Gibberellins and tuberization in potato

The evidence for a role of gibberellins in the regulation of potato tuber f ormation is reviewed. Endogenous gibberellin levels in plants are high unde r non-inducing conditions and decrease under inducing conditions. Exogenous ly applied gibberellins inhibit tuber formation, whereas applying inhibitor s of gibberellin biosynthesis has the opposite effect. Cellular events invo lved in tuberization, viz., cell division, cell enlargement and orientation of micro-tubules, are also reviewed. Based on available evidence, a major regulatory role of gibberellins is suggested. However, it is also argued th at tuber formation is not simply regulated by gibberellins acting as the so le signal between above-ground and below-ground parts, since stolen tips ar e able to synthesize their own gibberellins, and the phenotype of phytochro me B-antisense plants cannot be explained only by altered levels of GAs.