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34 Cards in this Set
- Front
- Back
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Auxins |
Any substance that promotes the elongation of coleoptiles |
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Major auxin in plants |
Indoleacetic acid (IAA) |
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Auxin is produced from |
Amino acid tryptophan |
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Chief function of auxin |
Stimulate elongation of cells in young shoots |
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Major site of ausin synthesis |
Shoot apical meristems |
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Auxin facilitates cell growth by |
Altering gene expression rapidly - cells in the region of elongation produce new proteins within minutes
Stimulating the production of more cytoplasm and cell wall material to support cell growth |
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Synthetic auxin in weed control |
High doses of auxin stimulate ethylene production |
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Effects of ethylene production in weed control |
Inhibits elongation Leaf withering and stem curling Kills the plant |
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Agent Orange contamination |
Contaminated with TCDD due to overheating during manufacturing process |
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Dioxins |
Group of chemically related compounds that are environmental pollutants |
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2 main ingredients of Agent Orange |
2,4-D 2,4,5-T |
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Other functions of auxin |
Promotes lateral & adventitious root formation
Stimulates secondary growth by inducing cell division in the vascular cambium and differentiation of secondary xylem
Developing seeds synthesize auxin, promoting growth of fruit
Enhances apical dominance of terminal bud
Slow leaf drop
Influences phototropic responses |
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Brassinosteroids |
Effects are similar to those of auxin
Structure similar to animal steroid hormones |
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Functions of brassinosteroids |
Induce cell elongation & division in stem segments and seedlings
Slow leaf abcission
Promote xylem differentiation |
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Cytokinins |
Stimulate cytokinesis |
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Most common naturally occurring cytokinin |
Zeatin (from Zea mays) |
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Where cytokinins are produced |
Roots Embryos Fruits |
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Absence of cytokinins with auxin |
Cells do not divide |
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Presence of cytokinins and auxins |
Cells divide |
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Ratio of cytokinins & auxins is balanced |
Mass of growing cells remains undifferentiated |
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Cytokinin levels are raised above auxin |
Shoot buds form from the callus |
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Auxin levels are raised above cytokinin |
Roots form |
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What helps in anti-aging effects |
Cytokinins |
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Gibberellins |
Promotes cell elongation and cell division and lengthens stem
Increase internode length
Produced in roots and young leaves |
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For fruit to develop |
Both auxin and gibberellins must be present |
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Function of strigolactones |
Stimulate seed germination Help control apical dominance (suppress lateral buds) |
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Abscisic Acid (ABA) |
Slows down plant growth |
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ABA during drought |
ABA accumulation causes stomata to close rapidly to prevent water evaporation |
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Ethylene |
Produced as a response to stress |
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Triple response to mechanical stress |
Stem elongation slows Stem thickens Curvature causes the stem to start growing horizontally |
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Thylene promotes |
Senescence - progressive and irreversible changes within a cell that eventually lead to cell death |
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Cause of autumn leaf color changes |
Ethylene promoting senescence |
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Change in the balance of auxin and ethylene controls |
Leaf abscission |
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Ethylene triggers |
Fruit ripening |
