Intracellular pH in rice and wheat root tips under hypoxic and anoxic conditions.

The influence of anoxia and hypoxia on dynamic of intracellurar pH and ATP content in rice and wheat root tips was investigated with (31)P-NMR spectroscopy. Both cereals responded to hypoxia similarly, by rapid cytoplasmic acidification (from pH 7.6-7.7 to 7.1), which was followed by slow partial recovery (0.3 units). Anoxia led to a dramatic pH(cyt) drop in tissues of both species (from pH 7.6-7.7 to less than 7.0) and partial recovery took place in rice only. In wheat, the acidification continued to pH 6.8 after 6 h of exposure. Anoxic wheat root tips were deficient in ADH induction, whereas increased activity of alcoholic fermentation enzymes took place in anoxic rice root tips, as well as in both species after hypoxic treatment. In both plants, NTP content followed the dynamics of pH(cyt). There was a strong correlation between NTP content and cytoplasmic H(+) activity ([H(+)](cyt) = 10(-pHcyt)) for both hypoxic and anoxic conditions. In this addendum we want to focus the reader's attention on the importance of adequate experimental design when hypoxia is under investigation and on some further perspectives of intracellular pH regulation in plants under anaerobic conditions.