Effect of Calcium Chloride Concentration on Growth and Sporulation of Saprolegnia terrestris Cookson ex Seymour

As CaCl₂ concentration in the growth medium was reduced from27.4 to 0.107 µM the range of oospore number per oogoniumin Saprolegnia terrestris increased from 1 to 8 to 1 to 25 ormore, oospore size decreased and the precision of correlationbetween oospore number per oogonium and oogonial diameter decreased,but colony d. wt was not affected. The threshold CaCl₂concentrationrequired to give the lower range of oospore number per oogoniumwas independent of the concentration of other mineral nutrientsin the growth medium. The number of oogonia formed per unitarea of colony was affected by the concentration both of CaCl₂and of other mineral nutrients. Oospores formed in 0.107 µMCaCl₂ medium were often multinucleate but otherwise of normalappearance. The oospore abortion rate was increased from 3.09per cent at 27.4 µM CaCl₂ to 8.2 per cent at 0.107 µMCaCl₂. calcium, oogonia, oospores, Saprolegnia terrestris Cookson ex Seymour