Plant movements - Tropisms
Plants develop roots, so that they cannot move around. This is a big disadvantage, when compared to animals, because it causes vulnerability. Animals can flee from predators. PLants had to develop other means of defending themselves, like having substances that are poisonous or simply unpleasant to animals that may want to eat them. These substances are part of the secondary metabolism of the plant; the primary metabolism consists of the reactions and substances that are needed to maintain the fundamental processes, like respiration or photosynthesis.
However, plants do realize some movements. They move towards light (phototropism) or towards the earth (geotropisms).