Abstract
It's well known that plant cell elongation requires acidic condition in cell wall. This is called "acid-growth theory." However, its exact molecular mechanism is unclear. If this theory is true of all plant species, root elongation should be inhibited by high pH. But optimum pH for root elongation of chenopodiaceous Suaeda salsa was 6~8. The objective of this study is a survey of variation in the optimum pH for root elongation among plant species. It's also interesting whether halophilic or salt-tolerant characters correlate with the optimum pH for root elongation, since S. salsa is grown on the sodic soil. For this purpose, we used model plant Arabidopsis thaliana and Thellungiella halophila, a salt-tolerant relative of A. thaliana, chenopodiaceous Spinacia oleracea and Kochia scoparia.
We measured tap root elongation during 48 hours in buffer solution containing 5mM each of MES, HEPES and CHES at pH5.0, 6.0, 7.5, and 10.0.
Tap root elongation of A. thaliana, T. halophila, and S. oleracea was best at pH5.0 and 6.0, and extremely inhibited at pH10.0. The optimum pH for K. scoparia was 7.5, and tap root elongation was inhibited at pH10.0 to a lesser extent of other plants.
