Among CKs, tZ was characterized by the highest activity in Chlorella vulgaris.
The activity order of BRs is: BL > 24-epiBL>28-homoBL > CS > 24-epiCS>28-homoCS.
The level of endogenous BRs in algal cells was stimulated in response to tZ.
The mixture of BL with tZ has the highest stimulating effect on algal cells.
CKs make more cells sensitive to exogenously applied BRs in C. vulgaris.