Transcript Plant Growth Requirements

Plant Growth Requirements
http://expage.com/page/waxnsteel
Topic 2019
By Torey Birchmeier
http://199.212.16.18/msc/as/index_e.html
Major Factors for Plant
Growth

Temperature
 Light
 Moisture
 Carbon Dioxide
 Hormones
http://home.earthlink.net/`bob4mvg/Time_n_Temperature.htm
Temperature

As temperature increases, reaction rates
increase
– ie-Photosynthesis is slower at lower
temperatures: however the rate increases up to a
cerain point as the temperature goes up

Plant growth functions such as absorption
of minerals and water are determined by
temperature
Temperature

Plants have an optional temperature range at
which they function best
 Plants have a minimum temperature
tolerance below which the plant may be
injured or killed
– Monocots have an advantage because the growth point remains
below the ground
– Dicots’ growing point is pushed above the ground and do not
tolerate fluctuating temperatures or frost
Temperature
http;//expage.com/page/waxnsteel

Sun scald can occur at high temperatures
– High temperatures cause desiccation or may
may directly kill protoplasm of cells

Plants should be selected according to the
growth conditions and climate of the area
– An exception is the greenhouse where
temperature conditions can be controlled
Light effects plants based on
its quality, intensity and
duration.

Quality
 The major source of light is the sun
 Normal plant growth requires white light or
sunlight
 Chlorophyll absorbs the red and blue
portions of the light spectrum. Leaves are
green, since the chlorophyll reflects green
light
Quality

Light is important and must contain
important wavelenghts
 These wavelengths are represented by the
rainbow
http://204.97.147.10/card/paper.htm
Light Intensity provides energy
for photosynthesis

Rate of photosynthesis is effected by water,
carbon dioxide and sunlight

In the absence of light, plants will grow
until there food reserves are exhausted
– This growth will be elongated and abnormal
Light Intensity

Phototropism is the tendency to grow in the
direction of the greatest light intensity
 Plants vary in the intensity of light that they
need
– ie-Impatiens grow better in shade with indirect
light
– Zinnias grow best in full sunlight
Light Duration

Photoperiodism is a growth response to the
length of dark period
 This determines if a plants is growing
vegetatively or is in the flowering stage
– In a greenhouse we can force a plant to bloom
by controlling the duration of light

Flowering plants include shortday, long-day and day-neutral
plants
Short-day Plants-must be exposed to light
periods shorter than some critical length for
flowering to occur
– ie-Poinsettia

Long-day Plants-must be exposed to light
periods longer than some critical length for
flowering to occur
– ie-Azalea
Long-day, Short-day and
Day-nuetral

Day-neutral Plants-These plants flower
regardless the day length
– ie-Dandelion
http://home.jtan.com/`russ/terri/trash.htm
Ways to influence blooming or
vegetative growth

Use a black cloth to shorten days. This
involves covering the plants with an opaque
cover to shorten days

Artificial light stimulates long days by
adding light in the evening hours
Other Light Effects

Phototropism is the growth response in
which plants turn or bend in the direction of
the light soource

Geotropism is the growth response in which
plants turn or bend in response to gravity
http://biosci.cbs.umn.edu/labs/koukkari/teaching
/courses/Angiosperms_30May.html
Moisture is also essential for
plant growth

Water carries essential nutrients from the
roots and acts as a solvent for salts and
minerals
 Water translocates photosynthetic products
from the leaves via the phloem
 Water is a chemical reactant in may plant
processes including photosynthesis and
respiration
Moisture

Water quality is important to plants
 Excessive salt can cause leaf burn, root
corrosion, poor seed germination, wilting
and killing
 Capillary water is used by the plants
– Capillary is when the water makes contact with
the soil and it is elevated of depressed
depending on the relative attraction of the
molecules or water
Moisture

Capillary continued
http://199.212.16.18/msc/as/index_e.html
– Water moves freely in the soil and can move up
or down, horizontally
– ie-dip the end of a napkin into a glass of water
and observe water as it moves up through the
napkin
Moisture Not Available To
Plants

Gravity water-which is lost due to drainage
 Hygroscopic water that bonds to soil
particles
– The bonding is ionic charge related to the size
of the soil particle and its electrical charge
– The charge is opposite that if water and will
attract or hold the water in the soil making it
unavailable to plants
Moisture

Plants with large thin leaves lose water
more readily and have high water
requirements
 Plants with small waxy leaves have a
tendency to lose less water to transpiration
and have less water requirements
– Desert plants have small leaf surfaces while
tropical plants have a large leaf surface
Carbon Dioxide is Required
for Photosynthesis

Carbon Dioxide is taken in through the
stomata
 Air contains .03% Carbon Dioxide
 Greenhouses need to have CO2 added
– Roses, carnations and tomatoes need 12%
– This can be accomplished by using gas burners
http://csee.lbl.gov/ScienceEd/Tony/chemistry/html
Carbon Dioxide

Plants use 16 essential nutrients and are
available in the soil
 Primary nutrients-N, P, K
 Secondary nutrients-Ca, S, Mg
 Trace nutrients-Mn, Fe, Zn, Cu, Cl, B, Mo
 C, H, O-usually not limited since they are
freely available in the air and water
Hormones

Hormones are low molecular weight
chemicals produced in the plant to regulate
growth
 Auxin-promotes cell elongation, apical
dominance, induces roots on cuttings,
stimulates fruit development and stimulates
ethylene synthesis
Hormones

ABA-Stimulates stomatal closure, may be
necessary for abscission and dormancy in some
species
 Cytokinin-Promotes apical dominance, shoot
growth and fruit development
 Giberellins-GA-Flowering stimulation in long-day
plants and biennials, shoot elongation and
regulates production of seed enzymes in cereals
Hormones

Ethylene-Promotes fruit ripening, leaf and
flower senescence and abscission
References
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Carbon Dioxide Picture: http://csee.lbl.gov/ScienceEd/Tony/chemistry/html
Dandelion Picture: http://home.jtan.com/`russ/terri/trash.htm
Rain Drop Picture: http://199.212.16.18/msc/as/index_e.html
Rainbow Picture: http://204.97.147.10/card/paper.htm
Sunflower Picture:
http://biosci.cbs.umn.edu/labs/koukkari/teaching/course/Angiosperms_30May.html
Sun Picture: http://expage.com/page/waxsteel
Thermometer Picture: http://home.earthlink.net/`bob4mvg/Time_n_Temperature.htm
Conclusion

Moisture, Temperature, Light, Carbon
Dioxide and Hormones are required in
various amounts for different plants but are
all requirements for a plant to grow.