Belgian endive-derived biostimulant activity in Arabidopsis, lettuce, and sweet pepper at different developmental stages, environmental conditions, and application methods.

Belgian endive-derived biostimulant (BEE) has been previously shown to enhance root and shoot growth of Arabidopsis thaliana and Plectranthus esculentus in in vitro culturing conditions. In this study, we evaluated the effect of BEE on A. thaliana subjected to abiotic stresses and assessed the translatability of its bioactivity to lettuce (Lactuca sativa) and sweet pepper (Capsicum annuum) grown in substrate and soil. A first set of experiments tested the impact of BEE on protection during and on recovery after osmotic or salt (NaCl) stress. BEE treatment had little to no restorative effect when plants were exposed to osmotic stress. In contrast, BEE strongly promoted shoot development and leaf health under both standard and NaCl stress conditions. Under mild NaCl stress, BEE enhanced photosynthetic efficiency and chlorophyll content in Arabidopsis, whereas it did not significantly alleviate osmotic stress induced by sorbitol. To evaluate its effect under ex vitro conditions, BEE was applied via root drenching to substrate-grown A. thaliana, lettuce, and sweet pepper. BEE improved leaf greenness and photosynthesis, enhancing Arabidopsis rosette development, but did not increase lettuce head weight. In sweet pepper, BEE increased fruit yield and promoted fruit maturation. Under drought stress conditions, however, BEE application did not improve sweet pepper yield. These results indicate that in vitro BEE growth promotion is translatable to ex vitro cultivation system and its effect under stress conditions vary depending on the kind of stress. Additionally, BEE is consistent in improving photosynthesis parameters,fruit maturation and ripening.