Nectar

Nectar is a viscous, sugar-rich liquid produced by plants in glands called nectaries, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, which in turn provide herbivore protection.

Common nectar-consuming pollinators include mosquitoes, hoverflies, wasps, bees, butterflies and moths, hummingbirds, honeyeaters and bats.

[3] Some derive the word from νε- or νη- "not" plus κτα- or κτεν- "kill"[citation needed], meaning "unkillable", thus "immortal".

[4] The different types of floral nectaries include:[5] Most members of Lamiaceae have a nectariferous disc which surrounds the ovary base and derived from developing ovarian tissue.

Nectar is secreted from epidermal cells of the nectaries, which have a dense cytoplasm, by means of trichomes or modified stomata.

Adjacent vascular tissue conducts phloem bringing sugars to the secretory region, where it is secreted from the cells through vesicles packaged by the endoplasmic reticulum.

They allow for pollinators to land on the elongated tissue and more easily reach the nectaries and obtain the nectar reward.

In tobacco plants, these proteins have antimicrobial and antifungal properties and can be secreted to defend the gynoecium from certain pathogens.

Sepal and petal nectaries are often more common in species that are pollinated by short-tongued insects that cannot reach so far into the flower.

The leaves of some tropical eudicots (e.g., Fabaceae) and magnoliids (e.g., Piperaceae) possess pearl glands or bodies which are globular trichomes specialised to attract ants.

[20][22][23] While their function is not always clear, and may be related to regulation of sugars, in most cases they appear to facilitate plant insect relationships.

[20][21] Among passion flowers, for example, extrafloral nectaries prevent herbivores by attracting ants and deterring two species of butterflies from laying eggs.

[26] Charles Darwin understood that extrafloral nectar "though small in quantity, is greedily sought by insects" but believed that "their visits do not in any way benefit the plant".

Their defensive functions were first recognized by the Italian botanist Federico Delpino in his important monograph Funzione mirmecofila nel regno vegetale (1886).

[22] Other genera with extrafloral nectaries include Salix (Salicaceae), Prunus (Rosaceae) and Gossypium (Malvaceae).

However, fern nectaries did not diversify remarkably until nearly 100 million years later, in the Cenozoic, with weak support for a role played by arthropod herbivore diversifications.

[32] 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 benzylacetone, but the plant also adds bitter nicotine, which is less aromatic, so may not be detected by the bird until after taking a drink.

[34] Nectar contains water, essential oils, carbohydrates, amino acids, ions, and numerous other compounds.