Question

Why does exogenous application of auxin on older leaves and fruit cause abscission

Answer 1

Answer:

How does ethylene affect leaf abscission and fruit ripening?

Evidence supporting the hypothesis that ethylene is involved in the control of senescence and abscission is reviewed. The data indicate that ethylene causes abscission in vivo by inhibiting auxin synthesis and transport or enhancing auxin destruction, thus lowering the diffusible auxin level.