SEED PRE-CONDITIONING WITH AMBIOL^®, A DERIVATIVE OF 5-HYDROXYBENZIMIDAZOLE, ACCLIMATES TOMATO (LYCOPERSICON ESCULENTUM MILL.) SEEDLINGS TO DROUGHT

Water deficit in the root zone leads to oxidative stress through generation of free radicals, which lead to several physiological and metabolic perturbations. As a result, drought results in decreased plant growth, crop yield, and fruit quality. This study verified the hypothesis that seed preconditioning using a synthetic antioxidant, Ambiol, a derivative of 5-hydroxybenzimidazole, protects plants exposed to drought and promotes drought tolerance. The experiment consisted of 2 factors, Ambiol pre¬conditioning (0, 0.1, 1.0, and 10 mg/L) and water stress (stressed and unstressed) with 5 replications in each treatment combination. Plants were grown in a controlled environment growth chamber (25/10°C, 16 h photoperiod) and watered to field capacity each day for 14 d. Water stress was imposed by withholding water for 7 d on the 15th day after seedling emergence. Drought significantly decreased dry mass by 46%, photosynthesis by 95%, transpiration by 98%, and leaf area by 50% compared to the unstressed control. However, the 10 mg/L Ambiol preconditioning treatment was the most effective for conferring protection and promoting drought tolerance by significantly enhancing dry matter production by 26%, leaf area by 54%, and a 4-fold increase in photosynthesis in plants under drought. Ambiol promoted drought tolerance and sustained plant growth by increasing water use efficiency potentially modifying root architecture, thus sustaining hydraulic conductivity and root function, facilitating leaf expansion.