Evaluation of flower yield and some quantitative and qualitative traits of chamomile (Matricaria chamomilla L.) in response to potassium fertilizer under drought stress

The production and processing of medicinal plants is increasing day by day due to less side effects. The quality and quantity of medicinal plants are particularly affected by genetics, environmental factors and their interaction. Among natural limiting factors, water shortage is the most important factor that, especially in arid and semi-arid regions of the world, in various ways causes the restriction of planting and reduces the production of crops and medicinal plants. On the other hand, nutrients such as potassium can play an important role in plant resistance to environmental stresses. Therefore, this experiment was performed to investigate the effects of drought stress and potassium fertilizer on quantitative and qualitative characteristics and yield of German chamomile.

In order to investigate the effect of drought stress and different levels of potassium fertilizer on quantitative and qualitative characteristics of chamomile, a split plot experiment was conducted in a randomized complete block design with three replications in the Field of University Research Zabol. The treatments included drought stress in three levels, control (90% Field Capacity= FC), medium stress (70% FC), severe stress (50% FC) as the main factor and different levels of potassium sulfate fertilizer in four levels, non-consumption Potassium fertilizer (control), 50, 100 and 150 kg of potassium sulfate per hectare were considered as a sub-factor. The studied traits were as follows: plant height, number of stems, plant dry weight, number of flowers per plant, yield of dried flowers, essential oil content, potassium percentage, carbohydrate content, total chlorophyll, carotenoids and proline. Data analysis of variance was performed using SAS software and version 9.1. The mean of treatments was compared using Duncan's multiple range test at 5% level of probability.Results

The results showed that the effect of drought stress and potassium fertilizer on stem number, plant dry weight, number of flowers, carbohydrate and carotenoid content was significant. With increasing drought stress intensity to 50% FC, the number of stems and number of flowers per plant decreased by 36.08% and 39.57%, respectively, but with increasing drought stress intensity, the amount of carotenoids was 1.6 times that of non-stress treatment and the amount of carbohydrates 31.12% increase compared to non-stress treatment. The results showed that with increasing the amount of potassium fertilizer from 50 to 150 kg.ha-1, the number of stems and the concentration of carotenoids were 1.62 and 1.44 times, respectively, and the number of chamomile flowers per plant and the amount of carbohydrates were 30.52 and 41.20. Percentages increased. The results showed that plant height, dried flower yield, essential oil content, potassium percentage and proline were significantly affected by the interaction of drought stress and potassium fertilizer levels. With increasing stress intensity in all fertilizer treatments, a decrease in dried flower yield and an increase in proline content were observed. Application of potassium fertilizer had a significant positive effect on these traits under stress conditions so that by increasing the amount of potassium fertilizer from zero to 150 kg.ha-1 in severe drought stress plant height, dry flower yield, potassium and leaf proline, respectively. 2, 1.59, 2.64 and 1.95 times were control and the percentage of essential oil increased by 0.32%.

In general, it seems application of potassium within increase flower yield, can improve quantitative and qualitative traits of plant undser of drought stress, and decreased damages of drought stress