Auxin deficiency at the onset on root growth in Allium cepa.

3-Indolylacetic acid (IAA) increased the length of the epidermis cells of onion roots during the initial stage of root growth, when cell length has not yet reached its maximum value, by up to 50% (10(-11) M), while in the later, steady-state or dynamic equilibrium stage no promotive effects were present. It is suggested that the lesser elongation capacity of the cells at the onset of root growth is related to a deficiency in auxin while the steady-state phase is characterized by hormonal balance.