For years, man has been trying to find a single chemical that triggers flowering in plants. Although this single chemical has not been found, several of the Gibberellins show promising results as an active florigen such as GA5 and GA6 and possibly GA1 and GA4. Results have shown that these GAs seem to travel intact from the leaf to the shoot apex just after a single long day photoperiod. Gibberellins also seem to accumulate in sufficient amounts to trigger flowering. Gibberellins have also been shown to cause petiole elongation. Much research still needs to be done to draw definite conclusions about the role of Gibberellins as a florigen, but much of the evidence looks promising.
[...] Moreover, the At GAMYB and LFY genes are strongly unregulated when GA is applied to the shoot, which indicates that these genes play a key role in the action of GA on flowering (King & Evans, 323). Further study needs to be done into these interactions to better understand the flowering mechanism in grasses. Conclusion: Much work still needs to be done in the area of Gibberellins and how they affect flowering. Several apparently contradictory findings (i.e. the action and degradation of GA4) need to be better [...]
[...] Certain Gibberellins seem to have a greater effect on flowering than others. It also seems to be the GAs that do not contribute to plant growth that are responsible for flowering. After labeling GA5, the pathway between the leaf and the shoot apex can be tracked and the molecule has been shown to travel intact to its destination at the apex of the plant (King & Evans, 323). It has also been shown that [2H4] GA5 can travel intact from the leaf blade to the shoot apex and seems to trigger flowering at the same time. [...]
[...] In other words, without a long day photoperiod, flowering is dependent on GAs (Blazquez, 3547). King and Evans describe the advancement in proving that Gibberellins can replace the Long Day photoperiod in flowering plants (King & Evans, 310). It is now thought that a long day photoperiod increases the amount of GAs in L. temulentum. In fact, it was shown that a single LD could increase the levels of GA1 and GA4 in the leaf by 5 to 20 fold, which eventually led to flowering (Gocal et al, 1271). [...]
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