Annals of Botany

AsPi-ring to disallow arsenic access

Significant numbers of consumers in the more affluent nations now express concerns about pesticide and herbicide residues on or in their food plants. Some of that concern is justified in that specific safety limits have been laid down for certain compounds and the relevant food safety organizations are charged with ensuring that those limits are not exceeded. However, it is rare for concerns to be expressed about what is in plants ‘naturally’ and yet chemicals that are injurious to human health may well be synthesized or accumulated by plants, including some crop species. Arsenic is a case in point: phosphate and arsenate are taken up into plants by the same transport systems. Chemically, the two are very similar but, of course, one is an essential nutrient and the other is a poison. For the most part, this is not a problem and, anyway, the food safety regulators have also set limits for arsenic in food plants. However, in soils with high arsenic contents, arsenate accumulation is a problem. On a global scale, more marginal land, including land containing arsenic, is likely to come under cultivation. Accordingly, the work of Zhu et al. (Beijing and Shanghai, China and Adelaide, Australia, pp. 631–636) is particularly important. They have examined the uptake, from hydroponic solution, of arsenate and phosphate by two wheat cultivars and by doubled haploid lines derived from these cultivars. The kinetics of uptake were consistent with the well-known two-component transport model and gave a clear picture of the relative affinities for phosphate and arsenate. More significantly, one of the parental lines and three of the derived genotypes were shown to discriminate against arsenic. The molecular basis for this discrimination has yet to be determined but it will be extremely interesting to follow further progress as the inheritable molecular basis for this discrimination is uncovered.

Professor J. A. Bryant
University of Exeter, UK
j.a.bryant{at}exeter.ac.uk