Water & Nutrient Stress Increase Root Exudation

Utah State University DigitalCommons@USU Water Stress Research 2002 Water & Nutrient Stress Increase Root Exudation A Henry Utah State University J Chard Utah State University J Norton Utah State University M Petersen Utah State University Bruce Bugbee Utah State University, bruce.bugbee@usu.edu M Hamilton INEEL See next page for additional authors Follow this and additional works at: https://digitalcommons.usu.edu/cpl_waterstress Part of the Plant Sciences Commons Recommended Citation Henry, A.; Chard, J.; Norton, J.; Petersen, M.; Bugbee, Bruce; Hamilton, M.; Palmer, C.; and Hess, J R., "Water & Nutrient Stress Increase Root Exudation" (2002) Water Stress Paper https://digitalcommons.usu.edu/cpl_waterstress/2 This Presentation is brought to you for free and open access by the Research at DigitalCommons@USU It has been accepted for inclusion in Water Stress by an authorized administrator of DigitalCommons@USU For more information, please contact digitalcommons@usu.edu Authors A Henry, J Chard, J Norton, M Petersen, Bruce Bugbee, M Hamilton, C Palmer, and J R Hess This presentation is available at DigitalCommons@USU: https://digitalcommons.usu.edu/cpl_waterstress/2 Water & Nutrient Stress Increase Root Exudation A Henry, J Chard, J Norton M Petersen, B Bugbee M Hamilton, C Palmer, J.R Hess Objectives Develop procedures to: • Grow healthy plants under sterile conditions • Manipulate root exudation with stress • Quantify total organic carbon in exudates • Determine composition of exudates using GC-MS Implications for Phytoremediation Our focus for the qualitative analysis: organic acids The chelating properties of these compounds can be useful for phytoremediation, and they are a class of compound most likely to be found in root exudate Increased plant uptake Co-metabolism Increased/decreased contaminant mobility System for sterile culture Foam plug Septum Groundglass joint Air filter Ottawa sand Silicone stoppers Amber vial HPS lamps Laminar flow hood Treatments ƒ High NH4+ ƒ K+ stress ƒ Drought ƒ Flooding 100 Trial improved planting technique % Sterile Plants 80 Trial in growth chamber 60 Trial enclosed shoot 40 Trial in laminar flow hood 20 0 10 15 20 25 30 35 40 45 Days After Planting 50 55 60 65 Assessing microbial contamination Verifying Plate Counts: Acridine Orange Stain of Leachate Clean sample 10 µm Root debris Verifying Plate Counts: Acridine Orange Stain of Leachate Contaminated sample 10 µm bacteria Phenolic Aniline Blue Stain of Root Clean root 10 µm Phenolic Aniline Blue Stain of Root Contaminated root 10 µm bacteria Treatment Averages µg C exuded per day 1000 800 The K+ stressed plants had the highest amount of carbon exuded at any point in time We think this is because the plants were releasing a compound to sequester K+ from the soil + K stress Treatments started 600 flood 400 drought 200 control NH4+ treatment 20 30 40 50 days after planting 60 70 Cumulative carbon exuded per gram dry plant mg C exuded per g dry plant Percent of control Average Std dev 2.6 0.4 2.3 0.1 90 K+ 3.7 0.6 144 flood 3.8 0.9 145 drought 4.4 0.5 170 control NH4+ Primary types of exudates Compounds released by roots Sloughed-off cells Distribution of Carbon Rhizosphere sand Bulk sand Leachates Soluble Insoluble Based on the distribution of carbon released by the roots (mostly soluble with not much left on the sand), we conclude that the exudates we’re seeing are mostly compounds released directly from the root, not whole cells released from the root 17 % 9% 63 % 11 % 100 % Unlike the TOC graph, organic acids were exuded in the largest amounts from the drought and flooding treatments This may be due to buildup of osmotic potential to deal with the low water potentials in the drought treatment, or just leakier root cells due to the stress treatments GC-MS Data: Exudates Fumaric Acid drought control K+ stress NH4+ trtmt flood 30 35 40 45 50 55 60 Days after planting 65 70 Concentration (mg/L) flood drought 30 35 40 45 50 55 control K+ stress NH4+ trtmt 60 65 70 10 Oxalic Acid flood drought control K+ stress NH4+ trtmt 30 Malonic Acid Days after planting 10 Concentration (mg/L) 10 35 40 45 50 55 60 Days after planting 65 70 Concentration (mg/L) Concentration (mg/L) 10 Succinic Acid drought 30 K+ stress control NH4+ trtmt flood 35 40 45 50 55 60 Days after planting 65 70 What’s in the root vs what’s released by the root Fumaric Acid 10 r2 Exudate (mg/L) Exudate (mg/L) 12 = 0.54 0 500 1000 1500 2000 14 12 10 Succinic Acid r2 = 0.55 100 400 500 Oxalic Acid 10 r2 = ns 50 100 150 200 250 300 350 400 Root (mg/kg) Exudate (mg/L) 12 Exudate (mg/L) 300 Root (mg/kg) Root (mg/kg) 200 Malonic Acid r2 = ns 0 20 40 60 80 Root (mg/kg) 100 120 Treatment Averages flood 400 drought 200 control NH4+ treatment 20 30 40 50 60 70 days after planting 10 Concentration (mg/L) Concentrations of succinic and fumaric acid in the root correlated with amounts released by the root + K stress 600 Succinic Acid drought 14 12 10 K+ stress control NH4+ trtmt flood 30 Exudate (mg/L) Stress increases root exudation Drought and flooding treatments increased release of organic acids 800 µg C exuded per day Conclusions 1000 35 40 45 50 55 60 Days after planting 65 70 Succinic Acid r2 = 0.55 100 200 300 Root (mg/kg) 400 500 ... is available at DigitalCommons@USU: https://digitalcommons.usu.edu/cpl_waterstress/2 Water & Nutrient Stress Increase Root Exudation A Henry, J Chard, J Norton M Petersen, B Bugbee M Hamilton,... acid in the root correlated with amounts released by the root + K stress 600 Succinic Acid drought 14 12 10 K+ stress control NH4+ trtmt flood 30 Exudate (mg/L) Stress increases root exudation. .. to deal with the low water potentials in the drought treatment, or just leakier root cells due to the stress treatments GC-MS Data: Exudates Fumaric Acid drought control K+ stress NH4+ trtmt flood