Impact of High Light Intensity and Low Temperature on the Growth and Phenylpropanoid Profile of Azolla filiculoides .

Exposure to high light intensity (HL) and cold treatment (CT) induces reddish pigmentation in , an aquatic fern. Nevertheless, how these conditions, alone or in combination, influence growth and pigment synthesis remains to be fully elucidated. Likewise, the regulatory network underpinning the accumulation of flavonoids in ferns is still unclear. Here, we grew under HL and/or CT conditions for 20 days and evaluated the biomass doubling time, relative growth rate, photosynthetic and non-photosynthetic pigment contents, and photosynthetic efficiency by chlorophyll fluorescence measurements. Furthermore, from the genome, we mined the homologs of , , and genes, which form the MBW flavonoid regulatory complex in higher plants, to investigate their expression by qRT-PCR. We report that optimizes photosynthesis at lower light intensities, regardless of the temperature. In addition, we show that CT does not severely hamper growth, although it causes the onset of photoinhibition. Coupling CT with HL stimulates the accumulation of flavonoids, which likely prevents irreversible photoinhibition-induced damage. Although our data do not support the formation of MBW complexes, we identified candidate and regulators of flavonoids. Overall, the present findings are of fundamental and pragmatic relevance to 's biology.