Transcript Plant Growth Phases

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