. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ION CURRENTS, GROWTH REGULATORS 69. Figure 6. Effect of exogenously applied 1CT4 MIAA on the current pattern generated by 6 day old Zea roots. The effects of IAA at pH (A), (D), and (O) are compared with their respective APW controls: (A). (•). and (•). cell elongation (O'Neil and Scott, 1983). It is significant that in all cases where an alkalinization of the growing tip environment has been reported, intact plants were used as experimental material. In some experiments, ac- tivation of growth in root segments b
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ION CURRENTS, GROWTH REGULATORS 69. Figure 6. Effect of exogenously applied 1CT4 MIAA on the current pattern generated by 6 day old Zea roots. The effects of IAA at pH (A), (D), and (O) are compared with their respective APW controls: (A). (•). and (•). cell elongation (O'Neil and Scott, 1983). It is significant that in all cases where an alkalinization of the growing tip environment has been reported, intact plants were used as experimental material. In some experiments, ac- tivation of growth in root segments by low pH and low pH-inducing factors ( IAA and fusicoccin) may have resulted from accelerated recovery from excision or abra- sion injury (Hanson and Trewavas, 1982). It is difficult to reconcile the proposition that fusicoc- cin enhances just a proton influx with more than a de- cade of work suggesting it stimulates energy-linked net H+ efflux (Marre, 1985). Although we detected no fusi- coccin-induced stimulation of the outward current in the apical 5 mm of roots (Fig. 5), this represents only a small portion of the total root surface area of a 6-day-old seed- ling. Therefore, our data may represent only one limb of an enhanced ion circulation stimulated by fusicoccin. Some concern has been expressed about the validity of comparing results obtained from exposing fusicoccin to excised tissues, to those derived (as in this case) from in- tact tissues (Gronewald, Cheeseman and Hanson, 1979). In addition, little consideration has been given to the effect of fusicoccin on tissues of different developmental states. Where this has been taken into account, it would appear that the capacity of root tissues to acidify their bathing medium in the presence of fusicoccin increases with the age and the differentiation of the root (Gabella and Pilet, 1979). The integration of the effects of fusicoc- cin on intact roots into a spatially separated yet balanced flux may explain the ob
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
