The effect of humi-forthi and L-arginine amino acid on growth, physiological and ‎biochemical characteristics of Marigold (Tagetes erecta) under drought stress

In order to investigate effect of humi-forthi biostimulator and L-arginine amino acid on growth, physiological and biochemical characteristics of marigold (Tagetes erecta) under drought stress, a factorial experiment based on a completely randomized design with three replications was carried out. The first factor was humi-forthi at three levels (0, 2.5 and 5 mg/l), the second factor was L-arginine at three levels (0, 1.5 and 3 mM), and the thirs factor was drought stress at three levels (100%, 70%, and 40% FC). Traits including the number of flowers, flower diameter, total chlorophyll content, SOD enzyme activities, andNPK concentrations were measured. The results indicated that drought stress, especially 40% FC, significantly influenced all morpho-physiological traits of marigold. There was observed a reduction flower diameter and number, chlorophyll content, and NPK under drought stress, whereas an increase was recorded for SOD activity and carotenoid. In most traits, 5 mg/l humi-forthi was more effective in respect to 2.5 mg/l and control. In addition, 3 mM L-arginine significantly had greater impact in respect to control and 1.5 mM. The interaction of humi-forthi, L-arginine and drought stress was significant on total chlorophyll, SOD activity, P and K (P≤0.05). The treatment of 5 mg/l humi-forthi + 3 mM L-arginine is the most effective treatment for alleviating the adverse effect of drought stress particularly 40 % FC.