Interaction of late season drought stress and foliar application of osmolytes on the yield and yield components of German chamomile (Chamomilla recutita L.)

In order to evaluate the effects of foliar application of osmolytes on the quantitative and qualitative yield of German chamomile (Chamomilla recutita L.) in drought stress conditions, a split-plot experiment was conducted based on randomized complete block design with three replications at Research Center of Medicinal Plants, Shahed University. The treatments included irrigation as the main factor in three levels [(irrigation after 50 (without stress), 100 (moderate stress) and 150 mm evaporation from the class A pan (severe stress)] and foliar application of osmolytes as sub-plots in seven levels [(without Spraying (NS), distilled water (W), methyl jasmonate (MJ= 75mM), salicylic acid (SA= 2mM), humic acid (HA= 2.5lit/1000), glycine betaine (GB= 5mM), and g- aminobutyric acid (GABA= 50mM). The electrical conductivity of the irrigation water was 4.8 dS/m. Mean comparisons showed that GABA combined with severe stress had the highest essential oil yield (3.7 kg ha-1). In plants treated with GABA under severe stress, essential oil harvest index was increased by 60 and 58%, respectively, compared to W and NS treatments. The highest and lowest capitol harvest index with 70.81% and 23.28% were respectively obtained from GB combined without stress and W with severe stress. SA, GB, and GABA increased the capitol yield in severe stress compared with the moderate stress. Severe stress caused a significant increase in essential oil content from 0.66 to 1.13%, a 35% reduction in seed harvest index compared to control treatment, and a significant reduction in biomass yield rather than moderate stress. MJ and SA increased seed yield compared with NS in moderate stress.