growth factor
DESCRIPTION
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Topics Topics
Growth factors (4 des)Growth regulators / phytohormones (4 -11
des)Seed germination (11 des)Plant movements (? des)Photoperiodism ( ?)Senescence (?)
Plant Growth RequirementsPlant Growth Requirementshttp://expage.com/page/waxnsteel
http://199.212.16.18/msc/as/index_e.html
Major Factors for Plant Major Factors for Plant GrowthGrowth
TemperatureLight MoistureCarbon DioxideHormones http://home.earthlink.net/`bob4mvg/Time_n_Temperature.htm
TemperatureTemperature
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
TemperatureTemperature
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 Temperature
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
http;//expage.com/page/waxnsteel
Light effects plants based on its quality, Light effects plants based on its quality,
intensity and durationintensity and duration..Quality
The major source of light is the sunNormal plant growth requires white light or
sunlightChlorophyll absorbs the red and blue
portions of the light spectrum. Leaves are green, since the chlorophyll reflects green light
QualityQuality
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 Light Intensity provides energy for photosynthesisenergy 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 IntensityLight 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 DurationLight 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 short-day, long-Flowering plants include short-day, long-day and day-neutral plantsday 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 Long-day, Short-day and Day-neutralDay-neutral
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 Ways to influence blooming or vegetative growthvegetative 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 EffectsOther 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/courses/Angiosperms_30May.html
Moisture is also essential for Moisture is also essential for plant growthplant 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
MoistureMoistureWater quality is important to plantsExcessive 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
MoistureMoisture
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
http://199.212.16.18/msc/as/index_e.html
Moisture Not Available To Moisture Not Available To PlantsPlants
Gravity water-which is lost due to drainageHygroscopic 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
MoistureMoisture
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 Carbon Dioxide is Required for Photosynthesisfor Photosynthesis
Carbon Dioxide is taken in through the stomata
Air contains .03% Carbon DioxideGreenhouses 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 DioxideCarbon Dioxide
Plants use 16 essential nutrients and are available in the soil
Primary nutrients-N, P, KSecondary nutrients-Ca, S, MgTrace nutrients-Mn, Fe, Zn, Cu, Cl, B, MoC, H, O-usually not limited since they are
freely available in the air and water
HormonesHormones
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
HormonesHormones 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
HormonesHormones
Ethylene-Promotes fruit ripening, leaf and flower senescence and abscission
ConclusionConclusion
Moisture, Temperature, Light, Carbon Dioxide and Hormones are required in various amounts for different plants but are all requirements for a plant to grow.