AUXIN AS A POSITIONAL SIGNAL IN PATTERN-FORMATION IN PLANTS

By using a novel, extremely sensitive and specific gas chromatography- mass spectrometry technique we demonstrate in Pinus sylvestris (L.) tr ees the existence of a steep radial concentration gradient of the endo genous auxin, indole-3-acetic acid, over the lateral meristem responsi ble for the hulk of plant secondary growth, the vascular cambium. This is the first evidence that plant morphogens, such as indole-3-acetic acid, occur in concentration gradients over developing tissues, This f inding gives evidence for a regulatory system in plants based on posit ional signaling, similar to animal systems.