Gibberellins and flowering in long day plants, with special reference to Lolium temulentum

The relation between gibberellins (GAs) and flowering in some long day (LD) plants is reviewed, with particular emphasis on Lolium temulentum. Lang's early experiments with rosette plants established the effectiveness of several GAs in replacing the need for LD. Subsequent work with mutants, especially of Arabidopsis, has clarified genetic and environmental control points in GA synthesis, various feedback effects and some of the factors affecting responsiveness to, as well as synthesis of, GAs in the flowering process. Further complexities are revealed in the experiments with Lolium temulentum, which have clearly shown that the structural requirements for effectiveness of GAs in the flowering process are quite different from those for elongation growth. The precise role of GAs in the long day induction of flowering remains unclear.