Nitrate Transport intoChara corallinaCells using ClO3-as an Analogue for Nitrate

The effects of Cl⁻ and $NO3-$ pretreatment on ³⁶Cl⁻influx and $ClO3-$/$NO3-$ influx into Chara corallina cells were examined. Both treatments reduced ³⁶Cl⁻ influx into C. corallina cells in the acid pH range (4.5–7.0). $NO3-$ pretreatment stimulated /$NO3-$ influx into C. corallina cells, but Cl⁻ pretreatment had no effect. There was a direct inhibitory effect of CI on $ClO3-$/$NO3-$ influx into C. corallina cells, but no apparent effect on net NO$NO3-$ uptake. The time course of ³⁶Cl accumulation into cytoplasmic and vacuolar compartments during incubation of the cells with $ClO3-$ showed that significant radioactivity appeared in the vacuolar sap after 30 min. There was a linear increase in the percentage of total ³⁶CI which crossed the tonoplast (φ_c-v). There was no effect of Cl⁻ or $NO3-$ pretreatment on accumulation of radioactivity in the vacuole. Thin layer chromatography of the vacuolar sap showed that after 2 h only one component was present which had an R_F which was similar to ³⁶CI⁻. The rate of accumulation of ³⁶C1⁻ in the vacuole could be used to estimate rates of $ClO3-$ reduction.