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Barley ( Hordeum vulgare L.), genetically modified with the Al3+ resistance gene of wheat ( TaALMT1), was compared with a non-transformed sibling line when grown on an acidic and highly phosphate-fixing ferrosol supplied with a range of phosphorus concentrations. In short-term pot trials (26 days), transgenic barley expressing TaALMT1 (GP-ALMT1) was more efficient than a non-transformed sibling line (GP) at taking up phosphorus on acid soil, but the genotypes did not differ when the soil was limed. Differences in phosphorus uptake efficiency on acid soil could be attributed not only to the differential effects of aluminium toxicity on root growth between the genotypes, but also to differences in phosphorus uptake per unit root length. Although GP-ALMT1 out-performed GP on acid soil, it was still not as efficient at taking up phosphorus as plants grown on limed soil. GP-ALMT1 plants grown in acid soil possessed substantially smaller rhizosheaths than those grown in limed soil, suggesting that root hairs were shorter. This is a probable reason for the lower phosphorus uptake efficiency. When grown to maturity in large pots, GP-ALMT1 plants produced more than twice the grain as GP plants grown on acid soil and 80% of the grain produced by limed controls. Expression of TaALMT1 in barley was not associated with a penalty in either total shoot or grain production in the absence of Al3+, with both genotypes showing equivalent yields in limed soil. These findings demonstrate that an important crop species can be genetically engineered to successfully increase grain production on an acid soil. [ABSTRACT FROM AUTHOR]

Grevillea leucopteris is a large xeromorphic shrub from nutrient-deficient sandy heathland in south-western Australia. The fruit of G. leucopteris is a follicle which contains two seeds. Leaves and follicles have very low levels of essential nutrients, but seeds have very high levels, especially N, P and trace elements, as well as substantial oil reserves (30% w/w). Grevillea leucopteris appears to be a Ca accumulator because of the very high concentrations of this element in leaves, follicles and seeds. Phloem exudate from incisions in fruiting branches and xylem sap were used to study transport of nutrients to fruits. Phloem sap had 14 to 17% sugar. Glutamine was the major amino compound in xylem and phloem sap. Arginine comprised 37% of the N in xylem sap but was absent in phloem, suggesting its release from storage pools in roots and stems and metabolism in leaves. K dominated the mineral spectrum of phloem sap, and Ca that of xylem. Ca levels in xylem and phloem sap were very high (200 and 500 μg cm-3 respectively), and K: Ca ratios were very low: xylem 05:phloem 3.7. The phloem: xylem concentration ratio for all minerals was 8.7. Reduced transpiration by enclosing fruits in plastic bags or foil changed their K:Ca ratio from 0.95 to 3.13 or 4.48. Each fruit used 11.5 cm³ of water during growth, 76% estimated to arrive in the xylem, the rest via the phloem. The water use efficiency of G. leucopteris fruits was 29.9 cm-3 g-1 dry matter produced, close to values reported for mesomorphic species such as lupin and pea. The high levels of Ca in G. leucopteris fruits are due to high levels of Ca in transport fluids rather than elevated transpiration. [ABSTRACT FROM AUTHOR]