Mitigation of Heat Stress Effects on Chamomile and its Essential Oil Using Melatonin or Gibberellic Acid and some Agricultural Treatments.

Temperature change risk in horticultural crops includes modified phonology (timing) of leafing, flowering, and harvest. The yield of essential oil of chamomile depends on some factors such as the plant region's environmental conditions. Therefore, this study was carried out during two successive growing seasons on chamomile plants grown under either region; northern Egypt and East of Cairo to reduce the impact of heat stress on growth, oil yield and its components which, the seedlings had been cultivated at half of October and the half of November and sprayed with either gibberellin or melatonin. We observed that spraying melatonin or gibberellins improved growth characteristics compared to control. There was a clear superiority, there was a clear superiority of melatonin on chamomile plants grown under Nubaria which improved most of the previous characteristics. Chamomile seedling can be grown from mid-October to mid-November, so it can be harvested in March before the heat rises and maintains the resulting oil quality maintains the resulting oil quality. The main component of Chamomile oil is (Bisabolol oxide A) and was higher under the conditions of Nubaria when seedling was treated with gibberellin followed in the lowest order by treatment with melatonin, but it was the opposite under the conditions of Sekam region. The second component was (Bisabolol oxide B).