eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2016-02-05 4 2 769 772 6292 article A. K. Pandey 1 P.N. Dongre 1 Y. K. Singh 1 S. N. Tiwari 2 Biological Research Lab. Department of Botany and Biotechnology Kutir P.G. College Chakkey, Jaunpur - 222 146 (India) P.G. Department of Botany, K.N.P.G. College Gyanpur, S.R.N.(Bhodohi) (India) Toxicity of the herbicide 2, 4-Dichlorophenoxy acetic acid to unicellular cyanobacterium Aphanothece Sp. has been studied. Stimulation in cyanobacterial growth was observed at 100 ug ml-1 while higher concentrations had inhibitory effect with 1600 μg ml-1 being completely lethal. The sublethal concentration (1200 μg ml-1) allowed few cell (frequency approx 10-7) of cyanobacterium population into filamentous aseptate structure and regained the normal course of the unicellular pattern of differentiation in absence of the herbicide. 2, 4-D resulted in decline of chlorophyll a and no effect on DNA content even at the growth stimulatory concentration (100 μg ml-1). However, cell protein, RNA and phycobillin contents were increased up to 400 μg ml-1 , while higher concentrations have inhibitory effects. Cellular abnormalities by higher concentration and possible mode of action of 2, 4-D at the level of cell division are discussed. https://www.biotech-asia.org/vol4no2/regulation-of-growth-and-biomolecule-of-aphanothece-sp-by-phenoxy-herbicide-2-4-d/ Growth Biomolecules; Aphanothece sp. Phenoxy herbicide 2 4-D