Use of Ore-Derived Humic Acids With Diverse Chemistries to Elucidate Structure-Activity Relationships (SAR) of Humic Acids in Plant Phenotypic Expression

We report the results of a structure-activity relationship study that was undertaken to identify humic substance chemistries that drive the plant biostimulant response. The effects of seven extensively chemically characterized, ore-derived humic acids (HA) on corn seedling biomass and root and shoot...

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Autores principales:	Richard T. Lamar, Hiarhi Monda, Rachel Sleighter
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	humic substances humic acid biostimulants electron accepting capacity electron donating capacity mechanism of action Plant culture SB1-1110
Acceso en línea:	https://doaj.org/article/8f1910616dd94a998e57f0ec01040335
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spelling	oai:doaj.org-article:8f1910616dd94a998e57f0ec010403352021-12-02T01:01:55ZUse of Ore-Derived Humic Acids With Diverse Chemistries to Elucidate Structure-Activity Relationships (SAR) of Humic Acids in Plant Phenotypic Expression1664-462X10.3389/fpls.2021.758424https://doaj.org/article/8f1910616dd94a998e57f0ec010403352021-12-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fpls.2021.758424/fullhttps://doaj.org/toc/1664-462XWe report the results of a structure-activity relationship study that was undertaken to identify humic substance chemistries that drive the plant biostimulant response. The effects of seven extensively chemically characterized, ore-derived humic acids (HA) on corn seedling biomass and root and shoot morphological parameters were investigated. Chemometric analyses were then conducted to identify correlations between HA chemical features and plant biomass and morphological characteristics. The primary chemical driver of plant biomass and morphology was the ratio between HA electron accepting capacity (EAC) and electron donating capacity (EDC). The HA electron accepting capacity is found in quinones and semiquinone free radicals, while the HA electron donating capacity is found in polyphenolics and glycosylated polyphenolics. Based on our results, we propose a mechanism of action for ore-derived HA plant biostimulation that involves the interplay of pro-oxidants, in the form of quinones and semiquinone radicals, and antioxidants, in the form of polyphenols and possibly glycones and carbohydrates. The quinones/semiquinones initiate an oxidative stress response via the stimulation of transmembrane electron flow that results in both reactive oxygen species (ROS) production (i.e., an oxidative burst) and membrane depolarization, the latter of which allows Ca2+ flux from the apoplast into the cytoplasm. Based on the magnitude of depolarization, a specific cytoplasmic Ca2+ signature is produced. As a secondary messenger Ca2+, via binding to Ca2+− sensor proteins, transmits the signature signal, resulting in specific intracellular responses that include changes to plant morphology. The greater the EAC, the greater the ROS production and magnitude of plasma membrane depolarization and resulting stress response. The HA antioxidants are able to scavenge and quench the ROS and thus modulate the intensity and extent of the stress response to greater or lesser degrees, based on their concentrations and radical scavenging efficiencies, and thus modify the Ca2+ signature and ultimately the intracellular molecular responses.Richard T. LamarHiarhi MondaRachel SleighterFrontiers Media S.A.articlehumic substanceshumic acidbiostimulantselectron accepting capacityelectron donating capacitymechanism of actionPlant cultureSB1-1110ENFrontiers in Plant Science, Vol 12 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	humic substances humic acid biostimulants electron accepting capacity electron donating capacity mechanism of action Plant culture SB1-1110
spellingShingle	humic substances humic acid biostimulants electron accepting capacity electron donating capacity mechanism of action Plant culture SB1-1110 Richard T. Lamar Hiarhi Monda Rachel Sleighter Use of Ore-Derived Humic Acids With Diverse Chemistries to Elucidate Structure-Activity Relationships (SAR) of Humic Acids in Plant Phenotypic Expression
description	We report the results of a structure-activity relationship study that was undertaken to identify humic substance chemistries that drive the plant biostimulant response. The effects of seven extensively chemically characterized, ore-derived humic acids (HA) on corn seedling biomass and root and shoot morphological parameters were investigated. Chemometric analyses were then conducted to identify correlations between HA chemical features and plant biomass and morphological characteristics. The primary chemical driver of plant biomass and morphology was the ratio between HA electron accepting capacity (EAC) and electron donating capacity (EDC). The HA electron accepting capacity is found in quinones and semiquinone free radicals, while the HA electron donating capacity is found in polyphenolics and glycosylated polyphenolics. Based on our results, we propose a mechanism of action for ore-derived HA plant biostimulation that involves the interplay of pro-oxidants, in the form of quinones and semiquinone radicals, and antioxidants, in the form of polyphenols and possibly glycones and carbohydrates. The quinones/semiquinones initiate an oxidative stress response via the stimulation of transmembrane electron flow that results in both reactive oxygen species (ROS) production (i.e., an oxidative burst) and membrane depolarization, the latter of which allows Ca2+ flux from the apoplast into the cytoplasm. Based on the magnitude of depolarization, a specific cytoplasmic Ca2+ signature is produced. As a secondary messenger Ca2+, via binding to Ca2+− sensor proteins, transmits the signature signal, resulting in specific intracellular responses that include changes to plant morphology. The greater the EAC, the greater the ROS production and magnitude of plasma membrane depolarization and resulting stress response. The HA antioxidants are able to scavenge and quench the ROS and thus modulate the intensity and extent of the stress response to greater or lesser degrees, based on their concentrations and radical scavenging efficiencies, and thus modify the Ca2+ signature and ultimately the intracellular molecular responses.
format	article
author	Richard T. Lamar Hiarhi Monda Rachel Sleighter
author_facet	Richard T. Lamar Hiarhi Monda Rachel Sleighter
author_sort	Richard T. Lamar
title	Use of Ore-Derived Humic Acids With Diverse Chemistries to Elucidate Structure-Activity Relationships (SAR) of Humic Acids in Plant Phenotypic Expression
title_short	Use of Ore-Derived Humic Acids With Diverse Chemistries to Elucidate Structure-Activity Relationships (SAR) of Humic Acids in Plant Phenotypic Expression
title_full	Use of Ore-Derived Humic Acids With Diverse Chemistries to Elucidate Structure-Activity Relationships (SAR) of Humic Acids in Plant Phenotypic Expression
title_fullStr	Use of Ore-Derived Humic Acids With Diverse Chemistries to Elucidate Structure-Activity Relationships (SAR) of Humic Acids in Plant Phenotypic Expression
title_full_unstemmed	Use of Ore-Derived Humic Acids With Diverse Chemistries to Elucidate Structure-Activity Relationships (SAR) of Humic Acids in Plant Phenotypic Expression
title_sort	use of ore-derived humic acids with diverse chemistries to elucidate structure-activity relationships (sar) of humic acids in plant phenotypic expression
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/8f1910616dd94a998e57f0ec01040335
work_keys_str_mv	AT richardtlamar useoforederivedhumicacidswithdiversechemistriestoelucidatestructureactivityrelationshipssarofhumicacidsinplantphenotypicexpression AT hiarhimonda useoforederivedhumicacidswithdiversechemistriestoelucidatestructureactivityrelationshipssarofhumicacidsinplantphenotypicexpression AT rachelsleighter useoforederivedhumicacidswithdiversechemistriestoelucidatestructureactivityrelationshipssarofhumicacidsinplantphenotypicexpression
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Use of Ore-Derived Humic Acids With Diverse Chemistries to Elucidate Structure-Activity Relationships (SAR) of Humic Acids in Plant Phenotypic Expression

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