the petiole of a Prunus avium leaf.

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  Extrafloral nectaries on Prunus africana

Natural components of nectar

Although its main ingredient is natural sugar (i.e., sucrose (table sugar), glucose, and fructose),^[6] nectar is a brew of many chemicals. For example, the Nicotiana attenuata, a tobacco plant native to the US state of Utah, uses several volatile aromas to attract pollinating birds and moths. The strongest such aroma is benzyl acetone, but the plant also adds bitter nicotine, which is less aromatic and therefore may not be detected by the bird until after taking a drink. Researchers speculate the purpose of this addition is to drive the bird away after only a sip, motivating it to visit other plants to fill its hunger, and therefore maximizing the pollination efficiency gained by the plant for a minimum nectar output.^[7] Neurotoxins such as aesculin are present in some nectars such as that of the California Buckeye.^[8] All twenty of the normal amino acids found in protein have been identified in various nectars, with alanine, arginine, serine, proline, glycine, isoleucine, threonine, and valine being the most prevalent.^[1]

See also

• Nectar guide
• Nectar source
• Nectarivore
• Northern nectar sources for honey bees

References

Bibliography

• Baker, H.G. and Baker, I. (1973) Amino acids in nectar and their evolutionary significance. Nature 241:543–545.
• Baker, H.G. and Baker, I. (1981) Chemical constituents of nectar in relation to pollination mechanisms and phylogeny. In Biochemical aspects of evolutionary biology. 131–171.
• Baker, H.G. and Baker, I. (1975) Studies of nectar-constitution and pollinator-plant coevolution. In Coevolution of animals and plants. Gilbert, L.E. and Raven, P.H. ed. Univ. of Texas Press, Austin, 100–140.
• Beutler, R. (1935) Nectar. Bee World 24:106–116, 128–136, 156–162.
• Burquez, A. and Corbet, S.A. (1991) Do flowers reabsorb nectar? Funct. Ecol. 5:369–379.
• Carter, C., Graham, R. and Thornburg, R.W. (1999) Nectarin I is a novel, soluble germin-like protein expressed in the nectar of Nicotiana sp. Plant Mol. Biol. 41:207–216.
• Deinzer, M.L.,tomson p.m, Burgett, D.M. and Isaacson, D.L. (1977) Pyrrolizidine alkaloids: Their occurrence in honey from tansy ragwort (Senecio jacobaea L.). Science 195:497–499.
• Ecroyd, C.E., Franich, R.A., Kroese, H.W. and Steward, D. (1995) Volatile constituents of Dactylanthus taylorii flower nectar in relation to flower pollination and browsing by animals. Phytochemistry 40:1387–1389.
• Esau, K. (1977) Anatomy of seed plants. John Wiley & Sons, New York.
• Ferreres, F., Andrade, P., Gil, M.I. and Tomas Barberan, F.A. (1996) Floral nectar phenolics as biochemical markers for the botanical origin of heather honey. Zeitschrift fur Lebensmittel Untersuchung und Forschung. 202:40–44.
• Frey-Wyssling, A. (1955) The phloem supply to the nectaries. Acta Bot. Neerl. 4:358–369.
• Griebel, C. and Hess, G. (1940) The vitamin C content of flower nectar of certain Labiatae. Zeit. Untersuch. Lebensmitt. 79:168–171.
• Heinrich, G. (1989) Analysis of cations in nectars by means of a laser microprobe mass analyser (LAMMA). Beitr. Biol. Pflanz64:293–308.
• Heslop-Harrison, Y. and Knox, R.B. (1971) A cytochemical study of the leaf-gland enzymes of insectivorus plants of the genusPinguicula. Planta 96:183–211.
• Peumans, W.J., Smeets, K., Van Nerum, K., Van Leuven, F. and Van Damme, E.J.M. (1997) Lectin and alliinase are the predominant proteins in nectar from leek (Allium porrum L.) flowers. Planta 201:298–302.
• Rodriguez-Arce, A.L. and Diaz, N. (1992) The stability of beta-carotene in mango nectar. J. Agric. Univ. P.R. Rio Piedras, P.R.76:101–102.
• Roshchina, V.V. and Roshchina, V.D. (1993) The excretory function of higher plants. Springer-Verlag, Berlin.
• Scala, J., Iott, K., Schwab, W. and Semersky, F.E. (1969) Digestive secretion of Dionaea muscipula (Venus's-Flytrap). Plant Physiol. 44:367–371.
• Smith, L.L., Lanza, J. and Smith, G.C. (1990) Amino acid concentrations in extrafloral nectar of Impatiens sultani increase after simulated herbivory. Ecol. Publ. Ecol. Soc. Am. 71:107–115.
• Vogel, S. (1969) Flowers offering fatty oil instead of nectar. Abstracts XIth Internatl. Bot. Congr. Seattle.

External links

Wikimedia Commons has media related to: Nectaries

• Nectar Plants Database
• Converting Venom into Nectar