Influence of day length and leaf insertion on the composition of marjoram essential oil

The influence of the photoperiod on the growth and quality of marjoram, Origanum majorana L., showed it to be a long‐day plant, as upright growth and flower formation were observed only at a day length of at least 13 h. The day length also influenced the composition of the essential oil; cis‐sabinene hydrate, the main component, was produced in larger quantities in plants grown under 16 h light conditions than in those grown with a day length of 13 h and 10 h, whereas the content of terpinenes decreased with increasing day length. Regarding the leaf position, lower (older) leaves contained an essential oil with a relatively higher terpinene concentration.