Flower Nectar

Pollinators like insects and hummingbirds are attracted to the nectar of flowers, allowing the flowers to be pollinated.  A small amount of nectar is secreted at a specific time, encouraging the pollinating insects to return frequently and therefore increasing the likelihood of successful fertilization in the plant.

A group of different glands known as nectaries exudes the nectar as a sugary fluid.  Floral nectaries are typically found in the flower's base; extrafloral nectaries are located on various exterior portions of the plant. (Nectar)

The placement of floral nectaries near the perianth means that pollinators generally must brush up against the reproductive structures of the flower (anthers and pistil) to gain access to the nectar.

When production of nectar is on the flower's exterior, predatory insects are attracted and serve two functions in pollination: they will both eat the nectar and protect the flower by eating any lingering plant-eating insects, essentially acting as “bodyguards.”  Located generally on the leaf margin, mid-rib, or petioles, extrafloral nectaries are believed to be a type of modified trichome, and exude their nectar via phloem sap.  Various kinds of extrafloral nectaries are found on plants of the genera Gossypium, Prunus, and Salix. In the case of a number of carnivorous plants, nectar is useful in attracting insects as prey. (Nectar)

Like the lights on a runway, the nectar guides of the flower direct the pollinators toward the flower's center, where the nectar can be found.  These nectar guides extend from the source of nectar and form a zone of highly contrasted, low ultraviolet reflection around the center of the petal. 

Our eyesight doesn't allow us to see these patterns – the visual spectrum of humans renders ultraviolet light invisible.  Bees, on the other hand, are able to recognize ultraviolet light.  This allows the nectar guide to help the bee quickly find the center of the flower, where the nectar is located.  This unique adaptation carries benefits for both the bee and the flower: the bee can more rapidly collect nectar, and the flower has a better chance at successful pollination.  (Nectar Guide)

Unlike those which self-pollinate or are dependent on the wind for pollination, the overwhelming majority of plants rely on bees, hummingbirds, bats, and butterflies to transport pollen from plant to plant.  As is the case with animals, plants contain female and male reproductive parts.  The seeds of the plant – carried in the pollen grains – must make their way to the ovary of a separate plant of the same species in order for reproduction to succeed.  In order to attract the pollinators that are required for reproduction, the ovary and the pollen are located inside bright, colorful, scent-filled flowers that the pollinators find appealing.  The calorie-rich, sugary nectar has the greatest allure for the pollinators; most pollination assistance comes from pollinators simply searching for a meal. (Welter)

Flowers have a wide array of ways to attract and reward pollinators. The complex factors linking nectar temperature as a reward and a cue, as well as its influence on other rewards and cues, are gradually being understood. Bees are also getting warmth and a hot, sweet drink. What more could any chilly pollinator ask for? What the bees appear to be doing is similar to drinking a hot drink on a cold day. If you need to warm up, you can produce your own heat, at the expense of some of your energy reserves, or you can consume a warm drink, and save on investing your own energy. A fascinating observation is that bees do not just prefer the warmer drinks, they also learn to predict the flower’s temperature from its color. (Whitney and Chittka)

Hummingbirds, with their long beaks and tongues, feed on flowers which are much too long or thin for most other animals to access.  As the hummingbird uses it beak to sip up the nectar, pollen grains stick to the side of the beak.  At its next stop, the hummingbird transfers some of the pollen grains to the different flower.  If both are the same flower species, pollination takes place.

The most popular color of flower for pollinators is red, though orange, pink, and other colorful flowers are also frequented.  Flowers in the shape of a trumpet or tube are also preferred. (Welter)

This is why hummingbird feeders are usually red and have feeding tubes that resemble flowers. There are top fill feeders designed not only for attracting hummingbirds, but also for easy cleaning and filling with hummingbird food. The nectar is even red, and the feeding stations resemble flowers, such as the magnolia or primrose.

Designed for easy cleaning and filling, these top fill feeders feature a sports bottle technology: you push to seal it, pour in the hummingbird food (nectar), and pull to open it like a sports bottle. Unlike other feeders, top fill feeders have a large opening and don't require a funnel to fill. In addition, since these feeders open from the top, they don't need to be turned upside down to be filled and then flipped right side up to be hung, eliminating the mess most often experienced when refilling other feeders. Another advantage of the top fill feeders is its fewer parts: cleaning is simple, so you won’t have to worry about old, residual nectar spoiling the new batch.

Nectar. 19 April 2010 <http://www.cactus-art.biz/note-book/Dictionary/Dictionary_N/dictionary_nectar.htm>.

Nectar. 5 April 2010. 19 April 2010 <http://en.wikipedia.org/wiki/Nectar>.

Nectar Guide. April 19 2010 <http://www.cactus-art.biz/note-book/Dictionary/Dictionary_N/dictionary_nectar_guide.htm>.

Welter, Sonya. How Do Hummingbirds Help Pollination? 19 April 2010 <http://www.ehow.com/how-does_4566837_hummingbirds-help-pollination.html>.

Whitney, Heather and Lars Chittka. "Warm flowers, happy pollinators." Biologist (2007): 154-159.