Plant Growth

Phases of plant growthDormancy:Period of inactivity. Often environmentally regulatedEx: Winter or droughtIn Vermont, most plants go dormant by October and remain dormant through AprilLength of dormancy- depends on your geographic location and the plant species

Phases of plant growthTwo 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 environmentFebruary to April

Phases of plant growthWhy important?If you try and force cut stems into flower, you must wait until they have completed their rest phaseTemperate plants need a dormancy period or they will die (important for bonsai/penjing)

Forsythia

Crabapples

Phases of plant growthVegetative phaseFood resources directed at production of leaves, stems and roots

Juvenile phase- part of the vegetative phase where reproduction cannot be induced

Reproductive phaseSugars and starches are storedThe plant flowers, produces seeds & fruit

Phases of plant growthSenescence: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 growthVegetative/Reproductive cycles are regulated by:Age/maturity of the plant

Carbohydrate/nitrogen balance in the plantCarbohydrates come from photosynthesis in leavesNitrogen is taken up by the rootsToo much nitrogen fertilizer can prevent a plant from becoming reproductive (flowering)

CellsCytology = the study of cellsCell wallPolysaccharides = long chains of simple sugars like glucoseCellulose ( unbranched polymer of several 1000 glucose molecules)Hemicellulose (branched chain)CombustibleDirectly indigestible by mammals (lack enzyme to break bonds between glucose units)Ruminants (animals with special bacteria in stomach)

Robert Hookes light microscope1665

CellsLignin = polymers of phenolic acidHardens cellulose walls (lignifies)Resists microbial decompositionCauses yellowing in paper (photo-oxidation)

Pectin = acidic polysaccharides = gelWater-soluble