Growth Behavior of Protosiphon Alga under the Impact of Thiobencarb Herbicide

摘要

Thiobencarb herbicide toxicity to growth of Protosiphon botryoides (Chlorococcal alga) isolated from an Egyptian paddy was studied using batch culture technique. After sixteen days of incubation in growth medium in presence of 2 ppm thiobencarb, Protosiphon cells count, chlorophyll a content and growth rate were significantly reduced. On the other hand, generation time elevated to be 10.8 day~(-1) respect to control 6.9 day~(-1). Electron microscope examination of Protosiphon cells exposed to sublethal concentration (2 ppm) revealed that spores liberation from mother cell wall was delayed; this phenomenon may be attributed to changes in the cell wall structure of the treated cells or physiological reasons induced by the used herbicide or both factors. In conclusion, ultrastructural result implies that reduction in growth of the treated Protosiphon was due to the effect of thiobencarb herbicide high concentration on algal reproduction through retardation on liberation of spores from the mother cell.