Plant Growth Requirements

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Plant Growth Requirements
http//expage.com/page/waxnsteel

• Topic 2019
• By Matt Jakubik

http//199.212.16.18/msc/as/index_e.html
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Major Factors for Plant Growth

• Temperature
• Light
• Moisture
• Carbon Dioxide
• Hormones

http//home.earthlink.net/bob4mvg/Time_n_Temperat
ure.htm
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Temperature

• As temperature increases, reaction rates increase
• ie-Photosynthesis is slower at lower
  temperatures however the rate increases up to a
  certain point as the temperature goes up
• Plant growth functions such as absorption of
  minerals and water are determined by temperature

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Temperature

• Plants have an optimal 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

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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

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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

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Quality

• Light is important and must contain important
  wavelengths
• These wavelengths are represented by the rainbow

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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

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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

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Light Duration

• Photoperiodism is a growth response to the length
  of dark period
• This determines if a plants is growing vegetative
  or is in the flowering stage
• In a greenhouse we can force a plant to bloom by
  controlling the duration of light

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Flowering plants include short-day, 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

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Long-day, Short-day and Day-neutral

• Day-neutral Plants-These plants flower regardless
  the day length
• ie-Dandelion

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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

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Other Light Effects

• Phototropism is the growth response in which
  plants turn or bend in the direction of the light
  source
• Geotropism is the growth response in which plants
  turn or bend in response to gravity

http//biosci.cbs.umn.edu/labs/koukkari/teaching/c
ourses/Angiosperms_30May.html
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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 many plant
  processes including photosynthesis and respiration

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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

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Moisture

• Capillary continued
• 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

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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

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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

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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
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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

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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

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Hormones

• ABA-Stimulates stomata closure, may be necessary
  for abscission and dormancy in some species
• Cytokine-Promotes apical dominance, shoot growth
  and fruit development
• Gibberellins-GA-Flowering stimulation in long-day
  plants and biennials, shoot elongation and
  regulates production of seed enzymes in cereals

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Hormones

• Ethylene-Promotes fruit ripening, leaf and flower
  senescence and abscission

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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.

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References

• Carbon Dioxide Picture http//csee.lbl.gov/Scienc
  eEd/Tony/chemistry/html
• Dandelion Picture http//home.jtan.com/russ/ter
  ri/trash.htm
• Rain Drop Picture http//199.212.16.18/msc/as/in
  dex_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/b
  ob4mvg/Time_n_Temperature.htm