1. Plant Respond To Their Environment How many of you have ever been alone in a room watching a movie and the phone rings and you have jumped? You responded to a stimulus. Stimulus/Stimuli: is any factor in the environment that causes a response in an organism. These responses can be external or internal.

2. Plant Respond To Their Environment Tropism: is a plants response to external stimuli. What Environmental changes will plants respond to? Sun Darkness Temperature Changes, Weather, Climate Water Gravity Touch How plants respond to these factors (stimuli) will determine their ability to survive in a certain environment.

3. Plant Respond To Their Environment Plants Respond to the Sun Phototropism – Plants respond to sun or light by growing towards the sun or light source. Heliotropism – Plants respond to the sun’s movement across the sky by turning flowers, leaves, and stems toward the sun as it moves. Hormone called Auxin allows plant stems and leaves to bend and move to follow the sun.

4. Plant Respond To Their Environment Photoperiodism – A plant’s response to the number of hours it receives sunlight. Long Day Plants – require more than 10 – 12 hours of sunlight. These plants will bloom in spring and summer months when the days are long. Short Day Plants – require more than 12 hours of darkness. These plants will bloom in winter months when the days are short.

5. Plant Respond To Their Environment How do plants respond to changes in temperature in their environment? Thermotropism – a plant’s response to changes in temperature. Example: Dormancy Dormancy – A period which plants will not grow while waiting on preferred environmental conditions such as temperature.

6. Plant Respond To Their Environment Plants also respond to Gravity Gravitropism – a plant’s response to gravity on earth. Plant’s respond positively to gravity because the roots grow down toward the center of earth. Plant’s respond negatively to gravity because the stems grow up against gravity.

7. Plant Respond To Their Environment Plants respond to a decrease or increase of water in their environment. Hydrotropism – a plant’s response to water levels in their environment. Plants will open or close the stomata of leaves to increase or decrease transpiration if there is a change in available water. Roots will grow towards a water source.

8. Plant Respond To Their Environment Plants respond to being touched by things in their environment. Thigmotropism – a plant’s response to touch. Plants respond by closing their leaves Plants respond by growing around an object it touches Plants respond by closing and trapping the object it touches

9. Let’s Break these words down to help us remember Photo – Means Light Helio – Means related to the sun Period – Amount of Time Hydro – Water Thigmo – To Touch Gravi – Gravity Thermo – Temperature or Heat Tropism – A plant’s response to a stimulus