Relationship Between Metabolism and the Lateral Transport of IAA in Corn Coleoptiles

Abstract

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

A Cytokinin Perception Mutant Colonized by Rhizobium in the Absence of Nodule Organogenesis

“…Additional validation of HIT1 function in nodule organogenesis was provided by the analysis of the L. japonicus root hairless (Ljrhl1-1) and hit1-1 double mutant. In response to inoculation with M. loti, Ljrhl1-1 initially develops a large number of uncolonized NP, a consequence of the absence of root hairs and associated ITs (22). We reasoned that if HIT1 mediates nodule primordia organogenesis, the presence of a mutant hit1-1 allele should prevent or significantly attenuate NP formation in Ljrhl1-1.…”

Independence of Lateral and Differential Longitudinal Movement of Indoleactic Acid in Geotropically Stimulated Coleoptiles of Zea mays

“…This gradient arises principally from the induction of a metabolically dependent, polarized, lateral movement of IAA from the upper to the lower half of the horizontal coleoptile (4,5,7). Recently, a second phenomenon which might contribute to the establishment of the gradient has been observed (5).…”

“…The occurrence of this second phenomenon has given rise to the suggestion that it may in fact cause the lateral movement of IAA from the upper to the lower half of the organ (5). If such a causal relationship were to exist, the lateral movement of IAA would still be dependent upon metabolism (7), since the development of the differential capacity to transport auxin basipetally in the upper and lower halves of the coleoptile would itself undoubtedly be dependent upon metabolic energy (8).…”