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32 Cards in this Set
- Front
- Back
What are the 5 classical groups of hormones?
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Auxin, Gibberellins, Cytokinins, Ethylene, Abscisic acid
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Which hormone is a gas?
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Ethylene
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Which two hormones are involved in apical dominance?
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Auxin and Ethylene
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Which hormone is involved in abscission (the shedding of leaves)?
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ehtylene
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What hormone do insects produce that stimulates the formation of galls on leaves?
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Cytokinin
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What element is auxin often dependent on as a second messenger?
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Calcium
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Which two hormones can stimulate parthenocarpic fruits?
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Auxin and gibberellins
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Which hormone is involved in "bolting" in cabbage and normal Growth in dwarf plants?
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Gibberellin
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The three steps in Signal Transduction are...
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...Reception, Transduction, Induction
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What part of the plant is Cytokinins most likely produced?
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The roots
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Which hormone is refered to as the plant stress hormone?
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Abscisic acid
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What are the main actions of auxin?
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Promotes cambial activity and differentiation of cells into vascular tissue.
Promotes adventitious roots on stems. Stimulates fruit production. Inhibits abscission. Enlarges cells in tropic responses |
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What are the main action of Gibberellins?
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Induces cell division and elongation.
Breaks seed dormancy. Induces juvenile leaves. Involved in the development of parthenocarpic fruits. |
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What are the main actions of the Cytokinins?
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In the presence of auxin: stimulates cell division and organogenesis.
Expansion of cotyledons. affect organogenesis. formation of galls. |
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What are the main actions of Ethylene?
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Inhibits cell expansion.
Inhibits flowering. Involved in fruit ripening. Stimulates breakdown of cell walls. Promotes growth of root hairs. Promotes abscission |
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What are the main actions of Abscisic acid?
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Promotes seed dormancy.
Opening/closing of stomata. Inhibits stimulating effects of other hormones. |
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What is apical dominance?
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Where the main stem of the plant is dominant over the lateral stems (ie it grows more strongly)
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What are tropisms?
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A growth response toward (positive) or away (negative) from an external stimulus.
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The 3 naturally occurring auxins are...
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Indole 3 acetic acid (IAA)
4chloro IAA Phenylacetic acid |
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Which is the most common auxin and where is it synthesised?
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IAA in leaf primordia, young leaves, tips of grasses, developing fruits, seeds, flowers and pollen.
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Where in the plant does IAA move?
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Through the parenchyma of the pith, cortex and vascular tissue (always towards the base of the plant)
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What does adaptation imply?
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A genetically determined capability to acclimate to either sun or shade.
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What are three features that optimise the light received?
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Absorbtion, interception and processing
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What are some common features of a sun plant? (opposite for a shade plant)
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Large cells, small chloroplasts.
Few/thin grana stacks. low chloryphyll/rubisco ratio Small/thick leaves High stomatal conductance High photosynthetic capacity Low leaf area ratio high root:shoot ratio vertical leaf orientation high compensation irradiance |
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What does light interception depend on?
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Orientation, size, angle, surface features of the photosynthetic organ, arrangement of ph/syn tissues within those organs
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Where do the largerst leaves occur?
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In the rain-forest understorey.
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What are some features that can increase light reflection on leaves?
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Hair, wax, salt crystals.
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The costs of higher photosynthesis capacity are...
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Higher respiration rates in leaves
This rate is due to Increased carbohydrate processing in high light. Increased costs of contructing sun leaves. High costs of maintaining sun leaves. |
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What does absorbtion of excess sunlight lead to?
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Photo inhibition, less photosynthate per unit of light.
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What are xanthophylls?
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Yellow carotenoids that modulate light energy in leaves.
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What is D1?
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A protein that FACILITATES electron transport. Exists in D1 dissipative centres. If these become damaged the photosystem becomes non functional.
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What is rubisco?
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an enzyme involved in the Calvin cycle that catalyzes the first major step of carbon fixation, a process by which the atoms of atmospheric carbon dioxide are made available to organisms in the form of energy-rich molecules such as glucose.
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