Plant Hormones and Tropisms Response in Plants TROPISM

Plant Hormones and Tropisms Response in Plants

TROPISM is a biological phenomenon, indicating growth or turning movement a plant demonstrates in response to an environmental stimulus

TROPISM POSITIVE If the plant moves TOWARD the stimulus NEGATIVE If the plant moves AWAY from the stimulus

Phototropism Movement of plants toward light Why? Maximize amount of sun for photosynthesis to make their food. Phototropism http: //www. youtube. com/watch? NR=1&v=KQOC_b. Prq. Fs&safety_ mode=true&persist_safety_mode=1

Gravitropism Movement of plants in response to gravity Positive is toward gravity (roots grow down) Negative is away from gravity (shoot, stems, and leaves grow up) Why? Allows plants to grow properly and get nutrients and sunlight http: //www. youtube. com/watch? v=m. YZXax 8 V_L 0&feature=related&safety_mode=tru e&persist_safety_mode=1

Hydrotropism Movement by plants toward water. Why? Roots search for and grow toward water, because it is needed for photosynthesis and to support cell structure. http: //virtualastronaut. tietronix. com/textonly/act 25/text-plants. html

Thigmotropism Plants moving in response to touch. Positive is toward touch (vines wrap around structures) Negative is away from touch (some plants close up when touched) Why? to support leaves as they grow higher to reach the sun to make more food (photosynthesis). http: //www. youtube. com/watch? v =8 Heed. WWe 6 VA&feature=relate d&safety_mode=true&persist_saf ety_mode=1

Gravitropism Gravity In causes a response in plant growth the picture above, which part of the plant exhibits positive tropism, and which exhibits negative tropism?

Hydrotropism The way a plant grows or bends in response to water Why would it be important for some parts of a plant to be pulled toward water?

Thigmotropism Plants What bend and grow because of touch. are some other ways a plant can be “touched”?

Phototropism The way a plant grows or bends in response to light. Why do you think sunflowers were given their nickname?

Hydroptropism

Gravitropism

Phototropism

Gravitropism

Phototropism

Thigmotropism

HORMONES • A hormone is a chemical substance that controls a plant’s patterns of growth and development as well as a plant’s responses to environment • Hormones belong to the lipid class of biomolecules

AUXINS • • Produced in the apical meristem Stimulate elongation of plant stem cells Trigger phototropism (more on this later) Inhibit lateral bud growth

CYTOKININS • Plant development through cell division • Delay leaf loss by plant and help transport auxins through the plant

NASTIC MOVEMENTS • Hormones in plants or animals do not cause rapid changes. Rapid responses are due to changes in osmotic pressure (mimosa leaves, Venus fly trap) • Nastic Movements – Movement without growth

TROPISM QUIZ Identify the type of tropism in the following pictures

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7 http: //www. youtube. com/watch? v=Ze 8 NV 7 cv W 8 k&feature=results_main&playnext=1&list= PL 5464 C 68 C 7644 DD 4 D&safety_mode=true& persist_safety_mode=1

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11 http: //www. youtube. com/watch? v=9 sgg. QQu. B U 40&feature=related&safety_mode=true&per sist_safety_mode=1

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18 http: //www. youtube. com/watch? v=Zq 3 Uu. Hl. PL QU&feature=related&safety_mode=true&persi st_safety_mode=1

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20 http: //www. youtube. com/watch? v=frmyz. Ih. D 29 Q&safety_mode=true&persist_safety_mode=1