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In order to optimize the water and nitrogen management mode and realize the efficient scale production of sweet pepper, from 2021 to 2022, field experiments on sweet pepper cultivation with different water and nitrogen coupling modes were conducted in the Hexi Oasis irrigation areas. The regulation effects of the water–nitrogen coupling mode on the dry matter accumulation characteristics, photosynthesis, yield, and water–nitrogen utilization efficiency of sweet pepper were further discussed. Irrigation was set for full irrigation (W1, 75–85% FC [field capacity]), mild (W2, 65–75% FC), and moderate (W3, 55–65% FC) water deficit levels. Three levels of nitrogen were applied, high (N1, 300 kg·ha−1), medium (N2, 225 kg·ha−1) and low (N3, 150 kg·ha−1), with full irrigation and no nitrogen application used as the control (CK). The results showed that the appropriate water–nitrogen coupling mode could enhance the photosynthetic rate, increase dry matter accumulation and the accumulation rate, advance the days of a maximum rate of dry matter accumulation, and improve yield and water–nitrogen utilization efficiency. N1W1 had the greatest dry matter accumulation, the mean rate and the maximum increase rate of dry matter accumulation in sweet pepper, which was not a significant difference from N2W2, but significantly increased by 19.61%, 19.67%, and 23.45%, respectively, compared with CK. Water deficit significantly advanced the days of a maximum rate of dry matter accumulation. The days of a maximum rate of dry matter accumulation appeared 1.18–5.79 days earlier at W3 than at W2 and W1, and the maximum rate appeared gradually later with increasing irrigation. The net photosynthetic rate, the transpiration rate, and stomatal conductance of N2W2 sweet pepper showed the best performance at all growth stages, significantly increasing by 23.87%, 27.71%, and 27.39%, respectively, compared with CK. Moreover, the Intercellular CO2 concentration was significantly reduced by 14.77% in N2W2 compared to CK. The N2W2 had the highest yield, water use efficiency, and irrigation water use efficiency of sweet pepper, significantly increasing 26.89%, 33.74%, and 31.22% compared to CK. Excessive water and nitrogen dosage reduced nitrogen partial factor productivity, while an appropriate increase in irrigation under reduced nitrogen conditions facilitated the water nitrogen potential. Passage path analysis further showed that water–nitrogen coupling promotes plant biomass formation and distribution by increasing photosynthetic assimilation capacity, ultimately increasing yield. Therefore, the N2W2 treatment (65–75% FC, 225 kg·ha−1) is the ideal water and nitrogen mode for obtaining higher yields and water and nitrogen use efficiency of sweet pepper in a cold and arid environment.

Melatonin is a crucial biological hormone associated with many physiological and biochemical processes in plants and also enhances resistance against various abiotic stresses. However, the mechanisms underlying the melatonin-assisted mitigation of salt stress in tomato (Solanum lycopersicum L.) plant are still poorly understood. A hydroponic experiment was conducted to investigate the protective role of melatonin in two tomato cultivars (Roma and FM9) under a highly saline growth medium (160 mM NaCl). The one level of melatonin (1.0 µmol L−1) was applied exogenously, sole, or in combination with the salinity stress. NaCl-induced phytotoxicity significantly (P < 0.05) reduced shoot and root dry matter accumulation, chlorophyll contents, relative water contents (RWC), membrane stability index (MSI), and antioxidant enzymatic activities in both cultivars as compared to the control treatment. Moreover, salt treatment alone increased soluble sugar contents (sucrose and fructose), sodium (Na+) uptake, as well as oxidative damage in the leaves of tomato seedlings. However, exogenous supply of melatonin alleviated salt toxicity in tomato seedlings which were more obvious in Roma cultivar as compared to FM 9 cultivar, as demonstrated by a higher increment in the values of growth indicators, RWC, MSI, gaseous exchange attributes, activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). In addition, melatonin also alleviated salt-induced oxidative stress by suppressing malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents as well as significantly reduced Na+ uptake at the root surface of tomato plants. It can be concluded that melatonin-induced salt tolerance in tomato is due to enhancement of plant water relations, and improved photosynthetic and antioxidant capacity along with ion homeostasis.

Aims Nitrogen (N) fertilizer application greatly enhances grain yield by improving dry matter accumulation and grain filling in winter wheat. However, the regulation mechanism of N rates on dry matter accumulation, transportation, and grain filling in winter wheat under dry farming could be more precise. Methods Five N treatments viz. 0, 75, 150, 225, and 300 kg·N·ha −1 , designated as N0, N75, N150, N225, and N300, were tested in two growing seasons of 2017–18 and 2018–19. Results Fertilization significantly increased dry matter accumulation and intensity and assimilated accumulation after anthesis and its contribution to grain yield. N fertilizer significantly improved the superior and inferior grain weights, with the highest at N225, and increased by 22.29% and 24.41% in 2017–18 and 22.06% and 12.68% in 2018–19, respectively, compared to N0 ( P  < 0.05). Moreover, N fertilization increased the initial grain-filling potential and mean filling rate, shortened the days achieving the maximal grain-filling rate. N fertilizer increased the filling rate in the three periods, shortening the duration of the first-middle period, prolonging the late period, and increasing the contribution of the mid-late filling period to grain weight. However, excessive N application led to a reduction in the filling rate for each period. It prolonged the duration in the mid-late periods, which was not conducive to further increases in grain weight. Conclusions The N225 can be a more suitable N fertilizer for improving the accumulation and transfer of dry matter, promoting grain-filling, and increasing wheat yield in dry farming in the Loess Plateau. Graphical abstract

Solar radiation is the energy source for crop growth, as well as for the processes of accumulation, distribution, and transfer of photosynthetic products that determine maize yield. Therefore, learning the effects of different solar radiation amounts on maize growth is especially important. The present study focused on the quantitative relationships between solar radiation amounts and dry matter accumulations and transfers in maize. Over two continuous years (2017 and 2018) of field experiments, maize hybrids XY335 and ZD958 were grown at densities of 4.5 × 10 4 (D1), 7.5 × 10 4 (D2), 9 × 10 4 (D3), 10.5 × 10 4 (D4), and 12 × 10 4 (D5) plants/ha at Qitai Farm (89°34′E, 44°12′N), Xinjiang, China. Shading levels were 15% (S1), 30% (S2), and 50% (S3) of natural light and no shading (CK). The results showed that the yields of the commonly planted cultivars XY335 and ZD958 at S1, S2, and S3 (increasing shade treatments) were 7.3, 21.2, and 57.6% and 11.7, 31.0, and 61.8% lower than the control yields, respectively. Also, vegetative organ dry matter translocation (DMT) and its contribution to grain increased as shading levels increased under different densities. The dry matter assimilation amount after silking (AADMAS) increased as solar radiation and planting density increased. When solar radiation was <580.9 and 663.6 MJ/m 2 , for XY335 and ZD958, respectively, the increase in the AADMAS was primarily related to solar radiation amounts; and when solar radiation was higher than those amounts for those hybrids, an increase in the AADMAS was primarily related to planting density. Photosynthate accumulation is a key determinant of maize yield, and the contributions of the vegetative organs to the grain did not compensate for the reduced yield caused by insufficient light. Between the two cultivars, XY335 showed a better resistance to weak light than ZD958 did. To help guarantee a high maize yield under weak light conditions, it is imperative to select cultivars that have great stay-green and photosynthetic efficiency characteristics.

This article introduces the FAO crop model AquaCrop. It simulates attainable yields of major herbaceous crops as a function of water consumption under rainfed, supplemental, deficit, and full irrigation conditions. The growth engine of AquaCrop is water-driven, in that transpiration is calculated first and translated into biomass using a conservative, crop-specific parameter: the biomass water productivity, normalized for atmospheric evaporative demand and air CO2 concentration. The normalization is to make AquaCrop applicable to diverse locations and seasons. Simulations are performed on thermal time, but can be on calendar time, in daily time-steps. The model uses canopy ground cover instead of leaf area index (LAI) as the basis to calculate transpiration and to separate out soil evaporation from transpiration. Crop yield is calculated as the product of biomass and harvest index (HI). At the start of yield formation period, HI increases linearly with time after a lag phase, until near physiological maturity. Other than for the yield, there is no biomass partitioning into the various organs. Crop responses to water deficits are simulated with four modifiers that are functions of fractional available soil water modulated by evaporative demand, based on the differential sensitivity to water stress of four key plant processes: canopy expansion, stomatal control of transpiration, canopy senescence, and HI. The HI can be modified negatively or positively, depending on stress level, timing, and canopy duration. AquaCrop uses a relatively small number of parameters (explicit and mostly intuitive) and attempts to balance simplicity, accuracy, and robustness. The model is aimed mainly at practitioner-type end-users such as those working for extension services, consulting engineers, governmental agencies, nongovernmental organizations, and various kinds of farmers associations. It is also designed to fit the need of economists and policy specialists who use simple models for planning and scenario analysis.

Intercropping can obtain yield advantages, but the mechanism of yield advantages of maize-legume intercropping is still unclear. Then, we explored the effects of cropping systems and N input on yield advantages in a two-year experiment. Cropping systems included monoculture maize ( Zea mays L.) (MM), monoculture soybean ( Glycine max L. Merr.) (MS), monoculture peanut ( Arachis hypogaea L.) (MP), maize-soybean substitutive relay intercropping (IMS), and maize-peanut substitutive strip intercropping (IMP). N input included without N (N0) and N addition (N1). Results showed that maize’s leaf area index was 31.0% and 34.6% higher in IMS and IMP than in MM. The specific leaf weight and chlorophyll a (chl a) of maize were notably higher by 8.0% and 18.8% in IMS, 3.1%, and 18.6% in IMP compared with MM. Finally, N addition resulted in a higher thousand kernels weight of maize in IMS and IMP than that in MM. More dry matter accumulated and partitioned to the grain, maize's averaged partial land equivalent ratio and the net effect were 0.76 and 2.75 t ha −1 in IMS, 0.78 and 2.83 t ha −1 in IMP. The leaf area index and specific leaf weight of intercropped soybean were 16.8% and 26% higher than MS. Although soybean suffers from shade during coexistence, recovered growth strengthens leaf functional traits and increases dry matter accumulation. The averaged partial land equivalent ratio and the net effect of intercropped soybean were 0.76 and 0.47 t ha −1 . The leaf area index and specific leaf weight of peanuts in IMP were 69.1% and 14.4% lower than in the MP. The chlorophyll a and chlorophyll b of peanut in MP were 17.0% and 24.4% higher than in IMP. A less dry matter was partitioned to the grain for intercropped peanut. The averaged pLER and NE of intercropped peanuts were 0.26 and -0.55 t ha −1 . In conclusion, the strengthened leaf functional traits promote dry matter accumulation, maize-soybean relay intercropping obtained a win–win yield advantage, and maize-peanut strip intercropping achieved a trade-off yield advantage.

Waterlogging represents a serious abiotic stress for plants that retards crop growth and reduces production. Therefore, exploration of effective ways to alleviate the impacts of waterlogging has important theoretical and practical applications. This study investigated the responses of seedlings of two sorghum cultivars with different waterlogging tolerances to exogenous foliar treatment with melatonin (MT) and nitrogen (N) under waterlogged conditions. The chlorophyll fluorescence, photosynthetic capabilities, and antioxidant enzyme activities of these seedlings were measured after treatments with waterlogging and either exogenous application of MT, N, or both. The results showed that waterlogging severely limited sorghum growth and reduced dry matter accumulation in both cultivars. However, the negative effects of waterlogging were mitigated by spaying MT and N on leaves, especially of the waterlogging sensitive cultivar. Notably, exogenous foliar spraying of MT and N enhanced the chlorophyll content and improved the maximal quantum yield of photosystem II photochemistry (Fv/Fm), resulting in higher rates of photosynthesis. In addition, exogenous spraying of MT and N markedly decreased the malondialdehyde (MDA) content by upregulating antioxidant enzyme activities. The results also show that the combined effects of MT and N were better than the application of either alone and that exogenous foliar spraying of MT and N significantly increased the soluble protein content of leaves of sorghum. Overall, these results indicate the beneficial roles of MT and N in alleviating waterlogging stress in sorghum and show that their application may represent a strategy to mitigate waterlogging stress during agricultural production.

To develop sustainable nano-agriculture, biogenic ZnO nanoparticles have been prepared using brown seaweed Turbinaria ornata (T. ornata) extract as a priming agent to promote rice seed quality and crop yield attributing to rice seeds. The results of various physico-chemical characterization analysis indicate the formation of ZnO nanoparticles. Rice seeds primed with seaweed-based biogenic ZnO nanoparticles at 10 mg/L showed that there has been enhancement in the seed germination (100%), shoot length (100 mm), shoot width (1.0 mm), root length (185.0 mm) root width (0.5 mm), seedling length (216 mm), leaf length 33.0 mm), leaf width (2.0 mm), seedling vigor (28,500 vigor index) and dry matter production (DMP) compared to the conventional hydropriming. Consequently, a micro-plot experiment has been conducted with foliar application of biogenic ZnO nanoparticles and the results revealed that at 10 mg/L recorded improvement in grain weight (653 g/m2), seed length (8.0 mm), seed thickness (1.71 mm) and seed width (3.23 mm) compared to hydroprimed seeds under. HR-SEM micrograph confirms the presence and assimilation of biogenic ZnO nanoparticles in treated seed/foliar applied leaf of rice plant. Further, ICP-MS analysis also confirmed the increase in Zn content in the nanoprimed rice seedlings and foliar applied rice crop in a dose-dependent manner. The experimental results thus demonstrate that the application of seaweed biogenic ZnO nanoparticles improving agronomical characteristics of rice.

Nitrogen (N) is an essential nutrient element in plants that participates in physiological and biochemical regulation. However, the effects of different N applications on cigar tobacco (Nicotiana tabacum L.) growth are not well known. In this study, the differences in agronomical characteristics and nutritional quality of cigar tobacco leaves at the mature and curing stages under different exogenous N applications were explored. The dry matter accumulation of cigar tobacco leaves increased with increasing N application rates. In the two stages, the nutritional quality of cigar tobacco leaves was similar, but the concentrations of N and Cl were increased. To understand the effect of exogenous N on cigar tobacco metabolism, untargeted metabolomics was applied. Six significantly differential metabolites, including phenylalanine, phosphoserine, glutamate, oxoproline, succinylhomoserine, and homoserine, were identified, and the main metabolic pathways around the tricarboxylic acid cycle were identified. These results provide a better understanding of the effects of exogenous N application on the physiological, biochemical, and metabolic processes of cigar tobacco and provide a reference for fertilization control in cigar tobacco production. Core Ideas Agronomical characteristics of cigar tobacco were significantly affected by N application rates. Effect of N application rates on nutrient quality were reflected in several indices. Amino acid metabolism of cigar tobacco was mainly affected by N application rates.

Key messageModel training on data from all selection cycles yielded the highest prediction accuracy by attenuating specific effects of individual cycles. Expected reliability was a robust predictor of accuracies obtained with different calibration sets.The transition from phenotypic to genome-based selection requires a profound understanding of factors that determine genomic prediction accuracy. We analysed experimental data from a commercial maize breeding programme to investigate if genomic measures can assist in identifying optimal calibration sets for model training. The data set consisted of six contiguous selection cycles comprising testcrosses of 5968 doubled haploid lines genotyped with a minimum of 12,000 SNP markers. We evaluated genomic prediction accuracies in two independent prediction sets in combination with calibration sets differing in sample size and genomic measures (effective sample size, average maximum kinship, expected reliability, number of common polymorphic SNPs and linkage phase similarity). Our results indicate that across selection cycles prediction accuracies were as high as 0.57 for grain dry matter yield and 0.76 for grain dry matter content. Including data from all selection cycles in model training yielded the best results because interactions between calibration and prediction sets as well as the effects of different testers and specific years were attenuated. Among genomic measures, the expected reliability of genomic breeding values was the best predictor of empirical accuracies obtained with different calibration sets. For grain yield, a large difference between expected and empirical reliability was observed in one prediction set. We propose to use this difference as guidance for determining the weight phenotypic data of a given selection cycle should receive in model retraining and for selection when both genomic breeding values and phenotypes are available.