Unlike the common plants, micropropagation of Hymenocrater longiforus Benth. (Sura-halala) under in vitro conditions has neither been accurately set nor commercialized thus far. Similarly, there is no study available to address the impacts of phytohormones on this plant; therefore, this study was conducted to appraise the efects of salicylic acid (SA) at three levels (0, 0.5, and 1 mM) and simvastatin (SV) at four levels (0, 5, 10, and 20 μM) on the morpho-physiological and biochemical features of Sura-halala under in vitro propagation. Accordingly, SA application increased shoot and root length, shoot and root dry weight, total soluble protein, total soluble carbohydrate, and photosynthetic pigment contents. The results indicated that 0.5 mM application of SA resulted in the highest means of these traits, under almost all SV levels. Besides, SV applica- tion under a constant level of SA, either one of 0, 0.5 or 1 mM, induced the length and number of regenerated shoots, but reduced the root regeneration ability. Our fnal results indicated that application of low concentration of SV (5 μM) coupled with the medium concentration of SA (around 0.5 mM) was an appropriate treatment combination to obtain a higher pro- duction of Sura-halala under in vitro propagation. Also, the results indicated the requirement of further investigation on the interaction efect of SA and SV, at lower concentrations, together with other plant growth regulators (PGR) on Sura-halala production under in vitro propagation.
