Distribution and transport of IAA in tomato plants

We determined as to indole-3-acetic acid (IAA), endogenous levels by liquid chromatography-mass spectrometry using C-13(6)-IAA, diffusible levels by fluorometric detection using indole-propionic acid, and polar transport activity by radioactive IAA in 3-month-old tomato plants (stems, leaves or roots). The IAA concentration in the apoplast (AP) solution was higher than those in the symplast (SP) solution in both the upper and lower parts of stems, showing that IAA analysis of AP solution is important. Younger leaves exported much more diffusible IAA than older leaves. The IAA concentration in the main roots was almost at the same level as in the stems. The results suggested that the transport capacity of IAA is probably the limiting factor for the amount of IAA transported in stems and the amount of polar IAA transport might be only 19% of the endogenous IAA amount in stems.