Effects of abscisic acid on sequestration and exchange of Na+by barley roots

✍ Scribed by R. Behl; K. Raschke

• Publisher: Springer-Verlag
• Year: 1986
• Tongue: English
• Weight: 587 KB
• Volume: 167
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00391233

✦ Synopsis

Excised Na § barley roots were suspended in solutions of Na + in combination with NO3-, CI-, and S042-, and effects of the added phytohormone, abscisic acid (ABA), to the medium were determined. Abscisic acid increased the rate of Na + (22Na+) accumulation and the amount of Na + deposited in the vacuoles. These stimulating effects of ABA were modified by anions following the sequence NO3 > C1-> SO42-. Testing whether the magnitude of the pH gradient across the plasmalemma of the cells of the root cortex affects rates of Na + accumulation and their dependence upon ABA, we observed that, in the pH range from 4 to 8, the ABA-induced stimulation was strongest at pH 5.8, and least at pH 4. Changes in pH during the experiment caused changes in the rates of Na + accumulation in agreement with experiments performed at constant pH values. Simultaneously with ABA-enhanced accumulation, loss of Na + occurred. Loss of Na + was strongest at pH 4 and was affected by anions, being greatest with S042and following the sequence 8042-~> C1-> NO3-. On the basis of the finding that initial acceleration of uptake as well as loss of Na + depended on the pH of the medium we suggest that, in barley roots, ABA stimulates an exchange of Na + for H + at the plasmalemma of the cortical cells. The results indicate that ABA-stimulated expulsion of Na § in combination with ABA-stimulated sequestration in the vacuoles, constitutes one of the mechanisms which enable barley plants to tolerate higher than normal levels of Na +.