Differential Production of Phenolics, Lipids, Carbohydrates and Proteins in Stressed and Unstressed Aquatic Plants, Azolla filiculoides and Azolla pinnata

Abstract

The metabolic plasticity of shikimate and phenylpropanoid pathways redirects carbon flow to different sink products in order to protect sessile plants from environmental stresses. This study assessed the biochemical responses of two Azolla species, A. filiculoides and A. pinnata, to the combined effects of environmental and nutritional stresses experienced while growing outdoors under Australian summer conditions. These stresses triggered a more than 2-fold increase in the production of total phenols and their representatives, anthocyanins (up to 18-fold), flavonoids (up to 4.7-fold), and condensed tannins (up to 2.7-fold), which led to intense red coloration of the leaves. These changes were also associated with an increase in the concentration of carbohydrates and a decrease in concentrations of lipids and total proteins. Changes in lipid biosynthesis did not cause significant changes in concentrations of palmitoleic acid (C16:0), linolenic acid (C18:3), and linoleic acid (C18:2), the fatty acid signatures of Azolla species. However, a reduction in protein production triggered changes in biosynthesis of alanine, arginine, leucine, tyrosine, threonine, valine, and methionine amino acids. Stress-triggered changes in key nutritional components, phenolics, lipids, proteins, and carbohydrates could have a significant impact on the nutritional value of both Azolla species, which are widely used as a sustainable food supplement for livestock, poultry, and fish industries.

Light and Temperature Shape the Phenylpropanoid Profile of Azolla filiculoides Fronds

“…The reddish color observed in A. filiculoides under high light intensity and low temperature conditions was attributed to the accumulation of anthocyanins. In contrast, Nham Tran et al ( 2020 ) documented a more than 2-fold increase in the production of total phenols, an 18-fold increase in the production of anthocyanins, and up to 2.7 fold increase in the production of condensed tannins in A. filiculoides plants grown outdoor and stressed by a combination of starving and direct exposure to high light intensity (5–10 Klux daytime) vs. shaded plants grown outdoor without starvation. Changes in the pigment and phenolic accumulation of A. filiculoides challenged with sodium dodecyl sulfate (SDS) or metals have also been described (Sánchez-Viveros et al, 2010 , 2011 ; Dai et al, 2012 ; Forni et al, 2012 ).…”

“…The occurrence of PAs in Azolla spp. has been documented for decades (Markham, 1988 ), with these stress-inducible compounds thought to be the most abundant soluble phenolics in both A. filiculoides and Azolla pinnata (Nham Tran et al, 2020 ). On this ground, both the spectrophotometric and LC-HRMS analyses documented higher levels of PA in the BG samples.…”

“…To the best of our knowledge, this avenue remains to be followed. Several studies have addressed the metabolic changes triggered by stresses in these species (Dai et al, 2012 ; Brouwer et al, 2017 ; Nham Tran et al, 2020 ; Güngör et al, 2021 ). However, information on how and to what extent environmental determinants affect the accumulation of secondary metabolites in ferns remain scanty and fragmented.…”

Technological and Sensory Aspects of Macaroni with Free or Encapsulated Azolla Fern Powder

“…It is also thought to be an excellent source of natural antioxidants [ 3 ]. The most abundant phenolic compounds identified in Azolla include anthocyanidins, Quercetin, coumarins, flavonols, flavones, and condensed tannins [ 4 , 5 , 6 , 7 , 8 ].…”

Valorization of green biomass Azolla pinnata fern: multi‐parameter evaluation of processing conditions on protein extractability and their influence on the physicochemical, structural, techno‐functional properties and protein quality

“…Also, it possesses several health benefits such as antioxidant, anti‐inflammatory and anti‐apoptotic activities 14 . Azolla pinnata , as an underexploited fern, has been identified as one of the most promising sustainable sources due to the high protein content (20–30%) and favourable amino acid profile 15,6 . Thus, it can be considered as a novel plant‐based protein for utilization as food ingredients for human consumption at a reasonable cost.…”