The effect of 24- Epibrassinolid on germination and tube growth of in vitro Petunia hybrida L. pollen under cadmium stress

Cadmium is one of environmental pollutant heavy metals that is very toxic for plants. Pollen grains are more sensitive than vegetative parts of plant to cadmium. Brassinostroids are a group of effective hormones in ameliorative in various biotic and abiotic stresses in plants. To evalute the effect of 24- epibrassinolid on alleviation of cadmium stress on Petunia hybrida L., pollen germination and tube growth of plants were secreened in semi-solid medium on Petri-dishes. The experiment was laid out using split plot experiment based on a randomized complete block design with three replications. The main factors were two epibrasinid levels (0 and 0.05 mM) and six cadmium (CdCl2) concentration including 1, 10, 50, 100, 200 and 300 µM. It was observed that cadmium in concentrations more than 100 micromolar decreased germination and growth of pollen tube grains, while, Cd in 10 µM stimulated germination of pollens. 24- Epibrassinolid in higher concentrations than 50 µM of cadmium increased germination and growth of pollen grains, but in lower concentrations did not have any effect on pollen germination and tube growth. Concentration of 10 µM Cd increased pollen tube length in comparison with control. Based on the results, it can be concluded that 24-epibrassinolide did not increase pollen tube length in control and 10 µM Cd. However, in concentrations higher than 10 µM, hormone treatment increased growth of pollen tubes significantly.