Nutrition and Transport in Plants Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Copyright © 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 present  Ferns = aluminum  Locoweeds = 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 water  Factors 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

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

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