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Plant Growth and Development Starr/Taggart’s Biology: The Unity and Diversity of Life, 9e Chapter 32.

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Presentation on theme: "Plant Growth and Development Starr/Taggart’s Biology: The Unity and Diversity of Life, 9e Chapter 32."— Presentation transcript:

1 Plant Growth and Development Starr/Taggart’s Biology: The Unity and Diversity of Life, 9e Chapter 32

2 Key Concepts: zHormones influence growth and development zHormones are signaling molecules between cells zThe known plant hormones are auxins, gibberillins, cytokinins, abscisic acid, and ethylene

3 Key Concepts: zHormones help bring about predictable patterns of development zEnvironmental changes such as seasons and temperature influence hormone production zHormones interact with each other to produce specific effects on growth and development

4 Patterns of Early Growth and Development zSeed germination zDependent on yTemperature yMoisture yOxygen yDaylight hours zImbibition yCoat ruptures xSeed swells from H 2 O update

5 Growth vs Development zGrowth yQuantitative yNumber, size, and volume increase zDevelopment yQualitative yEmergence of specialized body parts

6 Categories of Plant Hormones zGibberillins yPromote stem lengthening yHelp end dormancy of seeds and buds yContribute to flowering yNotable amounts in apical meristems of buds, roots, and leaves and in embryos

7 Categories of Plant Hormones zAuxins yPromote cell elongation in coleoptiles and stems yRoles in phototropism and gravitropism yNotable amounts in bud and leaf meristems and in embryos in seeds yIndoleacetic acid (IAA) most common auxin in nature

8 Categories of Plant Hormones zCytokinins yPromote cell division and leaf expansion, retard leaf aging ySynthesized in roots and travel elsewhere zAbscisic Acid yPromotes stomatal closure, bud and seed dormancy zEthylene yPromotes ripening of fruit, abscission of leaves, flowers, and fruits

9 Adjustment in the Rate and Direction of Growth zPlant tropism yShoot turns toward or away from an environmental stimulus zGravitropism yResponse to gravity xRoot curves down zStatoliths yGravity-sensing mechanisms yStarch grains in plastids

10 Phototropism in Coleotile

11 Adjustment in the Rate and Direction of Growth zThigmotropism yShift in direction of growth when contact occurs yVines yTendrils zMechanical stress yWind yDecrease growth

12 Biological Clocks zPhytochrome is part of the switching mechanism that promotes or inhibits growth of a variety of plant parts

13 Biological Clocks zCircadian rhythm zBiological activity that recurs in cycles, each of which lasts for about 24 hours zRhythmic leaf movements zPhytochrome is part of the control over leaf movements

14 Flowering - A Case of Photoperiodism zShort-day plants zLong-day plants zDay-neutral plants

15 Life Cycles End and Turn Again zSenescence yDeath of plant or some parts yAbscission xDropping of leaves, fruits and flowers yDecrease in daylight yDrought, wounds, nutrient deficiencies

16 Life Cycles End and Turn Again zDormancy yGrowth stops yInduced by daylight and cold zVernalization yChanges in temperature yStimulation of buds yFlower when spring comes zDormancy beaks yHormones yTemperature

17 In Conclusion zPlant growth involves increases in the number, size, and volume of cells by mitosis zInteractions among genes, hormones, and the environment influence plant growth zFive types of plant hormones have been identified: gibberillins, auxins, cytokinins, abscisic acid, and ethylene

18 In Conclusion zPlant hormones bring about patterns of growth and development zOnce the primary root breaks through the seed coat, germination ends zAfter germination, a plant increases in volume and mass zPlants make tropic responses to the environment

19 In Conclusion zPlant response to mechanical stress zPlants have biological clocks that make daily and seasonal adjustments in patterns of growth, development and reproduction zIn photoperiodism, plants respond to the lengths of daylight and darkness zSenescence is the sum of the processes which lead to the death of a plant or some parts

20 In Conclusion zDormancy is the state where a plant stops growing zBreaking dormancy involves exposure to certain temperatures and hormones zdeveloped by M. Roig


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