The effect of chlorsulfuron and diclofop-methyl on the uptake and utilization of zinc by wheat

Abstract

The effects of the herbicides Hoegrass and Glean on the uptake of zinc by wheat were examined in two glasshouse experiments. Application of the active ingredients chlorsulfuron and diclofop-methyl decreased shoot weight, root weight and zinc uptake similarly to the herbicides Glean and Hoegrass. It can therefore be concluded that the effects of Hoegrass and Glean on zinc uptake in wheat can be attributed to these active ingredients and not to other constituents of the commercial herbicide preparations. Effects of chlorsulfuron on zinc uptake in soil were different from those obtained in solution. In soil, chlorsulfuron decreased both zinc concentrations in the youngest emerged blade and zinc content of shoots, while in solution where uptake is not likely to be limited by the rate of zinc diffusion to sites of absorption, there were no significant effects on zinc uptake. However, in both soil and solution, shoot and root weights were decreased by herbicide, particularly at low rates of zinc supply. Roots were shorter and thicker when herbicide concentrations in solution were increased.

Chlorsulfuron Reduces Extension of Wheat Root Tips in Low-zinc Solution Culture

“…Split-root experiments showed direct contact between roots and chlorsulfuron was required to decrease Zn concentrations in the shoots, an indication that direct contact between chlorsulfuron and Zn in the soil was decreasing uptake rather than reducing translocation of Zn within the plant (Robson and Snowball, 1990). Zinc concentration of leaves was also decreased in wheat plants treated with chlorsulfuron (Robson and Snowball, 1990 ;McLay and Robson, 1992). These effects diminished with time as the herbicide degraded in soil (Osborne and Robson, 1992).…”

“…Zinc can be translocated via the phloem towards root tips of low-Zn plants (Pearson and Rengel, 1995), even though the amounts translocated may not be sufficient for all requirements (Webb and Loneragan, 1990). Since Zn is transported through soil towards roots primarily by diffusion (Kochian, 1993), chlorsulfuron-induced inhibition of root growth will result in reduced root surface area available for Zn uptake, and consequently, reduced Zn concentrations within plants (McLay and Robson, 1992 ;Dong et al, 1995). These effects will have a deleterious effect on wheat growth, especially on soils low in plant-available Zn, such as those that abound in southern and western parts of Australia.…”

“…Wheat root length and surface area were reduced by Zn deficiency and by chlorsulfuron addition (McLay and Robson, 1992 ;Dong, Rengel and Graham, 1995). Chlorsulfuron exposure decreased the total length of small roots ( 0n2 mm diameter), hence decreasing surface area and Zn, Cu and Mn uptake .…”

“…Application of Glean at recommended rates reduced growth and tillering but not final yield of several cultivars varying in chlorsulfuron tolerance. Subsequent experiments showed chlorsulfuron decreased root and shoot dry weights of wheat at low soil-Zn concentrations Snowball, 1989, 1990 ;McLay and Robson, 1992). Split-root experiments showed direct contact between roots and chlorsulfuron was required to decrease Zn concentrations in the shoots, an indication that direct contact between chlorsulfuron and Zn in the soil was decreasing uptake rather than reducing translocation of Zn within the plant (Robson and Snowball, 1990).…”

What is the significance of herbicide-nutrient interactions on wheat?

“…In the glasshouse, c h l o r s u l f u r o n strongly decreased the uptake of phosphorus, zinc and copper by wheat but had no effect on nitrogen uptake (Tablel, Robson and Snowball, 1990;McLay and Robson, 1992;Osborne and Robson, 1992;Osborne et al, 1993). In the field chlorsulfuron decreased the concentrations of nutrients in wheat shoots.…”