auxins, one of a number of groups of natural hormones present in vines which regulate growth. They are produced in vine parts which are actively growing, such as shoot and root tips. Auxins favour cell growth over cell division, but are also involved in inhibiting the growth of lateral shoots. Many chemicals have been synthesized which are chemically related and have a similar biological function. For example, the compounds 2,4-D and 2,4,5-T are auxin-like and form the basis of some herbicides, which are used widely in cereal production. Vines, like tomatoes and cotton, are very sensitive to 2,4-D vapours such as can drift over vineyards when neighbouring farmers use aerial spraying, even from many miles away. Most vine-growing regions have now enacted laws to protect vineyards from the effects of such spraying.