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Nutrition and Transport in Plants
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill CompaniesCopyright © McGraw-Hill Companies Permission required for reproduction or display
Outline
Plant Nutrients
Soil
Nutritional Adaptations
Overview of Water and Mineral Movement
Water and Mineral Absorption
Water and Mineral Movement
Bidirectional Phloem Transport Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Plant Nutrients
Photosynthesis is the major source of plant nutrition.
Plants also require a number of inorganic molecules; essential nutrients.
Macronutrients
Carbon, Hydrogen, Oxygen, Nitrogen, Potassium,Calcium, Phosphorus, Magnesium and Sulfur.
Each may exceed 1% dry weight of plant.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Plant Nutrients
Micronutrients = Iron, Chlorine, Copper, Manganese, Zinc, Molybdenum, and Boron.
Constitute from less than one, to several hundred, parts per million in most plants.
Nutritional requirements assessed in hydroponic cultures.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Plant Nutrients
.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Slogan to remember macro/micronutrients
Plant Nutrients Beneficial Nutrients = either are required
for or enhance the growth of a particular plant
Horsetails = silicon; mineral nutrient.Sugar beets = sodium; enhance
growth.Soybeans = nickel; when root nodules
are presentFerns = aluminumLocoweeds = aluminum; fatal to
livestock
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Soil
Defined as a mixture of particles, decaying organic material, living organisms, air, and water.
Minerals, microorganisms and humus provides for the richness of the soil
Forms from the weathering of rock.
About half total soil volume is occupied by spaces or pores.
Filled with air or water, depending on environmental conditions.
Soil
Plant growth affected by soil composition.
Most roots found in topsoil.
Minerals, microorganisms and humus.
About half total soil volume is occupied by spaces or pores.
Filled with air or water, depending on environmental conditions.
Soil Profile: Top soil = A horizon
Contains litter and humus
Subsoil = B horizon
Little or no organic matter but contains the inorganic nutrients leached from A horizon
Weathered rock = C horizon
Soil
Cultivation
In natural communities, nutrients are recycled on a continual basis.
Cultivated soils are more exposed to erosion and nutrient loss.
Crop Rotation
Plowing under leftover plant material.
Fertilizers
Nitrogen, Phosphorus, Potassium
Water and Mineral Uptake Occurs between the porous cells
through the root hairs to enter endodermal cells when they have lower osmotic pressure
Minerals are actively taken up by plant cells Proton pump Chemosmois Protein channels
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Water and Mineral Uptake
Adaptations of Roots for Mineral Uptake:
Mutualistic Relationships
Root nodules – between plants and bacteria plants contribute
Plants contribute carbohydrates and bacteria fix nitrogen into nitrate
Mycorrhizae – between plants and fungi
Fungi breakdown organic matter in the soil and release nutrients to the plant.
Transport Mechanisms
Xylem and Phloem
Water Properties
Water Potential – energy of waterFactors that determine water potential
water pressure across a membrane and solute concentration across a membrane
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Transport Mechanisms Xylem and Phloem
Water Properties
Turgor Pressure - Physical pressure resulting from water entering cell vacuole is referred to as pressure potential.
Osmotic Potential - Smallest amount of pressure needed to stop osmosis.
Water Potential - Total potential energy of water in a plant.
Water moves to a cell with more negative water potential.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Mineral Transport in Roots
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Copyright © McGraw-Hill Companies Permission required for reproduction or display
Water Transport
Root Pressure - Movement of water into the plant and up the xylem columns despite absence of transpiration; positive pressure.
Active transport increases solute potential of roots.
High root pressure may lead to guttation.
Occurs through groups of cells located near edge of leaf.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Cohesion-Tension Model of Xylem Transport
Cohesion = water molecules cling to each other creating a water column in xylem
Adhesion = ability of water to interact with the molecules making up the walls in xylem, thus giving the water column extra strength and preventing it from slipping back
Transpiration = evaporation of water through leaf stomata•Exerts a pulling force or tension that draws the water column through the xylem to replace the water lost.
Water and Mineral Movement
Evaporation from leaves produces a tension on entire water column extending down to the roots.
Water has inherent tensile strength that varies inversely with the diameter of the column.
Air bubbles cause xylem to fail.
Plants must admit carbon dioxide, but must control water loss.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Water and Mineral Movement
Regulation of Transpiration
Stomata open and close due to changes in turgor pressure of guard cells.
Turgor results from active uptake of potassium (K+) ions.
Increase in K+ concentration creates a water potential that causes water to enter osmotically, guard cells to become turgid, and stomata to open.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Stomata Opening and Closing
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Copyright © McGraw-Hill Companies Permission required for reproduction or display
Other Factors Regulating Transpiration
Carbon Dioxide
Light
Temperature
Water Loss Regulation
Dormancy
Deciduous Leaves
Thick, Hard Leaves
Trichomes
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies
Copyright © McGraw-Hill Companies Permission required for reproduction or display
The End.