Variation in yield and biochemical factors of German chamomile (Matricaria recutita L.) under foliar application of osmolytes and drought stress conditions

Chamomile is one of the oldest and most valuable medicinal plants from the Asteraceae family. In addition to pharmaceutical uses, its essential oil is extensively used in perfumery, cosmetics, food industry and aromatherapy. This experiment was conducted with the aim of investigating the effect of osmolytes foliar application on biochemical characteristics, and the yield of German chamomile under drought stress conditions. The experiment was conducted as a split plot with randomized complete block design with three replications during the 2016-2017 growing season. Three levels of irrigation, 50 (control), 100 (mild stress) and 150 mm (severe stress) evaporation from evaporation pan class A, and spraying treatments, NS (no-spraying), W (distilled water), MeJA (methyl jasmonate), SA (salicylic acid), HA (humic acid), GB (glycine betaine) and GABA (γ-aminobutyric acid) were considered as the main plots and sub-plots, respectively. Analyzed data indicated that proline, total soluble sugars (TSS), and essential oil yield were enhanced with the increase of drought intensity and the maximum amount was registered under severe stress, while the severe drought caused a substantial reduction in protein concentration of leaves and dried flower yield. Proline concentration of leaves significantly increased with exogenously applied spraying treatments under severe drought. All spraying treatments except GB under severe stress, caused higher TSS concentration than those subjected to mild stress. SA, HA, and GABA treated plants had significantly higher protein concentration compared to NS treatment. Plants that treated with GABA had the highest dried flower and essential oil yield. The present study suggests that osmolytes foliar application can ameliorate the detrimental effects of drought on chamomile plant through alteration in yield and biochemical variables.