Modulation of jasmonic acid and polyamines by 24-epibrassinolide in Brassica juncea L. under copper stress

It has been widely reported in literature that brassinosteroids play a pivotal role in stress mitigation in plants. The present study was undertaken to assess the effect of 24-epibrasssinolide (24-EpiBR) on the growth, endogenous levels of total sugars, reducing sugars and plant growth regulators (PGRs) such as jasmonic acid and polyamines (PAs) like spermine, spermidine, putrescine and cadaverine in 30-day old Brassica juncea L. plants raised from seeds pre-soaked with the hormone and grown in soils amended with 0, 0.25, 0.50 and 0.75 mM concentrations of Cu(II). The shoot and root lengths of the plants grown in Cu(II) amended soils improved on seed pre-soaking with 24-EpiBR. The elevated levels of jasmonic acid which had a negative influence on the growth of plants under Cu(II) stress were brought to normal values by 24-EpiBR treatment. 24-EpiBR showed a positive effect on the endogenous levels of total sugars, reducing sugars and PAs under Cu(II) stress. Sugars help in the maintenance of osmoregulation and PAs serve as antioxidants. Thus, our results confirm the hypothesis that the exogenous application of 24-EpiBR makes the plants more capable to survive under Cu(II) stress.