Abstract

Brassinosteroids are a group of plant hormones that have significant biological effects on plant growth and development. The effects of 28-homobrassinolide (HBR) on growth, photosynthesis, chlorophyll content, carbohydrate fractions and essential oil content of savory herbs (Satureja khuzestanica Jamzad) were investigated. Foliar application of 28-homobrassinolide at 10^-10, 10^-8and 10^-6 M concentrations substantially increased growth. 28-homobrassinolide at 10^-6 M concentrations improved herbage yield as reflected in the increase of foliar biomass. Exogenous application of 28-homobrassinolide increased the rate of photosynthesis. Growth promotion was also associated with increased chlorophyll content and resulted in the accumulation of carbohydrate fractions. At 10^-6 and 10^-8 M concentrations, 28-homobrassinolide also incremented the total content of essential oils. The quantitative analysis of savory oil from the savory plant treated with 10^-6 M concentration revealed an increase in carvacrol and para-cymene contents and a decrease in the γ-terpinene content. Collectively, the present study demonstrates a positive impact of the new group of phytohormones on the agronomic performance of savory plant, a highly valued aromatic plant.

Key words: Satureja khuzestanica, 28-homobrassinolide, growth, photosynthesis, essential oil, carbohydrates, chlorophylls, savory.

Abbreviation

HBR, 28-Homobrassinolide; EBL, 24-epibrassinolide; BRs, brassinoesteroids.