S04 - Session P1 - New Tools I - Evaluating the potential of different agents in alleviating drought stress induced by polyethylene glycol in Thymus lotocephalus in vitro cultures

Authors: Inês Mansinhos *, Sandra Gonçalves, Anabela Romano

The Mediterranean region is one of the regions in the world that will be strongly affected by climate change, especially by droughts. The present study was conducted to investigate the potential of salicylic acid (SA), methyl jasmonate (MJ) and iron oxide nanoparticles (Fe 3 O 4 ) in alleviating drought stress induced by 2, 5 and 7% polyethylene glycol (PEG 6000) in in vitro cultures of T hymus lotocephalus Lopez and Morales. This is a Mediterranean aromatic plant endemic to the Algarve region (southern Portugal) that produces bioactive compounds. Exposure of the cultures to a 7-week drought stress caused oxidative stress in a PEG dose-dependent manner, increasing H2O2 levels and decreasing shoot growth, photosynthetic pigments and accumulation of secondary metabolites. Among the tested mitigants, MJ was effective in protecting photosynthetic pigments and cells from oxidative damage and increasing the accumulation of phenolic compounds and the antioxidant activity of the extracts. MJ also induced the accumulation of proline, an important osmoprotectant that can stabilise cell membranes and scavenge reactive oxygen species. The results obtained demonstrated the important role of MJ as a signalling molecule in reducing the adverse effects of drought stress on T. lotocephalus under in vitro conditions. Moreover, the three tested agents induced a significant accumulation of phenols, indicating a great potential as elicitors.