Rhythm of zoospore production of pythium on lettuce cultured hydroponically

Abstract

Zoospore production of Pythium dissotocum Drechs. in the nutrient solution of hydroponically-grown lettuce, in the greenhouse, was shown to be cyclic. The number of zoospores detected in the nutrient solution was lowest around noontime, (11:00-14:00 hr) and highest around 20:00 hr. Growth chamber studies were conducted to determine the effect of different light periods on zoospore production. Under continuous light or continuous darkness, the population of zoospores in the nutrient solution decreased. But under 12 hours light, and 12 hours darkness or two periods of light each for 3 hours, zoospore populations decreased during the light period but increased during the dark period.