Floral scent

Floral scent or flower scent is composed of all the volatile organic compounds (VOCs), or aroma compounds, emitted by floral tissue (e.g. flower petals). Floral scent is also referred to as aroma, fragrance, floral odour or perfume. Flower scent of most flowering plant species encompass a diversity of VOCs, sometimes up to several hundred different compounds. The primary functions of floral scent are to deter herbivorous and especially florivorous insects (see Plant defense against herbivory), and to attract pollinators. Floral scent is one of the most important communication channels mediating plant-pollinator interactions, along with visual cues (flower color, shape, etc.).

Flower visitors such as insects and bats detect floral scent thanks to chemoreceptors of variable specificity to a specific VOC. The fixation of a VOC on a chemoreceptor triggers the activation of an antennal glomerulus, further projecting on an olfactory receptor neuron and finally triggering a behavioral response after processing of the information (see also Olfaction, Insect olfaction). The simultaneous perception of various VOCs may cause the activation of several glomeruli, but the output signal may not be additive due to synergistic or antagonistic mechanisms linked with inter-neuronal activity. Therefore, the perception of a VOC within a floral blend may trigger a different behavioral response than when perceived isolated. Similarly, the output signal is not proportional to the amount of VOCs, with some VOCs in low amount in the floral blend having major effects on pollinator behavior. A good characterization of floral scent, both qualitative and quantitative, is necessary to understand and potentially predict flower visitors' behaviour.

Flower visitors use floral scent to detect, recognize and locate their host species, and even to discriminate among flowers of the same plant. This is made possible by the high specificity of floral scent, where both the diversity of VOCs and their relative amount may characterize the flowering species, an individual plant, a flower of the individual plant, and the distance of the plume from the source.

To make the best use of this specific information, flower visitors rely on long-term and short-term memory that allow them to efficiently choose their flower. They learn to associate the floral scent of a plant to a reward such as nectar and pollen, and have different behavioral responses to known scents versus unknown ones. They are also able to react similarly to slightly different odor blends.

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