Evaluation of 24-Epi-brassinosteroid effects on some properties of fenugreek (Trigonella foenum-graecum L.) under high temperature stress

The aim of this study was to investigate the effect of 24-epi-brassinosteroid on some of the physiological properties of fenugreek under high temperature stress. The treatments consisted of 24-epi-brassinosteroid (2, 5 and 10 ppm), different harvest times (6 and 24 h) and high temperature stress (42° C). Results showed that high temperature stress reduced chlorophyll a, b and total chlorophyll and carotenoid contents and increased malondialdehyde content and electrolyte leakage.  24-epi-brassinosteroid treatment during stress significantly prevented carotenoid, chlorophyll a,  b and total chlorophyll contents to be deceased.  Applying different levels of 24-epi-brassinosteroid (2 and 5 ppm) at high temperatures decreased malondialdehyde and increased fenugreek tolerance, due to the reduced non-fatty acid peroxidation. The activity of catalase, guaiacol peroxidase and ascorbate peroxidase enzymes enhanced in stress condition and application of 2 and 5 ppm 24-epi-brassinosteroid resulted in further increase of these enzymes activity. The application of 24-epi-brassinosteroid resulted in increased defense gene activity and enhanced content of antioxidant enzymes including ascorbate peroxidase, catalase and guaiacol peroxidase by stimulating the plant defense system. Overall, the results of this study showed that 24-epi-brassinosteroid stimulates the activity of genes involved in either photosynthesis or the antioxidant defense system of fenugreek, and fenugreek tolerance to high temperature stress increased, by reducing oxidative stress.