Plant Growth Phases of plant growth Dormancy Period

Phases of plant growth • Dormancy: – Period of inactivity. Often environmentally regulated –

Phases of plant growth • Two phases of dormancy: – 1. ) Rest period

Phases of plant growth • Why important? – If you try and force cut

Phases of plant growth • Vegetative phase – Food resources directed at production of

Phases of plant growth • Senescence: – Rapid or gradual cycle until death –

Phases of plant growth • Vegetative/Reproductive cycles are regulated by: – Age/maturity of the

Cells • Cytology = the study of cells • Cell wall – Polysaccharides =

Cells – Lignin = polymers of phenolic acid • • • Hardens cellulose walls

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Plant Growth

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

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

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)

Forsythia

Crabapples

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

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

Sedum

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)

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)

Robert Hooke’s light microscope 1665

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