Why GA3 is used as an external plant growth hormone while the active form of GA in plants are GA1 and GA4?

Question

It is known that Gibberellic acid (GA1 and GA4) are the active form of GA in plants. in contrast to this fact people apply external GA3 to promote growth or germination. I am curious why tthey don't directly use GA1 or GA4.

Answer 1

I believe GA3 and be converted to either GA1 or GA4 and it is probably best to take in GA3 because of probably the solubility differences and how the plant metabolises the GA3.