Mechanisms of Plant Growth Enhancement and Drought Tolerance Induced by Micro- Carbon™-Based Phosphorus (MCT-P)

Plant biostimulants comprise a diverse range of biologically active substances that influence plant growth and development through mechanisms independent of direct mineral nutrition. This study investigated the mode of action of a phosphorus-based biostimulant (MCT-P) and its effects under drought stress conditions. A series of standardized experiments were conducted using corn ( Zea mays ), lettuce ( Lactuca sativa ), and Arabidopsis thaliana . MCT-P was applied across a range of concentrations in two main assays: a one-week bioassay for root morphology analysis using WinRHIZO™, and a two-week bioassay to evaluate photobiological responses, root morphological and plant biomass parameters, mineral nutrition, and biochemical parameters under both normal and drought-stressed conditions. Optimal concentrations were determined to be 20 mL/L for corn and lettuce, and 10 mL/L for A. thaliana . MCT-P significantly altered root architecture and biomass accumulation, enhanced transient root acidification, and improved nutrient uptake. Additionally, it elevated levels of leaf sucrose and glucose, increased Brix values, stimulated root sugar exudation, and upregulated key growth-related genes such as TOR , H⁺-ATPase , and LAX3 . MCT-P also boosted photosynthetic pigment content, modified chlorophyll a fluorescence parameters, and promoted drought tolerance.