Using of microbial fertilizer as biostimulant alleviates damage from drought stress in guar (Cyamopsis tetragonoloba (L.) Taub.) seedlings

Drought is a significant environmental stress that limits plant growth and yield. In this study, an investigation of guar, grown under different drought level conditions [(S0: 100% of field capacity), S1 (depletion of 75% the available water holding capacity), S2 (depletion of 50% the available water holding capacity), S3 (depletion of 25% the available water holding capacity), S4 (no applied irrigation water)] with regards to the impact of Chlorella vulgaris based microbial fertilizer on physiological, morphological, and enzymatic activity was performed. Microbial fertilizer applications significantly increased shoot length, fresh and dry weight of the shoot and root, and leaf number and area of guar plants compared to the only drought stress treatments. In addition, following the above-mentioned procedures, there were significant increases in the relative water content, total phenolic and flavonoid contents, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutation reductase (GR) activity. However, the malondialdehyde (MDA) content were significantly decreased. Hence, the results support the administration of a foliar application to the microbial fertilizer containing microalgae in order to increase the guar plant’s defense system, enabling it to tolerate the negative effects resulting from drought stress.