Localization of gibberellic acid-induced acid phosphatase activity in the endoplasmic reticulum of barley aleurone cells with the electron microscope.

A metal-salt precipitation method with p-nitrophenyl phosphate as substrate has been used to localize in the electron microscope acid phosphatase activity in isolated aleurone layers of barley (Hordeum vulgare L.), treated for 16 h in the presence or absence of gibberellic acid (GA3). The paper confirms results obtained earlier with an azo-dye precipitation method of enzyme localization. In addition the results show for the first time that in GA3-treated tissue enzyme activity is associated with the endoplasmic reticulum (ER), there being reaction product deposited in the ER cisternae. It is suggested that this activity represents new enzyme synthesized on ER in response to GA3 and probably destined for secretion.