Green pea (Pisum sativum L. var. Alaska) stem segments that were aged in buffer responded differently after aging depending on whether they were floating or submerged, or bubbled with air or N(2). Segments aged anaerobically for only 1 to 2 hours at 23 C responded to subsequent aerobic conditions by elongating more rapidly than aerobically aged sections. Longer periods of anaerobic treatment (up to 5 hours at 23 C) caused sections to exhibit an auxin-insensitive growth lag and reversible shrinkage. The shrinkage accelerated upon return to aerobic conditions but reversed after 1 to 2 hours. Green pea stem segments therefore require vigorous aeration during aging and growth measurements.