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The selenium (Se) status in South Australian adults from 1977 to 2002 is studied. It is concluded that men had a marginally higher plasma Se concentration than women.

Increasing chloride (Cl) concentration in soil solution has been shown to increase cadmium (Cd) concentration in soil solution and Cd uptake by plants, when grown in phosphate fertilizer– or biosolid‐amended soils. However, previous experiments did not distinguish between the effect of Cl on biosolid‐borne Cd compared with soil‐borne Cd inherited from previous fertilizer history. A factorial pot experiment was conducted with biosolid application rates of 0, 20, 40, and 80 g biosolids kg−1and Cl concentration in soil solution ranging from 1 to 160 mMCl. The Cd uptake of wheat (Triticum aestivumL. cv. Halberd) was measured and major cations and anions in soil solution were determined. Cadmium speciation in soil solution was calculated using GEOCHEM‐PC. The Cd concentration in plant shoots and soil solution increased with biosolid application rates up to 40 g kg−1, but decreased slightly in the 80 g kg−1biosolid treatment. Across biosolid application rates, the Cd concentration in soil solution and plant shoots was positively correlated with the Cl concentration in soil solution. This suggests that biosolid‐borne Cd is also mobilized by chloride ligands in soil solution. The soil solution CdCl+activity correlated best with the Cd uptake of plants, although little of the variation in plant Cd concentrations was explained by activity of CdCl+in higher sludge treatments. It was concluded that chloro‐complexation of Cd increased the phytoavailability of biosolid‐borne Cd to a similar degree as soil (fertilizer) Cd. There was a nonlinear increase in plant uptake and solubility of Cd in biosolid‐amended soils, with highest plant Cd found at the 40 g kg−1rate of biosolid application, and higher rates (80 g kg−1) producing lower plant Cd uptake and lower Cd solubility in soil. This is postulated to be a result of Cd retention by CaCO3formed as a result of the high alkalinity induced by biosolid application.

Boron (B) deficiency is a common abiotic stress in many countries and is known to reduce canola yields. Growing B-efficient canola cultivars on deficient soils can reduce the impact of this deficiency, but to date little is known of the mechanisms associated with the efficiency trait. This work investigated the factors underlying the observed genotypic variation in the ability of different cultivars of canola (Brassica napus L.) to grow under low B supply. Previous studies have identified the cultivars Huashuang-2 and Dunkeld as B-efficient and the cultivar Barossa as B-inefficient. It was found that in Huashuang-2, efficiency was not related to uptake of B to the shoots, possibly indicating efficiency in B utilisation. A correlation was established between B efficiency and the ratio of the B concentration in the younger relative to the older leaves. Comparison of the distribution of B in young and old leaves under deficient and adequate B conditions showed that when B was limited, the concentration of B in the older leaves decreased with plant age, whereas when sufficient B was supplied, the concentration in these leaves continued to increase with age. The loss of B from mature leaves under deficient conditions suggested retranslocation to other tissues. Experiments in which boric acid enriched with 10 B was applied to mature leaves showed that in only one of the efficient cultivars, Huashuang-2, was B retranslocated to younger leaves. In the other two cultivars, the sink for the 10 B exported from the older leaves was not identified. It was concluded that there exist multiple mechanisms for B efficiency in canola. Keywords: boron, Brassica napus L., canola, efficiency, phloem, retranslocation.

Nineteen annual Medicagogenotypes from eight species were grown in Mt. Compass sand at three levels of soil Zn application (0, 0.1 and 0.9 mg Zn kg-1) to achieve Zn status from deficiency to adequacy. Genotypes differed in growth response: under Zn deficiency, those classified as Zn-efficient had less reduction in shoot growth, a higher root mass, greater concentration of Zn in the shoot and total Zn content per plant, and a stable shoot/root ratio compared with Zn-inefficient genotypes. While seed Zn content did not influence the Zn-efficiency ranking, it did affect yield, and so it plays an important role in yield response and Zn accumulation as Zn supply decreases.

In the search for genetic material with high iron and zinc concentration in wheat grain, a significant positive correlation has been found between iron and zinc concentrations, suggesting that these two traits may be combined relatively easily during breeding. In future research, the very high values of iron and zinc in the grain seen in wild types and landraces need to be confirmed in trials in which all the best material is planted in the same location and year. In addition, it is important to determine if these high levels of iron and zinc in the grain can be maintained in high-yielding material.The production of semi-dwarf wheat through the introduction of therht genes has resulted in substantial yield increases. However, this is associated with a reduction in iron and zinc concentrations in some bread wheat genotypes, but not in durum wheat. The presence of the 1B/1R translocation in the wheat germplasm ofthe Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT) to increase leaf rust resistance may have had a positive effect on the concentration of iron and zinc, but a negative effect was ruled out. There is a strong positive correlation between grain yield and year of release in the CIMMYT wheat varieties. There is a small negative but statistically significant relationship between the time of release and the concentrations of iron, zinc, total phosphorus, and phytate. The positive effect of nitrogen applications on iron and zinc concentrations is more important than declines in these concentrations due to breeding during the last 42 years

In 1992 the International Rice Research Institute (IRRI) began to examine the effect of certain soil characteristics on the iron content of rice grains. As part of the Consultative Group for International Agricultural Research (CGIAR) Micronutrients Project, this effort was expanded in 1995 to include analysis of both iron and zinc, in collaboration with the University of Adelaide in Australia. Since then, germplasm screening has shown large genetic variation for iron and zinc concentrations in brown rice. Common cultivars contain about 12 mg of iron and 25 mg of zinc per kilogram. Some traditional varieties have double these amounts. Genetic-by-environmental interactions are sufficiently moderate that breeding for higher iron and zinc content is considered worthwhile. The next major research step will be to further study the genetics of trace mineral accumulation in the grain to determine the best selection techniques for use in breeding. High iron and zinc traits can be combined with improved agronomic traits. This has already been demonstrated in the serendipitous discovery in the IRRI testing programme of an aromatic variety (IR68144-3B-2-2-3) that has a high concentration of grain iron, about 21 mg/kg in brown rice. This elite line has good tolerance to rice tungro virus and to mineral-deficient soils and has excellent grain qualities. The yields are about 10% below those of IR72, but in partial compensation, maturity is earlier. After 15 minutes of polishing, IR68144-4B-2-2-3 had about 80% more iron than IR64, a widely grown commercial variety. It remains to be shown that this extra iron can improve the iron status of iron-deficient human subjects. A human feeding trial is being planned.

Micronutrient malnutrition currently affects over 2 billion people worldwide. Poor health, low worker productivity, high rates of mortality and morbidity, increased rates of chronic diseases (coronary heart disease, cancer, stroke, and diabetes), and permanent impairment of cognitive abilities of infants born to micronutrient-deficient mothers are all consequences of micronutrient malnutrition. Furthermore, these deficiencies are contributing to lethargic national development efforts, continued high population growth rates, and a vicious cycle of poverty for massive numbers of underprivileged people in all nations. Food systems globally are not providing enough balanced nutrient output to meet all the nutritional needs of every person, especially resource-poor women, infants, and children in developing countries. Agriculture is partly responsible. It has never made adequate and balanced nutrient output an explicit goal of its production systems. Many agricultural policies may have fostered a decline in nutrition and diet diversity for the poor during the past four decades. Additionally, the nutrition and health communities have never considered using agriculture as a primary tool in their programmes directed at alleviating poor nutrition and ill health globally. A new paradigm for agriculture and nutrition is now needed. We must consider ways that agriculture can contribute to finding sustainable solutions to food system failures through holistic food-based system approaches, thereby closely linking agricultural production to improving human health, livelihood, and well-being. Such action will rouse support for agricultural research worldwide, because it addresses consumer issues as well as agricultural production issues and is, therefore, politically supportable.

The general objective of the Consultative Group on International Agricultural Research (CGIAR) Micronutrients Project is to assemble the package of tools that plant breeders will need to produce mineral- and vitamin-dense cultivars. The target crops are rice, wheat, maize, phaseolus beans, and cassava. The target micronutrients are iron, zinc, and vitamin A. The combining of benefits for human nutrition and agricultural productivity, resulting from breeding staple food crops that are more efficient in the uptake of trace minerals from the soil and that load more trace minerals into their seeds, results in extremely highex ante estimates of benefit–cost ratios for investments in agricultural research in this area. This finding derives from the confluence of several complementary factors. The rates of micronutrient malnutrition are high, as are the consequent costs to human welfare and economic productivity. High trace mineral density in seeds produces more viable and vigorous seedlings, and efficiency in the uptake of trace minerals improves disease resistance. Trace-mineral-“deficient” soils in fact contain high amounts of trace minerals that are “unavailable” to staple crop varieties presently grown. Adoption of nutritionally improved varieties by farmers can rely on profit incentives; delivery to consumers can rely on existing demand behaviour. Relatively small investments in agricultural research at a central research location may be disseminated widely. Breeding advances are derived from initial, fixed costs, with low recurring costs. The encouraging research results obtained to date under the project would seem to justify a much expanded effort in the future.

As part of the Consultative Group on International Agricultural Research (CGIAR) Micronutrients Project, we have investigated the content of carotenoids in staple foods, particularly wheat. Wheat varies widely in carotenoid content, depending on the variety and type. Durum (pasta) wheat is generally higher in carotenoid content, because the market has continued to demand strong pigment in pasta and noodle products, whereas in bread wheat the market demands flour as white as possible. Consequently, twentieth-century wheat breeders have consciously selected wheat varieties low in carotenoid content, although older, high-carotenoid bread wheats are still available and the trait is not lost. The entire carotenoid biosynthetic pathway exists in wheat grains, so varieties high in β-carotene and/or other carotenoids can be reintroduced if and when education in nutrition creates the demand. Numerous high-yielding maize varieties high in β-carotene already exist and have been used to eliminate vitamin A deficiency in livestock. A β-carotene–rich rice has been genetically engineered recently. Although the carotenoid content of beans has not yet been explored, high–β-carotene lines of cassava exist, and the trait is easily handled in a breeding programme. Yellow types of most staples are known, for example, sorghum, potatoes, and sweet potatoes. The amounts present are such that we can assert that vitamin A deficiency could easily be eliminated globally by delivering the required amounts via food staples. Moreover, there are strong signs that other benefits in eye health, enhanced absorption of iron from non-haem sources, anticarcinogenic effects, enhanced aroma, and better storage life may also result.

AbstractFood-based approaches to addressing micronutrient malnutrition in much of the human population have hitherto been based mainly on balancing cereal-based diets with vegetables, and to a lesser extent, animal products. Although high in micronutrients, these commodities are more expensive foods than staples, and also more seasonal, subject to spoilage, and difficult to store and transport. Moreover, their availability in some countries is only 10–15% of what is required to meet the needs of the people (Ali et al., 1994). Because of the wide availability of staples, their high proportion in the diet of the most malnourished, because field fortification has several advantages over fortification during processing, and because staples are known for their low content of these essentials, we have studied the possibility of breeding to improve plant staples as sources of micronutrients for humans. This is in response to the WHO/FAO call for a food-based solution to micronutrient malnutrition which is considered now to affect more than 2 billion people world-wide (WHO, 1992).

Because copper is extremely important to the development of normal polllen, an attempt was made to induce male sterility in wheat by applying specific copper-binding ligands to wheat plants. Four different chelates were used at two rates in three methods of application. All four chelates, cupferron, neocuproine, benzotriazole and cuprizone, reduced grain yield at high concentration applied to the soil at sowing but benzotriazole was most effective, even when applied at late tillering to either soil or foliage, and it also reduced yield to a lesser extent when applied at low concentration. At high concentration of benzotriazole (50 mg kg-1 of dry soil) the percentage of pollen staining with I2/KI was very low (0–7%) depending on method of chelate application), and this soil treatment resulted in complete male sterility. The appearance of the pollen, anthers, grain, ears and leaves in many cases mimicked that of normal copper deficiency, and also that caused by other recognised gametocides. These results raise the question of whether binding of copper or some other disturbance of copper metabolism may be the mechanism by which andro-gametocidal chemicals work and if so, dictate a theoretical basis for selecting such chemicals for testing.

The hypothesis that Zn deficiency enhances the accumulation of B in barley (Hordeum vulgareL.) was tested in plants grown in nutrient solutions containing varying concentrations of B. Mean daily B uptake rates in 3‐week‐old seedlings supplied no Zn (−Zn treatment) were from 2 to 2.5 times higher as in plants supplied 2 µMZn (+ Zn treatment). These effects were observed after only 7 d growth without added Zn. During this time, Zn in grain reserves and contaminant‐Zn were still adequate to maintain all plants with an internal tissue Zn concentration well above the critical tissue concentration (about 15 mg kg−1Zn on a dry weight basis), and no yield response to Zn supplementation occurred. The effects of Zn on B uptake, therefore, support the concept that Zn performs a protective role at the external surfaces of, or in, root‐cell membranes. When the concentration of B in the nutrient solution was extremely high (e.g., 3000 µM), this protective effect of Zn disappeared and plants in all treatments developed B toxicity symptoms and accumulated high B concentrations. Other nutrients were also accumulated under Zn deprivation—namely, P, NO3, S, Ca, Mg, K, and Cu, but not Fe. Higher concentrations of P in the nutrient solution resulted in higher uptake rates of all ions, especially in the ‐Zn plants. A similar but smaller effect of added P on ion uptake occurred in +Zn plants.

The effect of length of dry storage period and subsequent moist incubation on the availability of Mn was examined in a calcareous soil. Increasing the time of dry storage (for up to 4 years) generally increased the availability of Mn as determined by plant growth and Mn concentration in wheat and barley. Moist incubation of stored soil had variable effects on Mn availability depending on how long the soil had been stored before use and on the method used to assess Mn availability. When assessed by Mn concentration in plant tissues, increasing the moist incubation time (from 0 to 30 days) of soil stored dry for 4 years increased Mn availability in soil initially and thereafter decreased it. However, incubation time had little effect on Mn availability in soil stored for only 1 year or soil used fresh from the field. When Mn availability was assessed using a chemical extractant (DTPA; diethylenetriaminepentaacetic acid), both soils showed an initial increase in Mn availability immediately on wetting. However, Mn availability in the soil stored for only 1 year decreased rapidly and remained consistently below that of soil stored for 4 years. In the latter soil, Mn availability also decreased but only after a few days. Microbial studies indicated that there was a decrease in the ratio of Mn oxidising to Mn reducing microorganisms with increasing storage time. Inoculation of one soil with another suggested that the factor responsible for the low Mn availability in soils stored for a short period could be transferred to soils stored for a longer period. These results suggest that the change in Mn availability in a calcareous soil with dry storage is a result of changes in microbial populations that cannot be fully restored by moist incubation.

THE aim in producing Triticale was to combine the hardiness and tolerance of low soil fertility of rye with the superior yield and bread-making qualities of wheat1, but there has been little experimental evidence that triticales carry the desirable characteristics from rye2. We present here evidence of the tolerance of triticale to low concentrations of available copper in soil, a condition widely associated with poor sandy soils in Australia3. Such soils may contain enough total copper for tens of thousands of crops but it is relatively unavailable to widely grown cultivars of wheat, oats and barley. In contrast, rye rarely shows a response to copper on these soils4–7.

For Abstract see ChemInform Abstract in Full Text.

Worldwide, barley is often grown on zinc (Zn) deficient soils. Screening for varieties tolerant of low soil Zn (Zn-efficient varieties) generally involves assessing growth or yield of plants grown at different levels of Zn supply. Seed nutrient reserves can influence the growth of the plant; however, there have been no reports on the effect of seed Zn content on the growth of barley. In 2 experiments, we studied the effect of seed Zn content on early growth of barley in 2 genotypes, Amagi Nijo and Tantangara. In Expt 1, the amounts of Zn in the seed ranged from 0.4 to 0.7 µg/seed, whereas in Expt 2, seed Zn ranged from 0.7 to 5.0 µg/seed. The plants were grown in a Zn-deficient siliceous sand with Zn added at 0, 0.04, 0.2, 0.8, and 3.2 mg Zn/kg soil in Expt 1 and at 0, 0.04, and 0.8 mg Zn/kg soil in Expt 2, and harvested at tillering. Growth and expression of visual symptoms were measured. Plants grown from seed with low Zn content developed symptoms of Zn deficiency by the 2-leaf stage in soil with no soil-applied Zn. Symptoms were reduced markedly as seed Zn content increased. Shoot and root growth increased as the amount of Zn in seed increased, but the effect was most evident when soil Zn supply was limiting plant growth (≤0.04 mg Zn/kg soil). For instance, when no Zn was added to the soil, shoot dry weight of plants grown from high-Zn seed was 108% greater than that of plants grown from low-Zn seed, whereas at 0.04 and 0.8 mg Zn/kg soil, the increases were only 52% and 18%, respectively. Soil Zn application significantly increased tissue Zn concentrations. However, the effect of seed Zn content on tissue Zn concentrations was significant only at very high levels of seed Zn. The results presented showed that seed Zn improves vegetative growth in barley, especially when Zn supply is deficient for plant growth. Seed Zn content also affected the determination of Zn efficiency of genotypes, and comparisons of dry matter production of seedlings grown from seed with a wide range in Zn content may alter their rankings for Zn efficiency as determined in this pot assay. The results indicate that seed of similar Zn content needs to be used when comparing genotypes for determination of Zn efficiency. Additional keywords: Zn deficiency, Zn efficiency.

Transmembrane potentials (PD) of root cortical cells were measured between the vacuole and the external solution while the roots remained attached to the plants. External solution concentration was varied by using a range of dilutions of a balanced nutrient solution. In all cases the PD was more negative than that due to diffusion alone indicating the presence of an electrogenic or metabolically derived component. This component contributed an additional –80 mV to the PD and was relatively independent of the external solution concentration. The metabolic component was eliminated by metabolic inhibitors, placing the shoot in darkness, ringing the phloem, or severing the rootlet from the shoot; it was restored again by removing the inhibitor, by light, or, in the case of severance, by adding 25 mM sucrose to the medium. The magnitude of the electrogenic component of the PD was dependent on the antecedent light intensity in a way reminiscent of translocation itself.

The effect of ringing the stem on the electrical potential difference (PD) in the root cortical cells of H. annuus was studied. PD and salt transport were followed simultaneously. By ringing it was possible to separate the PD from K+, $$N{O}_{3}^{-}$$, and Cl− uptake and H+ efflux. The uptake of phosphate however was found to be closely connected with a component of the PD. It was concluded that there is an electrogenic pump for phosphate in these roots which generates 60–80 mV.

Perturbations in the local electric field sensed during the passage of a micro-electrode through cellular tissue cannot be recorded with a conventional chart recorder because the response time is far too slow. This was overcome by using a micro-computer to record the rapid changes in electrical potential difference (PD). Transient PDs were rapidly collected and digitized, stored digitally, and replayed in analog at a slower speed afterwards. Some ‘control’ experiments to verify the speed of the data acquisition system and demonstrate the absence of quantitative artefacts in this procedure were performed. We have used this system to investigate cell PDs in the roots of wheat seedlings. Certain abrupt transients clearly represented the boundaries of the cells; this enabled further interpretation of individual cell PDs. Cyanide addition resulted in a major change in the transients within a minute, with a smaller component of the cell PD, interpreted as the diffusion potential, remaining. Ethanol treatment gave a predictable loss of membrane integrity, seen as discharging membrane PDs. The value of this new use of a digital data system is discussed.

Time of application of Cu as soil dressing or foliar spray had large effects on grain yield of wheat plants grown in Cu-deficient soil in the glasshouse. Times of application of Cu (4 mg per pot in one dose) ranged from sowing to maturity in weekly intervals. The soil dressing of Cu produced excellent grain yield if applied any time from sowing to early boot stage. Little or no grain formed on any tillers which had passed this critical early boot stage at the time of application; the pollen produced by these tillers was non-viable, anthers were not exserted, and maturation was delayed. These results suggest that microsporogenesis was interrupted by Cu deficiency at or near meiosis. Tillering was the optimum time for foliar application of Cu (CuSO4 + Ca(0H)2 in suspension); early or late applications failed to produce grain. However, this form of Cu proved unsatisfactory for foliar application under glasshouse conditions, possibly owing to the absence of rain or dew.