The term used to describe the process by which plants make sugar is photosynthesis. It comes from the Greek words 'photo' (light) and 'synthesis' (joining).
Plants produce the sugars sucrose, glucose and fructose, these are then stored in the plant. These sugars give fruits their distinctive sweet taste. Sucrose is the sugar most commonly extracted from plants by man.
Sugar beet and sugar cane are the only plants used in the processing of table sugar as it is only these plants that produce and store a sufficient quantity of sucrose.
There are a whole range of substances which make up the family of sugars. These include the sugars made by plants during photosynthesis, milk sugars and honey. Our bodies use all sugars in basically the same way, whatever the source, to give us energy for life.
| Sugar |
Source of sugar |
| Glucose |
fruit, vegetables, honey |
| Maltose |
barley |
| Sucrose |
sugar beet, sugar cane, fruits |
| Lactose |
milk |
| Fructose |
fruits, honey |
The sugars produced by photosynthesis provide an immediate source of energy for plants to live and grow. Sugars are also used as the building blocks of complex structures within the plant. For example, cellulose (dietary fibre) forms plant cell walls and provides the plant with structure and support.
Sugars can be stored as starch, which provides an energy reserve at night, when plants are unable to photosynthesise (because of a lack of sunlight).
Starch is also used as a compact energy source in seeds. The young seedlings are unable to photosynthesise and instead rely on this source of energy for growth. Starch is found in large quantities in potatoes, rice and cereal grains (eg wheat).