Effect of mechanical and chemical treatments on germination characteristic, total phenolic compound and enzyme activity of henna seeds (Lawsonia inermis L.)

Henna is one of the valuable ornamental and medicinal shrubs that is cultivated in some tropical and subtropical regions of Iran. Its seeds have dormancy and don't germinate rapidly. To investigate the effect of different mechanical and chemical treatments on dormancy and germination characteristics of henna seeds, two separate experiments were conductedbasedon two completely randomized designs with three replications. In the first experiment, various treatments including running water (for 24, 48 and 72 h.), soaking in hot water (90° C, for 150, 300 and 450 sec.), mechanical scarification with sandpaper (for 20 sec.), chemical scarification with concentrated sulfuric acid (98% for 10, 15 and 20 min.), different concentrations of gibberellic acid (GA3; 250, 500, 750 and 1000 ppm), osmopriming with polyethylene glycol (-8 bar for 72 h), complete darkness and control were tested for breaking seed dormancy. In the second experiment, the most effective treatments of the first experiment along with control were selected, and then α-amylase activity and the amount of total phenolic compounds (TPC) were evaluated in the seeds. Results revealed that seed germination percentage was significantly decreased when incubated in complete darkness. Among other treatments, soaking in running water for 48 h. was more effective and increased the germination percentage up to 94.7%. In the second experiment, results showed that there was a negative and significantcorrelation (r= -0/99) betweentotal phenolic compounds and α-amylase activity. According to the obtained results running water (48 h.) would be suggested as the most efficient treatment to break seed dormancy of Henna.