Ecklonia maxima-derivate seaweed extract supply as mitigation strategy to alleviate drought stress in chicory plants

Extreme climatic conditions have a severe repercussion on agriculture and on food availability. Ecological means to overcome drought are important to improve agroecosystems sustainability and resilience. The use of an Ecklonia maxima-derivate seaweed extract (SwE) as a tool to mitigate drought constrain in chicory plants grown in greenhouse was evaluated. Plants were cultivated in plastic pots filled with peat and subjected to drought stress by retaining moisture range at 90-100% of water holding capacity (WHC) [well-watered (WW)], 60-70% WHC [moderate drought stress (MDS)] or 30-40% WHC [severe drought stress (SDS)]. Drought stress decreased plant growth traits and yield. However, in plants supplied with SwE, head fresh mass was 7.6% higher than control. Water constrain reduced relative water content (RWC), whereas, SwE improved RWC when plants were exposed to drought. Moreover, water use efficiency (WUE) increased as drought intensity increased and plants exposed to drought significantly improved WUE when supplied with SwE. Drought stress intensity linearly reduced nitrogen use efficiency (NUE) in plants exposed to MDS and SDS, compared with WW plants. SwE application enhanced NUE by 7.7% compared with control plants. Exposing chicory plants to drought stress resulted in a significantly higher N and Mg concentration compared to WW plants. Conversely, drought reduced P and K in leaf tissues. SwE supply increased P, K, Ca and Mg content, whereas reduced N. Chlorophyll was reduced by drought, while SwE supply increased its concentration. Sugars increased as drought stress intensity increased. Water constrain enhanced malondialdehyde, especially in SwE non-treated plants. Drought stress improved proline and total polyphenols in plants supplied with SwE. Biostimulated plants grown under WW or MDS conditions showed higher ascorbic acid level than those exposed to SDS and non-biostimulated. The study proved that SwE application is a useful practice to mitigate drought in chicory plants, safeguarding yield and quality features.