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Background: Molybdenum (Mo) is an essential microelement for higher plants and plays a significant role in nitrogen (N) metabolism, which includes nitrate reduction, assimilation, and efficient N acquisition. Its deficiency in soil may induce the reduction of N uptake and wheat yield. Aims: We aimed to explore the Mo‐induced effects on N uptake efficiency and recovery in Mo‐inefficient winter wheat cultivar using a 15N isotope tracer under different N forms (Nf) and N rates (Nr). Methods: The experiment was conducted in greenhouse conditions, and the treatments included three Nf in the form of 15NH4Cl as sole NH4+, Ca (15NO3)2 as sole NO3−, and 15NH415NO3) under two Nr [low (L) 0.05 and high (H) 0.25 g N kg–1 soil], with (+Mo) in form of [(NH4)6Mo7O24 ∙ 4H2O] and without (–Mo) Mo application. The plant biomass, Mo content, total N uptake, fertilizer 15N uptake, soil N uptake, as well as N uptake, agronomic and physiological efficiency were evaluated. Furthermore, the fertilizer 15N recovery in various wheat organs was also studied. Results: The results revealed that Mo application increased N uptake efficiency in wheat to 38.26%, 68.24%, and 71.53% when the plants are treated with low rates of NH4+, NO3−, and NH4NO3, respectively. While at a high N rate, N uptake efficiency increases to 46.26% and 45.34% in the case of NO3− and NH4NO3 treatments, respectively, and it was slightly reduced to 10.84% when plants were supplied with NH4+ form. Mo supply increased 15N recovery from fertilizer in grain organ under low N rate with all supplied Nf, that is, NH4+, NO3−, and NH4NO3, while at high N rate, Mo enhanced 15N recovery in grains organ in case of NO3− and NH4NO3 forms. Conclusion: This study shows that Mo fertilization may be a promising strategy to improve N uptake efficiency and recovery in wheat when nitrate is the main N form. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo), an essential microelement for plants, animals, and microorganisms, is reported can reduce soil nitrogen (N) residues and regulate plant root growth, but little is known about its effect on soil N transformation in plant-root region. A specially designed rhizobox was used in the present study to investigate the N processes in rhizosphere and non-rhizosphere soils of winter wheat applied with different rates of Mo fertilizer. (1) In the rhizosphere soil, pH values increased with increasing rates of Mo application, nitrate (NO3−-N) accumulated at the rates of 0.15 and 0.3 mg Mo kg−1, potential denitrification activity (PDA) was significantly reduced by application of 0.15-1 mg Mo kg−1, and the copy numbers of narG and nosZ genes were increased by application of 0.15-1 mg Mo kg−1. (2) In the non-rhizosphere soil, NO3−-N content decreased by application of 0.15-0.3 mg Mo kg−1, and narG gene abundance increased obviously by application of 0.3-1 mg Mo kg−1. (3) Soil pH, NO3−-N, apparent nitrification rate (ANR), and nosZ gene abundance were significantly higher in rhizosphere than in non-rhizosphere soil. On the contrary, NH4+-N and total N, PDA, the abundance of AOB, and nirK and nirS genes were significantly higher in non-rhizosphere soil. The results indicated that the N transformations in rhizosphere and non-rhizosphere soils were differently affected by soil application of Mo fertilizer, and rhizosphere played a more important role in soil N cycle processes. The regulatory effects of Mo on these processes were to increase plant biomass and N uptake, promote the NO3−-N accumulation in rhizosphere soil, and weaken the denitrification in both rhizosphere and non-rhizosphere soils. [ABSTRACT FROM AUTHOR]

A pot trial with acid yellow-brown soil was conducted to investigate the effects of molybdenum (Mo) and phosphorus (P) fertilizers on cold resistances of winter wheat. Molybdenum was applied at two rates (0 and 0.15 mg Mo kg−1soil) and P at four rates [0, 100, 200, and 300 mg phosphorus pentoxide (P2O5) kg−1soil] in experiment 1. Both Mo and P fertilizers were applied at two rates (0 and 0.15 mg Mo kg−1soil; 0, 150 mg P2O5kg−1soil) in experiment 2. Seed yield, soluble sugar, water-soluble protein, ascorbic acid (AsA), malondialdehyde (MDA), and abscisic acid (ABA) concentrations were studied. The results indicated that Mo and P fertilizer increased seed yield, soluble sugar, water-soluble protein, and AsA but decreased the MDA. It implied that appropriate Mo applied with P application had beneficial effects on increasing seed yield and enhancing the cold resistance ability through changing biological substances concentration in winter wheat. [ABSTRACT FROM PUBLISHER]

Highlights • NO signal is involved in Mo-improved root growth in wheat under drought stress. • Root pressure is the power of Mo-increased root water uptake. • Aquaporin expression and extensive root morphology play important roles in Mo-increased root water uptake. • Mo supply maintains the mineral nutrient homeostasis in wheat under drought stress. Abstract Molybdenum (Mo) despite elevating drought tolerance is comparatively little understood with regard to underlying mechanisms involved. We herein investigated the effects of Mo on root morphology, root water uptake, aquaporin (AQP) expressions and mineral nutrient concentrations in winter wheat under polyethylene glycol 6000-simulated drought stress (PSD). Our study firstly demonstrated that nitric oxide (NO) signal was involved in Mo-regulated root growth, mainly reflected in Mo supply and NO donors enhanced root morphology such as lateral root length and root tips due to increased NO production; however, NO scavengers decreased root morphology due to decreased NO production under PSD. The root water uptake rate was enhanced by Mo, which positively correlated with root tips and lateral root length. Mo supply improved AQPs expressions, particularly TaPIPs , suggesting that the improvements of root growth and AQPs expressions were involved in Mo-increased water uptake in wheat root under PSD. Further study showed that Mo application decreased wheat leaf transpiration, but increased root osmotic-adjustment ions K+, Ca2+ and Mg2+ concentrations, indicating that root osmotic pressure induced by increased ionic concentrations was the power of Mo-increased water uptake, but not transpirational pull induced by transpiration. This study suggests that Mo improves water uptake via extensive root morphology, AQP expressions and increased ionic concentrations in wheat under drought stress. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo), as an essential trace element in plants, plays an essential role in abiotic stress tolerance of plants. To obtain a better understanding of drought tolerance enhanced by Mo, a hydroponic trial was conducted to investigate the effects of Mo on water utilization, antioxidant enzymes, non-enzymatic antioxidants, and osmotic-adjustment products in the Mo-efficient ‘97003’ and Mo-inefficient ‘97014’ under PEG simulated drought stress. Our results indicate that Mo application significantly enhanced P n , chlorophyll, dry matter, grain yield, biomass, RWC and WUE and decreased T r , G s and water loss of wheat under drought stress, suggesting that Mo application improved the water utilization capacity in wheat. The activities of antioxidant enzymes such as superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and the contents of non-enzymatic antioxidants content such as ascorbic acid, reduced glutathione, carotenoid were significantly increased and malonaldehyde contents were decreased by Mo application under PEG simulated drought stress, suggesting that Mo application enhanced the ability of scavenging active oxygen species. The osmotic-adjustment products such as soluble protein, proline and soluble sugar were also increased by Mo application under PEG simulated drought stress, indicating that Mo improved the osmotic adjustment ability in wheat. It is hypothesized that Mo application might improve the drought tolerance of wheat by enhancing water utilization capability and the abilities of antioxidative defense and osmotic adjustment. Similarities and differences between the Mo-efficient and Mo-inefficient cultivars wheat in response to Mo under drought stress are discussed. [ABSTRACT FROM AUTHOR]

Abstract: A hydroponic experiment was conducted to investigate the effects of arsenic (As) stress on growth, nutrition and As uptake, and speciation in shoots and roots of winter wheat (Triticum aestivum L.). Winter wheat has high tolerance to As. Most As is accumulated in the roots, and an As concentration of 4,421 mg/kg was observed at a solution concentration of 20 mg/L As. Arsenic concentrations in roots were approximately 40–100 times greater than those in shoots. Arsenic in winter wheat roots and shoots occurred as both As3+ and As5+ species, although As3+ was the main species in winter wheat tissues. Arsenic significantly decreased the biomass of winter wheat shoots and roots and affected absorption and transport of micro- and macro-elements in winter wheat tissue. Arsenic treatment significantly increased the concentrations of total Magnesium (Mg) and calcium (Ca) in shoots and enhanced the transport of Mg and Ca from roots to shoots but decreased potassium (K), nitrogen (N), and phosphorus (P) concentrations in both shoots and roots, particularly the concentration of P. Concentrations of iron, copper, and zinc in winter wheat shoots were negatively related to As rates, with correlation coefficients (R2) of 0.93, 0.94, and 0.97, respectively. [Copyright &y& Elsevier]

Molybdenum (Mo) is an essential trace element for higher plants. Winter wheat cultivar 97003 has a higher Mo efficiency than 97014 under Mo-deficiency stress. Mo efficiency is related to Mo uptake, transfer and assimilation in plants. Several genes are involved in regulating Mo uptake, transfer and assimilation in plants. To obtain a better understanding of the aforementioned difference in Mo uptake, we have conducted a hydroponic trail to investigate the expression of genes related to Mo uptake, transfer and assimilation in the above two cultivars. The results indicate a closed relationship between Mo uptake and TaSultr5.1, TaSultr5.2 and TaCnx1 expression, according to a stepwise regression analysis of the time course of Mo uptake in the two cultivars. Meanwhile, expression of TaSultr5.2 in roots also showed a positive relationship with Mo uptake rates. 97003 had stronger Mo uptake than 97014 at low Mo-application rates (less than 1 μmol Mo L−1) due to the higher expression of TaSultr5.2, TaSultr5.1 and TaCnx1 in roots. On the contrary, Mo uptake of 97003 was weaker than 97014 at high Mo application rates (ranging from 5 to 20 μmol Mo L−1), which was related to significant down-regulation of TaSultr5.2 and TaCnx1 genes in roots of 97003 compared to 97014. Therefore, we speculated that the differential-expression intensities of TaSultr5.2, TaSultr5.1 and TaCnx1 could be the cause of the difference in Mo uptake between the two winter wheat cultivars at low and high Mo application levels. [ABSTRACT FROM AUTHOR]