Effects of Brassinosteroid Application on Seed Germination of Scots Pine under Standard and Heat Stress Conditions

We assessed the effect of brassinosteroid 2 alpha, 3 alpha, 17 beta-trihydroxy-5 alpha-androstan-6-one on seed germination of Pinus sylvestris L. Brassinosteroids are phytohormones that play a key role in plant growth and affect a substantial part of their physiological processes. A total of 6,400 seeds were used in the experiment, divided into 8 groups based on a combination of temperature stress and concentration of the applied brassinosteroid solution in which the samples were soaked before testing. The four brassinosteroid treatments in order of their concentrations were as follows: control (0 mg/l), low (0.004 mg/l), medium (0.04 mg/l) and high (0.4 mg/l), combined with either stress temperature regime, where the seeds were temporarily exposed to high temperature up to 39 degrees C, or normal temperature regime without any heat stress. Germination capacity and the length of radicles were evaluated weekly. The results showed a positive effect on seed germination under standard regime for low brassinosteroid concentration (0.004 mg/l), while no significant effect was recorded for seeds treated with medium (0.04 mg/l) and high (0.4 mg/l) brassinosteroid concentration The application of convenient brassinosteroid concentrations reduced the negative impact of heat stress and improved the germination ratio of seeds that were not heat-stressed.