Unit 5 vegetation lecture 1

Unit 5 vegetation lecture 1 - Unit 5: Vegetation Inundation...

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Unformatted text preview: Unit 5: Vegetation Inundation and Environmental Stresses Gas Diffusion Fick’s First Law Fick’ F = -D(dC/do) F= D= C= X= Flux (M/L2/T) Fickian mass transport coefficient (L2/T) Concentration (M/L3) Distance of concentration gradient (L) Diffusion coefficients for oxygen and carbon dioxide in air and water Medium Air Water O2 D cm 2 sec-1 CO2 0.181 2.04 X 10 -5 0.226 2.6 X 10 -5 1 Relationship between air-filled porosity of airsoil and the volume of anaerobic sites Saturated conditions Volume of anaerobic sites Field capacity Air-filled porosity (Sa) Gas Exchange in Soil-Water-Plant System Drained Soil Flooded Soil O2 O2 CO2 ? Dissloved metals sulfides, and organic acids CO2, CH4, and other gases Hypoxia vs. Anoxia Anoxia (anaerobic) - absence of oxygen. Anoxia Hypoxia - concentration at which oxygen Hypoxia becomes a stress to organism. 2 Point of Oxygen Stress Pasture point Pasture Oxygen concentration at which organism can no longer Oxygen respire aerobically. Critical concentration of oxygen varies and is dependant Critical upon body size (1% saturation for microbes) body circulatory system circulatory rate of consumption rate rate of diffusion rate Diurnal Oxygen Concentration P = Photosynthesis Oxygen Concentration P>R R = Respiration P>R R >> P midday midnight midday Vegetative Tissue Stressed by Inundation roots roots rootlets rootlets rhizome rhizome seeds seeds developing shoot developing submerged shoot submerged 3 Plant Aerobic Metabolism Glycolysis glucose Fermentation glycolysis ATP ADP Net gain per mole of glucose is 38 ATP Electron Transport Chain flavoprotein 2H+ NADox NADred 2enon-heme Fe 2H coenzyme Q 2H+ Krebs Cycle CO2 pyruvate isocitrate cicaconitate H2O 2ecytochrome B 2e- cytochrome C ATPase A ketoglutarate CO2 NADred citrate NADred NADox acetyl CoA succinate fumarae NADox oxaloacetate malate 1/ + 2O2+2H 2OH- 2H2O ADP+P ATP Fatty Acids Anaerobic Metabolism Glycolysis glucose Fermentation glycolysis ATP ADP NADox NADred flavoprotein Electron Transport Chain 2H+ 2enon-heme Fe 2H coenzyme Q 2H+ Krebs Cycle CO2 pyruvate isocitrate cicaconitate H2O 2ecytochrome B 2e- cytochrome C ATPase A ketoglutarate NADred citrate NADred NADox acetyl CoA succinate fumarae NADox oxaloacetate malate 1/ + 2O2+2H 2OH- 2H2O ADP+P ATP Fatty Acids Glycolysis glucose Fermentation glycolysis ATP ADP Plant Anaerobic Metabolism acetaldehyde NADox ADH pyruvate ethanol NADred NADred NADox acetyl CoA Net energy production per mole of glucose is 2 moles ATP Fatty Acids 4 Cell Energy Charge Absence of oxygen reduces ATP production in cell from Absence 38 ATP to 2 ATP. Cell available energy can be measured to determine Cell “health” health” EC=(ATP)+0.5 (ADP)/(ATP)+(ADP)+(AMP) Normal energy charge in cell under aerobic conditions is Normal 0.8. Energy charge under anoxia is 0.5 or less. Metabolic Impacts on Plant Cell membrane and enzymes Cell damage can occur without repair or replacement. damage Glycosidic acidosis Glycosidic Inhibition of H+ transport from cytoplasm along electron Inhibition transport chain causes pH to drop. Acetaldehyde and ethanol Acetaldehyde Accumulates as a toxic metabolite Accumulates Cyanogenesis Cyanogenesis some plants produce cyanogenic glycosides to inhibit herbivorie some hydrolysis under anaerobic conditions produces cyanide hydrolysis death in 24 hours death Death by Anaerobic Starvation Low ATP yield for glycolysis Low Increased carbohydrate Increased consumption to offset low energy yields. Complete consumption of Complete carbohydrates results in starvation. Rate of consumption can be Rate regulated and is partially temperature dependant. 5 Post Anoxic Injury Superoxides Superoxide radicals present under aerobic conditions, but Superoxide enzymes and antioxidants protect plant tissue (superoxide dismuytase) Under anaerobic conditions, superoxides are not present and Under plant does not produce anti-oxidizing enzymes. antiAfter flooding, rapid return to aerobic conditions can lead to After toxicity from superoxides with no enzyme protection. Post Anoxic Injury Toxic Metabolites Upon return to aerobic conditions ethanol is oxidized to Upon acetaldehyde. Actaldehyde is more toxic than ethanol Actaldehyde Plant can reduce toxic effect by regulating production and Plant accumulation of ethanol. reduce glycolytic rate reduce porous rhizome porous Hormonal Imbalance Gibberellins and Cytokinins Gibberellins Produced in root and branch tips. Produced Anaerobic conditions can disrupt Anaerobic production and translocation. Can cause wilting, chlorosis, Can epinasty Loss of apical dominance, copicing Loss Abscisic Acid Abscisic Increases within hours Increases Leads to stomatal closure Leads Reduced growth Reduced Leaf epinasty Leaf www.maryrose.org/.../woodwork/images/coppice.jpg http://igfri.ernet.in/images/Wardan.jpg 6 Water Balance Suberization of roots Suberization Deposition of suberin between xylem Deposition and phloem reduces water uptake reduces Some water loss still occurs even though Some stomates are often closed Eventual loss of turger pressure Eventual plant wilts plant sols.unlv.edu/Schulte/Anatomy/Roots/Roots.html Soil Toxicity Anaerobic conditions in soils can create potentially toxic Anaerobic concentrations of some compounds. mobility of compound can change mobility toxicity of compound can change toxicity Mn+2 - Phytotoxic and highly soluble Mn Fe+2 - Soluble and toxic at high levels. Fe H2S - Toxic at relatively low levels Can effect nitrogen uptake – saltmarsh zonation Can Salt Stress Coastal communities along Coastal transition between marine and freshwater Saline – hypersaline - fresh Saline Differences in osmotic Differences potential. If osmotic pressure is higher If outside the plant, water will diffuse out of the plant causing loss of turger and desiccation. 7 Fire Some wetlands have an Some increased probability of fire Fire can damage Fire apical/terminal growth bud. Fire can damage cambium Fire and impedes water and nutrient transport in plant. Summary Stresses on Plant Summary Decrease in Cell Energy Charge Decrease Can’t produce or maintain enzymes and cell membrane Can’ Glycosidic acidosis due to loss of ion gradients Glycosidic Hormonal imbalance Hormonal Accumulation of toxic compounds under anaerobic metabolism Accumulation (acetaldehyde, ethanol) (acetaldehyde, Cyanogenesis Cyanogenesis Hydrolysis of cyanogenic glycosides produce Cyanide Hydrolysis Death by Anaerobic Starvation Death Inefficient metabolism of non structural carbohydrates Inefficient Water Balance Water Suberization and loss of root area for water uptake Suberization 8 ...
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This note was uploaded on 03/01/2010 for the course PCB 4683 taught by Professor Williams,j during the Spring '08 term at University of Central Florida.

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