Meeting Tissue Needs II Chapter 36 (738-755) Chapter 37 (756-770) Cellular Currency Plants harvest solar energy Photosynthesis Produces sugars Proteins, nucleic acids, lipids? H 2 O CO 2 Plants cells still need ATP Cellular respiration Inorganic minerals O 2 Sugar Review these processes H 2 O CO 2 ATP The Necessities Each cell needs: A supply of each reactant CO 2 H 2 O O 2 Glucose Minerals A waste removal system O 2 Nitrogenous wastes A mechanism to connect these systems The vascular system 1
A Matter of Size Movement by diffusion or bulk flow Size matters No vascular tissue Larger plants Basic Nutrition Autotrophy Carbon compounds Generation of ATP Generation of macromolecules Essential minerals Carbon dioxide Nitrogen Sulphur Nitrogen Phosphorous Nitrogen Iron Magnesium Potassium Calcium Mineral Deficiencies Symptoms depend on function Yellow midribs Chlorophyll deficiency Chlorosis Yellow margins Necrotic tips Reddish margins Anthocyanins 2
Source of Minerals Good soil Minerals and water Cation retention PO 4 retention Anion leaching Nitrates Uptake by roots Active Transport Primary Proton pumps Membrane potential Secondary Electrochemical gradient Cotransport Effectiveness Bulk flow Fluid movement Sap in the vascular tissues Pressure Positive pressure Negative pressure 3
The Vascular System Xylem Vessels & tracheids Water & minerals Xylem sap Root to shoot Phloem Sieve tubes & companion cells Photosynthates Phloem sap Shoot to root Root to shoot Water Transport Driving force Pure water 0.1 M solution Water potential (Ψ; MPa) Tendency for osmosis Direction of osmosis High to low Solute potential Increased concentration Pressure potential Physical pressure Positive pressure Water Transport Transpiration-Cohesion-Adhesion mechanism Transpiration Cohesion Adhesion Energy cost Water potentials 4
Stomata Opening & closing When open: Carbon dioxide Oxygen Water Transpiration Water Potentials Saturated air spaces Moist cell walls Ψ = -7 MPa Xylem Unsaturated outside air Ψ = -100 MPa Variable Tendency for osmosis? Direction of osmosis? Air space Stoma Water Potentials Mesophyll cell walls Ψ = -1.0 MPa Water leaving air spaces is replaced Trunk xylem Ψ = -0.8 08MPa Root xylem Ψ = -0.6 MPa Soil Ψ = -0.3 MPa Xylem Air space Stoma 5
Transpiration Water potentials Negative pressure Cohesion Adhesion Phloem Transport Translocation Photosynthates Source to sink Source Production/liberation site Sink Utilization site Mass Flow Hypothesis Pressure gradient Source to sink At source 1. Sugar sieve tube Active 2. Water potential ti decreases Hydrostatic pressure 3. Bulk flow At sink 4. Sugars transported out Opposite effect Vessel (xylem) H 2O H 2O Sieve tube (phloem) 3 1 2 Source cell H 2O Sink cell 4 Sucrose 6
Sources & Sinks Summer Source Sink Spring Source Sink Absorption Young growing roots Primary tissue region Root hair zone Epidermal trichomes High turnover Nutrient absorption Cations Anions Water Oxygen K + SO 2-4 Mg ++ PO - 4 Ca ++ NO 3 - NH 4 + I Get By With a little help from my friends Mycorrhizae Ectomycorrhizae Endomycorrhizae 7
Nitrogen Availability Nitrogen fixing bacteria Rhizobium N 2 NH 4 + Root nodules Soil Nitrifying bacteria Nitrosomonas & Nitrobacter NH 4+ NO 2- NO 3 - Soil Absorption Pathways Vertical transport Lateral transport Plasmodesmata Transmembrane route Symplast route Apoplast route Control? Control Transmembrane & symplastic routes Apoplastic route Endodermis Casparian strip 8
Lateral Water Transport Epidermis Active mineral/water absorption Hydrophilic cell walls Root hair Vessels (xylem) Epidermis Endodermis Stele Lateral Water Transport Cortex Symplastic route Apoplastic route Transmembrane route Endodermis Controls transport Vascular cylinder Root hair Vessels (xylem) Epidermis Endodermis Stele Root Pressure Smaller herbaceous plants Nocturnal flow Stomata Transipration Water/minerals pushed Positive pressure Endodermal active transport 9
Root Pressure Endodermis 1. Active transport Into vascular cylinder 2. Root xylem Ψ Hypertonic 3. Water movement Limits of size Mineral Absorption Active transport Requirements 1. 2. 3. O 2 CO 2 CR ATP H + PO - 4 H + H + H + H + K + or H + NO - 3 Endodermis selectivity Mg ++ Fe 3+ Ca ++ 10