Nitrogen Allocation Research Articles

Integrative Analysis of Metabolome and Transcriptome Reveals Molecular Mechanisms Regulating Oil and Protein Content in Peanut (Arachis hypogaea L).

Peanut (Arachis hypogaea L.) is an important source of edible vegetable oils and plant proteins globally. However, the complex mechanisms regulating the oil and protein contents of peanut seeds remain unclear. Here, comparative broad-target metabolomics and quantitative lipidomics, together with transcriptome analysis, of peanut seeds at four developmental stages from the high-oil content variety "YH15" and high-protein content variety "KB008" were performed to search for oil and protein content control genes. A total of 984 differential metabolites, including 128 amino acids and derivatives and 310 differentially accumulated lipids, were identified between "YH15" and "KB008" in four seed developmental stages. The weighted gene coexpression network analysis and module-trait relationship analysis revealed that MEbrown, MEyellow, and MEturquoise modules were key contributors to the quality discrepancies observed between "YH15" and "KB008." Crucial genes potentially regulating the differences in oil and protein contents between "YH15" and "KB008" were identified within the aforementioned three modules, including genes involved in amino acid synthesis and degradation, nitrogen allocation, triglyceride synthesis and degradation, and fatty acid synthesis and degradation, as well as transcription factors. Overall, this study provides valuable insights into the molecular regulation of oil and protein contents in peanut seeds and may help cultivate specialized peanut varieties with enhanced nutritional and economic values.

Saline-alkaline conditions altered Bolboschoenus planiculmis carbon and nitrogen allocation tradeoffs

Soil salinization is an important factor that limits global agricultural production, specifically limiting the effectiveness of nitrogen-carbon resources and inhibiting plant growth. However, previous observations have focused on resource allocation, and there is little information about the coordination of carbon-nitrogen acquisition, allocation, and regulatory processes.We performed glasshouse pot experiments under different saline-alkaline conditions, and we measured 66 above- and belowground functional traits of Bolboschoenus planiculmis, to examine carbon-nitrogen resource acquisition and allocation strategies and their driving processes.Saline-alkaline conditions shifted B. planiculmis root-leaf functional traits toward a more acquisitive phenotype. Under low saline-alkaline conditions, although the root-leaf economic strategy inhibited resource acquisition efficiency, the opportunistic carbon-nitrogen capture and allocation strategy contributed to the maintenance of normal growth. However, highly saline-alkaline conditions led to the early enrichment of carbon-nitrogen resources in the corm. Additionally, saline-alkaline conditions altered the importance of physiological and biochemical processes in the carbon and nitrogen allocation regulatory network.In summary, B. planiculmis uses an opportunistic resource acquisition strategy under saline-alkaline conditions and a salt-avoidance allocation strategy under highly saline-alkaline conditions. This approach enables the maintenance of growth dominance under saline-alkaline conditions via gradient resource utilization.

Changes in the growth, photosynthesis, and nitrogen allocation characteristics of hydroponically grown lettuce under different nitrate levels in a nutrient solution

Changes in the growth, photosynthesis, and nitrogen allocation characteristics of hydroponically grown lettuce under different nitrate levels in a nutrient solution

Carbon and Nitrogen Allocation and Input in Soil with Grain Crops Post-Harvest Residues: East-European Plain Case Study

Carbon and Nitrogen Allocation and Input in Soil with Grain Crops Post-Harvest Residues: East-European Plain Case Study

Understanding nitrogen allocation dynamics in Indian mustard: Insights from enzyme activity and ideotype analysis

The study explores the effect of varying levels of nitrogen (N) application on N allocation in Indian mustard (Brassica juncea) genotypes from vegetative to the generative phases. The use of a heat map and PCA biplot analysis identifies two distinct sets of ideotypes. The first set is represented by genotype IC212031 having “Stay-green” phenotype with effective N regulating enzymes, high N uptake (NUpt) and better root development. The second set of ideotype is represented by HB9902 having delayed flowering phenology phases. The study highlights the relevance of Nitrate reductase (NR) in the final oil buildup in seeds (r = 0.5, p = 0.09). The considerable rise in NR activity from pre-anthesis to post-anthesis stages translates to higher seed storage compounds such as oil (r=−0.65, p = 0.03). And the developed prediction models confirmed the significance of these stages (pre-anthesis and post-anthesis) in the accumulation of seed storage components with emphasis on oil content. Similarly, this prediction model helps us to study the cause and effect relationship between various factors and oil content. The notable rise in Nitrite reductase (NiR) activity during the post-anthesis phase suggests its role in assimilating N for the storage of seed components, most likely proteins. Further, the inverse relationship between seed N (−0.53,p= 0.09) and oil content (−0.65, p= 0.03) confirmed that at the post anthesis stage the allocation of N towards precursor carbon compounds happens, which in turn forms either proteins or lipids. This becomes a critical factor in determining the final composition of the seed. Irrespective of N treatment and genotype, the N allocation follows the pattern: seed > siliquae husk > stover > root. However, higher N application rates primarily result in increased NUpt, but not necessarily improve utilisation. Overall, the study highlights the roles of root characteristics, N metabolising enzymes, and flowering phenology in enhancing N allocation and seed production in Indian mustard offering valuable insights for breeding strategies to enhance seed yield, oil content and nutrient efficiency in oilseed crops.

Symbiotic nitrogen fixation reduces belowground biomass carbon costs of nitrogen acquisition under low, but not high, nitrogen availability.

Many plant species form symbiotic associations with nitrogen-fixing bacteria. Through this symbiosis, plants allocate photosynthate belowground to the bacteria in exchange for nitrogen fixed from the atmosphere. This symbiosis forms an important link between carbon and nitrogen cycles in many ecosystems. However, the economics of this relationship under soil nitrogen availability gradients is not well understood, as plant investment toward symbiotic nitrogen fixation tends to decrease with increasing soil nitrogen availability. Here, we used a manipulation experiment to examine how costs of nitrogen acquisition vary under a factorial combination of soil nitrogen availability and inoculation with Bradyrhizobium japonicum in Glycine max L. (Merr.). We found that inoculation decreased belowground biomass carbon costs to acquire nitrogen and increased total leaf area and total biomass, but these patterns were only observed under low fertilization and were the result of increased plant nitrogen uptake and no change in belowground carbon allocation. These results suggest that symbioses with nitrogen-fixing bacteria reduce carbon costs of nitrogen acquisition by increasing plant nitrogen uptake, but only when soil nitrogen is low, allowing individuals to increase nitrogen allocation to structures that support aboveground growth. This pattern may help explain the prevalence of plants capable of forming these associations in less fertile soils and provides useful insight into understanding the role of nutrient acquisition strategy on plant nitrogen uptake across nitrogen availability gradients.

Low nitrogen priming enhances Rubisco activation and allocation of nitrogen to the photosynthetic apparatus as an adaptation to nitrogen-deficit stress in wheat seedling

Reducing nitrogen (N) application is crucial in addressing the low N utilization efficiency (NUE) and the risks of environmental pollution in wheat production. Improving low N (LN) tolerance in wheat can help balance the conflict between wheat growth and reduced N fertilization. Hydroponic experiments were conducted using Yangmai158 (LN-tolerant) and Zaoyangmai (LN-sensitive) cultivars to study whether LN priming (LNP) in the 3-leaf stage can improve the photosynthetic capacity of wheat seedlings under N-deficit stress at the 5-leaf stage. LNP increased the net photosynthetic rate (Pn), stomatal conductance (Gs), electron transfer rate (ETR), carboxylation efficiency (CE), maximum carboxylation rate (Vcmax), and the content and activity of Rubisco and Rubisco activase (RCA) in both cultivars, with Yangmai158 showing a greater increase than Zaoyangmai. After 14 days of N-deficit stress, the decreases in Pn, Gs, ETR, CE, Vcmax, and the content and activity of Rubisco and RCA of the two cultivars treated with LNP were significantly lower compared with those of the treatments without LNP. LNP improved the allocation proportion of leaf N to photosynthetic machinery, with the greatest increase in the carboxylation machinery. These results indicate that LNP can allocate more N to the photosynthetic apparatus, improving Rubisco content and activity to enhance the photosynthetic capacity and NUE of leaves under N-deficit stress.

Instantaneous growth: a compact measure of efficient carbon and nitrogen allocation in leaves and roots of C3 and C4 plants.

Elucidating plant functions and identifying crop productivity bottlenecks requires the accurate quantification of their performance. This task has been attained through photosynthetic models. However, their traditional focus on the leaf's capacity to uptake CO2 is becoming increasingly restrictive. Advanced bioengineering of C3 plants has made it possible to increase rates of CO2 assimilation by packing photosynthetic structures more densely within leaves. The operation of mechanisms that concentrate CO2 inside leaves can boost rates of assimilation while requiring a lower investment in carboxylating enzymes. Therefore, whether in the context of spontaneous plants or modern manipulation, considering trade-offs in resource utilization efficiency emerges as a critical necessity. I've developed a concise and versatile analytical model that simulates concurrent leaf and root growth by balancing instantaneous fluxes of carbon and nitrogen. Carbon is made available by leaf photosynthesis, encompassing all types of biochemistries, while nitrogen is either taken up by roots or remobilized after senescence. The allocation of leaf nitrogen between light or carbon reactions was determined using a fitting algorithm: growth maximisation was the only reliable fitting goal. Both the leaf nitrogen pool and the root-to-leaf ratio responded realistically to various environmental drivers (CO2 concentration, light intensity, soil nitrogen), replicating trends typically observed in plants. Furthermore, modifying the strength of CO2 concentrating mechanisms proved sufficient to alter the root-to-leaf ratio between C3 and C4 types. This direct and mechanistic one-to-one link convincingly demonstrates, for the first time, the functional dependence of a morphological trait on a single biochemical property.

Native arbuscular mycorrhizal fungi drive ecophysiology through phenotypic integration and functional plasticity under the Sonoran desert conditions.

Knowledge is scarce to what extent environmental drivers and native symbiotic fungi in soil induce abrupt (short-term), systemic (multiple traits), or specific (a subset of traits) shifts in C3 plants' ecophysiological/mycorrhizal responses. We cultivated an emblematic native C3 species (Capsicum annuum var. glabriusculum, "Chiltepín") to look at how the extreme heat of the Sonoran desert, sunlight regimes (low = 2, intermediate = 15, high = 46 mol m2 d-1) and density of native arbuscular mycorrhizal fungi in soil (low AMF = 1% v/v, high AMF = 100% v/v), drive shifts on mycorrhizal responses through multiple functional traits (106 traits). The warming thresholds were relentlessly harsh even under intensive shade (e.g. superheat maximum thresholds reached ranged between 47-63°C), and several pivotal traits were synergistically driven by AMF (e.g. photosynthetic capacity, biomass gain/allometry, and mycorrhizal colonization traits); whereas concurrently, sunlight regimes promoted most (76%) alterations in functional acclimation traits in the short-term and opposite directions (e.g. survival, phenology, photosynthetic, carbon/nitrogen economy). Multidimensional reduction analysis suggests that the AMF promotes a synergistic impact on plants' phenotypic integration and functional plasticity in response to sunlight regimes; however, complex relationships among traits suggest that phenotypic variation determines the robustness degree of ecophysiological/mycorrhizal phenotypes between/within environments. Photosynthetic canopy surface expansion, Rubisco activity, photosynthetic nitrogen allocation, carbon gain, and differential colonization traits could be central to plants' overall ecophysiological/mycorrhizal fitness strengthening. In conclusion, we found evidence that a strong combined effect among environmental factors in which AMF are key effectors could drive important trade-offs on plants' ecophysiological/mycorrhizal fitness in the short term.

Nitrogen topdressing at panicle initiation modulated nitrogen allocation between storage proteins and free nitrogenous compounds in grains of japonica rice

Nitrogen (N) topdressing often leads to a decline in cooking and eating quality due to alterations in grain chemical composition. Investigation into the response of N compounds in grains, such as protein-bound amino acids (PAA), free amino acids (FAA), and other residue N compounds (Nresidue), would be beneficial for understanding the impact of N on rice quality. The present study selected five japonica rice cultivars and conducted a two-year field experiment employing two N fertilization treatments: the CK treatment, where all N fertilizer was applied as basal fertilizer, and the topdressing treatment, where 50% of the total N was applied as topdressing at the panicle initiation stage. Averaging across years and cultivars, N topdressing resulted in a 16.3% increase in PAA and an 8.65% decrease in FAA, with no significant impact on Nresidue. N topdressing resulted in a decrease in the proportion of essential amino acids found in prolamins, as well as a reduction in the proportion of amino acids belonging to the aspartate family and arginine. Significant genotypic variations were observed in the response of nitrogen components to topdressing. Furthermore, elite cultivars with premium quality exhibited greater stability in amylose content compared to protein content.

Allocation of nitrogen and phosphorus in the leaves, stems, and roots of Artemisia: a case study in phylogenetic control.

The allocation of nitrogen (N) and phosphorus (P) among plant organs is an important strategy affecting growth and development as well as ecological processes in terrestrial ecosystems. However, due to lack of systematic investigation data, the allocation strategies of N and P in the three primary plant organs (e.g., leaves, stems and roots) are still unclear. A total of 912 individuals of 62 Artemisia species were examined across a broad environmental expanse in China, and the N and P concentrations of leaves, stems and roots were measured to explore the allocation strategies in different subgenera, ecosystem types, and local sites. Across all 62 species, the N vs. P scaling exponents for leaves, stems and roots were 0.67, 0.59 and 0.67, respectively. However, these numerical values differed among subgenera, ecosystem types, and local sites. Overall, the numerical values of N vs. P scaling exponents comply with a 2/3-power function for each Artemisia organ-type reflecting a phylogenetically conserved allocation strategy that has nevertheless diversified with respect to local environmental conditions. These results inform our understanding of N and P stoichiometric patterns and responses to abiotic factors in an ecologically broadly distributed angiosperm genus.

Flux Calculation for Primary Metabolism Reveals Changes in Allocation of Nitrogen to Different Amino Acid Families When Photorespiratory Activity Changes.

Photorespiration, caused by oxygenation of the enzyme Rubisco, is considered a wasteful process, because it reduces photosynthetic carbon gain, but it also supplies amino acids and is involved in amelioration of stress. Here, we show that a sudden increase in photorespiratory activity not only reduced carbon acquisition and production of sugars and starch, but also affected diurnal dynamics of amino acids not obviously involved in the process. Flux calculations based on diurnal metabolite profiles suggest that export of proline from leaves increases, while aspartate family members accumulate. An immense increase is observed for turnover in the cyclic reaction of glutamine synthetase/glutamine-oxoglutarate aminotransferase (GS/GOGAT), probably because of increased production of ammonium in photorespiration. The hpr1-1 mutant, defective in peroxisomal hydroxypyruvate reductase, shows substantial alterations in flux, leading to a shift from the oxoglutarate to the aspartate family of amino acids. This is coupled to a massive export of asparagine, which may serve in exchange for serine between shoot and root.

Physiological, transcriptomic and metabolomic insights of three extremophyte woody species living in the multi-stress environment of the Atacama Desert.

In contrast to Neltuma species, S. tamarugo exhibited higher stress tolerance, maintaining photosynthetic performance through enhanced gene expression and metabolites. Differentially accumulated metabolites include chlorophyll and carotenoids and accumulation of non-nitrogen osmoprotectants. Plant species have developed different adaptive strategies to live under extreme environmental conditions. Hypothetically, extremophyte species present a unique configuration of physiological functions that prioritize stress-tolerance mechanisms while carefully managing resource allocation for photosynthesis. This could be particularly challenging under a multi-stress environment, where the synthesis of multiple and sequential molecular mechanisms is induced. We explored this hypothesis in three phylogenetically related woody species co-occurring in the Atacama Desert, Strombocarpa tamarugo, Neltuma alba, and Neltuma chilensis, by analyzing their leaf dehydration and freezing tolerance and by characterizing their photosynthetic performance under natural growth conditions. Besides, the transcriptomic profiling, biochemical analyses of leaf pigments, and metabolite analysis by untargeted metabolomics were conducted to study gene expression and metabolomic landscape within this challenging multi-stress environment. S. tamarugo showed a higher photosynthetic capacity and leaf stress tolerance than the other species. In this species, a multifactorial response was observed, which involves high photochemical activity associated with a higher content of chlorophylls and β-carotene. The oxidative damage of the photosynthetic apparatus is probably attenuated by the synthesis of complex antioxidant molecules in the three species, but S. tamarugo showed the highest antioxidant capacity. Comparative transcriptomic and metabolomic analyses among the species showed the differential expression of genes involved in the biosynthetic pathways of key stress-related metabolites. Moreover, the synthesis of non-nitrogen osmoprotectant molecules, such as ciceritol and mannitol in S. tamarugo, would allow the nitrogen allocation to support its high photosynthetic capacity without compromising leaf dehydration tolerance and freezing stress avoidance.

Vertical Variations of Photosystem Energy Partitioning in the Canopy of the Subtropical Cropland

AbstractLeaf‐level photosynthetic capacity exhibits vertical variations along the canopy profile. The dynamics of photosystem energy partitioning involved in dissipating absorbed light energy, namely photochemical yield (ΦP), fluorescence yield (ΦF), and the efficiency of non‐photochemical quenching yield (ΦN) in dissipating excess light energy as heat, along the vertical canopy profile remain unclear. Here, vertical variations in photosystem energy partitioning and photosynthetic nitrogen allocation were measured at different canopy positions of rice using active fluorescence detection and photosynthetic gas exchange measurement in subtropical southern China. We observed the decline in leaf nitrogen per leaf mass (Nmass) from the top to the bottom of the canopy. ΦP significantly decreased from vegetative growth stage to ripening stage, while ΦN showed an opposite trend. The top and bottom leaves had consistent relationships between photosynthetic nitrogen allocation and photosystem energy partitioning. Our findings reveal the vertical variations in physiological traits of subtropical rice.

The above and the belowground nitrogen allocation strategy of Scirpus mariqueter based on 15N isotope tracing along an elevation gradient and its significance for coastal wetlands restoration

AbstractBackgroundEcological restoration of coastal wetlands has become particularly urgent worldwide as wetland areas have declined dramatically over the past two decades.AimsTo understand the nitrogen allocation strategy of Scirpus mariqueter (S. mariqueter) and provide theory support for future wetland management and restoration.MethodsThe study investigated the response mechanism of S. mariqueter to altitude spatial changes in Nanhui Dongtan from 2017 to 2019 using remote sensing imagery and field surveys. The ecological adaptability of S. mariqueter at different elevations (denoted as A, B, and C for elevations 2.40, 3.15, and 3.49 m, respectively) was analyzed through 15N stable isotope tracing technology. In July and September 2020, 15N‐enriched urea solution was uniformly sprayed onto the leaf surfaces of S. mariqueter at different sites. Plant samples were collected at the end of July and September, and the aboveground, belowground, seed, and rhizome biomass were measured, followed by 15N isotope tests.Results(1) From 2017 to 2019, the biomass of S. mariqueter significantly increased in the elevation change of 0.44–0.48 m, with the maximum aboveground biomass increase of 488.70 g dm−2. The density also increased significantly in the elevation change of 0.13–0.43 m, peaking at 674.02 plants m−2; (2) during the growing period, the biomass of A, B, and C increased. The aboveground portion of the 15N allocation rate accounted for 74%–84%. The belowground portion of the 15N allocation rate positively correlated with elevation; (3) during the reproductive period, elevation positively correlated with the 15N distribution rate of seeds and corms, as well as the biomass allocation rate of seeds and aboveground portions. The 15N allocation rate of the corms was higher than that of seeds. Additionally, elevation exhibited a negative correlation with belowground biomass allocation rate. (4) Point A has the highest difference of above and belowground biomass proportion, and 15N isotope allocation. Area of point A is the critical area affecting vegetation expansion and should be paid more attention in the future work of coastal management and restoration.ConclusionThere is an adaption strategy of S. mariqueter that affects the plant‐soil interaction and the biogeomorphological development process along the elevation gradient.

Floral deception in dioecious Actinidia polygama (Actinidiaceae) revealed by differential nitrogen investment in male organs

AbstractAnimal‐pollinated plants have evolved rewards and advertisements to attract pollinators, which learn to associate advertisements with rewards. Pollen‐collecting insects, such as bees, associate stamens with pollen (a reward) essential for brood rearing. In some dioecious plants, female flowers have stamens with sterile pollen grains to mimic male flowers. It is not yet fully understood whether females offer less nutritious pollen to pollinators in order to conserve nutrition. Here, we tested this hypothesis in a perennial vine, Actinidia polygama, which bears nectarless flowers. We quantified flower production and measured the dry mass of floral parts as well as carbon and nitrogen concentrations in floral parts and pollen in both sexes. Males produced more flowers per inflorescence and more inflorescences per shoot than females, while the dry mass of each flower was greater in females. The carbon allocation pattern was similar to that of biomass, but nitrogen allocation exhibited a remarkable reduction in sterile stamens and pollen of female flowers. In addition, as sterile pollen of females was sparse, when compared at the same volume, it was lighter than the pollen of males. Sterile pollen produced in female flowers appears to be as voluminous as that of male flowers but extremely poor in nutrients, especially in nitrogen, which clearly suggests that A. polygama females deceive pollen‐collecting pollinators for brood rearing.

Metabolomics analysis of different diameter classes of Taxus chinensis reveals that the resource allocation is related to carbon and nitrogen metabolism

Taxus chinensis (Taxus cuspidata Sieb. et Zucc.) is a traditional medicinal plant known for its anticancer substance paclitaxel, and its growth age is also an important factor affecting its medicinal value. However, how age affects the physiological and metabolic characteristics and active substances of T. chinensis is still unclear. In this study, carbon and nitrogen accumulation, contents of active substances and changes in primary metabolites in barks and annual leaves of T. chinensis of different diameter classes were investigated by using diameter classes instead of age. The results showed that leaves and barks of small diameter class (D1) had higher content of non-structural carbohydrates and C, which were effective in enhancing defense capacity, while N content was higher in medium (D2) and large diameter classes (D3). Active substances such as paclitaxel, baccatin III and cephalomannine also accumulated significantly in barks of large diameter classes. Moreover, 21 and 25 differential metabolites were identified in leaves and barks of different diameter classes, respectively. The differential metabolites were enhanced the TCA cycle and amino acid biosynthesis, accumulate metabolites such as organic acids, and promote the synthesis and accumulation of active substances such as paclitaxel in the medium and large diameter classes. These results revealed the carbon and nitrogen allocation mechanism of different diameter classes of T. chinensis, and its relationship with medicinal components, providing a guidance for the harvesting and utilization of wild T. chinensis.

Strong regulation of nitrogen supply and demand in a key desert legume tree

High abundance of legumes in drylands suggests that symbiotic nitrogen fixation provides an advantage in water-limited environments. However, the interactive effect of nitrogen availability and water scarcity on the nitrogen fixation strategies of dryland legumes remain largely unexplained. We conducted two experiments to test the effects of nitrogen availability and drought on symbiotic nitrogen fixation in two drought-adapted Acacia tree species. Seedlings were grown under deficient and sufficient levels of nitrogen and with and without an imposed drought to test the effect of resource availability on nitrogen fixation and plant growth. We found that seedlings that grew in extreme deficiency of nitrogen reached a similar biomass as seedling that grew with a sufficient supply of nitrogen, showing a high nitrogen-use efficiency. Nitrogen fixation was strongly downregulated (reduction of 90% in biomass allocation to nodules) when plants received sufficient nitrogen supply. Under nitrogen deficiency, drought had a slight negative effect on nodule biomass and total biomass. Under sufficient nitrogen, drought reduced nitrogen availability enough to induce an increase in symbiotic nitrogen fixation in the risk-averse A. raddiana but not in the risk-taking A. tortilis. We conclude that strong regulation of nitrogen fixation together with low nitrogen demand, and flexible strategies of carbon and nitrogen allocation, increase the chance of legume tree survival and establishment in dry and unpredictable environments.

Using leaf economic spectrum and photosynthetic acclimation to evaluate the potential performance of wintersweet under future climate conditions.

The function of landscape plants on the ecosystem can alleviate environmental issues of urbanization and global change. Global changes due to elevated CO2 affect plant growth and survival, but there is a lack of quantitative methods to evaluate the adaptability of landscape plants to future climate conditions. Leaf traits characterized by leaf economic spectrum (LES) are the universal currency for predicting the impact on plant ecosystem functions. Elevated CO2 usually leads to photosynthetic acclimation (PC), characterised by decreased photosynthetic capacity. Here, we proposed a theoretical and practical framework for the use of LES and PC to project the potential performance of landscape plants under future climatic conditions through principal component analysis, structural equation modelling, photosynthetic restriction analysis and nitrogen allocation analysis. We used wintersweet (an important landscaping species) to test the feasibility of this framework under elevated CO2 and different nitrogen (N) supplies. We found that elevated CO2 decreased the specific leaf area but increased leaf N concentration. The results suggest wintersweet may be characterized by an LES with high leaf construction costs, low photosynthetic return, and robust stress resistance. Elevated CO2 reduced photosynthetic capacity and stomatal conductance but increased photosynthetic rate and leaf area. These positive physio-ecological traits, e.g., larger leaf area (canopy), higher water use efficiency and stress resistance, may lead to improved performance of wintersweet under the predicted future climatic conditions. The results suggest planting more wintersweet in urban landscaping may be an effective adaptive strategy to climate change.

Optimization of inter-seasonal nitrogen allocation increases yield and resource-use efficiency in a water-limited wheat–maize cropping system in the North China Plain

Winter wheat–summer maize cropping system in the North China Plain often experiences drought-induced yield reduction in the wheat season and rainwater and nitrogen (N) fertilizer losses in the maize season. This study aimed to identify an optimal interseasonal water- and N-management strategy to alleviate these losses. Four ratios of allocation of 360 kg N ha−1 between the wheat and maize seasons under one-time presowing root-zone irrigation (W0) and additional jointing and anthesis irrigation (W2) in wheat and one irrigation after maize sowing were set as follows: N1 (120:240), N2 (180:180), N3 (240:120) and N4 (300:60). The results showed that under W0, the N3 treatment produced the highest annual yield, crop water productivity (WPC), and nitrogen partial factor productivity (PFPN). Increased N allocation in wheat under W0 improved wheat yield without affecting maize yield, as surplus nitrate after wheat harvest was retained in the topsoil layers and available for the subsequent maize. Under W2, annual yield was largest in the N2 treatment. The risk of nitrate leaching increased in W2 when N application rate in wheat exceeded that of the N2 treatment, especially in the wet year. Compared to W2N2, the W0N3 maintained 95.2% grain yield over two years. The WPC was higher in the W0 treatment than in the W2 treatment. Therefore, following limited total N rate, an appropriate fertilizer N transfer from maize to wheat season had the potential of a “triple win” for high annual yield, WPC and PFPN in a water-limited wheat–maize cropping system.