Abstract Detail

Systematics Section/ASPT

Bowsher, Alan [1], Donovan, Lisa A [2], Harding, Scott A [3], Tsai, Chung-Jui [4].

Metabolic analysis of H. annuus L. (sunflower) root exudates by GC/MS.

Plant root systems exude a diverse array of chemical compounds into the soil which are thought to mediate numerous ecological processes: one of the most widely cited is the influence of root exudates on nutrient acquisition by plants. Certain root-exuded compounds have been shown to mobilize soil nutrients, promote soil microbes that mineralize nutrients into plant-available forms, or stimulate mycorrhizal relationships; all of which can improve plant nutrient uptake. However, little is known about root exudate composition in wild, non-model species, or the factors by which it is affected. In this study, seedlings of Helianthus annuus (common sunflower) were grown by hydroponics under either full-strength (HIGH) or 5% strength (LOW) nutrient supply, and root exudates were collected for either 2, 4, or 6 hours in a full factorial design. Composition of the root exudates was analyzed by gas chromatography-mass spectrometry (GC-MS). In total, 117 compounds were detected in all treatment groups, including amino acids, carboxylic acids, sugars, sugar alcohols, and fatty acids. In terms of relative abundance, 46 compounds were significantly affected by collection time, 41 were affected by nutrient supply, and 19 were affected by both factors. In general (and confirmed by principal component analysis), the majority of detected compounds increased in relative abundance both over time (from 2 to 6 hours) as well as under high nutrient supply. In addition, thirteen compounds exhibited a significant interaction between collection time and nutrient supply, all due to a larger increase over time in high-nutrient treated than low-nutrient treated plants. These data suggest that the largest differences in relative abundance between treatment groups were likely due to accumulation of compounds over time (from 2 to 6 hours), but also suggests that the rapid growth rate of the high nutrient supply group results in higher overall exudation rates, potentially reflecting greater resource demand, mobilization, and/or transport in roots of faster-growing plants. Interestingly, however, low-nutrient treated plants trended towards higher exudation of glucose, as well as several carboxylates which have been suggested to improve phosphate availability in soils through ligand exchange, including malate, citrate, fumarate, and succinate, potentially representing an adaptive response to nutrient limitation in sunflower. This project constitutes the first analysis of root exudate composition of a wild, non-model species, and provides preliminary data for future investigations of the composition, function, and evolution of root exudate profiles across Helianthus.

1 - University of Georgia, Department of Plant Biology, 2502 Miller Plant Sciences, Athens, GA, 30602, USA
2 - University of Georgia, Department of Plant Biology, 2502 Miller Plant Sciences, Athens, GA, 30602
3 - University of Georgia, Department of Genetics, Warnell School of Forestry and Natural Resources, Athens, GA, 30602
4 - University of Georgia, Department of Genetics, Warnell School of Forestry and Natural Resources, Institute of Bioinformatics, Athens, GA, 30602, USA

Keywords:
root exudation
metabolomics
GC-MS
soil ecology
nutrient acquisition.

Presentation Type: Oral Paper:Papers for Sections
Session: 45
Location: River Fork/Grove
Date: Wednesday, July 30th, 2014
Time: 5:15 PM
Number: 45015
Abstract ID:316
Candidate for Awards:None