Paraquat and sustainable agriculture

Abstract

Sustainable agriculture is essential for man's survival, especially given our rapidly increasing population. Expansion of agriculture into remaining areas of natural vegetation is undesirable, as this would reduce biodiversity on the planet. Maintaining or indeed improving crop yields on existing farmed land, whether on a smallholder scale or on larger farms, is thus necessary. One of the limiting factors is often weed control; biological control of weeds is generally of limited use and mechanical control is either often difficult with machinery or very laborious by hand. Thus the use of herbicides has become very important. Minimum cultivation can also be important, as it reduces the power required to work the soil, limits erosion and helps to maintain the organic matter content of the soil. This last aspect helps preserve both the structure of soil and its populations of organisms, and also sustains the Earth's soil as a massive sink for carbon, an important consideration in the light of global warming. The introduction of the bipyridinium herbicide paraquat in the early 1960s greatly facilitated weed control in many crops. Paraquat has the unusual property of being active only by direct spray onto plants and not by uptake from soil in which strong binding deactivates it. Together with its rapid action in light in killing green plant tissue, such properties allow paraquat to be used in many crops, including those grown by low-tillage methods. This paper reviews the ways in which agricultural systems have been and are being developed to make use of these properties, and provides a risk/benefit analysis of the world-wide use of paraquat over nearly 40 years.

PARAQUAT RESISTANT1, a Golgi-Localized Putative Transporter Protein, Is Involved in Intracellular Transport of Paraquat

“…Moreover, paraquat exhibits nonselective and rapid action and is biologically inactive in soil. Despite these advantageous features, the application of paraquat in agriculture is relatively limited, and this herbicide is primarily used in orchards, plantation crops, and conservation tillage systems (Bromilow, 2004). This limitation is partly attributed to the lack of a molecular target that can be genetically modified to confer paraquat resistance to crops, in contrast to several other herbicides, such as glyphosate, whose utilization has been successfully manipulated by genetic engineering (Comai et al, 1983(Comai et al, , 1985.…”

“…In addition, paraquat has no effects on mature bark (Dodge, 1971;Suntres, 2002). Because of these characteristics, paraquat is widely used in orchards, plantation crops, conservation tillage systems, and other applications (Bromilow, 2004).…”

Interactions Between Ionic Pesticides and Model Systems for Soil Fractions

“…Studies of PQ adsorption to clays in the pH range 5.0-7.0 reveal surface concentrations of between 0.18 and 4 µmol⋅m -2 , depending on the type of clay. The higher adsorption of PQ on clays is explained by the ability of the planar PQ molecules to enter the lattice layers (Bromilow, 2003) and the extent of the PQ adsorption on soils is determined by the amount and type of clay minerals present in the soils (Roberts et al, 2002) Phenoxyalkanoic acids (such as MCPA) and their derivatives constitute a large group of herbicides that are used extensively in agriculture. This type of organic pesticide has a carboxyl group that is mainly responsible for the interactions with soil components (Tunega et al, 2004).…”

H5N1 Influenza Virus Induces a Parkinsonian Pathology

“…Rotenone was first isolated from the roots and stems of several plants and has been used as a pesticide and fish poison (21,22). Highly lipophilic, rotenone easily penetrates the blood-brain barrier and accumulates in the mitochondria, inhibiting complex I of the electron transport chain.…”