LIFE 103 1st Edition Lecture 17Outline of Last Lecture I. Movement of sugarsII. PollinationIII. Animals attracted to pollen I. BeesII. Moths and butterfliesIII. BirdsIV. FliesV. BatsIV. Seeds I. CotyledonII. HypocotylIII. EpicotylIV. Seed coat V. ReproductionI. Fragmenting II. Self-fertilization Outline of Current Lecture I. Plant HormonesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.II. Auxins I III. Auxins II IV. Cytokinins V. Gibberellins VI. Abscisic acid Current Lecture: Signal transduction 1: hormonesClicker question: in which of the following places would you NOT find a meristem? Root hair because cells are not actively dividing. Apical meristem is at shoot tipClicker question: where is the force generated that moves water from soil into the roots? On themicrofibrils of the mesophyll cell in the leaf (cohesion is just sticking water molecules together) the last one of the water molecules is the force that generates it VII. Fig. 39.3, signal transduction What are plant hormones? VIII. HormonesI. A signaling molecule produced in tiny amounts in one part of the organismII. Transported to other parts, where it binds to a specific receptor and triggers responses in target cells IX. Hormone effects: I. Alter gene expressionII. Alter enzyme activityIII. Change membrane properties Auxins I I. IAA (Indole-3-acetic acid) is transported directionally through parenchyma tissues, from tip to base, highest concentration is at the bottom I. IAA transporter proteins found only at base of cells II. Stimulates cell elongation in young shoots I. Activates proton pumps to lower pH around cell wall II. Low pH activates expansin proteins that weaken cell wall III. Turgor pressure causes cell to expand III. Fig. 39.8 I. Cellulose microfibrils are glued together by sugarsII. When IAA is present, turns on pumps that put enzymes that make snips so that individual fibers can slide around freely Auxins II I. Apical dominance: central main stem grows more than side stems I. Auxins produced in apical meristems inhibit growth at axillary meristems II. “Rooting Powder” contains IAA, causes roots to form on plant cuttings III. Heribicide 2, 4-D is a synthetic auxin that kills eudicots but not monocots I. Eudicots grow unsustainably and dieII. Monocots rapidly inactivate 2, 4-D (could plant corn with this because it is a monocot) Cytokinins I. CK’s produced in roots and other actively growing areas. Transported through xylem II. CK’s act with auxin to affect parenchyma (classic plant cell) differentiation. IAA: CK ratio is important I. High ratio: cells become shoots II. Low ratio: cells become roots Gibberellins I. GA (gibberellic acid) enhance stem growth I. Mutants with dwarf growth grow to normal height when GA is sprayed on II. GA also signals seeds to break dormancy I. Water or light cues induce GA production III. Fig. 39.10 I. Gibberellin induced fruit growth does not mean they are genetically modified II. Affects plants Abscisic acid I. ABA slows growth, often acting in opposition to other hormones II. High ABA in seeds prevents their germination at the wrong timeI. Germination happens when ABA/GA ratio decreases III. Key signal for drought tolerance I. High ABA causes stomata to close IV. Fig.
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