P-31-NMR STUDY OF THE PHYSIOLOGICAL CONDITIONS IN INTACT ROOT-CELLS OF MUNG BEAN SEEDLINGS UNDER LOW-TEMPERATURE STRESS

Intracellular pH and levels of ATP in intact root-tip cells of mung be an (Vigna mungo [L.] Hepper) under low-temperature stress were investi gated in vivo by P-31 nuclear magnetic resonance (P-31-NMR) spectrosco py. Root-tips of 3 mm in length were excised from seedlings of mung be an that had been chilled at 0 degrees C after grown at 30 degrees C. C hilling for longer than 12 h caused changes in the intracellular pH an d decreased levels of ATP in the seedlings. The level of ATP recovered within 30 min but little change in pH was observed when samples were rewarmed to 20 degrees C after chilling at 5 degrees C. However, after chilling for longer than 48 h, neither the intracellular pH nor the l evel of ATP was restored. These results suggest that a decline in the activity of tonoplast H+-ATPase, induced by chillings, might be a sign ificant early event in cold-induced injury that leads to cell damage.