03. PLANTS AND ENVIRONMENTAL FACTORS

PLANTS AND ENVIRONMENTAL FACTORS 1

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An understanding of the ways individual plants and their physiology are impacted by different factors of the environment is an essential component in the design and management of cropping system

The ecological study of individual plant response to the diverse factors of environment (autecology or physiological ecology) is a foundation of agroecological understanding

2THE PLANTPhotosynthesisCarbon PartitioningTranspiration

31. PhotosynthesisPlants convert solar energy into chemical energy stored in the chemical bonds of sugar molecules

this process is IMPORTANT for plant growth and survival4Remember what plants need

Photosynthesis light reactionslightH2OCalvin cycleCO2 sun ground air5

Fotosintesis

Proses dimana organisme yang memiliki kloroplas mengubah energi cahaya matahari menjadi energi kimia Melibatkan 2 lintasan metabolik

Reaksi terang: mengubah energi matahari menjadi energi seluler

Siklus Calvin: reduksi CO2 menjadi CH2O6Simple equation :

6CO2 + 12H20 + light energy C6H12O6 + 6O2 + 6H2O

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Light energyECOSYSTEMCO2 + H2OPhotosynthesisin chloroplastsCellular respirationin mitochondriaOrganicmolecules+ O2ATPpowers most cellular work HeatenergyEnergi mengalir ke dalam suatu ekosistem sebagai cahaya matahari dan meninggalkannya dalam bentuk panas8Types of PhotosynthesisC3 photosynthesisMost plants

C4 photosynthesisA variety of plants, especially our summer annuals and many of our grasses

CAM photosynthesisCacti, agaves, bromeliads, and others

9C3 plantsThe first stable compound formed in dark reactions (Calvin cycle) is 3-carbon compound

A problem with C3, photosynthesis is always accompanied by photorespiration which consumes and releases CO2 in the presence of light

it wastes carbon fixed by photosynthesis - up to 50% of carbon fixed in photosynthesis may be used in photorespiration 10C4 plants A better way to capture CO21st step before Calvin cycle, fix carbon with enzymePEP carboxylase store as 4C compound adaptation to hot, dry climates have to close stomates a lotdifferent leaf anatomysugar cane, corn, other grasses

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cornsugar cane12Photorespiration is nearly absent in C4 plants - so greatly increases their efficiency - this is because a high CO2: low O2 concentration limits photorespiration

Thus net photosynthetic rates are higher for C4 plants (corn, sorghum, sugarcane) than in C3 relatives (wheat, rice, rye, oats)

13CAM (Crassulacean Acid Metabolism) plantsseparate carbon fixation from Calvin cycle by timeclose stomates during day open stomates during nightat night, open stomates & fix carbon in storage compoundsorganic acids: malic acid, isocitric acidin day, close stomates & release CO2 from storage compounds to Calvin cycleincreases concentration of CO2 in cellssucculents, pineapple, cactuses, agaves, bromeliads14CAM plants

152. Carbon Partitioninghow plant distributes the carbon compounds derived from photosynthesis and allocates them to different physiological processes and plant parts16

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3. Transpiration

the continual flow of water from the soil, into the roots, up the stem to the leaves, and out of the leaves through the stomata

Water moving between soil and plants flows down a water potential gradient

18Water movement between plants and soils

19Transpiration

20Interaction Plant -EnvironmentA Plants Place in the Environment- Each species occupies a particular place in the ecosystem, known as the habitat- within its habitat, the species carries out a particular ecological role or function, known as the ecological niche of that species21Interaction Plant -EnvironmentResponses to Factors of the EnvironmentSetiap fase perkembangan tanaman melibatkan respon perubahan secara fisiologis. Sebagian besar respon tanaman berkaitan langsung dengan kondisi lingkungan

- Triggered Responses- Dependent Responses- Independent Responses22Triggered Responsesrespon tanaman yang dipacu oleh adanya eksternal stimulus tertentuDependent Responses respon tanaman yang tergantung pada keberadaan kondisi lingkungan eksternal tertentu secara terus menerusIndependent Responses respon tanaman yang ditentukan oleh kondisi fisiologis tanaman; mis: tanaman jagung akan berbunga karena fase tertentu dari pertumbuhan dan perkembangan sudah tercapai.23Interaction Plant -EnvironmentLimits and TolerancesEach environmental factor has both minimum and maximum levels, tolerance limits, beyond which a particular species cannot survive24

25TugasBuat tulisan tentang- fotosintesis- partisi karbon (asimilat)- transpirasi26