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Summary: The high productive potential, heat resilience, and greater water use efficiency of C4 over C3 plants attract considerable interest in the face of global warming and increasing population, but C4 plants are often sensitive to dehydration, questioning the feasibility of their wider adoption.To resolve the primary effect of dehydration from slower from secondary leaf responses originating within leaves to combat stress, we conducted an innovative dehydration experiment. Four crops grown in hydroponics were forced to a rapid yet controlled decrease in leaf water potential by progressively raising roots of out of the solution while measuring leaf gas exchange.We show that, under rapid dehydration, assimilation decreased more steeply in C4 maize and sorghum than in C3 wheat and sunflower. This reduction was due to a rise of nonstomatal limitation at triple the rate in maize and sorghum than in wheat and sunflower.Rapid reductions in assimilation were previously measured in numerous C4 species across both laboratory and natural conditions. Hence, we deduce that high sensitivity to rapid dehydration might stem from the disturbance of an intrinsic aspect of C4 bicellular photosynthesis. We posit that an obstruction to metabolite transport between mesophyll and bundle sheath cells could be the cause. [ABSTRACT FROM AUTHOR]

Summary: Determining whether isotope fractionation occurs during root water uptake is a prerequisite for using stem or xylem water isotopes to trace water sources. However, it is unclear whether isotope fractionation occurs during root water uptake in gramineous crops.We conducted prevalidation experiments to estimate the isotope measurement bias associated with cryogenic vacuum distillation (CVD). Next, we assessed isotope fractionation during root water uptake in two common agronomic crops, wheat (Triticum aestivum L.) and maize (Zea mays L.), under flooding after postdrought stress conditions.Cryogenic vacuum distillation caused significant depletion of 2H but negligible effects on 18O for both soil and stem water. Surprisingly CVD caused depletion of 2H and enrichment of 18O in root water. Stem and root water δ18O were more than soil water δ18O, even considering the uncertainty of CVD. Soil water 18O was depleted compared with irrigation water 18O in the pots with plants but enriched relative to irrigation water 18O in the pots without plants.These results indicate that isotope fractionation occurred during wheat and maize root water uptake after full irrigation and led to a heavy isotope enrichment in stem water. Therefore, the xylem/stem water isotope approach widely used to trace water sources should be carefully evaluated. [ABSTRACT FROM AUTHOR]

Summary: The cereal crops rice (Oryza sativa), maize (Zea mays ssp. mays) and wheat (Triticum aestivum) provide half of the food eaten by humankind. However, understanding their biology has proved challenging due to their large size, long lifecycle and large genomes. The model plant Arabidopsis thaliana avoids these practical problems and has provided fundamental understanding of plant biology, however not all of this knowledge is directly transferrable to cereals. Recent developments in gene editing, speed breeding and genome assembly techniques mean that the challenges associated with working with the major cereal crops can be overcome. Resources such as mutant collections and genome sequences are now available for these crops, making them attractive experimental systems with which to make discoveries that are directly applicable to increasing crop production. Philippa Borrill is the joint winner, with Kai Zhu, of the 2019 New Phytologist Tansley Medal for excellence in plant science. See Lennon & Dolan in this issue of New Phytologist (2020, 228: 1697) for more details. [ABSTRACT FROM AUTHOR]

Summary: Increasing grain yields of food cereal crops is a major goal in future sustainable agriculture. We quantitatively analyzed the potential role of arbuscular mycorrhizal (AM) fungi in enhancing grain yields of seven cereal crops with exceptional importance for human nutrition across the globe: corn, wheat, rice, barley, sorghum, millet and oat.We conducted a meta‐analysis for three datasets including both English and Chinese language publications: the 'whole' dataset including both laboratory and field studies (168 articles); the 'field' dataset comprising only field studies (97 studies); and the 'field‐inoculation' dataset including only AM fungal inoculation studies conducted in field conditions (70 articles).We found that the AM fungal effect on grain yield was less pronounced in field and noninoculation studies. AM fungal inoculation in field led to a 16% increase (overall effect) based on the 'field‐inoculation' dataset; this effect was variable (77% trials had positive values), crop‐specific, lower for new cultivars released after 1950 and further modulated by soil pH.Although there are neutral and negative effects of AM fungi on grain yields, we emphasize the importance of integrating AM fungi in sustainable agriculture to increase grain yields of cereal crops. [ABSTRACT FROM AUTHOR]

Interspecific differences in functional traits are a key factor for explaining the positive diversity-productivity relationship in plant communities. However, the role of intraspecific variation attributable to phenotypic plasticity in diversity-productivity relationships has largely been overlooked. By taking a wheat ( Triticum aestivum)-maize ( Zea mays) intercrop as an elementary example of mixed vegetation, we show that plasticity in plant traits is an important factor contributing to complementary light capture in species mixtures., We conceptually separated net biodiversity effect into the effect attributable to interspecific trait differences and species distribution (community structure effect), and the effect attributable to phenotypic plasticity. Using a novel plant architectural modelling approach, whole-vegetation light capture was simulated for scenarios with and without plasticity based on empirical plant trait data., Light capture was 23% higher in the intercrop with plasticity than the expected value from monocultures, of which 36% was attributable to community structure and 64% was attributable to plasticity. For wheat, plasticity in tillering was the main reason for increased light capture, whereas for intercropped maize, plasticity induced a major reduction in light capture., The results illustrate the potential of plasticity for enhancing resource acquisition in mixed stands, and indicate the importance of plasticity in the performance of species-diverse plant communities. [ABSTRACT FROM AUTHOR]

Rates of tissue expansion, cell division and progression in the plant cycle are driven by temperature, following common Arrhenius-type response curves. [ABSTRACT FROM AUTHOR]

• With this study, we aimed to determine how elevated CO2 affects rhizodeposition and the cycling of rhizodeposited nitrogen (N) in the soil under C3 and C4 plants. In addition, we examined how cultivated genotypes of wheat ( Triticum turgidum) and maize ( Zea mays) responded to elevated CO2 in comparison with their wild relatives. • By constructing an N-transfer experiment we could directly assess cycling of the rhizodeposited N and trace the fate of rhizodeposited N in the soil and in receiver plants. • Biomass production, rhizodeposition and cycling of root-borne N in maize genotypes were not affected by elevated CO2. Elevated CO2 stimulated above- and below-ground biomass production of the wheat genotypes on average by 38%, and increased rhizodeposition and immobilization of root-derived N on average by 30%. Concurrently, elevated CO2 reduced mineral 15N and re-uptake of the root-derived N by 50% in wheat. • This study shows that elevated CO2 may enhance N limitation by increasing N rhizodeposition and subsequent immobilization of the root-derived N. [ABSTRACT FROM AUTHOR]

Lead transport has been characterized in corn (Zea mays L. cv. Fiesta) and ragweed (Ambrosia artemisiifolia L.), and the Pb phytoextraction efficiency of these species has been compared with that of Triticum aestivum, Thlaspi rotundifolium, Thiaspi caerulescens and Brassica juncea, using both nutrient solutions and Pb-contaminated soils. Our results demonstrated that plant species differ significantly in Pb uptake and translocation. In short term (60 min) experiments. Ph uptake by ragweed roots was threefold higher than that by corn roots. After 2 wk of Pb (100 μM) exposure in hydroponics, root-Pb concentration was 24000 mg kg-1 for ragweed and 4900 mg kg-1 for corn. In contrast to root-Pb concentration, shoot-Pb concentration was significantly higher in corn (560 mg kg-1) than in ragweed (30 mg kg-1). At an external Pb concentration of 20 μM, corn concentrated Pb in shoots by 90-fold, and ragweed concentrated Pb in shoots by 20-fold over the solution Pb concentration. Of the 11 species/cultivars tested using both nutrient solutions and Pb-contaminated soils, corn accumulated the highest shoot-Pb concentration. Using this corn cultivar, we investigated the role of synthetic chelates in Pb phytoextraction. Addition of HEDTA (2.0 g kg-1 soil) to a Pb-contaminated soil (total soil Pb 2500 mg kg-1) resulted in a surge of Pb accumulation in corn. The shoot Pb-concentration was increased from 40 mg kg-1 for the control (-HEDTA) to 10600 mg kg-1 for the HEDTA-treated soil. To our knowledge. this is the highest shoot Pb concentration reported in the literature for plants grown on Pb-contaminated soils Our results suggest that in combination with soil amendment, some agronomic crops, such as corn, might be used for the clean-up of Pb-contaminated soil. [ABSTRACT FROM AUTHOR]

summary: The effect of ammonium and nitrate nutrition on maize and wheat grown hydroponically and salinity stressed was assessed from measurements of growth rate and gas exchange. In both maize and wheat the ammonium‐grown plains were much more sensitive to salinity toxicity than nitrate‐grown plants particularly when exposed to 60–80 mM salinity. Shoot growth was retarded to a far greater extent than root growth in salinity‐stressed plants of both wheat and maize with either nitrogen source. There was no significant decrease of photosynthetic rate in salinity‐stressed plants of either species fed nitrate or ammonium, except in severely wilted plants of both species fed nitrate or ammonium at the highest (80 mM) salinity concentration. The same was true for stomatal conductance, transpiration rate and transpiration ratio (water use efficiency). In nitrate‐fed wheat, raising the calcium concentration from 2 to 12 mM in the presence of 60 mM salinity produced an 11% increase in growth. This effect is ascribed to improved nitrate uptake due to calcium protection of the nitrate transporter and was not evident in ammonium‐grown wheat. Possible reasons for the differential effects of ammonium and nitrate nutrition are discussed. [ABSTRACT FROM AUTHOR]

The effect of ammonium and nitrate nutrition on maize and wheat grown hydroponically and salinity stressed was assessed from measurements of growth rate and gas exchange. In both maize and wheat the ammonium-grown plants were much more sensitive to salinity toxicity than nitrate-grown plants particularly when exposed to 60-80mM salinity. Shoot growth was retarded to a far greater extent than root growth in salinity-stressed plants of both wheat and maize with either nitrogen source. There was no significant decrease of photosynthetic rate in salinity-stressed plants of either species fed nitrate or ammonium, except in severely wilted plants of both species fed nitrate or ammonium at the highest (80 mM) salinity concentration. The same was true for stomatal conductance, transpiration rate and transpiration ratio (water use efficiency). In nitrate-fed wheat, raising the calcium concentration from 2 to 12 mM in the presence of 60 mM salinity produced an 11% increase in growth. This effect is ascribed to improved nitrate uptake due to calcium protection of the nitrate transporter and was not evident in ammonium-grown wheat. Possible reasons for the differential effects of ammonium and nitrate are discussed. [ABSTRACT FROM AUTHOR]

This study was designed to test the hypothesis that disruption of the macrostructure of a previously zero-tilled soil is capable of reducing vesicular arbuscular (VA) mycorrhizal infection to a degree such that phosphorus (P) absorption is reduced. Undisturbed soil cores (within plastic cylinders) were excavated from long-term, zero-tilled plots. Soil removed from these plots, which was first subjected to structurally disruptive forces and then packed into identical cylinders, formed the disturbed comparisons. Maize (Zea mays L.), wheat ( Triticum aestivum L.), spinach (Spinacea oleracea L.) or rape (Brassica napus L.) were grown in the cores and P and zinc (Zn) absorption patterns monitored. Soil disturbance significantly reduced P and Zn absorption by maize grown in soil originating from three sites differing in local geography and/or texture Disturbance also reduced mycorrhizal infection in the three soils. A significant effect of disturbance upon the VA mycorrhizal infection of both maize and wheat roots (both mycorrhizal) and also upon the P absorption by these species was observed. None was found with respect to spinach and rape comparisons (non-mycorrhizal). Injection of benomyl, a potent inhibitor of mycorrhizal fungi, into the soil surface significantly reduced the influence of soil disturbance upon P absorption. No significant differences were found in VA mycorrhizal infection within fungicide-treated cores. We accepted our hypothesis based upon the above evidence. [ABSTRACT FROM AUTHOR]

De-embryonated grains of wheat and barley showed various responses when incubated with gibberellic acid (GA[sub3]). Amylase activity in the three cultivars studied showed similar responses to GA[sub3] concentration and period of incubation, Changes in o-dipheno1ase and monophenolase activities of polyphenol oxidase (o-Diphenol: oxygen oxidoreductase, E.C.1.10.3.1) which occurred when de-embryonated grains were incubated in the absence of GA[sub3], were enhanced by the hormone. Activity was promoted in extracts from wheat half-grains, but inhibited in extracts from the two barley cultivars. Whereas monophenolase activity was detected primarily in extracts of the wheat aleurone layer, it was only detectable in the barley endosperm extracts. The inhibitory effect of GA[sub3] on monophenolase activity in the barley cultivars is discussed. [ABSTRACT FROM AUTHOR]