Peter B. Barraclough

Co-ordinated expression of amino acid metabolism in response to N and S deficiency during wheat grain filling

Increasing demands for productivity together with environmental concerns about fertilizer use dictate that the future sustainability of agricultural systems will depend on improving fertilizer use efficiency. Characterization of the biological processes responsible for efficient fertilizer use will provide tools for crop improvement under reduced inputs. Transcriptomic and metabolomic approaches were used to study the impact of nitrogen (N) and sulphur (S) deficiency on N and S remobilization from senescing canopy tissues during grain filling in winter wheat (Triticum aestivum). Canopy tissue N was remobilized effectively to the grain after anthesis. S was less readily remobilized. Nuclear magnetic resonance (NMR) metabolite profiling revealed significant effects of suboptimal N or S supply in leaves but not in developing grain. Analysis of amino acid pools in the grain and leaves revealed a strategy whereby amino acid biosynthesis switches to the production of glutamine during grain filling. Glutamine accumulated in the first 7 d of grain development, prior to conversion to other amino acids and protein in the subsequent 21 d. Transcriptome analysis indicated that a down-regulation of the terminal steps in many amino acid biosynthetic pathways occurs to control pools of amino acids during leaf senescence. Grain N and S contents increased in parallel after anthesis and were not significantly affected by S deficiency, despite a suboptimal N:S ratio at final harvest. N deficiency resulted in much slower accumulation of grain N and S and lower final concentrations, indicating that vegetative tissue N has a greater control of the timing and extent of nutrient remobilization than S.

Predicting post-anthesis N requirements of bread wheat with a Minolta SPAD meter

Abstract Winter wheat ( Triticum aestivum L., cv. Hereward, a bread-making variety) was grown on different fields at Rothamsted (England) in eight seasons (1993–2001). Each crop received a range of N fertiliser (0–300 kg N/ha as granular ammonium nitrate) applied as soil top-dressings in March–April. The aim was to see if N concentrations in shoots and leaves at anthesis could be used to predict %N in grain at maturity, and therefore, the need for post-anthesis fertiliser to boost grain protein. The Minolta SPAD meter which estimates chlorophyll concentration in single leaves was also investigated as a potential indicator method. Grain yield ranged from 3 to 11 t/ha (85% DM), and grain N from 1.43 to 2.46% in response to N rate. A 13% protein target for milling quality (0% moisture), equivalent to a grain N concentration of 2.3% (assuming a conversion factor of 5.7), was associated with a yield of 11 t/ha (85% DM), and required N concentrations at anthesis of 2% in whole shoots and 4% in flag leaves. A yield of 11 t/ha (85% DM) combined with 2.3% N in grain equates to a grain N requirement of 215 kg/ha. SPAD readings in flag leaves at anthesis could also be used to predict %N in grain at maturity. The critical SPAD value was 52.4 for 2.3% grain N. The SPAD meter has potential for predicting grain N requirements, but further work is needed to establish SPAD calibrations for other wheat varieties under UK conditions.

Markedly different gene expression in wheat grown with organic or inorganic fertilizer

Nitrogen is the major determinant of crop yield and quality and the precise management of nitrogen fertilizer is an important issue for farmers and environmentalists. Despite this, little is known at the level of gene expression about the response of field crops to different amounts and forms of nitrogen fertilizer. Here we use expressed sequence tag (EST)-based wheat microarrays in combination with the oldest continuously running agricultural experiment in the world to show that gene expression is significantly influenced by the amount and form of nitrogenous fertilizer. In the Broadbalk winter wheat experiment at Rothamsted in the United Kingdom and at three other diverse test sites, we show that specific genes have surprisingly different expression levels in the grain endosperm when nitrogen is supplied either in an organic or an inorganic form. Many of the genes showing differential expression are known to participate in nitrogen metabolism and storage protein synthesis. However, others are of unknown function and therefore represent new leads for future investigation. Our observations show that specific gene expression is diagnostic for use of organic sources of nitrogen fertilizer and may therefore have useful applications in defining the differences between organically and conventionally grown wheat.

The Molecular and Physiological Basis of Nutrient Use Efficiency in Crops: Hawkesford/The Molecular and Physiological Basis of Nutrient Use Efficiency in Crops

Preface vii Contributors ix Part I: Generic Aspects of Crop Nutrition 3 Chapter 1 An Overview of Nutrient Use Effi ciency and Strategies for Crop Improvement 5 Malcolm J. Hawkesford Chapter 2 Crop Root Systems and Nutrient Uptake from Soils 21 Peter J. Gregory Chapter 3 The Role of the Rhizosphere in Nutrient Use Effi ciency in Crops 47 Petra Marschner Chapter 4 Optimizing Canopy Physiology Traits to Improve the Nutrient Utilization Effi ciency of Crops 65 M. John Foulkes and Erik H. Murchie Chapter 5 Senescence and Nutrient Remobilization in Crop Plants 83 Per L. Gregersen Chapter 6 Effects of Nitrogen and Sulfur Nutrition on Grain Composition and Properties of Wheat and Related Cereals 103 Peter R. Shewry Part II: Nitrogen as a Key Driver of Production 121 Chapter 7 Genetic Improvement of Nutrient Use Effi ciency in Wheat 123 Jacques Le Gouis Chapter 8 The Molecular Genetics of Nitrogen Use Effi ciency in Crops 139 Bertrand Hirel and Peter J. Lea Chapter 9 Biotechnological Approaches to Improving Nitrogen Use Effi ciency in Plants: Alanine Aminotransferase as a Case Study 165 Allen G. Good and Perrin H. Beatty Chapter 10 Transporters Involved in Nitrogen Uptake and Movement 193 Anthony J. Miller and Nick Chapman Chapter 11 Crop Improvement for Nitrogen Use Effi ciency in Irrigated Lowland Rice 211 Shaobing Peng Part III: Other Critical Macro- and Micronutrients 227 Chapter 12 Phosphorus as a Critical Macronutrient 229 Carroll P. Vance Chapter 13 Uptake, Distribution, and Physiological Functions of Potassium, Calcium, and Magnesium 265 Frans J.M. Maathuis and Dorina Podar Chapter 14 Sulfur Nutrition in Crop Plants 295 Luit J. De Kok, Ineke Stulen, and Malcolm J. Hawkesford Chapter 15 Iron Nutrition and Implications for Biomass Production and the Nutritional Quality of Plant Products 311 Jean-Francois Briat Chapter 16 Zinc in Soils and Crop Nutrition 335 Behzad Sadeghzadeh and Zed Rengel Chapter 17 Overview of the Acquisition and Utilization of Boron, Chlorine, Copper, Manganese, Molybdenum, and Nickel by Plants and Prospects for Improvement of Micronutrient Use Effi ciency 377 Patrick H. Brown and Elias Bassil Part IV: Specialized Case Studies 429 Chapter 18 Drought and Implications for Nutrition 431 Eric Ober and Martin A.J. Parry Chapter 19 Salt Resistance of Crop Plants: Physiological Characterization of a Multigenic Trait 443 Sven Schubert Chapter 20 Legumes and Nitrogen Fixation: Physiological, Molecular, Evolutionary Perspectives, and Applications 457 Muthusubramanian Venkateshwaran and Jean-Michel Ane Index 491

Measuring inorganic orthophosphate in oilseed rape using Reflectoquant technology

Reflectoquant analytical technology was assessed for measuring inorganic orthophosphate (Pi‐mainly H2PO4 − but also HPO4 2 −) in oilseed rape plants (Brassica napus). The Reflectoquant system consists of a hand‐held reflectometer (RQflex2) combined with phosphate sensitive test‐strips, which use molybdate‐blue chemistry. Reflectoquant slightly under‐estimated Pi concentrations in standard potassium phosphate solutions, and had a linear measurement range between 5–100 mg PO4 L− 1 (0.05–1.05 mM Pi). Variability in phosphate test‐strip performance was large with five test‐strips per sample being required for 95% confidence in the mean value. Potentially interfering ions and molecules at concentrations commonly found in plant sap—chloride, nitrate, citrate, ATP, fructose‐6‐phosphate, and NADP—had no significant effect on the Pi assays. The Reflectoquant method gave similar results to a typical laboratory assay for Pi in rape leaf blades. In practice, plant sap or tissue water samples would need to be diluted up to 40 times to bring Pi into the linear range of the Reflectoquant system and this also ensures minimal interference from other cell constituents. Five methods of extracting Pi from oilseed rape leaves were compared in the laboratory‐fresh, freeze‐thaw, freeze‐dry, microwave‐dry and oven‐dry. Tissue water was pressed from leaves in the first two methods, whilst Pi in the (milled) material from the three drying methods was extracted by shaking with 2% acetic acid. Tissue water and acid extracts were analyzed for Pi by the molybdate‐blue method using either a laboratory spectrometer or Reflectoquant technology. Extraction method, but not analytical method, had a significant effect on Pi concentrations which increased in the order oven‐dry > microwave‐dry > freeze‐thaw = freeze‐dry > fresh. The freeze‐thaw method coupled with Reflectoquant technology was deemed most suitable for the on‐farm measurement of Pi in oilseed rape leaves.