An Analysis of the Growth Inhibitory Characteristics of Alachlor and Metolachlor

Abstract

The effects of varying concentrations and duration of alachlor [2-chloro-2′,6′diethyl-N-(methoxymethyl)acetanilide] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] treatment on root growth, cell division, and cell enlargement were studied. Peas (Pisum sativumL. ‘Alaska’) and oats (Avena sativaL. ‘Victory’) were treated from 0 to 48 h with concentrations ranging from 1 × 10-8to 1 × 10-3M of each herbicide. After 48 h, average growth rates were significantly inhibited at concentrations of 1 × 10-7M alachlor and 5 × 10−8M metolachlor, and 5 × 10−7M alachlor and 1 × 10-6M metolachlor for peas and oats, respectively. When growth inhibitions were examined across time at concentrations greater than these, the degree of growth inhibition was a function of both concentration and duration of treatment. Often the greatest decrease in growth occurred between 0 and 12 h. Mitotic indices of root tip squashes from pea roots and paraffin sections from oat roots were determined. There was a significant reduction in the mitotic indices of pea roots treated for 48 h with 5 × 10−6M alachlor or 1 × 10-5M metolachlor. After a 30-h treatment, the mitotic indices of oat roots were significantly reduced by 1 × 10−7M metolachlor and 1 × 10−6M alachlor. Significant inhibition of elongation of etiolated oat coleoptiles were observed at 5 × 10−6M alachlor (27%) and 5 × 10−5M metolachlor (30%). Inhibition of pea hypocotyl elongation did not occur at concentrations below 5 × 10−4M. It was concluded that the growth inhibition of plants caused by alachlor and metolachlor results from both an inhibition of cell division and cell enlargement.

Towards the primary target of chloroacetamides -new findings pave the way

“…The first leaves coming out of the coleoptile and the cotyledons of dicotyledons are misformed and small. Using oats, it was concluded in 1980 that both cell division and cell enlargement are inhibited,5 which could also be shown with the microalgae Chlamydomonas reinhardtii Dangeard6 and Scenedesmus acutus Pringsh 6. For the latter, it was assumed that inhibition of cell division was due to impaired membrane formation 7…”

High availability of alachlor affects the roots and general growth of sunflower seedlings

“…With increasing alachlor concentrations, the roots became progressively stubbier, until almost no fine roots were left. Alachlor has been shown to inhibit root growth in cotton (Eshel, 1969) and in peas (Deal & Hess, 1980). Of the three cultivars tested, PNR 7204 was the least susceptible to alachlor as shown by most of the parameters measured (Table 2).…”

Residues of Metolachlor Herbicide in Soil and Potato Tubers Under Indian Tropical Conditions

“…Early seedling growth is restricted due to inhibition of cell division and enlargement, cortical cell expansion and mitotic activity (Deal and Hess 1980).…”