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HCS 2200 Plant Structure, Growth & Development
Pamela J Sherratt
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The Carbon Cycle & Energy Transfer
Radiant energy converted to
chemical energy, then
released to support the
metabolism of all living
organisms.
Carbon is the molecule that
is cycled and recycled through
these processes.
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Autotrophs (plants &
bacteria)
• Process – Captured solar energy is used to
synthesize carbon-based molecules called
carbohydrates from CO2 & water.
• Oxygen is released in the process
• Some of the energy used to make the
carbohydrates is now stored in the
carbohydrate molecules.
• Respiration breaks those carbohydrate
bonds, releasing the energy, along with
CO2 and water …
Photosynthesis
CO2 + H2O
Heterotrophs
Light
C(H2O) + O2
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Respiration
C6H12O6 + 6O2 + 36 ADP + 36 PO43-
6CO2 + 6H2O + 36 ATP
• Process – the transfer of carbohydrate energy to energy-rich
ATP energy.
• The transfer of energy to ATP requires carbohydrates, oxygen,
and ADP (low-energy molecule
• This then provides the energy for biological processes.
• In essence, respiration is the reverse of photosynthesis
• The CO2 released by respiration is then used again in
photosynthesis, thus completing the carbon cycle!
This Photo by Unknown Author is licensed under CC BY-SA
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Carbon Cycle Review
• Photosynthesis & respiration are generally in balance, with
the amount of carbon being reduced and oxidized being
nearly equal, resulting in little change to atmospheric CO2.
• The current rise in atmospheric CO2 is, in part, the result of
oxidization of carbohydrates produced long ago by the
plants that make up fossil fuels when those fuels are burned.
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Plant Growth and
Development
are NOT the same
thing!
These poinsettias are the same age.
Which has most growth?
Which is furthest along in development?
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Growth is defined as an irreversible increase in size (biomass).
Definition: Size increase by cell division and enlargement, including synthesis
of new cellular material and organization of subcellular organelles.
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Development is the changes that occur during ontogeny (the maturation process).
Stages of development: seed germination, growth of vegetative organs and tissues, initiation
& maturation of reproductive organs and tissues, fertilization, seed development and
maturation, scenescence and death.
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Senescence/death
Vegetative growth
Reproduction
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Life cycle of a coffee bean
https://www.reddit.com/r/Damnthatsinteresting/comments/b5kbiz/the_life_cycle_of_coffee/
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Plant Shoot Growth
• Determinate growth pattern – after a certain period of
vegetative growth, flower buds form at the shoot terminal
and shoot elongation stops
• Indeterminate growth pattern – Flowers form along the
shoot, which continues to grow until senescence or an
environmental influence
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Determinate or Indeterminate?
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Accumulation of Biomass (growth)
Plants can increase in size by
• taking up water
• accumulation of organic compounds created by photosynthesis.
Plant scientists often measure growth in terms of increase in dry matter
(photosynthates) rather than increase in size.
Dry matter is often referred to as biomass.
Question:
Why is biomass measured in dry weight, not fresh weight?
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Most producers of agricultural products are interested in biomass
more than water content of their crops.
For example:
•Farmers don’t want corn high in water and low in starch content
•Catsup producers don’t want watery tomatoes.
•Golf course superintendents don’t want weak, watery grass blades.
•Ornamentalists don’t want weak plants with little color or stamina.
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Question: What is/are the part/s of interest in the following?
Chrysanthemums
Soybeans
Lawn
Forages
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Biomass Partitioning
by which plants divide their energy amongst their parts
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Annual Plant
Herbaceous Perennial
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In the later stages of the life of an annual plant most of the photosynthetic product may be
directed to seed production.
Plant breeders of seed crops try to maximize the proportion allocated to seeds relative to
what’s allocated to leaves, roots, and particularly stems.
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In herbaceous perennials, resources produced in the latter half of the growing
season are diverted to the over-wintering structure, whether it is a bulb, root, or
rhizome.
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The direction of resource allocation is an important factor in controlling perennial weeds.
Herbicide is applied in the late summer to prevent the plant from allocating resources to the
structures it needs to survive the winter.
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Ontogeny
(Life Cycles)
is the developmental change an individual goes through in its lifetime - the socalled stages of life or maturation.
In a plant those stages can be germination, vegetative growth, flowering, fruit
development, seed production, senescence (aging) and death.
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Plant Lifecycles: Annual
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Annual Plants
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In Ohio
Winter cold kills geraniums,
Summer heat kills pansies,
a warm climate plant.
a cool climate plant.
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Summer Annuals
Mid-May
Summer
Question:
What are the traits of a true “annual” plant?
Name 3!
Mid-October
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Plant Lifecycles: Biennial
Year 2
Year 1
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Examples of biennials:
• Beets
• Brussel sprouts
• Cabbage
• Carrots
• Hollyhock
• Lettuce
• Onions
• Parsley
• Swiss Chard
• Sweet William
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Perennials live longer than 3 years.
The development of a perennial plant includes long
term and annual phenological events, such as:
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Plant Lifecycles: Perennial
Woody
perennial
Nonwoody or
herbaceous
perennial
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Specialised Stems & Roots:
(biennials & perennials)
Stems: Bulbs, corms, tubers,
rhizomes & stolons
(what’s the difference?)
Roots:Taproots and Tuberous
roots.
What purpose do they serve?
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Question: What plant part makes you
believe this dandelion weed is a
perennial, & why?
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Define the following:
1. Woody plants
2. Non woody (herbaceous) plants
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Plant Growth Regulators: Plant Hormones
• Auxin - cell enlargement, tropism, apical dominance, abscission of plants parts, flower initiation and
development, root initiation, fruit set and growth, cambial activity, tuber and bulb formation, seed germination
• Gibberelin – Cell division and cell elongation, flower initiation & sex expression, fruit set, senescence of
plant parts, overcoming dormancy
• Cytokinin – Cell division, cell enlargement, tissue differentiation, dormancy, phases of flowering and fruiting,
retardation of leaf senescence
• Ethylene (gaseous) -Fruit ripening, flower initiation, abscission
• Abscisic acid – Seed dormancy, abscission, closes stomata
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Tropisms in Plants
- Touch, light, water, gravity
Thigmotropism
Ref: http://www.untamedscience.com/science/wp-content/uploads/2013/10/how-phototropism-works.jpg
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Watch: Plant Hormones: Auxin
https://youtu.be/HR9KHW-e0pY
Watch: Tropisms in Plants
https://youtu.be/pCFstSMvAMI
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Synthetic Plant Growth Regulators
& Their Uses
Epinasty in dandelion
• Auxin : Rooting powder, weed control (2,4-D), inhibition of stem
sprouting, tissue culture/micro-propagation
• Gibberellin: Increasing size of seedless grapes, stimulation seed
germination & seedling growth, promoting male flowers in cucumbers,
overcoming cold requirement, promoting cell elongation (sugar cane)
• Cytokinin: Tissue culture
• Ethylene: Fruit ripening, flower initiation, changing sex expression,
degreening oranges, lemons and grapefruit, harvest aids (walnuts, cotton),
growth regulation, low O2 during transportation
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Tobacco stem. L-R: No trtm, Cytokinin = buds, auxin = roots & prevention of buds,
C+A = callus, no organ dev.
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Gibberellin
Overcoming dwarfness in
corn by spraying gibberellin.
(L-R: dwarf, nondwarf + G,
dwarf + G)
Effect of gibberellin on grape
seeds.
(L-R: no trtm, low, med, high
rate )
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Synthetic Growth Retardants
• Slow cell division & elongation. Most block
gibberellin synthesis
Growth reduction in chrysanthemum plants.
(L-R: control, medium rate, high rate)
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Common Name
Plant Growth Regulators used on Turf
Trade Name
Absorption
Mode of Action
Comments
Mefluidide
Embark
Foliar
Inhibits cell division (mitosis)
and differentiation in
meristematic tissue
Primarily used to inhibit Poa annua seedhead
formation. App. made in spring prior to seedhead
inflorescence emergence
Ethephon
Proxy
Foliar
Enhances release of ethylene
into the plant, regulating
growth through its influence
on cell size
Used alone or in combination with trinexapacethyl for Poa annua seedhead control
Paclobutrazol
Trimmit
Root
Early gibberellic acid (GA)
inhibitor
GA inhibitors were and are still used in the
gradual reduction of poa annua in creeping
bentgrass turf due to the greater inhibitory effect
on Poa.
Flurprimidol
Cutless
Root
Early gibberellic acid (GA)
inhibitor
Originally used in the same fashion as
paclobutrazol. With both paclobutrazol and
flurprimodol conversion to more bentgrass in
fairways is accomplished with spring and fall
applications at the higher end of the
recommended rate
Trinexapac-ethyl
Primo MAXX
(liquid)
Foliar
Late gibberellic acid (GA)
inhibitor
Most widely used plant growth regulator on high
quality turf. Implicated in enhancing summer
stress tolerance of turf, reduced disease severity
(in some cases) and improved turf quality
Governor
(granular)
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Knowledge Check:
• Have a basic understanding of photosynthesis & respiration (the carbon cycle)
• What is the difference between an autotroph & heterotroph? Indicate what each of the following would be:
orchid, polar bear, fungus, maple tree, rabbit
• Why is it not likely that the respiration of all living creatures on earth is a cause of increased atmospheric
CO2?
• What is the difference between plant growth and development?
• What is the difference between determinate and indeterminate growth?
• Biomass partitioning – the difference between annual and perennial plants
• Describe the life cycle of annual, biennial and perennial plant
• Hormones - give a natural function or production use for auxin, GAs, ABA, cytokinin and ethylene
• Tropisms - Geo, photo, thigmo
Why most plants are green?
It is mainly due to the influence of the photovoltaic conversion rate of operating
temperature and light conditions.When I was a child, I often thought about why
most of the plants in life are green. It must be wonderful if red plants or blue plants
can also occupy most of them. After I learned about plants, I understood the
principle.
The chloroplast photosystem is a living system that can adjust the ratio of pigments
according to the light intensity and wavelength of light concentration. For example,
most chloroplasts in cyanobacteria and eukaryotes are dark green to blue green,
while in deep sea cyanobacteria and eukaryotes The color of the chloroplast is close
to brown because of the higher proportion of lutein, and the chloroplast in the
place with strong sunlight has a higher proportion of carotene, resulting in a light
green color, which improves the conversion efficiency and avoids excessive
temperature.
Source: https://www.jic.ac.uk/blog/why-are-plants-green/ 0
What factors allow seeds to remain viable?
I worked at a place that sold seed, mostly grass and cover crop seed. Each year,
depending on the seed, an emergence test was done to determine the emergence
rate of that bag of seed. As you might expect usually it decreased year after year. I
would predict that most of the seed in the bag would be no good after 5-10 years.
However, during our greenhouse tours we were told that seeds can last hundreds
of years. How can this be? Do different seeds stay viable for different lengths of
time? How important are the storage environments of the seeds?
Source: Greenhouse Tours
11:09 AM, 3/5/2022
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