Field experiments were conducted on wheat to study the effects of foliar-applied iodine(I) alone, Zn (zinc) alone, and a micronutrient cocktail solution containing I, Zn, Se (selenium), and Fe (iron) on grain yield and grain concentrations of micronutrients. Plants were grown over 2 years in China, India, Mexico, Pakistan, South Africa, and Turkey. Grain-Zn was increased from 28.6 mg kg −1 to 46.0 mg −1 kg with Zn-spray and 47.1 mg −1 kg with micronutrient cocktail spray. Foliar-applied I and micronutrient cocktail increased grain I from 24 μg kg −1 to 361 μg kg −1 and 249 μg kg −1 , respectively. Micronutrient cocktail also increased grain-Se from 90 μg kg −1 to 338 μg kg −1 in all countries. Average increase in grain-Fe by micronutrient cocktail solution was about 12%. The results obtained demonstrated that foliar application of a cocktail micronutrient solution represents an effective strategy to biofortify wheat simultaneously with Zn, I, Se and partly with Fe without yield trade-off in wheat.

Summary• Nodulated lupins (Lupinus angustifolius cv. Wonga) were hydroponically grown under conditions of low phosphate (LP) or adequate phosphate (HP) to assess the effect of phosphoenolpyruvate carboxylase (PEPC)-derived organic acids on nitrogen assimilation in LP nodules.• LP conditions are linked to altered organic acid metabolism, by the engagement of PEP metabolism via PEPC. In LP nodules, the enhanced organic acid synthesis may reduce the available organic carbon for nitrogen assimilation. The diversion of carbon between the organic acid-and amino acid pools was assessed through key nodular enzymes and 14 CO 2 metabolism.• Under LP conditions, increased rates of organic acid synthesis via PEPC and malate dehydrogenase (MDH), coincided with reduced nitrogen assimilation via aspartate aminotransferase (AAT), aspartate synthetase (AS) and glutamine synthetase (GS)/ glutamate synthase (GOGAT) activities. There was a preferential metabolism of nodular 14 CO 2 into organic acids and particularly into malate. High malate levels were associated with reduced N 2 fixation and synthesis of amino acids.• These results indicate that phosphorus deficiency can enhance malate synthesis in nodules, but that excessive malate accumulation may inhibit N 2 fixation and nitrogen assimilation.

Summary• Here, nodulated lupins ( Lupinus angustifolius (cv Wonga)) were hydroponically grown at low phosphate (LP) or adequate phosphate (HP).• Routes of pyruvate synthesis were assessed in phosphorus (P)-starved roots and nodules, because P-starvation can enhance metabolism of phospho enol pyruvate (PEP) via the nonadenylate-requiring PEP carboxylase (PEPc) route. Since nodules and roots may not experience the same degree of P stress, it was postulated that decreases in metabolic inorganic phosphorus (P i ) of either organ, should favour more pyruvate being synthesized from PEPc-derived malate.• Compared with HP roots, the LP roots had a 50% decline in P i concentrations and 55% higher ADP : ATP ratios. However, LP nodules maintained constant P i levels and unchanged ADP : ATP ratios, relative to HP nodules. The LP roots had greater PEP metabolism via PEPc and synthesized more pyruvate from PEPc-derived malate. In nodules, P supply did not influence PEPc activities or levels of malate-derived pyruvate.• These results indicate that nodules were more efficient than roots in maintaining optimal metabolic P i and adenylate levels during LP supply. This caused an increase in PEPc-derived pyruvate synthesis in LP roots, but not in LP nodules.

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Phosphate (P) starvation is one of the most limiting nutrients to N z fixation in legumes. Soybeans and lupins present different climatic origins, nodule morphologies and metabolic complexities, which may have various adaptive responses to short-term P starvation. Lupins and soybeans were cultivated hydroponically for 3 weeks. Short-term P starvation was induced for 14 days by switching the P-supply to 2~M P. During P starvation. the lupins showed a lower decline in nodular P concentrations and maintained their biological N 2 fixation (BNF), in contrast to the soybeans. The lupins also maintained their photosynthetic rates and the nodular construction and growth respiration costs under P starvation, whilst soybeans showed a decrease in photosynthetic rates and an increase in nodular construction and growth respiration costs under P starvation. There was a also a shift towards more organic acid synthesis. relative to amino acid synthesis in lupin nodules than soybean nodules under P starvation. The lupins had higher amino acid concentrations in their nodules, whilst the soybean nodules maintained their ureide levels at the expense of a decline in amino acids. These results indicate that lupins may to be better adapted to maintainingBNF during short-term P starvation than the soybeans.