Rapeseed plant: biostimulation effects of plant growth-promoting Actinobacteria on metabolites and antioxidant defense system under elevated CO₂ conditions

BACKGROUNDThe present study set out to evaluate the potential of plant growth-promoting Actinobacteria (PGPB) in improving some physiological and molecular parameters of rapeseed (Brassica napus L.) plants under ambient and elevated CO2 conditions by assessing some nitrogen- and sulfur-containing metabolites, antioxidant defense system and antimicrobial activity. With this aim, a pot experiment was conducted where the rapeseed plants were treated with Actinobacterium sp. strain NCO2 (OQ451136) and were grown under two levels of air CO2 concentrations: ambient CO2 (aCO(2), 410 & mu;mol CO2 mol(-1)); and elevated CO2 (eCO(2), 710 & mu;mol CO2 mol(-1)). RESULTSThere was an increase in the photosynthetic pigments (+35-80%) and photosynthesis rate (+20-34%) in PGPB-treated plants under eCO(2) compared to control plants, resulting in further growth and biomass production (+53-294%). These results were associated with an enhancement in the content of total antioxidant capacity (+15-128%), polyphenols (+21-126%) and & alpha;-tocopherols (+20-138%) under both eCO(2) and PGPB application (in combination or individual application), while only the combined treatment (eCO(2) + PGPB) led to a significantly higher accumulation of antioxidant enzymes (+88-197%), & beta;-tocopherols (+177%) and flavonoids (+155%). Moreover, nitrogen- and sulfur-containing metabolites (glucosinolates and amino acids) were improved by PGPB treatment and/or CO2 levels, in which PGPB increased the amino acid-derived glucosinolate induction by eCO(2) with low levels of effective sulforaphane. CONCLUSIONSTherefore, the interaction effects of beneficial Actinobacteria and eCO(2) are expected to boost the level of antioxidant molecules and to have a helpful role in improving plant biomass and adaptability to complicated climate changes in the future. & COPY; 2023 Society of Chemical Industry.