Document Type : Full Paper
                            
                        
                                                    Authors
                            
                                                            
                                                                            1
                                                                        M.Sc. Student, Faculty of Agricultural Sciences and Food Industry, Islamic Azad University, Science and Research Branch, Tehran, Iran                                
                                                            
                                                                            2
                                                                        Assistant Professor, Faculty of Agricultural Sciences and Food Industry, Islamic Azad University, Science and Research Branch, Tehran, Iran                                
                                                            
                                                                            3
                                                                        Assistant Professor, Faculty of Agriculture, Payame Noor university, Tehran, Iran                                
                                                            
                                                                            4
                                                                        Professor, Department of Horticulture, College of Agriculture & Natural Resources, University of Tehran, Karaj, Iran                                
                            
                                                                            
                        
                        
                            Abstract
                            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.  
                        
                        
                        
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