Novagib

Gibberellins A4/A7 induces stimulation of tracheid production in the terminal shoot of intact plants is mediated through an increase in the IAA level in the cambial region[1].

[1] S.J. Wertheim, et al. Fruit set and June drop in Cox's Orange Pippin apple as affected by pollination and treatment with a mixture of gibberellins A4 and A7. Scientia Horticulturae. Volume 1, Issue 1, January 1973, Pages 85-105.