Plant Hormones and Tropisms

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Homeostasis Noun

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[hoh-mee-oh-stay-sis]

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Homeostasis

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The ability of an organism to maintain a stable, constant internal environment despite changes in external conditions.

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Example: This diagram shows how red blood cells transport oxygen from the lungs to the body's cells, a process that maintains stable oxygen levels.

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Phytohormones Noun

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[fahy-toh-hawr-mohnz]

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Phytohormones

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Chemical messengers, also known as plant hormones, that regulate various physiological processes and responses within a plant.

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Example: This chart shows five major types of phytohormones (plant hormones) and their roles in promoting or inhibiting key life cycle stages like germination and flowering.

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Synergism Noun

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[sin-er-jiz-uhm]

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Synergism

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An interaction where two or more hormones work together to produce a combined effect greater than their individual effects.

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Example: This diagram shows a nerve cell releasing chemical messengers (neurotransmitters) to send a signal to another nerve cell across a small gap called a synapse.

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Antagonism Noun

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[an-tag-uh-niz-uhm]

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Antagonism

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An interaction between hormones where one hormone counteracts the effects of another, resulting in opposing physiological responses.

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Example: This diagram shows how the body maintains balance (homeostasis) using opposing actions: storing sugar when levels are high and releasing it when levels are low.

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Auxins Noun

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[awk-sinz]

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Auxins

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A class of plant hormones that primarily stimulate cell elongation, root formation, apical dominance, and fruit development.

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Example: This diagram shows that the plant hormone auxin gathers on the shaded side of a plant shoot, causing cells there to grow longer and making the shoot bend toward sunlight.

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Gibberellins Noun

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[jib-uh-rel-inz]

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Gibberellins

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A group of plant hormones that regulate developmental processes, including stem elongation, germination, dormancy, and flowering.

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Example: This image shows that the plant hormone gibberellin causes stem elongation, making a dwarf plant grow into a tall plant.

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Ethene Noun

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[eth-een]

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Ethene

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A gaseous plant hormone that influences diverse processes such as fruit ripening, flower senescence, and leaf abscission.

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Example: This graph shows that the plant hormone ethene (ethylene) is released in a burst by some fruits after harvesting, causing them to ripen.

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Abscisic Acid Noun

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[ab-sis-ik as-id]

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Abscisic Acid

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A plant hormone that functions in many developmental processes, including inhibiting growth, promoting dormancy, and mediating stress responses.

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Example: The hormone Abscisic Acid (ABA) binds to guard cells, causing them to lose water and become flaccid, which closes the plant's stomata.

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Cytokinins Noun

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[sahy-toh-kahy-ninz]

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Cytokinins

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A class of plant hormones that promote cell division, or cytokinesis, in plant roots and shoots, affecting growth.

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Example: Cytokinins are plant hormones that cause more cell division (mitosis), which leads to the creation of more cells and results in plant growth.

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Tropism Noun

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[troh-piz-uhm]

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Tropism

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The directional growth or turning movement of a plant in response to a directional external stimulus like light or gravity.

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Example: This image shows geotropism, a type of tropism. A plant's stem grows away from gravity (negative tropism), while its roots grow towards gravity (positive tropism).