Plant Growth RequirementsPlant Growth Requirements

Topic 2019

By Torey Birchmeier

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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

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Light effects plants based on Light effects plants based on its quality, intensity and its quality, intensity and

duration.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

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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-Flowering plants include short-day, long-day and day-neutral day, long-day and day-neutral

plantsplantsShort-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-nuetralDay-nuetral

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

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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 soource

Geotropism is the growth response in which plants turn or bend in response to gravity

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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

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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

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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

ReferencesReferences

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

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.