Effect of sowing season on growth and oil chemical composition of ajowain (Carum capticom L.) under salinity stress

Saline lands can be utilized by planting native medicinal plants tolerant to salinity. The quantity and quality these plants are changed during various seasons in agriculture systems. Thus, this study carried out under salinity stress in order to examine the effect of sowing in two seasons on growth characteristics and essential oil  components of ajowan (Carum capticum L.), Different salinity treatments (EC= 0.3, 4, 8 and 12 dS/m) were used before flowering stage of ajowan in pot experimental at Khorasgan (Isfahan), Iran. Growth characteristics were measured and, the essential oil analyzed by GC/MS apparatus. Results showed that increasing salinity caused decrease plant height in spring planting and increase in number of branching in summer planting. The amounts of plant height, number of umbel, number of flower in main umbel and number of floret in main umbel in summer sowing was higher than spring sowing. Interaction effects of salinity and sowing season on growth characteristics showed that the highest plant height was obtained from summer sowing under salinity 4 dS/m treatment and the lowest amount of plant height obtained from spring sowing under salinity 12 dS/m treatment. In spring and summer sowing, ten and thirteen components were identified in the essential oil of C. capticum, respectively. The major compounds in the essential oil of C. capticum were of thymol and γ-terpinene. According to results of this study, It seems that sowing of C. capticum under saline soils (~EC=12 dS/m) for metabolic agronomy (especially thymol) in spring sowing could be is suitable.