CONCLUSIONS The main pathways for GA biosynthesis a metabolism in higher plants are well defined. The four pathways shown in Figs 4 and 11 are the main routes to Cro-GAs. Not all pathways can be demonstrated in all plants, instead most genera have two some additional structural elaborations in stems, with specifically in to the basic pathways occurring seven years seed tissues. Since the first edition of this book appeared including the ago several new metabolic conversions have been studied, with conversion of GA20- GA GA,. Substantial progress has been systems from and pumpkin, particularly with the further purification and characterization of the GA metabolism. This recently involved in the 20-oxidase pumpkin come to fruition with the of which is responsible for Cloning the locus in continue ent-kaurene synthesis has also been achieved. The gene dwarf es has growth retardants which new bably confirmed that 3B-hydroxyla specifically inhibit GA GA, and Cucum the primarily GA Future work ber) active in now address the mechanism for stem elongation. regulating the levels Of particular interest will developmental regulation of the enzymes involved in GA