Analysis of wild sunflower (Helianthus annuus L.) root exudates using gas chromatography‐mass spectrometry

Abstract

Plant root systems mediate ecological processes in the rhizosphere through the exudation of organic compounds. Although exudate composition is thought to depend strongly on plant nutrient status, little is known about the influence of multi‐nutrient stresses. In this study, we examined responses to short‐term (3 d) nutrient limitation in Helianthus annuus (common sunflower), and root exudates were collected for 2, 4, or 6 h with the trap‐solution method. Root exudates, analyzed by means of gas chromatography‐mass spectrometry, consisted of over 60 sugars, sugar alcohols, amino acids, organic acids, and phosphates, with sugars and organic acids generally detected in the highest quantities. Twenty‐five of the detected metabolites, including half of the organic acids, sugars, and sugar alcohols, differed in relative abundance among the three sampling intervals, exhibiting higher abundance in sampling intervals greater than 2 h. Similarly, 24 of the detected metabolites, including half of the amino acids, phosphates, and sugar alcohols, were affected by nutrient supply, with 20 exhibiting higher abundance in the high‐nutrient treatment. Fumaric acid, quinic acid, and glucose were detected at significantly higher levels in the low‐nutrient treatment, potentially representing an adaptive response to nutrient limitation in sunflower. However, as sampling interval exerted a strong influence on the apparent effects of nutrient supply, future studies should consider the potential impacts of sampling‐interval length in comparative analyses of genotypes or treatments.

Evolutionary Divergences in Root Exudate Composition among Ecologically-Contrasting Helianthus Species

“…Germinating seedlings were transferred to a growth chamber (Conviron, Winnipeg, Canada) programmed for a 12-hour 25/20°C day/night cycle with 70% relative humidity. Seedlings were grown hydroponically as described [ 48 ]. Briefly, one week after scarification, a small section of rock wool was wrapped around the hypocotyl of each seedling, and seedlings were suspended in individual 125 mL Erlenmeyer flasks wrapped in foil.…”

Root renovation: how an improved understanding of basic root biology could inform the development of elite crops that foster sustainable soil health

“…Several research studies have sought to identify the function of compounds in root exudates with regards to their influence on microbial communities. Such studies have had to overcome certain drawbacks including how metabolic content of root exudates vary depending on the plant species (Kidd et al 2018), between cultivars of the same plant species (Guo et al 2015;Mönchgesang et al 2016b), the developmental stage of the plant (Gransee and Wittenmayer 2000;Chaparro et al 2013), the part of root system involved (Pini et al 2017), soil and other environmental conditions (Bowsher et al 2015;Holz et al 2017;Liu et al 2017) and the microbial community in the soil (Guo et al 2015). Several root exudate compounds are associated with functions related to defence against pathogens (Baetz and Martinoia 2014) and/or to symbiotic facilitation (Li et al 2016).…”

Vicia Villosa Root Exudates Improve the Mobilization of Available P, K, Zn and Fe in Three Types of Purple Soil

“…At that time, Hairy vetch was in a vigorous period. The specific collection method was as follows [18]: 2 h into the light treatment on day 40, 15 plants were gently taken out of each pot and the roots were washed four times with deionized water. Roots were transferred to 1 L beakers containing 450 mL of deionized water and covered with aluminum foil [19].…”

“…The soil-cultivation experiment was carried out using the method of Zhao et al [18]. There were nine treatment combinations in a full-factorial setup.…”

“…Beakers were weighed daily and neutral deionized water was added to replace evaporated water. After 15 d, soil samples were removed from beakers and all samples were prepared according to the standard method of determination index [18].…”