Save my name, email, and website in this browser for the next time I comment. Skip to content Nectar is that sweet reward that flowering plants provide animals in exchange for their services as pollinators.
It sounds incredibly simple on one level — much like rewarding a dog with a treat after it obeys a command. Flowering plants will optimise the characteristics of their nectar in order to influence the foraging behaviours of pollinators and ultimately improve their reproductive fitness.
The characteristics of the nectar not only determine which pollinators are attracted and when they come, but how frequently they visit and how long they stay. Suddenly one realises that there is an extremely complex system of regulatory mechanisms behind nectar secretion, which have not only influenced the evolution of flowering plants, but of the pollinators themselves. Red Admiral butterfly Vanessa atalanta drinking nectar.
There is no denying, however, that carbohydrates — sugars such as glucose, sucrose and fructose — are usually the main constituent of nectar. Other sugars might also be present in small amounts as well as sugar alcohols, such as sorbitol. It is these sugars that are the primary energy source for nectar consumers. Amino acids and proteins are the next most abundant solute in nectar after the sugars. There are essential and non-essential amino acids, which are the building blocks for proteins and there are some non-protein amino acids that are constituents of enzymes and preservatives.
It is thought that the amino acid and protein content of nectar may play a role in the taste preferences of insects [1], presumably related to their nutritional needs. The water content of nectar may also be an important reward for pollinators, particularly in dry habitats.
Nectar also contains important ions, such as potassium, as well as antioxidants, trace amounts of lipids and some secondary compounds that seem to be associated with resistance to herbivory. Many species have also been shown to have antimicrobial compounds in their nectar, which prevents microbes from growing in the nectar as well as inhibiting florally transmitted diseases [2]. Terpinoids, which are the volatile organic compounds that give flowers their scent, also accumulate in the nectar.
Flowers frequented by hummingbirds, for example, generally produce nectar in small amounts with high sugar content, while those frequented by more generalist passerine birds produce dilute nectar in large quantities.
Bats also seem to prefer less viscous nectar, though will preferentially select more dilute nectar as the water content is extremely important for their rehydration.
Nectar is produced in glands known as nectaries. The glands are commonly found at the base of flowers, where they produce nectar as a reward for pollinators. Some nectar contains toxins that act as defense mechanisms. This nectar is produced in extrafloral nectaries, usually on the stems or edges of leaves.
Some toxins protect flowers from fungus while other nectar contains toxins to repel organisms that take the nectar without helping in reproduction. Some extrafloral nectaries attract insects that kill plant pests. Cathryn Whitehead graduated from the University of Michigan in She has published numerous articles for various websites. Her poems have been published in several anthologies and on Poetry.
Whitehead has done extensive research on health conditions and has a background in education, household management, music and child development.
Related Articles Diagram of the Parts of a Flower. What Part of the Plant Makes Seeds? What Is Function of the Pistil in Flowers? How is Fruit Formed in Plants? Six Basic Parts of a Plant. Importance of Flowers in Nature. What they are doing with these scent compounds remains a mystery. Plants use the energy in sunlight to make sugar from carbon dioxide and water — the process that's called photosynthesis. Most of the sugar is made in the leaves, the plant organ that is specialized to gather sunlight.
From the leaves this sugar travels through the plant's conducting tissues to the other parts of the plant, the roots, stems and flowers. These plant parts then remove the sugar from the conductive tissues and use it to fuel all their metabolic processes.
Each species of flower has its own phenology timing of life cycle events. The amount of nectar in a flower depends on the species. Even within a species, the quality and quantity of nectar can vary according to the age of the flower, the length of its season, the amount of precipitation, the ambient temperatures, and even the time of day. For example, in a study of dandelions in Alberta, researchers discovered:.
Larger flowers produce more nectar. The quantity and concentration of nectar was higher in flowers 2 days old than in those 1 day old. Most flowers open in the morning and close in the afternoon so nectar was not available all day.
Nectar-sugar concentration and sugar value h increasing temperature. High nectar-foraging activity by honeybees coincided with peak nectar-sugar production. A nectary is a nectar-secreting gland found in different locations in the flower. The different types of floral nectaries include 'septal nectaries' found on the sepal, 'petal nectaries', 'staminal nectaries' found on the stamen, and 'gynoecial nectaries' found on the ovary tissue. Nectaries can also be categorized as structural or non-structural.
Pollinators feed on the nectar and, depending on the location of the nectary, the pollinator assists in fertilization and outcrossing of the plant as they brush against the reproductive organs, the stamen and pistil, of the plant and pick up or deposit pollen. Nectar from floral nectaries is sometimes used as a reward to insects, such as ants, that protect the plant from predators.
Many floral families have evolved a nectar spur. These spurs are projections of various lengths formed from different tissues, such as the petals or sepals. They allow for pollinators to land on the elongated tissue and more easily reach the nectaries and obtain the nectar reward. Extra-floral nectaries are nectar-producing glands physically apart from the flower located on leaf laminae, petioles, rachids, bracts, stipules, pedicels, fruit, etc.
Their size, shape and secretions vary with plant species. Extra-floral nectar content differs from floral nectar and may or may not flow in a daily pattern.
Two functions for the extra-floral nectar have been hypothesized: 1 as an excretory organ for the plant to rid itself of metabolic wastes or 2 to attract beneficial insects for plant defense. The nectar attracts predatory insects that consume both the nectar and plant-eating arthropods, functioning as bodyguards.
Nectar-seeking ants expel herbivores and enhance the reproductive success of plants with extra-floral nectaries. The greater the importance of extra-floral nectar to the ants, the better for the plants, as this increases the ants' aggressiveness toward herbivores. The actual process of transforming the flower nectar into honey requires teamwork.
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