Mechanism of Growth Promotion by Ferrous Sulfate

Abstract

(1) Ferrous sulfate, at the concentration of 10^-5M, promotes the elongation of Avena coleoptile sections in IAA solution, at the concentration of 0.05mg./l.
(2) When the straight growth test is carried out, ferrous sulfate, at concentrations higher than 10^-5M, prevents the disappearance of IAA from the test solution during the incubation period.
(3) Ferrous sulfate does not promote the elongation of Avena coleoptile sections in NAA.
(4) The promotive action of ferrous sulfate on the elongation of the sections appears obviously when IAA is used at low concentrations and the incubation period is prolonged.
(5) Ferrous sulfate, at the concentration having promotive effect on the section growth, inhibits the action of IAA-oxidase obtained from Avena coleoptiles.
(6) The promoting effect of ferrous sulfate is larger in the earlier period of the Avena curvature test, and go decreasing thereafter.
(7) Ferrous sulfate promotes the transport of both IAA and NAA through a given length of the coleoptile section.
(8) Based on the data summarized above, it may be concluded that ferrous sulfate acts promotively on the Avena curvature test through its promoting effect on the transport or infiltration of auxin, and on the straight growth test through its inhibiting effect on IAA-oxidase.
(9) Therefore, the Avena curvature test sensitized by the application of ferrous ions seems to be useful for the detection of small amounts of auxin.