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Biology, 9th ed, Sylvia Mader
Chapter 26 Chapter 26 Plant Nutrition Nutrition and Transport in Plants
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Essential Inorganic Nutrients
Outline Essential Inorganic Nutrients Soil Formation Soil Profiles Soil Erosion Water & Mineral Uptake Transport Mechanisms Water Organic Nutrients
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Plant Nutrition and Soil
Essential Inorganic Nutrients About 95% of a plant’s dry weight is carbon, hydrogen, and oxygen Primary nutrients are carbon dioxide and water Essential nutrients have identifiable role, and a deficiency causes a plant to die Macronutrients Micronutrients
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Overview of Plant Nutrition
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Nutrient Deficiencies
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Soil formation begins with weathering of rock
Organisms also play an important role Lichens and Mosses Humus begins to accumulate Under ideal conditions, a centimeter of soil may develop within 15 years
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Nutritional Function of Soil
Soil is a mixture of: Soil particles Decaying organic material Living organisms Air, and Water Roots take up oxygen from air spaces Soil particles consist primarily of Sand Clay Silt
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Absorbing Minerals
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Soil Profiles Soil profile is a vertical section from ground surface to unaltered rock below Parallel layers - Horizons A (topsoil) - Litter and humus B (subsoil) - Inorganic nutrients C (weathered rock) Because parent material and climate differ, soil profile varies according to particular ecosystem
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Simplified Soil Profile
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Worldwide, removes about 25 billion tons of topsoil annually
Soil Erosion Soil erosion occurs when water or wind carry soil away to a new location Worldwide, removes about 25 billion tons of topsoil annually Deforestation Desertification Agricultural contaminants
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Adaptation of Roots for Mineral Uptake
Important Symbiotic Relationships Rhizobium bacteria fix atmospheric nitrogen Live in root nodules Mycorrhizal association between fungi and plant roots Ectomycorrhizas Endomycorrhizas
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Water and Mineral Uptake
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Root Nodules
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Mycorrhizae
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Spanish Moss
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Transport Mechanisms in Plants
Transported in vascular tissues Xylem transports water Two types of conducting cells Tracheids Vessel Elements Water flows passively from an area of higher water potential to an area of lower water potential
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Plant Transport System
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Conducting Cells of Xylem
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Transport Mechanisms in Plants
Transported in vascular tissues, cont. Phloem transports organic materials Conducting cells are sieve-tube members Have companion cells to provide proteins End walls are sieve plates Plasmodesmata extend through sieve plates
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Water entering roots creates a positive pressure (root pressure)
Water Transport Water entering roots creates a positive pressure (root pressure) Pushes xylem sap upward May be responsible for guttation Water forced out vein endings along edges of leaves
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Guttation
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Cohesion-Tension Model
Cohesion-tension model of xylem transport suggests a passive xylem transport Water molecules tend to cling together Polarity of water allows interaction with molecules of vessel walls Water column moves passively upward due to transpiration Column must be continuous Waxy cuticle prevents water loss
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Cohesion-tension Model of Xylem Transport
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Opening and Closing of Stomata
Each stoma in leaf epidermis is bordered by guard cells Increased turgor pressure in guard cells opens stoma Caused by active transport of K+ into guard cells
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Opening and Closing of Stomata
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Organic Nutrient Transport
Role of Phloem Phloem transports sugar Girdling of tree below the level of leaves causes bark to swell just above the cut Sugar accumulates in the swollen tissue
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Acquiring Phloem Sap
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Pressure-Flow of Phloem Transport
Positive pressure drives sap in sieve tubes Sucrose is actively transported into sieve tubes Water follows by osmosis Increase in volume creates flow that moves water and sucrose to a sink
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Pressure-flow Model of Phloem Transport
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Essential Inorganic Nutrients
Review Essential Inorganic Nutrients Soil Formation Soil Profiles Soil Erosion Water & Mineral Uptake Transport Mechanisms Water Organic Nutrients
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Biology, 9th ed, Sylvia Mader
Chapter 26 Ending Slide Chapter 26 Plant Nutrition Nutrition and Transport in Plants
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