. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 2. Ion substitution experiment on Zea in APW. Six-day-old seedlings were used with the media adjusted to pH The effect on the current density and pattern of removing Na+ (O), K+ (•), Cl~ (D), and Ca:* (A) compared to an APW control (•) is shown. Each point represents the mean value from three separate ion-substitution experi- ments. of the circulating current was monitored rapidly while the extracellular pH was adjusted between and (Fig. 3). Increasing the external pH resulted in an imme- diate reduction
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 2. Ion substitution experiment on Zea in APW. Six-day-old seedlings were used with the media adjusted to pH The effect on the current density and pattern of removing Na+ (O), K+ (•), Cl~ (D), and Ca:* (A) compared to an APW control (•) is shown. Each point represents the mean value from three separate ion-substitution experi- ments. of the circulating current was monitored rapidly while the extracellular pH was adjusted between and (Fig. 3). Increasing the external pH resulted in an imme- diate reduction of the current density and a decrease in the elongation rate of the root (Table I). Roots exposed to more acidic pH's generated larger current densities and extended faster. These observations supported the pro- posal that protons carried the major component of the inward current and indicated a correlation between growth rate, pH, and current density. There also ap- peared to be a basipetal extension of the zone of inward current as the external pH fell and an acropetal compres- sion of it as the pH increased. Effects of fusicoccin on the root-generated ion current and root growth The effect of 10~6 M fusicoccin on the ion current is illustrated in Figure 1. At pH , fusicoccin induced an approximate 3-fold increase in the inward limb of the current with little or no apparent stimulation of the out- ward limb over the length of root examined. Fusicoccin treatment also reversed the small outward current associ- ated with the root cap. The current cross-over point was unaltered following fusicoccin treatment. The current profiles displayed in Figure 4 illustrates the relationship between fusicoccin. pH, and current density. At pH ,. o 10 Figure 3. The relationship between the pH of the APW bathing medium and the pattern and density of current traversing a 6-day-old Zea root is illustrated. Media at pH (A). (A). (O), and (•) were flushed through the mea
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
