24-epibrassinolide mediated regulation of endogenous contents of auxins, abscisic acid, lipids and sugars in Brassica juncea L. under copper stress

Brassinosteroids (BRs) role in increasing plant tolerance to various abiotic stresses has been a well established fact. In the present investigation, we evaluated the effect of seed pre-soaking treatment of 24- epibrassinolide (24-EpiBR) on the soil Cu(II) stress tolerance of 30-day old Brassica juncea L. plants. It increases the ability of plants to survive under stress conditions by modulating the endogenous content of various plant growth regulators and other biomolecules. We observed that the application of 24-EpiBR improved the shoot weight and root weight of the plants under Cu(II) stress. Improvement in the content of various parameters when Cu(II) was supplemented with 24-EpiBR such as sugars (glucose and sucrose); lipids (phospholipids, total sterols and esterified sterols) and plant growth regulators (abscisic acid and auxins), further proved the role of 24-EpiBR in stress amelioration. It reduced the cellular damage by reactive oxygen species (ROS) generated by Cu(II) as evident by the reduction in malondialdehyde (MDA) content with its application under Cu(II) stress. Our study has given a further insight into the functions of 24-EpiBR in increasing plant survival under heavy metal stress in a more elaborate way.