EFFECTS OF pH ON THE ACTION OF Ca~(2+) AND EGTA ON HYPHAL TIP GROWTH OF SAPROLEGNIA FERAX
YUAN Sheng DOU Jie LU Ling (Department of Biology,Nanjing Normal University,Nanjing 210097) XUE Shao Bai (Department of Biology,Beijing Normal University,Beijing 100875)
The tip growth of hyphae was good in OM liquid medium (pH6. 0-8. 0),whereas reduced in the medium (pH5. 0)and completely ceased in the medium (pH3. 0-4. 0). For a shorter time of treatment (30min) ,low concentration CaCl2 stimulated tip growth of hyphae under pH 5. 0 condition (1 -5mmol/L CaCl2)or pH6. 0(1 mmol/L CaCl2), but inhibited the tip growth of hyphae under pH 7. 0-8. 0 conditions. 1 -20mmol/L EGTA inhibited tip growth of hyphae under pH5. 0 condition, whereas stimulated tip growth of hyphae under pH6. 0 - 8. 0 conditions. However, EGTA and CaCl2 could not resume growth of hyphae under pH 3. 0-4. 0 conditions. For a long time of treatment (8h),though the tip growth rate of hyphae grown in the medium(pH6. 8)containing 2 mmol/L EGTA was greater during first 30min, it gradualy decreased with prolongation of time and finally down to zero after about 8h,and meanwhile protoplasm usually bursted out from the tip of hyphae. Above results suggested that Ca2+ in cell wall may play dual roles as a extracellular Ca2+ resouces and a modification proportion of cell wall. Ca2+ channel blocker verapamil could inhibit tip growth of hyphae, which also impplied that Ca2+ needed for tip growth came from the outside of hyphae cell.