660 publications from this institution
Rice is the staple food for half of the world’s population. Consumption of rice is the major exposure route globally to the class one, non-threshold carcinogen inorganic arsenic. This book explains the sources of arsenic to paddy soils and the biogeochemical processes and plant physiological attributes of paddy soil-rice ecosystems that lead to high concentrations of arsenic in rice grain. It presents the global pattern of arsenic concentration and speciation in rice, discusses human exposures to inorganic arsenic from rice and the resulting health risks. It also highlights particular populations that have the highest rice consumptions, which include Southern and South East Asians, weaning babies, gluten intolerance sufferers and those consuming rice milk. The book also presents the information of arsenic concentration and speciation in other major crops and outlines approaches for lowering arsenic in rice grain and in the human diet through agronomic management.
• To examine whether root exudates of the Zn/Cd hyperaccumulator Thlaspi caerulescens play a role in metal hyperaccumulation, we compared the metal mobilization capacity of root exudates collected from two ecotypes of T. caerulescens, and from the nonaccumulators wheat (Triticum aestivum) and canola (Brassica napus). • Plants were grown hydroponically and three treatments (control, –Fe and –Zn) were later imposed for 2 wk before collection of root exudates. • On a basis of root d. wt, the total soluble organic C in the root exudates of T. caerulescens was similar to that of wheat, and significantly higher than that of canola. In all treatment, the root exudates of T. caerulescens and canola mobilized little Cu and Zn from Cu- or Zn-loaded resins, and little Zn, Cd, Cu or Fe from a contaminated calcareous soil. By contrast, the root exudates of wheat generally mobilized more metals from both resin and soil. In particular, the –Fe treatment, and to a lesser extent the –Zn treatment, elicited large increases in the metal mobilization capacity of the root exudates from wheat. • We conclude that root exudates from T. caerulescens do not significantly enhance mobilization of Zn and Cd, and therefore are not involved in Zn and Cd hyperaccumulation.
Summary Arsenic (As) is an element that is nonessential for and toxic to plants. Arsenic contamination in the environment occurs in many regions, and, depending on environmental factors, its accumulation in food crops may pose a health risk to humans. Recent progress in understanding the mechanisms of As uptake and metabolism in plants is reviewed here. Arsenate is taken up by phosphate transporters. A number of the aquaporin nodulin26‐like intrinsic proteins (NIPs) are able to transport arsenite, the predominant form of As in reducing environments. In rice ( Oryza sativa ), arsenite uptake shares the highly efficient silicon (Si) pathway of entry to root cells and efflux towards the xylem. In root cells arsenate is rapidly reduced to arsenite, which is effluxed to the external medium, complexed by thiol peptides or translocated to shoots. One type of arsenate reductase has been identified, but its in planta functions remain to be investigated. Some fern species in the Pteridaceae family are able to hyperaccumulate As in above‐ground tissues. Hyperaccumulation appears to involve enhanced arsenate uptake, decreased arsenite‐thiol complexation and arsenite efflux to the external medium, greatly enhanced xylem translocation of arsenite, and vacuolar sequestration of arsenite in fronds. Current knowledge gaps and future research directions are also identified. Contents Summary 777 I. Introduction 777 II. Mechanisms of arsenic uptake and efflux 778 III. Rhizosphere interactions 782 IV. Arsenic metabolism in planta 783 V. Long‐distance translocation of arsenic 786 VI. Arsenic hyperaccumulation 788 VII. Conclusions 788 Acknowledgements 789 References 789
No abstract is provided for this article.
No abstract is provided for this article.
Summary Yield losses in agricultural crops as a result of sulphur deficiency are increasing in the UK, because of the decrease in sulphur dioxide emissions and changes in fertiliser practices. Therefore, there is a need for a reliable and practical diagnostic indicator to predict early in the growing season whether it is necessary to apply S fertiliser, but also to avoid the application of fertiliser when not necessary. A successful diagnostic indicator should be reliable and stable throughout plant development, but also easily measured with great accuracy and as little effort as possible. In this paper the difficulties and problems with currently used diagnostic tests for S deficiency, such as total S, sulphate or the N:S ratio, will be discussed. A more reliable and practical indicator of S deficiency is the malate: sulphate peak area ratio which is at present being developed for use by commercial laboratories and their customers.
Rice (Oryza sativa) is a main source of human exposure to inorganic arsenic and mitigation measures are needed to decrease As accumulation in this staple c
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Salvia species is a member of the Lamiaceae family, and it also possesses medicinal and horticulture values. The genetic diversity was assessed through sequence-related amplified polymorphism. To uncover genetic diversity and species characteristics in Salvia species were studied through a combination of morphological and molecular data. One hundred forty-five individuals related to 30 Salvia were collected in 18 provinces. A total of 157 (Number of total loci) (NTL) DNA bands were produced through polymerase chain reaction (PCR) from 30 Salvia species. These bands were produced with the combinations of 10 selective primers. The total number of amplified fragments ranged from 10 to 20. The predicted unbiased heterozygosity (H) varied between 0.11 (Salvia urmiensis) and 0.31 (Salvia limbata). High Shannon’s information index was detected in Salvia limbata. The genetic similarities between 30 species are estimated from 0.46 to 0.91. Clustering results showed two major clusters. According to the SRAP (Sequence-related amplified polymorphism) markers analysis, Salvia hydrangea and Salvia sharifii had the lowest similarity. Salvia bracteata and Salvia suffruticosa were genetically dissimilar to each other. This study also detected a significant signature of isolation by distance. Present results showed that sequence-related amplified polymorphism has the potential to decipher genetic affinity between Salvia species. Current results have implications in biodiversity and conservation programs. Besides this, present results could pave the way for selecting suitable ecotypes for forage and pasture purposes in Iran.
Archived wheat (Triticum aestivum L.) grain and straw, and soil samples from the control plot of the Rothamsted Broadbalk Experiment, located in southeastern England and established in 1843, were used to investigate the effects of dramatically changing SO2 pollution inputs on the concentrations and stable isotope ratios (δ34S) of S in the samples. Representative coal samples from UK major coal fields were also determined for δ34S. Concentrations of S showed no clear trends in either grain or straw over the 155 years from 1845 to 1999. However, grain and straw δ34S decreased rapidly from 6 to 7‰ in 1845 to −2 to −5‰ in the early 1970s, and since then have increased to 0.5 to 2‰ in the late 1990s. This pattern mirrored the trend of UK SO2 emissions over the 155 years. Both grain and straw δ34S correlated strongly and negatively with UK SO2 emissions (R2 > 0.89), but the relationships were different for the pre- and post-1970 data sets. Soil δ34S also decreased considerably, from 8.2‰ in 1865 to 3.7 to 4.5‰ during 1965–1999. A negative δ34S value was inferred for the anthropogenic S deposited at the experimental site before 1970, and further confirmed by negative δ34S values (−6 to −10‰) found in the coal samples from southeastern England and southern Wales. Based on the S isotope ratios, we estimated that anthropogenic S contributed 62 to 78% of the S uptake by wheat at the peak of SO2 emissions, and accounted for 28 to 37% of the topsoil S in 1965.
