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The Effects of Light on Plants
 

The Effects of Light on Plants

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    The Effects of Light on Plants The Effects of Light on Plants Presentation Transcript

    • The Effects of Lights on Plants
      Tim Langley
      Biology 101
      Research project
    • Plants Importance to the World
      • Without light plants could not grow or reproduce, which means that all plants would die off
      • Plants are the only organism that produces its own food
      • Plants get their energy directly from the sun
      • Plants are the only organisms that produce oxygen, and we would suffocate without them
    • Photosynthesis
      • All organic molecules derive from photosynthesis
      • All of the oxygen on earth is a product of photosynthesis
      • Photosynthesis is an endergonic redox process
      • Occurs in two stages: the light reactions and the Calvin cycle
      • Takes place in the thylakoid membranes of the chloroplasts
    • The Two Stages of Photosynthesis
      Light Reactions
      The part of photosynthesis where light is converted to chemical energy
      Water and carbon dioxide combine to form carbohydrates and oxygen
      The light captured by chlorophyll is used to generate electrons with reducing potential
      These electrons are used to produce NADPH and ATP
      Occurs in the thylakoids of the chloroplasts
      Violet-blue and red light work best for photosynthesis
      Calvin Cycle
      CO2 from the air is incorporated into organic molecules in a process called carbon fixation
      The cycle spends ATP and NADPH to make sugar out of CO2
      Occurs in the stroma
      Returns ADP, inorganic phosphate, and NADP+ back to the light reactions
    • Chloroplasts
      • Found in the tissue in the interior of the leaf in the mesophyll cells
      • The structure is mainly made from the fluid, Stroma, and the Granum which is in the form of thylakoid sacs
      • Contains three types of pigments: Chlorophyll a, chlorophyll b, and carotenoids
      • Light energy is captured by the chlorophyll in the chloroplasts and transferred into chemical energy
    • Photons and Chlorophyll
      • When a photon is absorbed the electrons in the chlorophyll become excited and then have more potential energy
      • An excited electron is unstable and will drop back to the ground state and release its excess energy in the form of heat and fluorescence
      • Fluorescence is the afterglow of an isolated chlorophyll
    • Photosystems
      The light dependent part of photosynthesis is carried out by the photosystems (I and II)
      This occurs in the thylakoid membrane of the chloroplasts
      Each photosystem is driven by excited chlorophyll molecules
      They are composed of a reaction center complex and light harvesting complexes
      Pigment molecules and proteins allow photosystems to capture light over a larger surface
    • Linear Electron Flowthe flow of electrons through the photosystems
      A photon is absorbed by a pigment molecule in the light harvesting complex, exciting an electron
      As one electron falls back to ground state, another one rises
      This continues until the energy reaches the pair of chlorophyll a molecules in the reaction center complex in photosystem II
      An enzyme splits water in photosystem II into electrons, hydrogen ions, and oxygen
      The splitting of water molecules facilitates the flow of electrons through the electron transport chain to photosystem I to replace the electrons that were excited by light energy
      ATP is then synthesized from the energy created from the movement of electrons
      Light energy is transferred from the light harvesting complex pigments to the reaction center complex of photosystem I
      Photoexcited electrons move from the primary electron receptor of photosystem I to the second electron transport chain
      This is a light dependent reaction, creating NADPH and ATP which are then used in a light independent reaction, also known as the Calvin cycle
    • Linear Electron Flow
    • Light Receptors
      • Pigments are substances that absorb visible light
      • Pigments absorb different wavelengths of light
      • The absorption of different wavelengths changes the colors of the pigments
      • Leafs are green because they absorb red, and violet-blue light and they reflect green light
      • Light can only perform work if its absorbed by the chloroplasts
      A prism can bend light of different wavelengths at different angles
    • Electromagnetic Spectrum
      • This is the range of radiation
      • Wavelengths are the distances between the crests of electromagnetic waves
      • The wavelengths range from less than a nanometer to more than a kilometer
      • Visible light is from 380nm to 750nm in wavelength
      • The amount of energy a photon has is related to how long the wavelength is
      • Shorter wavelengths mean greater energy of the photon
    • Photosynthetic Pigments
      Each photosynthetic pigment absorbs light at different wavelengths
    • Photoperiodism
      The reaction of plants in relation to the length of the day
      Plants use it to measure the seasons and to coordinate seasonal events such as flowering
      Plants can be described in relation to their photoperiod responses as short-day, long-day, and day neutral
      The length of daylight effects vegetative growth and reproductive activities in plants
      The length of darkness a plant experiences plays a more crucial role in whether a plant flowers or not
    • Short Day Plants
      • A plant that requires a long period of darkness
      • Short day plants only form flowers when the length of the day is less than about 12 hours
      • Most spring and fall flowering plants are short day plants
      • Chrysanthemums, poinsettias, and goldenrods are examples of short day plants
      The chrysanthemum is in demand all year, which is why florist have to regulate their flowering using artificial lighting
    • Long Day Plants
      Ever notice all the roadside vegetable stands in the early summer months?
      • A plant that requires a short night to flower
      • These flowers only bloom when they receive more than 12 hours of light each day
      • The best time of the year for long day plants to flower is late spring or early summer, when the days are longer (this is opposite in the southern hemisphere)
      • Many garden vegetables are long day plants such as potatoes, lettuce, and barley
      After the summer solstice days become shorter, and long day plants are harvested shortly after.
    • Day Neutral Plants
      • Do not initiate flowering based on photoperiodism
      • They flower regardless of day length, but flower earlier and more often with longer days
      • More often, the age of the plant, and temperature around it effect flowering
      • Beans, tomatoes, and roses fall into the category of day neutral plants
      Roses are the most popular day neutral flowers
    • Works Cited
       Holley, Dennis. "Light and Temperature Influence Plant Growth." Suite101.com. N.p.,June, 11th, 2009. Web. 12 Oct 2010. <http://www.suite101.com/content/light-and-temperature-influence-plant-growth-a131226>.
       
      “Department of Physics." Florida Atlantic University. N.p.Web. 12 Oct 2010. <http://www.physics.fau.edu/observatory/lightpol-Plants.html>.
       
      "Plant Growth Factors: Light." Colorado Master Gardeners Program (2010): 142-1 to 142-4. Web. 11 Oct 2010. <http://www.cmg.colostate.edu/gardennotes/142.pdf>.
      howplantswork, . "Does the Moon Affect Plants? Part 2: Moonlight and Biorhythms." Wordpress. June, 25th, 2009. Web. 11 Oct 2010. <http://howplantswork.wordpress.com/2009/07/25/does-the-moon-affect-plants-part-2-moonlight-and-biorhythms/>.
       
    • Continued
       
      Leiser,Leopold,andShelley, . "Evaluation of light sources for plant growth.” Departments of horticulture and electrical engineering, Purdue university, Lafayette, Indiana 392-395. Web. 11 Oct 2010. <http://www.plantphysiol.org/cgi/reprint/35/3/392.pdf>.
      Lynn, Paul. Electricity from Sunlight. 1st ed. United Kingdom: John Wiley & Sons, 2010. Print.
      Tanaka, R., M. Rothbart, S. Oka, A. Takabayashi, K. Takahashi, M. Shibata, F. Myouga, R. Motohashi, K. Shinozaki, B. Grimm, and A. Tanaka. "LIL3, a light-harvesting-like protein, plays an essential role in chlorophyll and tocopherol biosynthesis. " Proceedings of the National Academy of Sciences of the United States of America  107.38 (2010): 16721.  Research Library Core, ProQuest. Web.  5 Nov. 2010.
       
      Campbell, Reece, First. Biology, Photosynthesis. eighth ed. San Fransisco, California: Pearson Education, Inc., 2008. 185-203. Print.