Epibrassinolide application improves Brassica juncea L. performance by augmenting gas exchange markers, stomatal behavior, cellular viability, enzymatic activities and yield attributes

Abstract

Epibrassinolide (EBL) is an emerging plant growth regulator of the brassinosteroids group that has the potential to modulate various morpho-physiological processes in plants. Therefore, due to its key role in boosting plant functioning mechanisms, it is widely used in agriculture to enhance crop growth and yield. The present research work was planned to investigate the role of exogenously applied EBL on the mustard crop by assessing morphological, physiochemical, and yield features. This randomized pot experiment contains three mustard cultivars i.e., Rohini (Roh), Chutki (Chk), and Nath Sona (Nas) and various graded levels of EBL, 0 (Control), 10−8 M, 10−7 M, 10−6 M, 10−5 M, and 10−4 M. EBL was applied twice by giving first spray at 50 days after sowing (DAS) and the second at 70 DAS. Evaluation of plants was done at 90 DAS to study phenological traits, gas exchange attributes, non-enzymatic antioxidant activities, and microscopical parameters. The yield and quality features were studied at 120 DAS. The results revealed that treatment of 10−6 M EBL proved effective and increased fresh weight by 17.76 %, 19.11 %, and 19.34 %, chlorophyll content by 26.50 %, 26.59 %, and 25.86 %, net photosynthetic rate by 45.67 %, 57.88 % and 49.76 %, protein content by 66.98 %, 68.62 % and 69.47 %, proline content by 25.70 %, 24.05 % and 21.87 %, ascorbate content by 94.91 %, 89.99 % and 87.43 %, carbonic anhydrase activity by 32.43 %, 30.84 % and 29.93 %, seed yield by 44.85 %, 51.36 %, and 57 % and oil yield by 68.75 %, 72.71 % and 74.34 % in cultivars Nas, Roh, and Chk respectively over the control plants. Moreover, 10−6 M EBL supplementation significantly improved stomatal aperture width and root cell longevity. Cultivar Nas, followed by cultivars Roh and Chk, showed better responses on nearly all characters studied. The effect of EBL treatment in terms of enhancing the performance of the crop being in the order of 10−6 M > 10−7 M > 10−8 M > 10−5 M > 10−4 M. It may be concluded that among sprayed EBL levels, two sprays of 10−6 M EBL proved efficacious in improving the phenotypic, physiochemical, and yield traits of mustard cultivars.