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SUN LIGHT . ENVIRONMENT FACTORS. Contents. Solar Radiation. The Atmosphere as Filter and Reflector. The Ecological Significance of Light on Earth. Characteristics of Visible Light Exposure. Determinant of Variations in the Light Environment. Other Forms of Response to Light.

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ENVIRONMENT FACTORS

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SUN LIGHT

ENVIRONMENT FACTORS


Contents

Solar Radiation

The Atmosphere as Filter and Reflector

The Ecological Significance of Light on Earth

Characteristics of Visible Light Exposure

Determinant of Variations in the Light Environment

Other Forms of Response to Light

Managing The Light Environment in Agroecosystem


SOLAR RADIATION

What is Light ?

  • Energy in the form of Electromagnetic Radiation (EMR) that produces a visual sensation

  • Light is that part of the radiant energy which is visible to the eye.

  • The chief radiation or energy source for the earth is the sun

  • Light is one of the most important factors determining the growth of plants and the development of vegetation.


Figure 1. The electromagnetic spectrum


  • wavelength and energy is inversely related

  • the higher the wavelength the lower the energy

E = h x v

v= E/h


THE ATMOSPHERE AS FILTER AND REFLECTOR


  • Cahayamatahari yang pertama kali sampaipadalapisanluaratmosfirterdiridari :

    • ± 10 % sinar ultraviolet (UV);

    • 50 % cahayatampak (Visible light)

    • 40 % sinar infra merah (IR)

  • Σenergimatahari yang sampaidipermukaanbumi (Rs) secaraumumditentukanolehtransparansiatmosfer (q) danbesarnyatetapansurya (solar constant = Io),

    Rs = q x Io

    Rs = jumlahenergimatahari yang sampaidipermukaanbumi

    q = trasnparansiatmosferdan

    Io = solar constant, yaituΣenergimatahari yang sampai

    padapermukaanterluaratmosfersecarategaklurus.


    • Apabilatransparansiatmosfersemakintinggi, menunjukkanatmosferbersihΣenergi yang diterimaolehbumisemakintinggi.

    • Apabiladiatmosferbanyakterkandunguap air (awan) / gas-gas polutan (ex : CO, NO2, SO2, CH4) danpartikulat(ex: debudanasap)

      nilaiq semakinrendah

    • Apabilaatmosfercerah, yaitubilakandunganawandan gas-gas rumahkacasedikit, berartinilaiq nyatinggi,

      Σ radiasimatahari yang sampaipermukaanbumisemakintinggi


    Radiasimataharidipermukaanbumi

    Di atmosfer, radiasi matahari mengalami pengurangan melalui :

    • Absorbsi

    • Refleksi

    • Re-radiasi

  • Di permukaan bumi, radiasi matahari mengalami:

    • Refleksi,

    • Absorbsi

    • Re-radiasi

    • konveksi,

    • konduksi dan untuk evaporasi


  • Figure 2. The fate of light upon reaching the earth


    THE ECOLOGICAL SIGNIFICANCE OF LIGHT ON EARTH

    • Ultraviolet Light

    • Photo synthetically Active Radiation (PAR)

    • Infrared Light


    A. Ultraviolet Light (UV)


    Ozone and Ultraviolet Radiation

    • UV “light” has a high energy level and can damage exposed cells and tissues.

    • Ozone in upper atmosphere absorbs strongly in ultraviolet portion of electromagnetic spectrum.

    • Chlorofluorocarbons (formerly used as propellants and refrigerants) react with and chemically destroy ozone:

      • ozone “holes” appeared in the atmosphere

        concern over this phenomenon led to strict controls on CFCs and other substances depleting ozone


    B. Photosynthetically Active Radiation (PAR)

    Figure 3. Visible light (PAR) spectrum


    Photosynthetically Active Radiation (PAR)

    • The photoreceptors in chlorophyll are most absorptive of violet-blue and orange-red light

    • Since chlorophyll cannot absorb green light very well, most of it is reflected back, making plants appear green


    Figure 4. Absorbance of chlorophyll in relation to the wavelength of light


    Plants Respond to Light

    Figure 5. The Absorption Spectra of Plants

    • Various substances (pigments) in plants have different absorption spectra:

      • chlorophyll in plants absorbs red orange and violet light, reflects green and yellow

      • water absorbs strongly in red and IR, scatters violet and blue, leaving green at depth


    C. Infrared Light (IR)

    • Infrared light energy with a wavelength from 800 nm to 3000 nm,

    • IR has an important role in influencing the hormones involved in germination, plant’s responses to changes to day length and other plant processes.


    CHARACTERISTICS OF VISIBLE LIGHT EXPOSURE

    • Quantity (Intensity)

      • photosynthesis

    • Quality (Wavelength - Color)

      • photomorphogenesis

    • Duration

      • photoperiodism


    Light Intensity

    • The total energy content of all the light in the PAR range that reaches a leaf surface

    • Energy units: Calories cm-2, Joule second-1, Lux or Watt. m-2

    • Intensity provides energy for photosynthesis

      The rate of photosynthesis is affected by the availability of water, CO2 and sunlight.


    PENGARUH INTENSITAS TERHADAP SIFAT FISIOLOGIS TANAMAN

    • Lajufotosintesis

    • Lajutranspirasi

    • Pertumbuhanbatang (memanjangdanmenujukearahdatangnyasinar)

    • Perkecambahanbenih

    • Pembungaan


    Figure 6. The relationship between solar radiation and

    photosynthetic rate


    KELOMPOK TANAMAN BERDASARKAN KEBUTUHAN DAN ADAPTASI RADIASI MATAHARI

    1. Sciophytes/shade species/shade loving

    tanaman yang tumbuhbaikpadatempat

    yang ternaungdenganintensitasradiasi

    mataharirendah. (kopi (30-50%,Coklat (25 %)

    2. Heliophytes/sun species/sun loving

    tanaman yang tumbuhbaikpadaintensitas

    radiasimataharipenuh.(padi,jagung,tebu,ubi

    kayudsb.)


    Light Quality

    KUALITAS RADIASI MATAHARI

    • Proporsipanjanggelombang yang diterimapadasuatutempatdanwaktutertentu

    • Menggambarkanspektrumcahaya yang dipancarkanolehmatahari yang terdiridariberbagaigelombang


    Figure 7. The electromagnetic spectrum


    • Light quality controls Photo-morphogenesis (plant development and form)

    • Mediated by phytochrome (protein pigment)

      • red light absorbing form (Pr)

      • FR light absorbing form (Pfr)

      • Forms are photoinconvertible, depending on the which type of light is absorbed


    Fitokhrommerupakansenyawa (pigmen) yang menentukanresponsifatmorfogenetiktanaman (inisiasibunga,perkecambahanbenih,perpanjanganruas (internode) batangdanpembentukanpigmen)

    Fitokhromberupasenyawatetrapirolseperti: klorofilterdiridarikhromoforedan protein.

    Khromoforesangatpekathdkualiasradiasi

    danbersifatreversible (dapatberubahubah)

    tergantungpadapanjanggelombangradiasiyang mengenaifitokfhrometsb.


    FAKTOR FAKTOR YANG BERPENGARUH DISTRIBUSI SPEKTRUM (PANJANG GELOMBANG)

    • Sudut datang matahari atau jarak antara matahari dan bumi

      - dataran rendah …….. Sinar merah

      - dataran tinggi………... Ultra violet

      2. Letak daun pada tajuk


    Peranan kualitas cahaya matahari dlm kehidupan Tanaman


    Photoreversibilitydarifitokhrom

    merah

    inframerah

    Benih lettuce ----- bunga Xanthium

    Figure 8. Responpanjanggelombangpadaperkecambahanbenihdanpembungaanpada


    Tabel 3. Persentase perkecambahan benih Lettuce sebagai akibat dari pemberian radiasi dengan panjang gelombang silih berganti


    Photoperiodism(Duration of the Light Period)

    • ialah : lamanyasiangharidihitungmulaimatahariterbithinggaterbenam

    • berpengaruhpada:

      1. inisiasibunga

      2. produksi

      3. pembentukanumbi

      4. dormansibenih

      5. pertumbuhantanaman (pembentukananakan

      percabangandanpertumbuhanmemanjang)


    Berdasarkan respon tumbuhan pada variasi panjang hari, maka dikenal :

    • Tumbuhan Hari Panjang (Long day plant) :

      kelompok tumbuhan yg akanmemasukifasegeneratifnya (membentuk organ reproduktif) hanyajikatumbuhantsbmenerimapenyinaran yang panjang (> 14 jam),

      contoh : spinasi, beberapajenis radish dansawi.

    • TumbuhanHariPendek (Short day plant) :

      kelompoktumbuhanygakanmemasukifasegeneratif (membentuk organ reproduktif) hanyajikatumbuhantersebutmenerimapenyinaran yang pendek (< 10 jam)

      contoh : labusiam, kecipirdanbayam.

    • TumbuhanHariNetral (Neutral day plant) :

      kelompoktumbuhanygfaseperkembangannyatidakdipengaruhioleh lama penyinaran. Kelompoktumbuhaninitetapakanmemasukifasegeneratifbaikjikamenerimaygpanjang/ pendek

      contoh : tomat, blewah, kacang-kacangandll.


    • We can control light and influence blooming or vegetative growth by:

      • Shortening day with black cloth: covering the growing plant with an opaque cover to exclude light.

      • Lengthening day with artificial light: adding light in the evening hours.


    DETERMINANT OF VARIATIONS IN THE LIGHT ENVIRONMENT

    • Seasonality

    • Latitude

    • Altitude

    • Topography

    • Air Quality

    • Vegetation Canopy Structure


    OTHER FORMS OF RESPONSE TO LIGHT

    • Germination

    • Growth and Development

      - Establishment

      - Plant Growth

      - Phototropism

      - Photoperiod

    • Production of the Harvestable Portion of the Plant


    • Phototropism: the tendency for plants to “lean” in the direction of the greatest light intensity.


    Phototropisms

    • Phototropic responses involve bending of growing stems toward light sources.

      • Individual leaves may also display phototrophic responses.

        • auxin most likely involved


    Plant Physiology Under Low Light Intensity

    1. Longer internodes, increased stem elongation

    2. Leaves have larger surface area

    3. Thinner leaves and stems

    4. Thinner cuticle

    5. One layer of palisade cells


    MANAGING THE LIGHT ENVIRONMENT IN AGROECOSYSTEM


    Ditinjaudariaspekenergi, fotosintensismrpproses yang tidakeffisien(1-2 % energimatahari yang jatuhdiubahmenjadienergikimiadalambentukkarbohidrat(hasilpanen).

    Contoh: Rata rataintensitasradiasidi Malang 400

    kal/cm2/hari. 1 gram karbohidratmengandung4000 Kal

    makahasilpanenyang diperolehseharusnya :

    ton karbohidrat/ ha/tahun

    Kenyataandilapanghasilterbaiktidaklebihdari 50 ton karbohidrat ( bahankering total tanaman = biji +batang + daun + akar ) per hektar per tahun


    Effisiensi :

    50/3650 x 100 % = 1,5 %

    Artinya : dari 100 % energimatahari yang jatuhhanya 1,5 % yang dapatdiuubahtanamanmenjadienergikimia


    Suatuprosesproduksipertanian (agronomi) ditinjaudariaspekenergimataharibertujuanuntukmeningkatkaneffisiensikonversienergimatahariataumengurangihilangnyaenergimatahariselamaprosesproduksiharusmengetahuikemanahilangnyaenergimataharitersebut.


    Energimatahari yang telahtertangkaptidakseluruhnyadapatdiserap (diabsorpsi) olehtanaman.

    • 65 % diserap (diabsorbsi),

    • 20 % dipantulkan (refleksi)

    • 15 % diteruskan (ditransmisi)

      Refleksidipengaruhioleh :

    • kekasarantajuk,

    • sudutdaun,

    • ILD (IndeksLuasDaun)

    • warnadaun

    • sudutdatangradiasimatahari.


    Figure 8. Light Strikes a Leaf

    reflected light 10-15 %

    light strike leaf 100 %

    most of absorbed energy lost in evaporation of water

    absorbed light 80-85 %

    only 0.50-3.50 % of total light energy used in photosynthesis

    transmitted light ±5 %


    Faktor yang perludiperhatikanpenyebabhilangnyaenergimatahari

    • Umurtanaman

    • Populasitanaman

    • Bentuktajuktanaman

    • Lajupertumbuhantanaman

    • Sistem/Polabertanam


    Gambar 9. Penyebaranradiasimataharipadawaktutanaman

    muda


    Gambar 10. Hubunganantarapopulasitanamandenganefesiensi

    konversienergimatahari


    Gambar 11. Profilradiasimatahariantaratanamanberdaun

    horisontal (A) dantanamanberdauntegak (B)


    How to manage the light environment in agroecosystem?

    • Crop Selection

    • Cropping Diversity and Canopy Structure

    • Temporal Management

    • Carbon Partitioning and Sustainability


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