Effects of water stress levels and nitrogen fertilizer on quantitative and qualitative characteristics of Dragonhead (Dracocephalum moldavica L.)

Drought is one of the most important factor limiting plant growth around the world and the most common environmental stress which is limited produce approximately 25% of the world's land. Production of secondary metabolites in medicinal plants changes by environmental condition and also water stress is effective factor in growth and synthesis natural compounds in this plants.Nutrient management in drought stress condition and investigate interaction between them on plant characteristics dragon head due to lack of adequate information is very important.Therefore, the aim of this study was to investigate the use of nitrogen fertilizer in drought stress on qualitative and quantitative characteristics of dragonhead plant.
In order to determine the effects of drought stress and nitrogen fertilizer on some quantitative and qualitative traits of dragonhead a field experiment was conducted based on a randomized complete block design with three replications in Khoy Firuraq during 2013. The treatments were consisted of irrigation (unstressed (control) and with holding irrigation during stem elongation and early flowering stages) and nitrogen fertilizer (without nitrogen (control), 150, 225 and 300 kg N ha-1). In this study, Plant height, distance between the first flower and ground, the number of lateral branches, number of flowering branches, total dry wight, percentage of essential oil, essential oil yield and seed yield of dragonhead were measured.
The results showed that irigation treatment had significant effects on all traits (except of essential oil percentage) and nitrogen fertilizer application was significant on number of branches, total dry weight, esential oil and seed yield of dragonhead. Drought stress during stem elongation and flowering stages reduced all traites of dragonhead. Withholding irrigation at stem elongation stage produced the least (6.17 kg ha-1) essential oil yield. High levels of nitrogen fertilizer application had no significant effect on the measured characteristics of dragonhead. Application of 150 kg N per ha produced the most of the flower branches ( 17.11), total dry weight ( 2484.44 kg ha-1), percentage of essential oil (.039), essential oil yield (9.62 kg ha-1) and seed yield (1493.11 kg ha-1) of dragonhead.
Drought stress during stem elongation and flowering stage decrease of dragonhead qualitative and quantitative characteristics, and the use of high levels of nitrogen fertilizer had not a positive effect on quantitative and qualitative characteristics of dragonhead. In the total, full irrigation and application of 150 kg N ha-1 is recommended as a superior treatment to achieve maximum qualitative and qualitave yield of dragonhead.