Plants and man : who needs who?

Abstract

About 300,000 different species make up the plant kingdom. It is not the largest kingdom, but many agree that it is the most important. The photosynthesis process enables plants to convert energy from sunlight into carbohydrates, starches and sugars, which are, in turn recycled in the food chain. Plants also contribute to atmospheric oxygen since they use carbon dioxide for photosynthesis and release oxygen into the atmosphere. Nearly all living organisms depend on plants to survive; the only exceptions being some bacteria which can synthesise energy from chemicals prevalent in their environment. Unable to obtain energy directly from sunlight, animals must eat plants, or each other, and break down the energy contained in their tissues. Bacteria and fungi are the final link in this cycle of life; they convert dead plants and animals into raw materials which plants can utilize as nutrients. Life itself in all of its complexities is driven by the energy obtained from sunlight - trapped and stored by plants. Some plants have complex interactions with other organisms. Nitrogen-fixing bacteria, micorrhizal fungi, insects and other pollinators, all have intimate relationships with plants. Many birds, animals and insects have coevolved with some particular plant, or group of plant species, and the result is harmony and mutual benefit.