Emergent growth: an auxin-mediated response.

Restoration of oxygenated conditions following 15 minutes to 2 hours of anoxia causes light-grown pea (Pisum sativum L. var. Alaska) stem segments to elongate 100 to 200% more than continuously aerated segments. This "emergent growth" response takes place in the presence of 5 mm F(-), an inhibitor of anaerobic respiration; therefore, a build-up of glycolytic products does not appear to be the mechanism underlying emergent growth. "Acid growth" does not appear to account directly for the hyperelongation, as extracellular pH does not drop following a return to aerobic conditions. Studies with (14)C-indoleacetic acid indicate that auxin is freed from some previously unavailable pool during O(2)-limited treatments. We suggest, therefore, that emergent growth is a response to auxin which is released during anaerobiosis: the newly mobile or diffusible auxin promoting growth when O(2) is no longer limiting.