k-Oligocarrageenan Promoting Growth of Hybrid Maize: Influence of Molecular Weight

Carrageenans as biostimulants and bio-elicitors: plant growth and defense responses

In the context of climate change, the need to ensure food security and safety has taken center stage. Chemical fertilizers and pesticides are traditionally used to achieve higher plant productivity and improved plant protection from biotic stresses. However, the widespread use of fertilizers and pesticides has led to significant risks to human health and the environment, which are further compounded by the emissions of greenhouse gases during fertilizer and pesticide production and application, contributing to global warming and climate change. The naturally occurring sulfated linear polysaccharides obtained from edible red seaweeds (Rhodophyta), carrageenans, could offer climate-friendly substitutes for these inputs due to their bi-functional activities. Carrageenans and their derivatives, known as oligo-carrageenans, facilitate plant growth through a multitude of metabolic courses, including chlorophyll metabolism, carbon fixation, photosynthesis, protein synthesis, secondary metabolite generation, and detoxification of reactive oxygen species. In parallel, these compounds suppress pathogens by their direct antimicrobial activities and/or improve plant resilience against pathogens by modulating biochemical changes via salicylate (SA) and/or jasmonate (JA) and ethylene (ET) signaling pathways, resulting in increased production of secondary metabolites, defense-related proteins, and antioxidants. The present review summarizes the usage of carrageenans for increasing plant development and defense responses to pathogenic challenges under climate change. In addition, the current state of knowledge regarding molecular mechanisms and metabolic alterations in plants during carrageenan-stimulated plant growth and plant disease defense responses has been discussed. This evaluation will highlight the potential use of these new biostimulants in increasing agricultural productivity under climate change.

Oligo-Carrageenan Kappa Increases Expression of Genes Encoding Proteins Involved in Photosynthesis, C, N, and S Assimilation, and Growth in Arabidopsis thaliana

To analyze the effect of oligo-carrageenan (OC) kappa in the stimulation of growth in Arabidopsis thaliana, plants were sprayed on leaves with an aqueous solution of OC kappa at 1 mg mL-1, 5 times every 2 days and cultivated for 5 or 15 additional days. Plants treated with OC kappa showed an increase in rosette diameter, fresh and dry weight, and primary root length. Plants treated with OC kappa once and cultivated for 0 to 24 h after treatment were subjected to transcriptomic analyses to identify differentially expressed genes, mainly at 12 h after treatment. Transcripts encoding proteins involved in growth and development and photosynthesis were upregulated as well as enzymes involved in primary metabolism. In addition, plants treated with OC kappa once and cultivated for 0 to 96 h showed increased levels of transcripts encoding enzymes involved in C, N, and S assimilation at 6 and 12 h after treatment that remain increased until 96 h. Therefore, OC kappa increased the expression of genes encoding proteins involved in photosynthesis, C, N, and S assimilation, and growth in A. thaliana.

Chitosan-, alginate- carrageenan-derived oligosaccharides stimulate defense against biotic and abiotic stresses, and growth in plants: A historical perspective

During the last 20 years, the mechanisms involved in the stimulation of defense against pathogens, and growth triggered by chitosan-, alginate- and carrageenan-derived oligosaccharides have been studied in plants. Oligo-chitosan stimulate protection against pathogens by activation of salicylic acid (SA) or jasmonic acid/ethylene (JA/ET)-dependent pathways, protection against abiotic stress through abscisic acid (ABA)-dependent pathway, and growth by increasing photosynthesis, auxin and gibberellin content, C and N assimilation, and synthesis of secondary metabolites with antipathogenic and medicinal properties. Oligo-alginates stimulate protection against pathogens through SA-dependent pathway, abiotic stress via ABA-dependent pathway, and growth by increasing photosynthesis, auxin and gibberellins contents, C and N assimilation, and synthesis of secondary metabolites with antipathogenic and medicinal properties. Oligo-carrageenan increased protection against pathogens through JA/ET, SA- and Target of Rapamycin (TOR)-dependent pathways, and growth by activation of TOR-dependent pathway leading to an increase in expression of genes involved in photosynthesis, C, N, S assimilation, and enzymes that synthesize phenolic compounds and terpenes having antipathogenic activities. Thus, the latter oligosaccharides induce similar biological effects, but through different signaling pathways in plants.

Evaluation of Carrageenan, Xanthan Gum and Depolymerized Chitosan Based Coatings for Pineapple Lily Plant Production

Some natural polysaccharides and their derivatives are used in horticulture to stimulate plant growth. This study investigated the effects of coating bulbs with carrageenan-depolymerized chitosan (C-DCh) or xanthan-depolymerized chitosan (X-DCh) on growth, flowering, and bulb yield as well as physiological and biochemical attributes of pineapple lily (Eucomis autumnalis). The results showed that treatment with C-DCh or X-DCh significantly increased all growth parameters, bulb yield, greenness index, stomatal conductance, total N, total K, and total sugar content of bulbs and accelerated anthesis as compared with untreated bulbs. The positive impact of coatings on plant growth and physiological attributes depended on the type of biopolymer complexes. The X-DCh treatment exhibited the greatest plant height, fresh weight, daughter bulb number, greenness index, stomatal conductance, total N, K, and sugar content. However, this treatment induced a significant decrease in L-ascorbic acid, total polyphenol content and antioxidant activity. Overall, the results of this study indicated high suitability of C-DCh and X-DCh as bulb coatings for pineapple lily plant production.