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Mineral Nutrition and Transport in Plants (Pages 198-217)
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Weathering Process Weathering is the gradual breakdown of rock in the formation of soil Soils form from fragmented rock Weathering processes can be Biological Growth of plant roots into cracks in the rock Chemical Acid Rain Physical Freezing and thawing of water in tiny cracks of the rock Erosion (due to topography of land & gravity)
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1. Inorganic Mineral Particles a) Sand -.02mm – 2 mm b) Silt -.002mm -.02 mm c) Clay - particles smaller than.002 mm d) Why isn’t gravel considered to be soil? 2. Organic matter (Humus) a) Litter (dead leaves and branches) b) Dung (animal droppings) c) Remains of dead plants, animals, and microorganisms 3. Water (Fills pore spaces) 4. Air (Fills pore spaces)
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Sandy Soils Do not hold water and mineral ions well Plants more susceptible to drought More susceptible to mineral deficiencies Provide support Aeration permeability Silty Soils Clay Soils Low pH (attract cations, K +, Mg 2+) Have poor drainage Do not provide enough oxygen Hold minerals and water well
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A loam is an ideal agricultural soil Has optimal combination of different-sized soil particles 40% Sand 40% Silt 20% Clay
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1 tsp of fertile agricultural soil may contain millions of microorganism such as Bacteria *most numerous Fungi Algae Protozoa Microscopic worms Other soil organisms Plant roots Earthworms (make castings) Insects Ants (aerate soil, bury seeds) Moles Gophers Snakes Groundhogs
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1. Decompose organic matter (Humus) 2. Release nutrients to be recycled to plant Nutrient cycling – the process by which matter cycles from the living world to the nonliving physical environment and back again 3. Produce Ammonia (NH3-) Anions 4. Lower soil pH (makes it more acidic)
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A technique of growing plants in aerated water – no soil! Minerals are dissolved into water solution Aerated by bubbles Soil-Free! Ideal for research of mineral usefulness
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Macronutrients (10) Element that is required in large amounts for normal plant growth Micronutrients (9) Element that is required in very small amounts for normal plant growth
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1. Carbon– (air) carbs, lipids, proteins, nucleic acid 2. Hydrogen– (water) carbs, lipids, proteins, nucleic acid 3. Oxygen– (water, air) carbs, lipids, proteins, nucleic acid 4. Nitrogen–* proteins, nucleic acids, chlorophyl 5. Potassium–* osmotic balance, stomata regulation 6. Calcium-* cell walls, membrane permeability 7. Magnesium-* Main component of chlorophyll 8. Phosphorus-* nucleic acids, phospholipids, ATP 9. Sulfur-* amino acids and vitamins 10. Silicon-*cell walls * soil
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Chlorine Iron Boron Manganese Sodium Zinc Copper Nickel Molybdenum
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Tension-cohesion model Water is pulled up the plant as result of a tension produced at the top of the plant by the evaporative pull of transpiration Transpiration is the loss of water vapor from the aerial parts of plants Tension sucks water upward in xylem (like a straw) from soil See Figure 10-11 p. 212
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The cohesion-tension theory describes how water moves from the roots to the leaf. Osmosis causes water to enter the xylem of roots from the soil. Due to the hydrogen bonding between the water molecules, water forms a string of molecules as it moves to the xylem. Constant transpiration at the top of the leaf pull the water molecules out of the plant. The differences in water potentials and pressures cause this fairly constant movement of water through the plant.
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Sugar molecules manufactured in leaves by photosynthesis are transported in phloem throughout plant, including into roots. Most water that plant absorbs is transpired into atmosphere. Once inside roots, water and minerals are transported upward in xylem to stems, leaves, flowers, fruits, and seeds. Roots obtain water and dissolved minerals from soil. Fig. 10-11, p. 212
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Sugar Translocation (the movement of sugar) in phloem States that dissolved sugar moves in phloem because of a pressure gradient between the source and the sink. Sugars move from source to sink Source – an area of excess sugar supply (leaf) Sink – an area of storage (root, apical meristem, fruit, seed)
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