Root exudate profiling of maize seedlings inoculated with Herbaspirillum seropedicaeand humic acids

Abstract

Background: Co-inoculation of maize with Herbaspirillum seropedicae and humic substances increases the sizes of plant-associated bacterial populations and enhances grain yields under laboratory and field conditions. Root exudation is a key mechanism in the regulation of plant-bacterial interactions in the rhizosphere; humic matter supplementation is known to change the exudation of H + ions and organic acids from maize roots. Our starting premise was that H. seropedicae and humic acids would modify maize seedling exudation profiles. We postulated that a better understanding of these shifts in exudate profiles might be useful in improving the chemical environment to promote better performance of plant growth-promoting bacteria delivered as bioinoculants. Thus, root exudates of maize were collected and analyzed by gas chromatography-mass spectrometry (GC-MS) and proton nuclear magnetic resonance (

Metabolite profiling of non‐sterile rhizosphere soil

“…In addition to plant genotype and nutrition, various other factors can influence root exudation chemistry, such as plant developmental stage, temperature, humidity and physiochemical soil properties (Boyes et al, 2001;Uren, 2007;Badri and Vivanco, 2009;Zhang et al, 2016). The environmental effects of root exudation chemistry have been studied mostly in (semi)sterile hydroponic systems (Song et al, 2012;Vranova et al, 2013;da Silva Lima et al, 2014). An important justification for the use of such soil-free growth conditions is that they allow for the tight maintenance of environmental variables (Ziegler et al, 2015;Bowsher et al, 2016).…”

Humic Substances and Efficient Microorganisms: Elicitation of Medicinal Plants—A Review

“…Researches show that humic substances contribute on the better absorption of nutrients (Halpern et al, 2015). They also perform indirect actions over the chemical and dynamic of the microorganism on the rhizosphere, altering the interaction soil-plant-microbiota in relation to the assimilation of macro and micro nutrients as a function of the increase on the permeability of the plasmatic membrane with the action of the humic substances (Silva Lima et al, 2014).…”

“…Changes on the uptake of nutrients and humic substances related to the absorption rates are explained by the kinetic parameters of absorption, which are estimated through the maximum absorption rate, ion concentration and minimum ion concentration in the solution taht the plant cannot absorb (Silva Lima et al, 2014). Therefore, the humic and the fulvic acid can influence directly and indirectly in the plants metabolism Vaccaro et al, 2015), altering the metal complexation, increasing the capacity of cationic exchange (Ateia et al, 2017;Lee et al, 2017;Kwiatkowska-Malina, 2018), nutrients supply and humidity retention, interfering on the ions transportation, respiratory activity, chlorophyll levels, nucleic acid synthesis and on the activity of several enzymes (Muscolo et al, 2013;Ozfidan-Konakci et al, 2018;Shahabivand et al, 2018).…”

Mycorrhizal Root Exudates Induce Changes in the Growth and Fumonisin Gene (FUM1) Expression of Fusarium proliferatum

“…Similar trends in the expressions of FUM1 and HOG1 genes found in our experiment suggest that arbuscular mycorrhizal fungal colonization did not only affect directly the growth and mycotoxin production of F. proliferatum, but also modulated indirectly a number of other mechanisms. Mycorrhizal inoculation showed potential as a biological control agent in the suppression of fumonisin production by F. proliferatum.Root exudates were collected from maize plants treated, as described previously, by removing all substrate particles from the roots and then submerging them into 50 mL of 0.01 M L −1 KOH according to da Silva Lima et al [38]. After 5 min, the root system was washed with tap water, then with Agronomy 2019, 9, 291 3 of 11 distilled water and were incubated in Erlenmeyer flasks filled with 50 mL sterilized distilled water for 24 h. Solutions were sterilized by filtration through 0.22 µm Ø nitrocellulose filters (Millipore, Burlington, MA, USA).…”

“…Root exudates were collected from maize plants treated, as described previously, by removing all substrate particles from the roots and then submerging them into 50 mL of 0.01 M L −1 KOH according to da Silva Lima et al [38]. After 5 min, the root system was washed with tap water, then with Agronomy 2019, 9, 291 3 of 11 distilled water and were incubated in Erlenmeyer flasks filled with 50 mL sterilized distilled water for 24 h. Solutions were sterilized by filtration through 0.22 µm Ø nitrocellulose filters (Millipore, Burlington, MA, USA).…”