Auxin (2,4-D) stimulation ( [formula omitted] and [formula omitted]) of polysaccharide synthesis in plasma membrane fragments isolated from onion stems

Abstract

Glucan synthetase activity associated with plasma membrane of onion stem was increased by adding the auxin herbicide 2,4-D. The effect was expressed either by pre-incubating the tissue with 2,4-D ( in vivo ) or by adding 2,4-D to the synthetase assay ( in vitro ). The 2,4-D effect was most pronounced on the synthesis of polysaccharides soluble in hot water. This is the first biochemical deomonstration of an in vitro response to auxin of magnitude comparable to that observed in vivo . The results show that initial responses to the hormone occur at the plasma membrane.