Gibberellins act in the elongation of intact plants as opposed to stem section elongation by auxin. (Salisbury and Ross, 1992) Much research on plant gibberellins has been possible do to gibberellin sensitive mutants. These mutants in maize, pea, and wheat have adequate levels of GA1 (the GA species most likely to be responsible for stem elongation) but can't respond to it. This may be due to lack of receptor protiens. An experiment examining the GA defficeint mutant (gal-2) in Arabidopsis thalina has questioned the effect of GA sensitivity on seasonal dormancy patterns. They hypothesize that the changes in sensitivity to GA may be due to:
**1 the number of receptors
**2 binding characteristics and/or a response chain initiated by the receptor
**3 temp without interference of light.
This experiment concluded that seasonal dormancy patterns are mainly regulated by changes in sensitivity to light but GA contributes to the pattern. (Derkx and Karssen, 1994) Other recent experiments on GA receptor sensitivity involves GA's effect on sex expression in flowering plants (buffalograss). This study concluded that GA could cause both male and female inflorescense depending on the concentration of GA and the concentration of different GA receptor proteins. (Yin and Quinn,1995)
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