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Abstract. The lateral movement of IAA in coleoptiles of Zea mays has been investigated under aerobic and anaerobic conditions. The IAA-1-14C was supplied asymmetrically to the apical end of the segment. The results were as follows: A) In air more 14C was found in the lower half of horizontal segments supplied with an upper donor than in the half opposite the donor in vertical segments. The enhanced lateral movement of 14C in geotropically stimulated segments of oorn coleoptiles under aerobic conditions has thus been oonfirmed. B) This increased lateral movement of 14C in geotropically stimulated segments is greatly reduced, but is not completely abollished, under anaerobic conditions. C) The lateral movement of 14C in vertical segments is significantly less under anaerobic conditions than in air. D) Under anaerobic conditions, the lateral movement of 14C in horizontal segments can be reduced to the level found in vertical segments by pre-soaking the tissue in a 1 mm solution of the metabolic inhibitor sodium fluoride for 2 hours. The inhibitor has no effect on lateral movement of '-C in vertical anaerobic segments. E) In air, sodium fluoride has no effect on the lateral movement o'f 14C in either vertical or 'horizontal segments.On

The basipetal movement of IAA in 5-mm Zea coleoptile segments is drastically reduced under anaerobic conditions, but it remains greater than acropetal movement which is closely similar in the presence and absence of oxygen. The polarity of IAA movement has thus been confirmed in Zea coleoptile segments which have been deprived of oxygen. This net polar flux is dependent upon anaerobic metabolism since it is abolished in the presence of the metabolic inhibitiors sodium fluoride and iodoacetic acid.Acropetal movement of IAA is unaffected by the presence of sodium fluoride in air or anaerobic conditions. Uptake of IAA from a basal donor is not affected by sodium fluoride in air, but under anaerobic conditions the inhibitor decreased uptake by approximately 13%.Under anaerobic conditions both inhibitors reduce basipetal movement of IAA to the level of acropetal movement, and both decrease the total uptake of IAA from an apical donor by up to 30-45%. Under aerobic conditions sodium fluoride has no marked effect upon either the uptake of IAA from an apical donor or the basipetal movement of IAA by the segments. On the other hand, iodoacetic acid greatly decreased the uptake of IAA by the segments in air, but the same fraction of the total IAA taken up was recovered in the receiving block in the presence and absence of the inhibitor.