A model formative assessment strategy to promote student-centered self-regulated learning in higher education

Adult learners are already involved in the process of self-regulation; hence, higher education institutions should focus on strengthening students’ self-regulatory skills. Self-regulation can be facilitated through formative assessment. This paper proposes a model formative assessment strategy that would complement existing university teaching, and can be used in higher education to promote student-centered self-regulated learning with minimal effort and time input from teachers. Based on this model, a real-world teaching example on writing an essay as a challenge task has also been developed. This model strategy incorporates Nicol and Macfarlane-Dick’s seven principles of good feedback practice that promotes self-regulation.Jayakumar Bose, Zed Renge

Synergism between feremycorrhizal symbiosis and free-living diazotrophs leads to improved growth and nutrition of wheat under nitrogen deficiency conditions

A controlled-environment study was conducted to explore possible synergistic interactions between the feremycorrhizal (FM) fungus Austroboletus occidentalis and soil free-living N2-fixing bacteria (diazotrophs). Wheat (Triticum aestivum) plants were grown under N deficiency conditions in a field soil without adding microbial inoculum (control: only containing soil indigenous microbes), or inoculated with a consortium containing four free-living diazotroph isolates (diazotrophs treatment), A. occidentalis inoculum (FM treatment), or both diazotrophs and A. occidentalis inoculums (dual treatment). After 7 weeks of growth, significantly greater shoot biomass was observed in plants inoculated with diazotrophs (by 25%), A. occidentalis (by 101%), and combined inoculums (by 106%), compared to the non-inoculated control treatment. All inoculated plants also had higher shoot nutrient contents (including N, P, K, Mg, Zn, Cu, and Mn) than the control treatment. Compared to the control and diazotrophs treatments, significantly greater shoot N content was observed in the FM treatment (i.e., synergism between the FM fungus and soil indigenous diazotrophs). Dually inoculated plants had the highest content of nutrients in shoots (e.g., N, P, K, S, Mg, Zn, Cu, and Mn) and soil total N (13–24% higher than the other treatments), i.e., synergism between the FM fungus and added diazotrophs. Root colonization by soil indigenous arbuscular mycorrhizal fungi declined in all inoculated plants compared to control. Non-metric multidimensional scaling (NMDS) analysis of the bacterial 16S rRNA gene amplicons revealed that the FM fungus modified the soil microbiome. Our in vitro study indicated that A. occidentalis could not grow on substrates containing lignocellulosic materials or sucrose, but grew on media supplemented with hexoses such as glucose and fructose, indicating that the FM fungus has limited saprotrophic capacity similar to ectomycorrhizal fungi. The results revealed synergistic interactions between A. occidentalis and soil free-living diazotrophs, indicating a potential to boost microbial N2 fixation for non-legume crops

Genotypic variation in phosphorus efficiency between wheat cultivars grown under greenhouse and field conditions

Phosphorus (P) efficiency (relative growth), which is described as the ratio of shoot dry matter or grain yield at deficient P supply to that obtained under adequate P supply, was compared in 25 winter wheat cultivars grown under greenhouse and field conditions with low and adequate P levels in a P-deficient calcareous soil. Adequate P supply resulted in significant increases in shoot dry weight and grain yield under both experimental conditions. In the greenhouse experiment, the increases in shoot dry weight under adequate P supply (80 mg kg(-1)) were from 0% (cv: C-1252) to 34% (cv: Dagdas). Under field conditions, the cultivars showed much greater variation in their response to adequate P supply (60 kg ha(-1)): the increases in shoot dry weight and grain yield with adequate P supply were between -2% (cv: Sivas-111/33) and 25% (cv: Kirac-66) for shoot dry matter production at the heading stage and between 0% (cv: Kirkpinar-79) and 76% (cv: Kate A-1) for grain yield at maturity. Almost all cultivars behaved totally different in their response to P deficiency under greenhouse and field conditions. Phosphorus efficiency ratios (relative growth) under greenhouse conditions did not correlate with the P efficiency ratios under field conditions. In general, durum wheat cultivars were found to be more P efficient compared with bread wheat cultivars. The results of this study indicated that there is wide variation in tolerance to P deficiency among wheat cultivars that can be exploited in breeding new wheat cultivars for high P deficiency tolerance. The results also demonstrated that P efficiency was expressed differently among the wheat cultivars when grown under greenhouse and field conditions and, therefore, special attention should be paid to growth conditions in screening wheat for P efficiency

Salicylic acid improves salinity tolerance in Arabidopsis by restoring membrane potential and preventing salt-induced K(+) loss via a GORK channel

Despite numerous reports implicating salicylic acid (SA) in plant salinity responses, the specific ionic mechanisms of SA-mediated adaptation to salt stress remain elusive. To address this issue, a non-invasive microelectrode ion flux estimation technique was used to study kinetics of NaCl-induced net ion fluxes in Arabidopsis thaliana in response to various SA concentrations and incubation times. NaCl-induced K+ efflux and H+ influx from the mature root zone were both significantly decreased in roots pretreated with 10–500 μM SA, with strongest effect being observed in the 10–50 μM SA range. Considering temporal dynamics (0–8-h SA pretreatment), the 1-h pretreatment was most effective in enhancing K+ retention in the cytosol. The pharmacological, membrane potential, and shoot K+ and Na+ accumulation data were all consistent with the model in which the SA pretreatment enhanced activity of H+-ATPase, decreased NaCl-induced membrane depolarization, and minimized NaCl-induced K+ leakage from the cell within the first hour of salt stress. In long-term treatments, SA increased shoot K+ and decreased shoot Na+ accumulation. The short-term NaCl-induced K+ efflux was smallest in the gork1-1 mutant, followed by the rbohD mutant, and was highest in the wild type. Most significantly, the SA pretreatment decreased the NaCl-induced K+ efflux from rbohD and the wild type to the level of gork1-1, whereas no effect was observed in gork1-1. These data provide the first direct evidence that the SA pretreatment ameliorates salinity stress by counteracting NaCl-induced membrane depolarization and by decreasing K+ efflux via GORK channels.Maheswari Jayakannan, Jayakumar Bose, Olga Babourina, Zed Rengel, and Sergey Shabal

Genetic basis for variation in wheat grain yield in response to varying nitrogen application

Nitrogen (N) is a major nutrient needed to attain optimal grain yield (GY) in all environments. Nitrogen fertilisers represent a significant production cost, in both monetary and environmental terms. Developing genotypes capable of taking up N early during development while limiting biomass production after establishment and showing high N-use efficiency (NUE) would be economically beneficial. Genetic variation in NUE has been shown previously. Here we describe the genetic characterisation of NUE and identify genetic loci underlying N response under different N fertiliser regimes in a bread wheat population of doubled-haploid lines derived from a cross between two Australian genotypes (RAC875 × Kukri) bred for a similar production environment. NUE field trials were carried out at four sites in South Australia and two in Western Australia across three seasons. There was genotype-by-environment- by-treatment interaction across the sites and also good transgressive segregation for yield under different N supply in the population. We detected some significant Quantitative Trait Loci (QTL) associated with NUE and N response at different rates of N application across the sites and years. It was also possible to identify lines showing positive N response based on the rankings of their Best Linear Unbiased Predictions (BLUPs) within a trial. Dissecting the complexity of the N effect on yield through QTL analysis is a key step towards elucidating the molecular and physiological basis of NUE in wheat.Saba Mahjourimajd, Julian Taylor, Beata Sznajder, Andy Timmins, Fahimeh Shahinnia, Zed Rengel, Hossein Khabaz-Saberi, Haydn Kuchel, Mamoru Okamoto, Peter Langridg

The NPR1-dependent salicylic acid signalling pathway is pivotal for enhanced salt and oxidative stress tolerance in Arabidopsis

The role of endogenous salicylic acid (SA) signalling cascades in plant responses to salt and oxidative stresses is unclear. Arabidopsis SA signalling mutants, namely npr1-5 (non-expresser of pathogenesis related gene1), which lacks NPR1-dependent SA signalling, and nudt7 (nudix hydrolase7), which has both constitutively expressed NPR1-dependent and NPR1-independent SA signalling pathways, were compared with the wild type (Col-0) during salt or oxidative stresses. Growth and viability staining showed that, compared with wild type, the npr1-5 mutant was sensitive to either salt or oxidative stress, whereas the nudt7 mutant was tolerant. Acute salt stress caused the strongest membrane potential depolarization, highest sodium and proton influx, and potassium loss from npr1-5 roots in comparison with the wild type and nudt7 mutant. Though salt stress-induced hydrogen peroxide production was lowest in the npr1-5 mutant, the reactive oxygen species (ROS) stress (induced by 1mM of hydroxyl-radical-generating copper-ascorbate mix, or either 1 or 10mM hydrogen peroxide) caused a higher potassium loss from the roots of the npr1-5 mutant than the wild type and nudt7 mutant. Long-term salt exposure resulted in the highest sodium and the lowest potassium concentration in the shoots of npr1-5 mutant in comparison with the wild type and nudt7 mutant. The above results demonstrate that NPR1-dependent SA signalling is pivotal to (i) controlling Na(+) entry into the root tissue and its subsequent long-distance transport into the shoot, and (ii) preventing a potassium loss through depolarization-activated outward-rectifying potassium and ROS-activated non-selective cation channels. In conclusion, NPR1-dependent SA signalling is central to the salt and oxidative stress tolerance in Arabidopsis.Maheswari Jayakannan, Jayakumar Bose, Olga Babourina, Sergey Shabala, Amandine Massart, Charlotte Poschenrieder and Zed Renge

Elucidating the source–sink relationships of zinc biofortification in wheat grains: a review

Zinc (Zn) concentration in wheat grains is generally low, with an average value of around 28–30 mg/kg. Therefore, increasing wheat grain Zn concentration for better human health is the focus of HarvestPlus global initiatives. Source–sink interactions have been intensively studied for decades to enhance crop yield potential, but less on grain nutritional quality. This review applies concepts of source, sink, and their interactions to the study of wheat grain Zn nutrition and biofortification. Increasing Zn sources to wheat (via soil and foliar application) could directly enlarge available Zn in vegetative tissues and grain Zn sink. Rational nitrogen (N) supply increases grain Zn accumulation (N‐Zn synergism), but phosphorus (P) input generally decreases (P‐Zn antagonism), and the potassium (K) effect is unclear. Conventional and genetic breeding have potential to stimulate Zn flow from source to sink (uptake from soil, root‐to‐shoot translocation, and remobilization). However, a rational manipulation to establish a well‐coordinated source–sink relationship is required to finally realize the grain Zn target (40–50 mg/kg) and increase on‐farm crop yield. Future studies should focus more on fertilization modes adopted by farmers (uses of compound, slow/controlled release, and organic and microbial fertilizers) and develop integrated agronomic and genetic strategies for Zn biofortification. A highly systematic and mechanistic model includes (a) migration paths of Zn (particularly from leaves to different grain parts) using isotopic labeling methods, (b) cross‐talks between Zn and carbon, N, P, K, or other divalent cations, (c) inherent physiological and biochemical processes of enzymes and signaling phytohormones, and (d) complex genetic systems governing Zn homeostasis and their relationships with other nutrients, signaling molecules, and increase or dilution/penalty of yield under different environmental conditions (soil, water, and future climatic changes) and managements (breeding and fertilization). These aspects require further elucidation to fully unravel the “black box” of Zn flow from source to sink

Simulating the interaction between plant roots, soil water and nutrient flows, and barriers and objects in soil using rootmap

Abstract: Plant productivity is directly affected by the capacity of the root system to forage for soil resources. An enhanced understanding of root-soil interactions provides the potential to improve crop performance in specific soil environments. Interactions between roots and soil are, however, complex. The root-soil environment is heterogeneous and difficult to visualise and measure, root architecture and root growth responses are complex and dynamic, and processes from the ionic and rhizosphere scale right up to the whole crop and even catchment scale are involved. For these reasons, pot experiments are used in root studies to simplify the environment, target specific interactions and aid with visualisation and measurement. Significant challenges exist, however, in relating pot studies to the field, requiring upscaling from a spatially confined and artificially contrived environment to the reality of a more complex cropping environment. Simulation models provide an opportunity to upscale complex root-soil interactions from the pot to the field, but to do so they must represent the way that plant roots explore a restricted pot environment. In this study ROOTMAP, a 3D functional-structural model of root growth and resource capture, was modified to enable the simulation of barriers in soil, and the interaction of plant roots and soil water and nutrients with those barriers. This barrier-modelling utilises custom coding, with the support of Boost.Geometry (Generic Geometry Library) where appropriate. The barrier approach defines the 3D shape and location of any number of what are termed Volume Objects. Roots and soil can be: wholly contained within one Volume Object such as in the case of roots growing in a pot; a plant can have roots distributed between two Volume Objects such as in a split-pot experiment; and they can be wholly outside one or more Volume Objects for simulating the presence of rocks or other hard objects in soil. Volume Objects can be wholly impermeable, such as; pot walls that contain roots within them, or impermeable rocks or hardpan layers that roots grow around. Volume Objects can also have varying degrees of permeability for representing layers or areas in soil that have varying degrees of hardness and varying root penetrability. In this initial version of the code, barriers or objects can be represented as rectangular prisms, giving flat barrier layers or square or rectangular objects such as root/rhizo boxes, or as cylinders, representing curved pots or smooth curved objects in soil. The barrier modelling code calculates the deflection of a root tip when it intersects a boundary, representing the way that plant roots grow around and along object surfaces. It also calculates the effect of semi-permeable objects in soil on root growth into and around those objects. Water and nutrients are distributed through the soil environment by use of a variable 3D grid of sub-volumes or cells. The water and nutrient routines then search for the presence of a barrier or wall (Volume Object) intersecting each cell and the volume of the cell contained inside/outside the barrier is calculated. This combined with the permeability of the barrier determines the water and nutrient transfer within the cell. The result is a model which can simulate the root, water and nutrient dynamics in a bounded-environment. This provides an opportunity to represent root architectural development and root-soil interactions in pots and rhizo-boxes, and investigate how these studies relate to root growth and resource capture in un-bounded field soil

Neighbouring plants modify maize root foraging for phosphorus:coupling nutrients and neighbours for improved nutrient-use efficiency

Nutrient distribution and neighbours can impact plant growth, but how neighbours shape root‐foraging strategy for nutrients is unclear. Here, we explore new patterns of plant foraging for nutrients as affected by neighbours to improve nutrient acquisition. Maize (Zea mays) was grown alone (maize), or with maize (maize/maize) or faba bean (Vicia faba) (maize/faba bean) as a neighbour on one side and with or without a phosphorus (P)‐rich zone on the other in a rhizo‐box experiment. Maize demonstrated root avoidance in maize/maize, with reduced root growth in ‘shared’ soil, and increased growth away from its neighbours. Conversely, maize proliferated roots in the proximity of neighbouring faba bean roots that had greater P availability in the rhizosphere (as a result of citrate and acid phosphatase exudation) compared with maize roots. Maize proliferated more roots, but spent less time to reach, and grow out of, the P patches away from neighbours in the maize/maize than in the maize/faba bean experiment. Maize shoot biomass and P uptake were greater in the heterogeneous P treatment with maize/faba bean than with maize/maize system. The foraging strategy of maize roots is an integrated function of heterogeneous distribution of nutrients and neighbouring plants, thus improving nutrient acquisition and maize growth. Understanding the foraging patterns is critical for optimizing nutrient management in crops