Plant Tropisms

Fill in the blank using the word bank. Use each word once. A tropism is a growth response to a plant to a directional stimulus. Light and gravity are directional stimuli because they act in a particular direction. A growth response towards the direction of the stimulus is positive tropism and away from the direction of the stimulus is negative tropism. ‘Photo’ means light and a growth response to light coming from one direction is known as phototropism. ‘Geo’ means Earth so geotropism is a response to the direction gravityis coming from. ‘Hydro’ means water. Shoots do not respond to water but the roots of some plant species are attracted to water showing positive hydrotropism. Thigmotropism is a plant’s response to touch. Stems of many vines show positive thigmotropism when they encounter something and wrap themselves around it.Plants do not have sense organs or a nervous system so their responses are coordinated by chemicals. These chemical messengers are called hormones or plant growth substances. One of the hormones involved in this process is auxin. Determine the stimulus and response (tropism). Stimulus Light Gravity Touch Water Response (tropism) Hydrotropism Phototropism Thigmotropism Geotropism Choose the correct stimulus and response for the following picture using the click word bank. Stimulus: SunlightResponse: Phototropism Choose the correct stimulus and response for the following picture using the click word bank. Stimulus: WaterResponse: Hydrotropism