Plants, like animals, need to
respond to changes in their environment. They need to know when
conditions are right for growing, reproducing, and under what
conditions to stop growing.
Hormones and other chemical
messengers control these processes. Hormones signal for genes to be
turned on and off in response to different cues, such as the amount
of time a plant spends in the dark before light strikes it.
Scientists have performed many
experiments on Earth and even in outer space to try to understand
just how plants do what they do. In this Lesson, well explore the
control systems in plants.