Alachlor action

Figure - Idealized curves for increases of particle number (%) and chlorophyll content (O) per culture vessel, and for alachlor action ( ) on these increases. A lachlor application at arrow.

Inhibition of the incorporation of uridine into RNA is caused by the herbicides referred to as the chloroacetanilides (e.g., acetochlor, alachlor, butachlor, and several others) and a group of fungicides referred to as phe-nylamides (metalaxyl, ofurace, and oxadixyl). They have similar structure and mode of action ... 

Alachlor is a selective preemergence soil herbicide with action similar to that of propachlor. With its poorer solubility in water it needs more soil moisture than propachlor to exert its action, and irrigation must be used in a dry spring to obtain a satisfactory herbicidal action. On a molar basis, alachlor is twice as efficient as propachlor, and its activity lasts 2-4 weeks longer (Evans et al., 1968). 

On the bais of information presently available, the biological mode of action of alachlor is probably the inhibition of protein synthesis. 

Butachlor is less soluble in water than alachlor by one order of magnitude and thus needs a higher soil moisture to exert a suitable herbicidal action. 

At the same application rate as alachlor, acetochlor has stronger and longer lasting action. It is also effective for the control of Agropyron repens and Cyperus spp. (Anonym, 1971). Its selectivity is the same as that of alachlor. 

The action of the tested herbicides was classified as follows (a) growth inhibition in the light without rapid phytotoxicity (metribuzin), (b) bleaching of the cells without rapid phytotoxicity (fluridone), (c) rapid phytotoxicity in the light (nitrofen, paraquat), (d) rapid phytotoxicity in the dark (PCP), (e) direct and rapid inhibition of cell division but not of cell growth (amiprophos -methyl, chlorpropham, trifluralin) and (f) indirect (delayed) inhibition of cell division and growth (alachlor). 

Table V. Action of 37 yuM alachlor on Chlamydomonas reinhardii growth and multiplication when present for different time-intervals during the growth cycle. Inoculation was with stationary algae with a cell volume of 90, um. Light phases were from 0-10, 24 - 3A and 48 - 58 h. C = Control, A = alachlor-treated.

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