Distribution of IAA and ABA in gravistimulated primary roots ofZea mays. L.

Abstract

The transport of14C-IAA and14C-ABA applied exogenously to root cap toward the elongation zone was investigated in gravi- and light-stimulated primary roots ofZea mays L. cv. Golden Cross Bantam 70. No significant difference of either IAA or ABA in radioactivities was observed between upper and lower halves of elongation zones during the latent period (0–60 min after the stimulation) of gravitropic response. When quantitative analysis of endogenous IAA and ABA by an internal standard method was carried out 60 min after gravi- and/or light-stimulation, no asymmetric redistribution of either IAA or ABA was observed between upper and lower halves of elongation zones. Light irradiation increased by 20% the contents of ABA in elongation zones. These results suggest that although both IAA and ABA are basipetally transportable and can transmit their information to the elongation zone during a latent period we cannot explain the gravitropic curvature by their redistributions between the two (upper and lower) halves of primary roots ofZea. On the basis of results from the present work and previous papers, the distribution of IAA and ABA in gravistimulatedZea roots is discussed.