Why plants respond to the environment 0.0 / 5 ? BiologyHuman, animal and plant behaviourA2/A-levelOCR Created by: Amie RobertsCreated on: 15-03-14 19:06 What is a plant's response when the stimulus is predation from herbivores? Rapid growth, spines & thorns, toxins in tissues 1 of 22 What is a plant's response when the stimulus is favourable conditions? Extra nutrient storage 2 of 22 What is a plant's response when the stimulus is competition from other plants? Growth to create shade, production of inhibiting chemicals 3 of 22 What is a plant's response when the stimulus is water shortage or low temperature? Arrested growth or dormancy 4 of 22 Define: Tropism A directional growth response in which the direction of the response is determined by the direction of the external stimulus 5 of 22 What is the tropism for light? Phototropism (eg. shoots are positive, roots are negative) 6 of 22 What is the tropism for gravity? Geotropism (eg. shoots are negative, roots are positive) 7 of 22 What is the tropism for water? Hydrotropism (eg roots are positive) 8 of 22 What is the tropism for a chemical stimulus? Chemotropism (eg. pollen tubes are positive) 9 of 22 What is the tropism for touch/solid surfaces? Thigmostropism (eg. shoots of climbing plants, such as ivy) 10 of 22 What is a nastic response? Also referred to as nasties, non-directional responses to environmental stimuli 11 of 22 What is an example of a nastic response? Mimosa pudica - a thigmonastic response where the plant's leaves suddenly droop when touched 12 of 22 What is the role of plant hormones? Also referred to as plant growth factors, they are chemical messengers that act on target cells/ tissues 13 of 22 What are the effects of Auxins? Promote cell elongation, inhibit the growth of side shoots, inhibit leaf abscission and are involved in phototropism 14 of 22 What are the effects of Giberellins? Promote seed germination and growth of stems 15 of 22 What are the effects of Cytokinins? Promote cell division 16 of 22 What are the effects of Ethene? Promote fruit ripening and leaf abscission 17 of 22 What are the effects of Abscissic acid (ABA)? Inhibit seed germination and growth, and causes stomatal closure when the plant is stressed by low water availability 18 of 22 What are the similarities between plant and animal hormones? They are; chemical messengers, act on target cells/tissues, can only bind to specific receptors on cell surface membrane with complementary shapes 19 of 22 What are the differences between plant and animal hormones? They are; produced in a variety of tissues (not endocrine glands), transported by mass flow in phloem or in xylem vessels (as opposed to blood) 20 of 22 What is synergy? Where some plant hormones amplify the effect of others 21 of 22 What is antagonsim? Where some plant hormones cancel out the effect of others 22 of 22
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