Maintenance of polar auxin transport in Zea coleoptiles by anaerobic metabolism

1969

Plant Physiol.

Self Cite

The possible interdependence of the differential longitudinal, and the lateral movement of indoleacetic acid (IAA) in horizontal Zea coleoptile segments has been examined. The coleoptiles have been opened out into flat pieces of tissue and supplied apically with IAA-1-(14)C.Opened-out segments orientated so that all the cells correspond with those at the ;bottom' of a normal horizontal coleoptile, transport more IAA basipetally than do segments in which all the cells are equivalent to those at the ;top' of the horizontal coleoptile.In opened-out segments orientated so that all the cells are equivalent to those at the side of the horizontal coleoptile cylinder, there is no difference in the basipetal transport capacity of the upper and lower halves. This is so even if the tissue has been in the horizontal position for 90 min before being bisected into its upper and lower halves. In this ;side' tissue, however, there is a polarized downward movement of IAA. At least 95% of the (14)C in both the upper and lower halves of the tissue is confined to the IAA molecule.In horizontal Zea coleoptiles the polarized lateral movement of IAA can therefore occur independently of the differential basipetal transport of IAA in the upper and lower halves of the organ.

mentioning

confidence: 99%

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

Cane

1969

Plant Physiol.

Self Cite

The movement of 2,4-dichlorophenoxy acetic acid in root segments of Pisum sativum L.

1975

Planta

The movement of 2,4-Dichlorophenoxy acetic acid (2,4-D) through subapical segments of the primary roots of Pisum seedlings has been investigated using [1-(14)C]2,4-D.Donation of [1-(14)C]2,4-D to the apical or basal ends of Pisum root segments at 25°C in darkness revealed a preferential movement of the compound towards the root apex i.e. an acropetal polarisation. Thus the movement of [1-(14)C]2,4-D into receiver blocks applied to the apical ends of the segments is greater than that into receiver blocks applied to the basal ends of the segments The low level of basipetal transport appears to be associated with a restriction of the movement of [1-(14)C]2,4-D to the half of the segment nearest the donor block.Acropetal transport of 2,4-D is faster than basipetal transport in root segments maintained at 15° and 35° C but is slower than basipetal transport if the segments are maintained at 25°C. Maximum velocitees are 0.71 and 0.83 mm h(-1) for acropetal and basipetal transport respectively.Evidence from experiments carried out (a) in an anaerobic environment in the presence or absence of sodium fluoride and (b) over a range of temperatures from 1-35°C, indicates that the movement of [1-(14)C]2,4-D is dependent on the metabolic activity of the Pisum root segments.Release of (14)CO2 during transport of [1-(14)C]2,4-D is small and supports chromatographic evidence that negligible degradation of the 2,4-D molecules takes place during transport through the root segments.

Auxin transport in roots

Scott²

1968

Planta

The dependence upon metabolism of the acropetal polar flux of IAA through 6-mm Zea root segments has been investigated using IAA-I-(14)C.The results are as follows: 1. At 0°C the acropetal movement of IAA is reduced to the level of basipetal movement and the polar flux is thus abolished, even after transport periods of 24 hours. 2. In dead tissue the acropetal polar flux is abolished and replaced by a basipetal polar flux. 3. On exposing segments to anaerobic conditions, the acropetal polar flux of IAA is severely reduced during the first 4 hours, but reappears during the subsequent 4 hours. The tissue thus appears to have the ability of adapting to anaerobic conditions and of resuming the acropetal transport of IAA. 4. The acropetal flux of IAA found in segments deprived of oxygen for 8 hours is dependent upon anaerobic metabolism since it is abolished and replaced by a net basipetal flux in the presence of sodium fluoride.The acropetal polar flux of IAA through the Zea root segments is thus entirely dependent upon metabolic energy.