Effects of some growth hormones on plant vigour and volatile oil of Origanum majorana L.

Origanum majorana L. treated with either 50 or 100 mg/l of maleic hydrazide (MH), 2.4-dichlorophenoxy acetic acid (2.4-D), N-dimethylaminosuccinamic acid (B995), [2-chloroethyl]-trimethyl ammonium chloride (CCC), indol-3-yl-acetic acid (IAA) or gibberellic acid (GA3) in the presence or absence of 25 mg/l kinetin, showed that only 100 mg/l GA3 with or without kinetin was able to increase plant height than all other treatments and the controls. On the other hand, both IAA and GA3 concentrations and 2000 mg/l CCC markedly increased the dry weight of the plants in the absence of kinetin, whereas when kinetin was combined, only IAA in both concentrations increased the dry weight of the whole plants. Concerning essential oil %, the highest yields were obtained using 100 mg/l MH, 50 mg/l 2.4-D and 2000 mg/l CCC for leaves and 100 mg/l MH, 1000 mg/l B995 and 50 mg/l 2.4-D for flowers in the absence of kinetin, whereas in the presence of kinetin, the higher yields of essential oil were obtained by using 1000 mg/l B995 and 25 mg/l 2.4-D for flowers and only 50 mg/l 2.4-D for leaves.