The inhibition of ammonium uptake in excised birch ( Betula pendula) roots by batatasin‐III

• Published in: Physiologia Plantarum
• Main Authors: Wallstedt, Anna, Sommarin, Marianne, Nilsson, Marie‐Charlotte, Munson, Alison D., Margolis, Hank A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2001
• Subjects: Northern Sweden
• Online Access: http://dx.doi.org/10.1034/j.1399-3054.2001.1130310.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1034%2Fj.1399-3054.2001.1130310.x; https://onlinelibrary.wiley.com/doi/pdf/10.1034/j.1399-3054.2001.1130310.x

In northern Sweden, plants growing in association with the clonal dwarf shrub Empetrum hermaphroditum usually exhibit limited growth and are N‐depleted. Previous studies suggest that this negative effect by E. hermaphroditum may be explained, at least in part, by the release of phenolic compounds, particularly the dihydrostilbene, batatasin‐III from foliage to soil. In the present work, we investigated whether batatasin‐III has the potential to interfere with NH 4 + uptake in birch ( Betula pendula ) roots. Excised birch roots were exposed to batatasin‐III during brief periods in 15 NH 4 + solutions, and then analyzed for labeled N. Batatasin‐III inhibited N‐NH 4 + uptake by 28, 89 and 95% compared with the control, when roots were treated with 0.1, 1.0 and 2.8 m M of batatasin‐III, respectively. The effect of 1.0‐m M batatasin‐III was greater at pH 4.2 than at pH 6.8. In addition, the inhibition of N‐NH 4 + uptake by batatasin‐III was not reversed after rinsing the roots in water and transferring them to a batatasin‐III free solution. Furthermore, birch seedlings immersed in a 1.0‐m M batatasin‐III solution for 2 h, and then replanted in pots with soil, had decreased growth, such that 10 weeks after treatment, the dry mass of both shoots and roots was reduced by 74 and 73%, respectively, compared with control seedlings. This suggests that a brief exposure to batatasin‐III may have a long‐term inhibitory effect on whole plant growth. Using plasma membrane vesicles isolated from easily extractable spinach ( Spinacia oleracea) leaves, it was found that batatasin‐III strongly inhibited proton pumping in isolated plasma membrane vesicles, while it only slightly inhibited ATP hydrolytic activity. The uncoupling of proton pumping from ATP hydrolytic activity suggests that batatasin‐III disturbs membrane integrity. This hypothesis was further supported by a greater efflux of ions from birch roots immersed in a batatasin‐III solution than from roots in a control solution.