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Transcript of GROWTH Factor

  • Topics Growth factors (4 des)Growth regulators / phytohormones (4 -11 des)Seed germination (11 des)Plant movements (? des)Photoperiodism ( ?)Senescence (?)

  • Plant Growth Requirements

  • Major Factors for Plant GrowthTemperatureLight MoistureCarbon DioxideHormones`bob4mvg/Time_n_Temperature.htm

  • TemperatureAs temperature increases, reaction rates increaseie-Photosynthesis is slower at lower temperatures: however the rate increases up to a cerain point as the temperature goes upPlant growth functions such as absorption of minerals and water are determined by temperature

  • TemperaturePlants have an optional temperature range at which they function bestPlants have a minimum temperature tolerance below which the plant may be injured or killedMonocots have an advantage because the growth point remains below the groundDicots growing point is pushed above the ground and do not tolerate fluctuating temperatures or frost

  • Temperature Sun scald can occur at high temperaturesHigh temperatures cause desiccation or may may directly kill protoplasm of cells

    Plants should be selected according to the growth conditions and climate of the areaAn exception is the greenhouse where temperature conditions can be controlledhttp;//

  • Light effects plants based on its quality, intensity and duration.QualityThe 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

  • QualityLight is important and must contain important wavelenghtsThese wavelengths are represented by the rainbow

  • Light Intensity provides energy for photosynthesisRate of photosynthesis is effected by water, carbon dioxide and sunlight

    In the absence of light, plants will grow until there food reserves are exhaustedThis growth will be elongated and abnormal

  • Light IntensityPhototropism is the tendency to grow in the direction of the greatest light intensityPlants vary in the intensity of light that they needie-Impatiens grow better in shade with indirect lightZinnias grow best in full sunlight

  • Light DurationPhotoperiodism is a growth response to the length of dark periodThis determines if a plants is growing vegetatively or is in the flowering stageIn a greenhouse we can force a plant to bloom by controlling the duration of light

  • Flowering plants include short-day, long-day and day-neutral plantsShort-day Plants-must be exposed to light periods shorter than some critical length for flowering to occurie-PoinsettiaLong-day Plants-must be exposed to light periods longer than some critical length for flowering to occurie-Azalea

  • Long-day, Short-day and Day-neutralDay-neutral Plants-These plants flower regardless the day lengthie-Dandelion`russ/terri/trash.htm

  • Ways to influence blooming or vegetative growthUse 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 EffectsPhototropism 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

  • Moisture is also essential for plant growthWater carries essential nutrients from the roots and acts as a solvent for salts and mineralsWater translocates photosynthetic products from the leaves via the phloemWater is a chemical reactant in may plant processes including photosynthesis and respiration

  • MoistureWater quality is important to plantsExcessive salt can cause leaf burn, root corrosion, poor seed germination, wilting and killing Capillary water is used by the plantsCapillary 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

  • MoistureCapillary continuedWater moves freely in the soil and can move up or down, horizontallyie-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 PlantsGravity water-which is lost due to drainageHygroscopic water that bonds to soil particlesThe bonding is ionic charge related to the size of the soil particle and its electrical chargeThe charge is opposite that if water and will attract or hold the water in the soil making it unavailable to plants

  • MoisturePlants with large thin leaves lose water more readily and have high water requirementsPlants with small waxy leaves have a tendency to lose less water to transpiration and have less water requirementsDesert plants have small leaf surfaces while tropical plants have a large leaf surface

  • Carbon Dioxide is Required for PhotosynthesisCarbon Dioxide is taken in through the stomataAir contains .03% Carbon DioxideGreenhouses need to have CO2 addedRoses, carnations and tomatoes need 12%This can be accomplished by using gas burners

  • Carbon DioxidePlants use 16 essential nutrients and are available in the soilPrimary 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 are low molecular weight chemicals produced in the plant to regulate growthAuxin-promotes cell elongation, apical dominance, induces roots on cuttings, stimulates fruit development and stimulates ethylene synthesis

  • HormonesABA-Stimulates stomatal closure, may be necessary for abscission and dormancy in some speciesCytokinin-Promotes apical dominance, shoot growth and fruit developmentGiberellins-GA-Flowering stimulation in long-day plants and biennials, shoot elongation and regulates production of seed enzymes in cereals

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

  • ConclusionMoisture, Temperature, Light, Carbon Dioxide and Hormones are required in various amounts for different plants but are all requirements for a plant to grow.