Comparative Basipetal Transport of 6‐Benzylaminopurine‐8‐¹⁴C, Gibberellin A₃‐³H, IAA‐2‐¹⁴C, and Sucrose‐¹⁴C in the Root of Intact Citrus aurantium Seedlings

Abstract

The transport and distribution of IAA‐2‐14C, gibberellin A3‐3H, 6‐benzylaminopurine‐8‐14C and sucrose‐14C (U) were studied in whole seedlings of Citrus aurantium L. after “replacing” the root tip with the solution of radiochemicals. All four substances were transported basipetally in the root and were distributed to the stem and leaves. The pattern of distribution of the label from 6‐benzylaminopurine was similar to that of sucrose, while a considerably larger amount of gibberellin A3 was transported to basal regions of the root, away from the tip, and into the shoot. Contrary to these three substances, the basipetal transport of IAA in the root was very low, and the majority of the label was retained in the terminal sections of the root. It is suggested that the different efficiencies at which various hormones move in the transpiration stream in the root may be an important factor in the attainment of a certain balance of hormones in the shoot.

The Arabidopsis NPF3 protein is a GA transporter

“…Whereas research over the past 15 years has elucidated the GA biosynthetic and signalling pathways at the molecular level, it remains to be determined precisely where GAs are active within the plant and how GAs are transported from sites of synthesis to sites of action. Studies using radiolabelled GA and grafting experiments with GA mutants, have demonstrated that GAs are mobile hormones and that their movement is essential for proper plant growth 14 15 16 17 18 19 . A recent Arabidopsis grafting experiment with a variety of GA biosynthetic mutants demonstrated long-distance transport of the inactive GA 12 (ref.…”