Movements in Plants

Front

Stimulus Noun

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[stim-yuh-lus]

Back

Stimulus

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A detectable change in an organism's internal or external environment that causes a specific functional reaction or response.

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Example: Sunlight acts as a stimulus, causing the plant hormone auxin to move to the shaded side, which makes cells grow longer and bend the shoot toward the light.

Front

Response Noun

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[ri-spons]

Back

Response

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An organism's reaction to a stimulus, which can manifest as a change in behavior, growth, or physiological processes.

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Example: A signal (ligand) binds to a cell's receptor, triggering an internal process that results in a specific cellular response.

Front

External Stimuli Noun

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[ek-stur-nl stim-yuh-lahy]

Back

External Stimuli

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A change originating from outside an organism's body that elicits a response, such as light, temperature, or touch.

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Example: This diagram shows a plant bending towards light, an external stimulus. It also explains the cellular process where auxin hormones cause this movement.

Front

Internal Stimuli Noun

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[in-tur-nl stim-yuh-lahy]

Back

Internal Stimuli

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A change originating from within an organism's body that elicits a response, such as hunger, thirst, or hormones.

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Example: The image shows how the human body maintains stable blood sugar levels, an example of homeostasis. This is an internal stimulus in animals, not plants.

Front

Photosynthesis Noun

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[foh-toh-sin-thuh-sis]

Back

Photosynthesis

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The process by which green plants and other organisms use sunlight to synthesize foods from carbon dioxide and water.

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Example: This diagram shows how a plant uses energy from sunlight, water from the soil, and carbon dioxide from the air to create its food (glucose) and release oxygen.

Front

Homeostasis Noun

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[hoh-mee-oh-stey-sis]

Back

Homeostasis

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The tendency of an organism or a cell to regulate its internal conditions to maintain a stable, constant state.

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Example: This image explains homeostasis by comparing how a house uses a fan or heater to control temperature with how the human body uses sweat or shivering.

Front

Hormones Noun

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[hawr-mohnz]

Back

Hormones

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Chemical substances produced in an organism that act as messengers to control and regulate the activity of certain cells.

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Example: This diagram shows a hormone molecule binding to a specific receptor protein on a cell membrane, a concept too advanced and unrelated to plant movements.

Front

Auxin Noun

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[awk-sin]

Back

Auxin

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A class of plant hormones that plays a crucial role in coordinating growth and behavioral processes, especially cell elongation.

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Example: This diagram shows how the hormone auxin (IAA) causes a plant shoot to bend toward light and grow away from gravity by controlling cell growth.

Front

Tropism Noun

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[troh-piz-uhm]

Back

Tropism

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The turning or bending movement of a plant or other organism in a particular direction in response to an external stimulus.

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Example: This image shows geotropism, where a plant's stem grows up (negative tropism) and roots grow down (positive tropism) in response to gravity.

Front

Phototropism Noun

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[foh-toh-troh-piz-uhm]

Back

Phototropism

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The directional growth of a plant in which the stem grows towards a light source to maximize photosynthetic potential.

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Example: This diagram shows a plant bending toward a light source and explains the mechanism: auxin hormones move to the shaded side, causing those cells to elongate.