Plants were treated with eight different brassinosteroids (24-epibrassinolide; 24- epicastasterone; 4154 compound and five androstane and pregnane analogues of brassinosteroids marked KR1, KR2, KR3, KR4 and KR5) in 49-59 DC (growth phase referred to a decimal code for the growth stages of cereals — from visible awns to complete inflorescence emergence) (Zadoks et al., 1974). All brassinosteroids were applied in the form of 1 nmol L-1 of efficient compound in the water solution by spraying on all aerial biomass. Each of the tested brassinosterids was applied in four parallel replicates (4 x 10 m2 field plots). Untreated plants were cultivated as well in tetraplicates as the control variant. Applied brassinosteroids (Fig. 1) were synthesized by the Institute of Organic Chemistry and Biochemistry of the Academy of Sciences of the Czech Republic. 24-epibrassinolide (24- epiBL) and 24-epicastasterone (24-epiCS) are naturally occurring plant phytohormones, compound 4154 is a synthetic brassinosteroid registered in the Czech Republic (Registration Nr. 294343, conferred on 4 Oct 2004) and the EU (Nr. 1401278, conferred on 28 Sep. 2005). Compounds KR1 — KR5 are synthetic permanently studied brassinolide analogues, which do not occur naturally in plants and will be published after finishing the synthesis of similar structures and protecting of these compounds by a patent (Vlasankova et al., 2009).

In pot experiment plants were treated with three brassinosteroids (24-epibrassinolide, 24- epicasterone, and 4154) in two different growth stages in four parallel replicates in each brassinosteroid. Plants or experimental pots were divided before the application of brassinosteroids into four groups that differed with growth stage in the date of treatment and number of brassinosteroids applications (Table 3).