Toward the molecular understanding of the action mechanism of Ascophyllum nodosum extracts on plants

Abstract

The importance of biostimulants, defined as plant growth-promoting agents that differ notably from fertilizers, is increasing steadily because of their potential contribution to a worldwide strategy for securing food production without burdening the environment. Based on folkloric evidence and ethnographic studies, seaweeds have been useful for diverse human activities through time, including medicine and agriculture. Currently, seaweed extracts, especially those derived from the common brown alga Ascophyllum nodosum, represent an interesting category of biostimulants. Although A. nodosum extracts (abbreviated ANEs) are readily used because of their capacity to improve plant growth and to mitigate abiotic and biotic stresses, fundamental insights into how these positive responses are accomplished are still fragmentary. Generally, the effects of ANEs on plants have been attributed to their hormonal content, their micronutrient value, and/or the presence of alga-specific polysaccharides, betaines, polyamines, and phenolic compounds that would, alone or in concert, bring about the observed phenotypic effects. However, only a few of these hypotheses have been validated at the molecular level. Transcriptomics and metabolomics are now emerging as tools to dissect the action mechanisms exerted by ANEs. Here, we provide an overview of the available in planta molecular data that shed light on the pathways modulated by ANEs that promote plant growth and render plants more resilient to diverse stresses, paving the way toward the elucidation of the modus operandi of these extracts.

Linking abiotic stress, plant metabolites, biostimulants and functional food

“…A plethora of reports describes the positive effects of seaweed‐based biostimulants on plant growth and quality, stress tolerance, nutrient acquisition, accumulation, biosynthesis, soil health and so on as reviewed by Shukla et al (2019). Recently, De Saeger et al (2020) gave an overview of the available in planta molecular data, which address the pathways modulated by Ascophyllum nodosum extracts that promote plant growth and their stress tolerance.…”

Seaweed extract to enhance marigold seed germination and seedling establishment

“…However, more detailed studies on the use of A. nodosum algae extract as a biostimulant should be performed. The effects of extracts can be attributed to their hormonal content, nutrient value, and/or the presence of alga-specific polysaccharides, betaines, polyamines, and phenolic compounds with phenotypic effects [28].…”

Biopriming of sweet pepper and tomato seeds with Ascophyllum nodosum

“…The biostimulant effect of brown seaweed extract can be related to many factors. Several studies report an increase in dry matter in seeds under the application of these compounds (Souza et al, 2017;Ali et al, 2019;Saeger et al, 2019). The action of plant hormones mainly controls the dry mass accumulation process.…”

“…According to Saeger et al (2019), A. nodosum extracts act on hormonal balance and regulate important processes in nutrient absorption and photosynthesis. However, the exact molecular basis of growth promotion caused by this application still needs to be elucidated, as it involves several processes in the plant (genome, enzyme activity and transcription, among others).…”

“…Priming of chicory seeds with A. nodosum caused an increase in the percentage and seedling emergence speed in greenhouse conditions (Ferraz et al, 2019). Spinach, canola and barley were evaluated by Saeger et al (2019) finding a positive impact on the germination and development. Sivritepe and Sivritepe ( 2016) observed that seaweed priming on tomato seed can increase the germination speed and uniformity.…”