Physiological and biochemical changes in response to Moringa oleifera biostimulant in petunia plants under water deficit

The present paper aimed to evaluate the effects of LME (Moringa oleifera leaf extract) in modifying growth, ornamental value and several physiological and chemical parameters of petunia (Petunia hybrida E.Vilm.) ‘GO!Tunia® Neon Pink’. Three level of water deficit were considered: control (100% of WCC, Water Container Capacity = 100% CC), 60% and 40% of WCC; for each level treatments with LME were also considered. Water deficit reduced growth parameters compared with full irrigation and LME application promoted almost all the growth parameters in both control and stressed conditions. The behavior in growth parameters is correlated with a decrease in photosynthesis activity and plant water status. Deficit irrigation reduced the Relative Water Content (RWC) without differences linked to LME application. The chlorophyll content was unchanged for effect of water deficit and enhanced by LME treatment. The capacity to accumulate protective compounds (Proline, MDA) allowed plant to reduce the negative effects of water stress; LME treatment is not always able to increase these compounds in more stressed plants. LME application increased GPX and SOD activities in plants grown under drought stress, and this facilitated the ROS scavenging and maintenance of plant growth under stress. Total phenol compounds (TPC) showed significant differences in relation to the water deficit treatments, but not to biostimulants; the interaction effect was significant. Total soluble sugars in the leaf tissues were significantly affected only by deficit irrigation treatments. Drought stress also affected the production of endogenous level of hormones and amino acid. The highest content for almost all free amino acids was observed in the most stressed treatment (40% CC and 40% CC + LME). The response of petunia plants to water deficit was related to its ability to decrease aerial growth and to modify leaf gas exchange, increasing secondary osmolytes and enzyme activity to contrast the ROS activity.