HOW DO STOMATA WORK

This paper discusses in detail now theories of the mechanisms of stomatal movements. Recent evidence is presented that suggests that stomata respond to changes in the soil water content, as occur during drought. Such a system requires root-to-shoot communication, and it has been suggested that the plant hormone abscisic acid (ABA) is synthesized in the roots in response to drought, and acts as the root-to-shoot messenger. Also discussed are the recent advances that have been made in determining how ABA can induce stomatal closure. The physiology and biochemistry of stomata can be studied at different levels of organization, from the whole plant to the genome. The techniques involved in such studies are described. Reference is made to source material which will allow simple experiments to be carried out in a school laboratory.