Plant response towards stimuli
The closed leaves of the sensitive mimosa (Mimosa pudica) after being touched.
This chapter focuses on how plants respond to external and internal cues. At the organismal level, plants and animals respond to environmental stimuli by very different means.
Animals, being mobile, respond mainly by behavioral mechanisms, moving toward positive stimuli and away from negative stimuli. Being stationary, a plant generally responds to environmental cues by adjusting its pattern of growth and development. All organisms receive specific environmental signals and respond to them in ways that enhance survival and reproductive success.
Plants, too, have cellular receptors that they use to detect important changes in their environment, whether the change is an increase in the concentration of a growth hormone, an injury from a caterpillar munching on leaves, or a decrease in day length a winter approaches.
For a stimulus to elicit a response, certain cells must have an appropriate receptor, a molecule affected by the stimulus. Upon receiving a stimulus, a receptor initiates a series of biochemical steps, a signal transduction pathway, that couples reception to response. This phenomenon is called as signal transduction of plants. Plants are sensitive to a wide range of stimuli, each initiating a specific signal transduction pathway.