Premium
Changes in Crested Wheatgrass Root Exudation Caused by Flood, Drought, and Nutrient Stress
Author(s) -
Henry Amelia,
Doucette William,
Norton Jeanette,
Bugbee Bruce
Publication year - 2007
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2006.0425sc
Subject(s) - rhizosphere , chemistry , nutrient , exudate , phytoremediation , malic acid , agronomy , total organic carbon , horticulture , environmental chemistry , botany , citric acid , biology , food science , heavy metals , genetics , organic chemistry , bacteria
Root exudates can chelate inorganic soil contaminants, change rhizosphere pH, and may increase degradation of organic contaminants by microbial cometabolism. Root‐zone stress may increase exudation and enhance phytoremediation. We studied the effects of low K + , high NH 4 + /NO 3 − ratio, drought, and flooding on the quantity and composition of exudates. Crested wheatgrass ( Agropyron cristatum ) was grown in Ottawa sand in sealed, flow‐through glass columns under axenic conditions for 70 d. Root exudates were collected and analyzed for total organic carbon (TOC) and organic acid content to compare treatment effects. Plants in the low K + treatment exuded 60% more TOC per plant per day ( p = 0.01) than the unstressed control. Drought stress increased cumulative TOC exuded per gram dry plant by 71% ( p = 0.05). The flooded treatment increased TOC exuded per gram dry plant by 45%, although this was not statistically significant based on the two replicate plants in this treatment. Exudation from the high NH 4 + /NO 3 − ratio treatment was 10% less than the control. Exudation rates in this study ranged from 8 to 50% of rates in four other published studies. Gas chromatography‐mass spectrometry (GC–MS) analysis indicated that malic acid was the predominant organic acid exuded. Fumaric, malonic, succinic, and oxalic acids were also detected in the exudates of all treatments. These results demonstrate that nutrient and water stress have significant effects on the quantity and composition of root exudates. Cultural manipulations to induce stress may change the quantity of root exudates and thus increase the effectiveness of phytoremediation.