Mohammad Modarresi

The objective of this study was to investigate the effect of exogenous application of salicylic acid concentrations on the physiological and biochemical traits and essential oil content of chamomile under normal and heat stress conditions as induced by delayed sowing. The experiments were conducted during 2011–2012 as a factorial using a randomized complete block design with three replications, in a very hot region. The factors included ?ve salicylic acid concentrations (0 (control), 1, 10, 25 and 100 mg¨L´1) and three chamomile cultivars (Bushehr, Bona, Bodegold). The seeds of chamomile were sown on two different sowing dates including an optimum planting date and a late planting date. The physiological traits (plant height, capitol diameter, 1000 grain weight, fresh and dried ?ower weight), total chlorophyll, proline and essential oil content were investigated. Analysis of variance showed that the effect of the environmental conditions (normal and heat stress) was signi?cant on all physiological and biochemical traits with the exception of the essential oil content. The heat stress decreased physiological traits and total chlorophyll in comparison with the normal conditions but it had no signi?cant effect on the essential oil content. Findings indicated that the application of exogenous salicylic acid improves essential oil content in chamomile cultivars under environmental heat stress conditions.