Overexpression of GA20‐OXIDASE1 impacts plant height, biomass allocation and saccharification efficiency in maize
Earlier work indicated that barley endosperm, freed from the embryo, responds to gibberellic acid (GA3) treatment with a loss in dry weight accompanied by release of reducing sugars and protein nitrogen ( 19, 20, 21). These results lead to the conclusion that the effects of the embryo and GA3 on the endosperm are identical, and suggest that endogenous gibberellin may be the hormone produced in the embryo which initiates the breakdown of endospermal reserves. In an attempt to trace the action of GA3 to a locus within the barley endosperm it was shown that the aleurone layer was the tissue directly affected (23). Isolated segments of aleurone tissue, peeled away fronm the starchy enclosperm, have demonstrated the ability to produce and release a-amylase as a result of GA3 treatment. The results prompted the conclusion that it is this amylase, as it diffuses from its site of production in the intact germinating seed which causes the release of reducing sugar by acting on starch in the inner portion of the endosperm. Identification of the aleurone layer as the cellular locus of GA3 action, and the development of techniques for its isolation have made it possible to follow, visually, the GA3-induced changes within this tissue. This report deals with ultrastructural manifestations of GA3 treatment, as observed with the electron microscope. A preliminary report has been presented elsewhere (12).