environment factors
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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ENVIRONMENT FACTORS
SUN LIGHT
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ContentsSolar 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
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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.
SOLAR RADIATION
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Figure 1. The electromagnetic spectrum
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E = h x v v= E/h
wavelength and energy is inversely related the higher the wavelength the lower the energy
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THE ATMOSPHERE AS FILTER AND REFLECTOR
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Cahaya matahari yang pertama kali sampai pada lapisan luar atmosfir terdiri dari :
± 10 % sinar ultraviolet (UV);
50 % cahaya tampak (Visible light)
40 % sinar infra merah (IR) Σ energi matahari yang sampai di permukaan bumi (Rs)
secara umum ditentukan oleh transparansi atmosfer (q) dan besarnya tetapan surya (solar constant = Io),
Rs = q x IoRs = jumlah energi matahari yang sampai di permukaan bumi q = trasnparansi atmosfer dan Io = solar constant, yaitu Σ energi matahari yang sampai pada permukaan terluar atmosfer secara tegak lurus.
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Apabila transparansi atmosfer semakin tinggi, menunjukkan atmosfer bersih Σ energi yang diterima oleh bumi semakin tinggi.
Apabila di atmosfer banyak terkandung uap air (awan) / gas-gas polutan (ex : CO, NO2, SO2, CH4) dan partikulat (ex: debu dan asap)
nilai q semakin rendah
Apabila atmosfer cerah, yaitu bila kandungan awan dan gas-gas rumah kaca sedikit, berarti nilai q nya tinggi,
Σ radiasi matahari yang sampai permukaan bumi semakin tinggi
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Di atmosfer, radiasi matahari mengalami pengurangan melalui :1. Absorbsi 2. Refleksi3. Re-radiasi
Di permukaan bumi, radiasi matahari mengalami:1. Refleksi, 2. Absorbsi3. Re-radiasi4. konveksi,5. konduksi dan untuk evaporasi
Radiasi matahari di permukaan bumi
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Figure 2. The fate of light upon reaching the earth
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THE ECOLOGICAL SIGNIFICANCE OF LIGHT ON EARTH
A. Ultraviolet LightB. Photo synthetically Active Radiation
(PAR)C. Infrared Light
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A. Ultraviolet Light (UV)
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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
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B. Photosynthetically Active Radiation (PAR)
Figure 3. Visible light (PAR) spectrum
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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
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Figure 4. Absorbance of chlorophyll in relation to the wavelength of light
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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 yellowwater absorbs strongly in red and IR, scatters violet and blue, leaving
green at depth
Plants Respond to Light
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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.
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CHARACTERISTICS OF VISIBLE LIGHT EXPOSURE
Quantity (Intensity)photosynthesis
Quality (Wavelength - Color)photomorphogenesis
Durationphotoperiodism
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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.
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PENGARUH INTENSITAS TERHADAP SIFAT FISIOLOGIS TANAMAN
Laju fotosintesis Laju transpirasi Pertumbuhan batang (memanjang
dan menuju kearah datangnya sinar)
Perkecambahan benih Pembungaan
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Figure 6. The relationship between solar radiation and photosynthetic rate
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KELOMPOK TANAMAN BERDASARKAN KEBUTUHAN DAN ADAPTASI RADIASI MATAHARI
1. Sciophytes/shade species/shade loving tanaman yang tumbuh baik pada tempat yang ternaung dengan intensitas radiasi matahari rendah. (kopi (30-50%,Coklat (25 %)
2. Heliophytes/sun species/sun loving tanaman yang tumbuh baik pada intensitas radiasi matahari penuh.(padi,jagung,tebu,ubi kayu dsb.)
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KUALITAS RADIASI MATAHARI
Proporsi panjang gelombang yang diterima pada suatu tempat dan waktu tertentu
Menggambarkan spektrum cahaya yang dipancarkan oleh matahari yang terdiri dari berbagai gelombang
Light Quality
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Figure 7. The electromagnetic spectrum
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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
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Fitokhrom merupakan senyawa (pigmen) yang menentukan respon sifat morfogenetik tanaman (inisiasi bunga,perkecambahan benih,perpanjangan ruas (internode) batang dan pembentukan pigmen)
Fitokhrom berupa senyawa tetrapirol seperti : klorofil terdiri dari khromofore dan protein.
Khromofore sangat peka thd kualias radiasi dan bersifat reversible (dapat berubah ubah) tergantung pada panjang gelombang radiasi
yang mengenai fitokfhrome tsb.
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FAKTOR FAKTOR YANG BERPENGARUH DISTRIBUSI SPEKTRUM (PANJANG GELOMBANG)
1. Sudut datang matahari atau jarak antara matahari dan bumi
- dataran rendah …….. Sinar merah - dataran tinggi………... Ultra violet2. Letak daun pada tajuk
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Peranan kualitas cahaya matahari dlm kehidupan Tanaman
Spektrum warna Panjang gelombang (nm)
Peranan bagi tanaman
Ultra violet < 280 Tanaman rusak280 -320 Sel tanaman mengalami kerusakan320 -405 Tanaman kerdil
Visible light(PAR)
405 -505 Diserap klorofil utk Fotosintesis (biru)
505 –552 Untuk pertumbuhan daun (hijau)
552–585 Untuk pembentukan pigmen (kuning)585–620 Untuk pembentukan fotoklorofil(jingga)620–760 diserap klorofil untuk fotosintesis
Near Infra Red (NIR) 760 –1.000 diterima tanaman untuk aktifitas foto-Morfo Genetik perkecambahan dan pertumbuhan memanjang
Far Infra Red (FIR) > 1.000 Diterima tan & dikonversikan dlm bentuk thermal, dan utk energi evapotranspirasi
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Benih lettuce ----- bunga Xanthium
Photoreversibility dari fitokhrom
merah infra merah
Figure 8. Respon panjang gelombang pada perkecambahan benih dan pembungaan pada
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Tabel 3. Persentase perkecambahan benih Lettuce sebagai akibat dari pemberian radiasi dengan panjang gelombang silih berganti
No Pemberian radiasi Daya kecambah (persen)
1 Merah 70
2 M-Infra Merah(IM) 6
3 M-IM-M 74
4 M-IM-M-IM 6
5 M-IM-M-IM-M 76
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Photoperiodism (Duration of the Light Period)
ialah : lamanya siang hari dihitung mulai matahari terbit hingga terbenam
berpengaruh pada: 1. inisiasi bunga 2. produksi 3. pembentukan umbi 4. dormansi benih 5. pertumbuhan tanaman (pembentukan anakan percabangan dan pertumbuhan memanjang)
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Berdasarkan respon tumbuhan pada variasi panjang hari, maka dikenal :
1. Tumbuhan Hari Panjang (Long day plant) : kelompok tumbuhan yg akan memasuki fase generatifnya (membentuk organ reproduktif) hanya jika tumbuhan tsb menerima penyinaran yang panjang (> 14 jam),
contoh : spinasi, beberapa jenis radish dan sawi.
2. Tumbuhan Hari Pendek (Short day plant) : kelompok tumbuhan yg akan memasuki fase generatif (membentuk organ reproduktif) hanya jika tumbuhan tersebut menerima penyinaran yang pendek (< 10 jam)
contoh : labu siam, kecipir dan bayam.
3. Tumbuhan Hari Netral (Neutral day plant) : kelompok tumbuhan yg fase perkembangannya tidak dipengaruhi oleh lama penyinaran. Kelompok tumbuhan ini tetap akan memasuki fase generatif baik jika menerima yg panjang/ pendek
contoh : tomat, blewah, kacang-kacangan dll.
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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.
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DETERMINANT OF VARIATIONS IN THE LIGHT ENVIRONMENT
Seasonality Latitude Altitude Topography Air Quality Vegetation Canopy Structure
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OTHER FORMS OF RESPONSE TO LIGHT
Germination
Growth and Development- Establishment- Plant Growth- Phototropism- Photoperiod
Production of the Harvestable Portion of the Plant
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• Phototropism: the tendency for plants to “lean” in the direction of the greatest light intensity.
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Phototropisms Phototropic responses involve bending of
growing stems toward light sources.Individual leaves may also display phototrophic
responses.○ auxin most likely involved
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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
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MANAGING THE LIGHT ENVIRONMENT IN AGROECOSYSTEM
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3650104
365104009
8
xxx ton karbohidrat/
ha/tahun
Ditinjau dari aspek energi, fotosintensis mrp proses yang tidak effisien (1-2 % energi matahari yang jatuh diubah menjadi energi kimia dalam bentuk karbohidrat (hasil panen).
Contoh : Rata rata intensitas radiasi di Malang 400 kal/cm2/hari. 1 gram karbohidrat mengandung 4000 Kal maka hasil panen yang diperoleh seharusnya :
Kenyataan di lapang hasil terbaik tidak lebih dari 50 ton karbohidrat ( bahan kering total tanaman = biji +batang + daun + akar ) per hektar per tahun
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Effisiensi :
50/3650 x 100 % = 1,5 %
Artinya : dari 100 % energi matahari yang jatuh hanya 1,5 % yang dapat diuubah tanaman menjadi energi kimia
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Tabel. Perbandingan hasil dan efisiensi konversi energi matahari pada beberapa tanaman dengan umur yang berbeda Jenis tanaman Hasil (t/Ha) Effisiensi
konversi (%)Umur (bulan)
Kentang
Bit gula
Wortel
Jagung
Tebu
9,60
16,00
6,86
15,52
129,48
0,50
0,90
0,39
1,05
1,43
5
6
6
4
12
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Suatu proses produksi pertanian (agronomi) ditinjau dari aspek energi matahari bertujuan untuk meningkatkan effisiensi konversi energi matahari atau mengurangi hilangnya energi matahari selama proses produksi harus mengetahui kemana hilangnya energi matahari tersebut.
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Energi matahari yang telah tertangkap tidak seluruhnya dapat diserap (diabsorpsi) oleh tanaman.
65 % diserap (diabsorbsi), 20 % dipantulkan (refleksi) 15 % diteruskan (ditransmisi)
Refleksi dipengaruhi oleh : kekasaran tajuk, sudut daun, ILD (Indeks Luas Daun) warna daun sudut datang radiasi matahari.
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Figure 8. Light Strikes a Leaf
reflected light 10-15 %
most of absorbed
energy lost in evaporation of
water
light strike leaf 100 %
only 0.50-3.50 % of total light energy used
in photosynthesistransmitted light ±5 %
absorbed light 80-85 %
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Faktor yang perlu diperhatikan penyebab hilangnya energi matahari
1. Umur tanaman2. Populasi tanaman 3. Bentuk tajuk tanaman4. Laju pertumbuhan tanaman5. Sistem/Pola bertanam
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Gambar 9. Penyebaran radiasi matahari pada waktu tanaman muda
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Gambar 10. Hubungan antara populasi tanaman dengan efesiensi konversi energi matahari
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Gambar 11. Profil radiasi matahari antara tanaman berdaun horisontal (A) dan tanaman berdaun tegak (B)
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How to manage the light environment in agroecosystem?
Crop Selection Cropping Diversity and Canopy Structure Temporal Management Carbon Partitioning and Sustainability