Immunohistochemical localization of indole-3-acetic acid in tulip shoots during low temperature treatment of bulbs

An immunohistochemical method was used to localize IAA in the internodes, 1(st) leaf, tepal, anther and pistil of tulip shoots. In all of the plant organs, the IAA signal was detected both in the cells and between the cells. In the internodes, there was no difference in the IAA signal at the epidermis, cortex and pith. In the 1(st) leaf and in the tepal, the IAA signal was detected in the cells on the cross sections. In the anther, the IAA signal was mainly detected at the pollen sacs and at the vascular bundles in the connective of the anther. In the pollen sacs, the tapetum showed a strong IAA signal. At the vascular bundles in the connective, the IAA signal was mainly detected between the cells. This distribution pattern of IAA did not change when the bulbs were stored at 20 degrees C continuously. The temporal pattern of IAA distribution in the internodes and anthers changed after the bulbs were transferred from 20 degrees C to 4 degrees C. But the pattern of IAA distribution did not change in the bulbs stored at 20 degrees C continuously. In the bulbs stored at 4 degrees C, IAA was detected in the internodes, leaves, tepal and anthers after the bulbs were treated for 4 weeks and the IAA signal was detectable till the end of the 12(th) week at 4 degrees C. Before the bulbs were treated at 4 degrees C, IAA was detected in the leaves and tepal, but not in the internodes and anthers.