The roselle (Hibiscus sabdariffa L., Malvaceae) is one of the most widely used medicinal plants due to its economic importance and high bioactive compounds. In the present study, the effects of two exogenous plant growth regulators (PGRs), [gibberellic acid (GA3) and Indole-3-scetic acid (IAA) at 400, 800 and 1200 mg L1], along with chitosan-based nanofiber (CNF, at 50, 100 and 200 mg L1) were investigated, individually and in combination, on plant height, calyx fresh and dry weights, number of flowers, total chlorophyll and ß-carotene, soluble sugar, anthocyanin, vitamin C, total polyphenols and flavonoids as well as antioxidant capacity in roselle plants. According to the results, a synergistic effect was observed between employed PGRs. Of interest, CNF was observed inside the calyxes using scanning electron microscopy (SEM) technique. Because of its unique physio-chemical properties, CNF further influenced the PGRs function on most of the traits evaluated. It was found that the combined use of IAA and GA3 could improve plant height, number of calyxes per plant, total chlorophyll, b-carotene, flavonoids and antioxidant activity in roselle. Furthermore, the results clearly demonstrated that PGRs in combination with CNF have a significant impact on various growth parameters in roselle plant. The present results suggest that the use of combined IAA+GA3+CNF (at 800 + 800 + 100 mg L1) stimulate both growth parameters and health-promoting phytochemicals content in roselle plants.
