Arsenic is not an essential element and can be toxic to both plants and animals in high concentration. There is a demonstrated association between soil arsenic (As) and the occurrence of straighthead (a physiological disorder in rice characterized by panicle sterility and yield loss); however, the relationship between grain-As accumulation and straighthead susceptibility in rice is not yet fully understood. The objective of the current study was to evaluate a set of diverse rice cultivars, including both indica and japonica subspecies, for total grain-As (TGAs) and As-species concentrations in 2004, 2005, and 2007, on a native (moderate As-concentration) paddy soil and an adjacent monosodium monomethylarsonate (MSMA) amended soil. Cultivars were evaluated under both continuously flooded and intermittently flooded (saturated) field conditions. The genotypic differences in the occurrence of straighthead, total grain-As (TGAs) and As-species concentrations, and their relationships with plant growth parameters, e.g., heading date, plant height, and yield were assessed. The cultivars exhibited a considerable range in both TGAs and grain-As species concentrations. In 2004 and 2005, twenty-one rice cultivars replicated on native soil under continuous flooding showed significant differences in TGAs and As-species concentrations by genotype and year. In 2005, heading was generally delayed in the rice cultivars, resulting in reduced yields that were likely associated with unusually high temperatures and prolonged exposure to stresses in the field, including prolonged flooding and associated soil-As induced stresses. Lower grain-As concentrations were generally associated with early maturing and high yielding genotypes, but with some exceptions. Total grain-As concentrations were not correlated to straighthead susceptibility suggesting that high As concentration in rice grain might not be a direct cause of the genotype-dependent panicle sterility associated with MSMA in soil. The rice cultivars grown on the MSMA-flooded treatment could be effectively differentiated for their relative straighthead susceptibility, with scores ranging from 1 to 8 for the most resistant to the most susceptible genotypes, respectively. In general, traits such as low grain-iAsIII concentration,early maturity, and high yield were correlated with straighthead resistance. In the MSMA-flooded treatment, very high grain-As accumulation resulted in elevated rice-grain dimethyl-AsV (DMAsV) concentration, whereas, the concentration of the more harmful inorganic-AsIII species was less affected. The TGAs and As-species concentrations were considerably higher in continuously--flooded soil than the intermittently-flooded soil. The variations in TGAs and grain-DMAsV concentrations were more highly influenced by water regime than by genotype, whereas, grain-iAIII concentrations were more highly genotype dependent. In the native soil with intermittent flooding, the concentrations of grain-DMAsV and the less desirable grain-iAIII concentrations were lowest. The study concluded that for attaining lower As accumulation in the rice grain both genotype selection and water management are potentially useful approaches.

Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 2002? / Bibliography: leaves 174-204.

No description available.

Thesis (Ph. D.)--University of Minnesota, 1926. / Biography. "Literature cited": p. 41-43.

Rice grows in saturated soil water condition and its requirement for water is highest amongst other cereal crops. In India, the southwest monsoon wind regime brings rainfall that provides a favourable environment for rice cultivation. Thus, there is significant dependency ofrice production on the southwest monsoon rainfall. Being a crop that grows across diverse climatic regions in India ranging from the humid to semi-arid, it offers possibility to explore therelationship between stable isotopic compositions in the grain organic matter with the climaticfactors relevant for its growth. In this thesis, we measured the isotopic compositions of oxygen, hydrogen and carbon of several rice genotypes that were cultivated during the southwest monsoon in diverse climatic regions across the Indian landmass. These isotopic values were then compared with the seasonalaverage values of climate factors such as relative humidity and temperature. Together with thiswe also studied the dependency of the oxygen isotope composition of the grain OM (δ18OOM) onthat of the source water (δ18OSW). Upon removal of δ18OSW effect from δ18OOM, we obtained astrong and significant relationship between the 18O enrichment in grain organic matter (definedas 18OOM) with relative humidity. The gradient recorded was 0.45‰ shift in 18OOM with 1%change in the relative humidity level. This relationship can potentially be used to estimate thepast variations in relative humidity (and by extension, can provide a measure of monsoon rainfallvariations). We further validated this relationship based on experiments carried out in aglasshouse where all the physical factors were well-monitored. Together with this, carbonisotopic composition measured in the rice grain organic matter were used to infer the water useefficiency of rice grown in different climatic settings. The stable isotope approach was furtherimplemented for studying the archaeological rice grains recovered from archaeological sites. Analysis of carbon isotopic composition of archaeological rice grains from seven archaeologicalsites (Balu, Kanmer, Ojiyana, Lahuradewa, JognaKhera, Hulas and Kunal), belonging to theHarappan civilization and other contemporary cultures provided a new suit of data on quantitativeestimate of the hydroclimatic condition (specifically relative humidity) and water availabilityduring the existence of this civilization.

Rice grows in saturated soil water condition and its requirement for water is highest amongst other cereal crops. In India, the southwest monsoon wind regime brings rainfall that provides a favourable environment for rice cultivation. Thus, there is significant dependency ofrice production on the southwest monsoon rainfall. Being a crop that grows across diverse climatic regions in India ranging from the humid to semi-arid, it offers possibility to explore therelationship between stable isotopic compositions in the grain organic matter with the climaticfactors relevant for its growth. In this thesis, we measured the isotopic compositions of oxygen, hydrogen and carbon of several rice genotypes that were cultivated during the southwest monsoon in diverse climatic regions across the Indian landmass. These isotopic values were then compared with the seasonalaverage values of climate factors such as relative humidity and temperature. Together with thiswe also studied the dependency of the oxygen isotope composition of the grain OM (δ18OOM) onthat of the source water (δ18OSW). Upon removal of δ18OSW effect from δ18OOM, we obtained astrong and significant relationship between the 18O enrichment in grain organic matter (definedas 18OOM) with relative humidity. The gradient recorded was 0.45‰ shift in 18OOM with 1%change in the relative humidity level. This relationship can potentially be used to estimate thepast variations in relative humidity (and by extension, can provide a measure of monsoon rainfallvariations). We further validated this relationship based on experiments carried out in aglasshouse where all the physical factors were well-monitored. Together with this, carbonisotopic composition measured in the rice grain organic matter were used to infer the water useefficiency of rice grown in different climatic settings. The stable isotope approach was furtherimplemented for studying the archaeological rice grains recovered from archaeological sites. Analysis of carbon isotopic composition of archaeological rice grains from seven archaeologicalsites (Balu, Kanmer, Ojiyana, Lahuradewa, JognaKhera, Hulas and Kunal), belonging to theHarappan civilization and other contemporary cultures provided a new suit of data on quantitativeestimate of the hydroclimatic condition (specifically relative humidity) and water availabilityduring the existence of this civilization

Rice grows in saturated soil water condition and its requirement for water is highest amongst other cereal crops. In India, the southwest monsoon wind regime brings rainfall that provides a favourable environment for rice cultivation. Thus, there is significant dependency ofrice production on the southwest monsoon rainfall. Being a crop that grows across diverse climatic regions in India ranging from the humid to semi-arid, it offers possibility to explore therelationship between stable isotopic compositions in the grain organic matter with the climaticfactors relevant for its growth. In this thesis, we measured the isotopic compositions of oxygen, hydrogen and carbon of several rice genotypes that were cultivated during the southwest monsoon in diverse climatic regions across the Indian landmass. These isotopic values were then compared with the seasonalaverage values of climate factors such as relative humidity and temperature. Together with thiswe also studied the dependency of the oxygen isotope composition of the grain OM (δ18OOM) onthat of the source water (δ18OSW). Upon removal of δ18OSW effect from δ18OOM, we obtained astrong and significant relationship between the 18O enrichment in grain organic matter (definedas 18OOM) with relative humidity. The gradient recorded was 0.45‰ shift in 18OOM with 1%change in the relative humidity level. This relationship can potentially be used to estimate thepast variations in relative humidity (and by extension, can provide a measure of monsoon rainfallvariations). We further validated this relationship based on experiments carried out in aglasshouse where all the physical factors were well-monitored. Together with this, carbonisotopic composition measured in the rice grain organic matter were used to infer the water useefficiency of rice grown in different climatic settings. The stable isotope approach was furtherimplemented for studying the archaeological rice grains recovered from archaeological sites. Analysis of carbon isotopic composition of archaeological rice grains from seven archaeologicalsites (Balu, Kanmer, Ojiyana, Lahuradewa, JognaKhera, Hulas and Kunal), belonging to theHarappan civilization and other contemporary cultures provided a new suit of data on quantitativeestimate of the hydroclimatic condition (specifically relative humidity) and water availabilityduring the existence of this civilization.