Growth parameters and essential oil percentage changes of dill (Anethum graveolens) as affected by drought stress and use of 28- homobrassinolide

Brassinostroids are group of plant hormones that have significant biological effects on plant growth and development including increase in plant tolerance to environmental stresses. In this study the effects of 28 - Homobrassinolide on growth parameters, yield and essential oil percentage in the dill (Anethum graveolens) under drought stress, were studied in greenhouse of arsanjan training and vocational teaching organization. Factorial experiment in randomized complete block design with four replications and 12 treatments were used. Total number of test pots 12 × 4 = 48 was the number. Treatments randomly were placed in each pot. The first treatment included drought factor (S) in three irrigation levels based on values of field capacity (FC), mild stress (LS-2 / 3 field capacity) and high stress (HS-1 / 3 field capacity) and the second treatment, included steroid hormone factor that 28 - Homobrassinolide four levels, control (zero), M 10-10, M -810 and M 10-6 in solution, before drought treatments were applied. The plants in pots containing clay loam soils planted. Young plants in 4 to 5 leaf stage with a solution of 10-8 M 28 Homobrassinolide containing 20 had been sprayed. After establishing plants in stage six branches drought stress treatments were applied. Results showed that different levels of drought stress reduced shoot and root dry weight, plant height and Essential oil yield but percentage of Essential oil significantly increased. Use of 28- Homobrassinolid improved, dry weight root and shoot, Essential oil yield and percentage of Essential oil under mild stress and high stress condition treatment.As a result, plants treating with Article 28 - Homobrassinolid percent significantly increased oil yield and the damage caused by the deficit irrigation stress reduced.