Part 1: The Plant Perspective 2: Plants Attracting Insects Check Access

About two thirds of all the species of flowering plants depend on pollination by insects for successful reproduction. Flowering plants have evolved a wealth of organic compounds to lure pollinators, including attractive volatiles in flowers, colorful pigments, and sweet sugars in floral nectars. Plant scents, most commonly analyzed by gas chromatography, are mixtures of many different volatile organic compounds. Hydrocarbons attracting beetle pollinators serve as an introduction to organic compounds, followed by volatile alcohols, aldehydes, and esters. The largest group of plant volatiles comprises the terpenes, with characteristic structures resulting from specific biosynthetic pathways. Terpenes serve as an introduction to different types of isomers, resulting in a huge number of different organic compounds that attract different pollinators. Volatile compounds containing sulfur or nitrogen atoms invite flies and some beetles. Sugars in sweet nectars in flowers further attract pollinators; their structures introduce carbohydrates and general aspects of solubility. Aside from sugars and other nutrients, some nectars contain toxins. Flower pigments and nectar guides, sometimes visible only to distinct insects, provide an introduction to different plant pigments and the chemistry of color. Pollen, formed in the anthers of many flowers, provides a major reward for visiting insects. The composition of pollen serves as an introduction to polymers. Some orchids emit volatile hydrocarbons that mimic pheromones of insects and attract them to perform pollination. The chapter concludes with thoughts on coevolution between plants and insects.