In greening mustard cotyledons, both photosystems (PS) 1 and 2 were significantly promoted by addition of gibberelic acid (GA) at low concentrations, i.e. upto 10 μΜ, while at higher concentrations no significant changes were recorded. PS2 activity in kinetin (KN) treated seedlings was promoted at concentrations upto 5 μΜ KN, while it showed a slight inhibition at higher concentrations. No significant change in PS1 activity was observed when compared to controls. Other particular photosynthetic electron transport reactions were also increased by GA and KN. KN03 showed concentration-dependent effects on photosynthetic electron transport reactions.