Evaluating the role of some selected herbal extracts as biostimulant for mitigating drought and heat stress in wheat crop

Emerging incidence of drought and heat stress are the major constrains for wheat production. Identifying natural and sustainable methods of crop protection are required to deal global climate change and environmental degradation. In view of our objective, the aim of the present study was designed to test four herbal plant extracts; Phyllanthus emblica , Plumbago zeylanica , Bacopa monnieri and Curcuma longa , as biostimulant to improve drought and heat stress tolerance in wheat crop. The effects of these extracts were assessed through morphological and biochemical parameters. The results indicated an increase in the tested parameters by all the herbal treatments, with P. emblica being the most effective one, causing around 1.4–2.4 fold increase in plant length, leaf biomass and seed biomass, whereas 2.0-2.6 fold increase in pigments, total phenolics, flavonoid, antioxidant activity and enzyme activity. Morphology-based stress tolerance index (STI) of 1.28–0.83 for the treatment as compared to 0.48–0.65 of control revealed significantly higher maintenance of growth and biomass in biostimulant treated plants. Composite performance index (CPI), integrating physiological and biochemical traits, demonstrated a coordinated enhancement of antioxidant defense and metabolic stability with values of 0.89 and 0.82 for treated plants as compared to 0.42 − 0.37 of control. Heat map visualization and principal component analysis (PCA) further confirmed clear discrimination between control and treated samples, identifying the role of herbal extract in stress resilience. We performed UHPLC-HRMS analysis to identify possible biostimulant in the natural extracts. A range of phytohormones involved in stress tolerance, such as salicylic acid, auxins and gibberellic acid were detected in the sample indicating their role in stress mitigation. The outcome of the research work will help in developing natural and sustainable methods of crop protection and will promote the usage of herbal biostimulant in crop fields.