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Plant Growth

Plant Growth

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Plant Growth

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  1. Plant Growth

  2. Phases of plant growth • Dormancy: • Period of inactivity. Often environmentally regulated • Ex: Winter or drought • In Vermont, most plants go dormant by October and remain dormant through April • Length of dormancy- depends on your geographic location and the plant species

  3. Phases of plant growth • Two phases of dormancy: • 1.) Rest period - plant will NOT grow even if given a favorable environment! • October to January • 2.) Dormant yet reactive - plant will grow if given a favorable environment • February to April

  4. Phases of plant growth • Why important? • If you try and force cut stems into flower, you must wait until they have completed their “rest” phase • Temperate plants need a dormancy period or they will die (important for bonsai/penjing)

  5. Forsythia

  6. Crabapples

  7. Phases of plant growth • Vegetative phase • Food resources directed at production of leaves, stems and roots • Juvenile phase- part of the vegetative phase where reproduction cannot be induced • Reproductive phase • Sugars and starches are stored • The plant flowers, produces seeds & fruit

  8. Phases of plant growth • Senescence: • Rapid or gradual cycle until death • In hardy perennials, only the above-ground portion senescences (roots/crown remain alive) • In woody trees and shrubs, only the leaves and fruit senescence each year

  9. Sedum

  10. Phases of plant growth • Vegetative/Reproductive cycles are regulated by: • Age/maturity of the plant • Carbohydrate/nitrogen balance in the plant • Carbohydrates come from photosynthesis in leaves • Nitrogen is taken up by the roots • Too much nitrogen fertilizer can prevent a plant from becoming reproductive (flowering)

  11. Cells • Cytology = the study of cells • Cell wall • Polysaccharides = long chains of simple sugars like glucose • Cellulose ( unbranched polymer of several 1000 glucose molecules) • Hemicellulose (branched chain) • Combustible • Directly indigestible by mammals (lack enzyme to break bonds between glucose units) • Ruminants (animals with special bacteria in stomach)

  12. Robert Hooke’s light microscope 1665

  13. Cells • Lignin = polymers of phenolic acid • Hardens cellulose walls (lignifies) • Resists microbial decomposition • Causes yellowing in paper (photo-oxidation) • Pectin = acidic polysaccharides = gel • Water-soluble