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Changes in leaf carbon and nitrogen traits are effective parameters for evaluating whether plants are growing normally and for guiding field management measures. Therefore, a nondestructive estimation of soybean leaf carbon content (LCC) and leaf nitrogen content (LNC) is important for managing soybean production. This study aims to investigate the properties of soybean LCC, LNC and leaf carbon and nitrogen ratio (LCNR) under different light conditions and to construct the estimation models for soybean LCC, LNC and LCNR on the basis of hyperspectral reflectance. A 3-year field trial was conducted from 2013 to 2015 to investigate the effect of five shade treatments (from 57% to 18% of normal photosynthetic active radiation) by regulating the distance between maize and soybean rows in an intercropping system. Results showed that the LNC is increased, and the LCC is decreased with the increase in shading level. A typical leaf hyperspectral reflectance showed that the changes in near infrared and around the green peak are approximately proportional to the LCC and analogously inverse to the LNC. The corresponding first-order derivative presented the changes in the red-edge positions as a ‘blue shift’ with the increase in shading level. General vegetation indices (VIs), uninformative variable elimination-partial least squares (UVE-PLS) and continuous wavelet transform (CWT) were used to develop the models. The linear models constructed using the CWT, compared with the VIs and UVE-PLS, had the highest determination coefficient and the lowest root mean square error (RMSE). The models were validated using independent data from 2015 with RMSE values of 1.9789, 0.6132 and 2.1587 for the LCC, LNC and LCNR, respectively. Moreover, these models obtained relative errors of 4.5%, 13.2% and 20% for the LCC, LNC and LCNR, respectively. Results indicated that soybean LNC and LCC can be accurately estimated using the CWT for assessing the physiological situation.

Soybean is an important oilseed crop grown globally. However, two examples of environmental stresses that drastically regulate soybean growth are low light and high-temperature. Emerging evidence suggests a possible interconnection between these two environmental stimuli. Low light and high-temperature as individual factors have been reported to regulate plant hypocotyl elongation. However, their interactive signal effect on soybean growth and development remains largely unclear. Here, we report that gibberellins (GAs) and auxin are required for soybean hypocotyl elongation under low light and high-temperature interaction. Our analysis indicated that low light and high-temperature interaction enhanced the regulation of soybean hypocotyl elongation and that the endogenous GA3 , GA7 , indole-3-acetic acid (IAA), and indole-3-pyruvate (IPA) contents significantly increased. Again, analysis of the effect of exogenous phytohormones and biosynthesis inhibitors treatments showed that exogenous GA, IAA, and paclobutrazol (PAC), 2, 3, 5,-triiodobenzoic acid (TIBA) treatments significantly regulated soybean seedlings growth under low light and high-temperature interaction. Further qRT-PCR analysis showed that the expression level of GA biosynthesis pathway genes (GmGA3ox1, GmGA3ox2 and GmGA3) and auxin biosynthesis pathway genes (GmYUCCA3, GmYUCCA5 and GmYUCCA7) significantly increased under (i) low light and high-temperature interaction and (ii) exogenous GA and IAA treatments. Altogether, these observations support the hypothesis that gibberellins and auxin regulate soybean hypocotyl elongation under low light and high-temperature stress interaction.

Background Shading includes low light intensity and varying quality. However, a low red/far-red (R/Fr) ratio of light is a signal that affects plant growth in intercropping and close- planting systems. Thus, the low R/Fr ratio uncoupling from shading conditions was assessed to identify the effect of light quality on photosynthesis and CO2 assimilation. Soybean plants were grown in a growth chamber with natural solar radiation under four treatments, that is, normal (N, sunlight), N + Fr, Low (L) + Fr, and L light. Results Low R/Fr ratio significantly increased the total biomass, leaf area, starch and sucrose contents, chlorophyll content, net photosynthetic rate, and quantum efficiency of the photosystem II compared with normal R/Fr ratio under the same light level (P 2 assimilation in the chloroplast. Among the 7834 proteins quantified, 12 showed a > 1.3-fold change in abundance, of which 1 was related to porphyrin and chlorophyll metabolism, 2 were involved in photosystem I (PS I), 4 were associated with PS II, 3 proteins participated in photosynthetic electron transport, and 2 were involved in starch and sucrose metabolism. The dynamic change in these proteins indicates that photosynthesis and CO2 assimilation were maintained in the L treatment by up-regulating the component protein levels compared with those in N treatment. Although low R/Fr ratio increased the photosynthetic CO2 assimilation parameters, the differences in most protein expression levels in N + Fr and L + Fr treatments compared with those in N treatment were insignificant. Similar trends were found in gene expression through quantitative reverse transcription polymerase chain reaction excluding the gene expression of sucrose synthase possible because light environment is one of the factors affecting carbon assimilation. Conclusions Low R/Fr ratio (high Fr light) can increase the photosynthetic CO2 assimilation in the same light intensity by improving the photosynthetic efficiency of the photosystems.

Background: The recent outbreak of novel coronavirus (2019-nCoV) has infected tens of thousands of patients in China. Studies have forecasted future trends of the incidence of 2019-nCoV infection, but appeared unsuccessful. Farr’s law is a classic epidemiology theory/practice for predicting epidemics. Therefore, we used and validated a model based on Farr’s law to predict the daily-incidence of 2019-nCoV infection in China and 2 regions of high-incidence. Methods: We extracted the 2019-nCoV incidence data of China, Hubei Province and Wuhan City from websites of the Chinese and Hubei health commissions. A model based on Farr’s law was developed using the data available on Feb. 8, 2020, and used to predict daily-incidence of 2019-nCoV infection in China, Hubei Province and Wuhan City afterward. Results: We observed 50,995 (37,001 on or before Feb. 8) incident cases in China from January 16 to February 15, 2020. The daily-incidence has peaked in China, Hubei Providence and Wuhan City, but with different downward slopes. If no major changes occur, our model shows that the daily-incidence of 2019-nCoV will drop to single-digit by February 25 for China and Hubei Province, but by March 8 for Wuhan city. However, predicted 75% confidence intervals of daily-incidence in all 3 regions of interest had an upward trend. The predicted trends overall match the prospectively-collected data, confirming usefulness of these models. Conclusions: This study shows the daily-incidence of 2019-nCoV in China, Hubei Province and Wuhan City has reached the peak and was decreasing. However, there is a possibility of upward trend.

BackgroundThe recent outbreak of novel coronavirus (2019-nCoV) has infected tens of thousands of patients in China. Studies have forecasted future trends of the incidence of 2019-nCoV infection, but appeared unsuccessful. Farr’s law is a classic epidemiology theory/practice for predicting epidemics. Therefore, we used and validated a model based on Farr’s law to predict the daily-incidence of 2019-nCoV infection in China and 2 regions of high-incidence.MethodsWe extracted the 2019-nCoV incidence data of China, Hubei Province and Wuhan City from websites of the Chinese and Hubei health commissions. A model based on Farr’s law was developed using the data available on Feb. 8, 2020, and used to predict daily-incidence of 2019-nCoV infection in China, Hubei Province and Wuhan City afterward.ResultsWe observed 50,995 (37001 on or before Feb. 8) incident cases in China from January 16 to February 15, 2020. The daily-incidence has peaked in China, Hubei Providence and Wuhan City, but with different downward slopes. If no major changes occur, our model shows that the daily-incidence of 2019-nCoV will drop to single-digit by February 25 for China and Hubei Province, but by March 8 for Wuhan city. However, predicted 75% confidence intervals of daily-incidence in all 3 regions of interest had an upward trend. The predicted trends overall match the prospectively-collected data, confirming usefulness of these models.ConclusionsThis study shows the daily-incidence of 2019-nCoV in China, Hubei Province and Wuhan City has reached the peak and was decreasing. However, there is a possibility of upward trend.

Additional file 3: Table S2. List of primers for characterizing Glycine max genes.

Additional file 1: Figure S1. Light response curves of net photosynthetic rate (A), light saturation point (B), and quantum yield of PSII (C) of soybean leaves under different treatments. N, N + Fr, L + Fr, and L denote normal light (normal PAR and normal R/Fr ratio), normal light plus far-red light (normal PAR and low R/Fr ratio), low light plus far-red light (low PAR and low R/Fr ratio), and low light (low PAR and normal R/Fr ratio), respectively. Pmax and LSP represent the maximum photosynthetic rate and the light saturation point. Data are expressed as the means ± SD of triplicates. Means followed by different letters are significantly different at P = 0.05.

Photosynthesis is dependent on the density and quality of light that reaches chloroplasts. Shade conditions are characterized by changes in light density and quality. These changes, which are represented by the red to far-red (R/Fr) ratio of light, directly affect the photosynthetic capacity of soybean in close-planting and intercropping systems. We postulated that high far-red light under shade conditions would improve crop photosynthesis. Herein, we conducted a quantitative proteomic analysis through the isobaric tagging for relative and absolute quantification approach to investigate the response of photosynthetic proteins to the interaction between light intensity and quality. We identified 7834 proteins (P value 1.3) from soybean leaves. Among these proteins, 98 are associated with differential chloroplast accumulation under shade (S, low light intensity and low R/Fr ratio) and normal light (N, normal light intensity and normal R/Fr ratio) conditions. Additionally, 134 are associated with differential chloroplast accumulation under low light (L, low light intensity and normal R/Fr ratio) and N conditions. Eight representative proteins that are involved in photosynthesis were differentially regulated under L and S treatments. These proteins included one protein involved in porphyrin and chlorophyll metabolism, three proteins involved in light-harvesting chlorophyll protein complex, and four proteins involved in photosynthesis. Among the eight differentially regulated proteins under L and S treatments, five up-regulated proteins (protochlorophyllide reductase; light-harvesting complex II chlorophyll a/b binding protein [Lhcb1]; Lhcb2; photosystem I subunit II; and plastocyanin [PetE]) and three down-regulated proteins (Lhcb4; Ferredoxin-1; and NADPH:quinone oxidoreductase [NQO]) were validated through quantitative reverse-transcription polymerase chain reaction and Western blot methods L and S treatments decreased net photosynthesis rate (Pn) but increased chlorophyll content; thylakoid stacking; and photosystem II (PSII), PSI, and electron transport associated protein levels. Likewise, N and S treatments decreased PetE and NQO protein expression levels. This effect, in turn, decreased P700 oxidation. In addition, the higher far-red light of the S treatment than that of the L treatment increased Pn by up-regulating the gene expressions of differential proteins. We conclude that light intensity directly affects photosynthesis by regulating the expression of photosynthetic proteins. High far-red light, however, can improve the photosynthetic capacity of plants under shade conditions.

Carboxymethyl cellulose nanocrystals (N-CMCs) were produced by carboxymethylation of cellulose nanocrystals (CNCs) that derived from sweet potato residue. Transmission electron microscopy showed that the N-CMCs which had a porous surface structure were more loosely packed and slightly larger with a uniform diameter ranging from 30 nm to 50 nm. N-CMCs with low viscosity (

Melatonin (MT) regulates several physiological activities in plants. However, information on how MT regulates soybean growth under low-temperature (LT) stress is lacking. To better understand how MT promotes plant growth and development under LT stress, we designed this study to evaluate the role of MT pretreatment on soybean seedlings exposed to LT stress. Our results showed that LT stress increased oxidative damage by increasing reactive oxygen species (ROS) accumulation, which affected the growth and development of soybean seedlings. However, the application of 5 µmol L–1 MT significantly decreased the oxidative damage by increasing plant mineral element concentrations and the transcript abundance of antioxidant related genes, which enhanced the decrease in ROS accumulation. These results collectively suggest the involvement of MT in improving LT stress tolerance of soybean seedlings by mediating plant mineral elements and the expression of genes involved in the antioxidant pathway.

Real-time PCR primers. (PDF 309 kb)

Background Intercropping and close planting are important cultivation methods that increase soybean yield in agricultural production. However, plant shading is a major abiotic stress factor that influences soybean growth and development. Although shade affects leaf morphological parameters and decreases leaf photosynthesis capacity, information on the responses of soybean leaf photosynthesis to shading at proteomic level is still lacking. Results Compared with leaves under normal light (CK) treatment, leaves under shading treatment exhibited decreased palisade and spongy tissue thicknesses but significantly increased cell gap. Although shade increased the number of the chloroplast, the thickness of the grana lamella and the photosynthetic pigments per unit mass, but the size of the chloroplast and starch grains and the rate of net photosynthesis decreased compared with those of under CK treatment. A total of 248 differentially expressed proteins, among which 138 were upregulated, and 110 were downregulated, in soybean leaves under shading and CK treatments were detected via isobaric tags for relative and absolute quantification labeling in the three biological repeats. Differentially expressed proteins were classified into 3 large and 20 small groups. Most proteins involved in porphyrin and chlorophyll metabolism, photosynthesis-antenna proteins and carbon fixation in photosynthetic organisms were upregulated. By contrast, proteins involved in photosynthesis were downregulated. The gene family members corresponding to differentially expressed proteins, including protochlorophyllide reductase (Glyma06g247100), geranylgeranyl hydrogenase (Ggh), LHCB1 (Lhcb1) and ferredoxin (N/A) involved in the porphyrin and chlorophyll metabolism, photosynthesis-antenna proteins and photosynthesis pathway were verified with real-time qPCR. The results showed that the expression patterns of the genes were consistent with the expression patterns of the corresponding proteins. Conclusions This study combined the variation of the soybean leaf structure and differentially expressed proteins of soybean leaves under shading. These results demonstrated that shade condition increased the light capture efficiency of photosystem II (PSII) in soybean leaves but decreased the capacity from PSII transmitted to photosystem II (PSI). This maybe the major reason that the photosynthetic capacity was decreased in shading. Electronic supplementary material The online version of this article (10.1186/s12870-019-1633-1) contains supplementary material, which is available to authorized users.

Predicting grain yield and protein content of maize using spectral reflectance data is very important for improved agricultural production. In this study, we predicted the grain yield and protein content of maize grown under different irrigation and nitrogen levels in 2018 and 2019 based on canopy spectral reflectance measurements at the V6 (sixth leaf), VT (tassel), and R2 (blister) stages. We developed a predictive approach, namely, spectral reflectance–physiological parameters–productivity, to predict grain yield and protein content on maize crop. First, the quantitative relationships between grain yield and protein content and physiological parameters (canopy chlorophyll content [CCC], leaf carbon accumulation [LCA], leaf nitrogen content [LNC], and leaf nitrogen accumulation [LNA]) were analysed. Then, vegetation indices (VIs) and wavelet features based on spectral reflectance were used to establish estimation models for physiological parameters. The physiological parameters were used as a bridge to connect the spectral reflectance data with grain yield and protein content. The purpose was to establish spectral inversion models to indirectly estimate grain yield and protein content. Results showed that grain yield had a significant linear relationship with CCC and LCA. In addition a grain protein content and LNC and LNA were also significantly related under different water, and nitrogen availability. The physiological parameter models with ratio vegetation indices (RVI), biorthogonal 3.3 (bior3.3), and reverse biorthogonal 1.5 (rbio1.5) were reliable in terms of predictability and applicability. Independent data verification suggested that grain yield was predicted using RVI769,758 (R2 = 0.773, RMSE = 2.509) in water availability, rbio1.5781,29 (R2 = 0.744, RMSE = 2.850) in nitrogen availability, and rbio1.5772,11 (R2 = 0.506, RMSE = 2.297) in water–nitrogen availability. In addition, the grain protein content was predicted using RVI793,757 (R2 = 0.704, RMSE = 0.744) in water availability, bior3.3743,19 (R2 = 0.717, RMSE = 0.957) in nitrogen availability, and RVI492,418 (R2 = 0.715, RMSE = 1.224) in water–nitrogen availability. Therefore, maize grain yield and protein content can be accurately predicted using our modelling approach.

Estimation of photosynthetic pigments status using hyperspectral remote sensing technology is highly significant for the effective evaluation of maize (Zea mays L.) productivity. Effective mathematical statistics and modeling methods can improve the accuracy and reliability of pigment contents. In this study, field experiments were conducted with different water and nitrogen levels to develop a quantitative assessment model that determines chlorophyll (Chl) and carotenoids (Car) contents in maize. A pigment prediction model was established by vegetation indices (VIs), wavelet feature, uninformative variable elimination (UVE), and UVE based on continuous wavelet transform (CWT-UVE) and then compared with various methods. The wavelet feature db1 of maize leaf reflectance had a better correlation with Chl and Car with correlation coefficients (r) of −0.9247 and −0.8705, respectively. By using a calibration set, the best results for monitoring the Chl and Car status were observed using the rbio3.3-UVE-PLS, which indicated fewer variables. The R2 and RMSE were respectively 0.9435 and 0.0937 for Chl, 0.8807, and 0.0130 for Car. In addition, tests conducted on the independent validation set showed that rbio3.3-UVE-PLS could be used to estimate the Chl (R2 = 0.8534; RMSE = 0.1773; RPD = 2.6458), and bior3.3-UVE-PLS can be used to estimate the Car (R2 = 0.8299; RMSE = 0.0187; RPD = 2.3832). Thus, Chl and Car are accurately monitored with the CWT-UVE-PLS method. This study provides an important support method for the practical application of photosynthetic pigment contents analysis in maize.

Anti-proliferation and apoptosis induction activities of sanshool isolated from Zanthoxylum bungeanum (Rutaceae) in HepG2 cells were investigated. Cell proliferation was analyzed using MTT assays. Apoptotic bodies were observed under scanning electron microscopy. Nucleus staining using dichlorofluorescin diacetate (DAPI) was performed and the mitochondrial membrane potential (ΔΨm) using rhodamine-123 was observed under laser confocal microscopy. Sanshool inhibited cell proliferation in both a dose and time-dependent manner. The anti-proliferation activity was stimulated with apoptosis induction based on an increase in the sub-G1 cell population, DNA fragmentation, and typical apoptotic morphological changes. Sanshool also disrupted ΔΨm and up-regulated mRNA and protein expressions of p53 and caspase-3. Sanshool induced apoptosis via a mitochondrion-dependent pathway. Thus, sanshool is a potential anticancer medicine.

Intercropping is an important agronomic practice adopted to increase crop production and resource efficiency in areas with intensive agricultural production. Two sequential field trials were conducted in 2015–2016 to investigate the effect of shading on the morphological features, leaf structure, and photosynthetic characteristics of soybean in a maize-soybean relay-strip intercropping system. Three treatments were designed on the basis of different row configurations A1 (“50 cm + 50 cm” one row of maize and one row of soybean with a 50 cm spacing between the rows), A2 (“160 cm + 40 cm” two rows of maize by wide-narrow row planting, where two rows of soybean were planted in the wide rows with a width of 40 cm, and with 60 cm row spacing was used between the maize and soybean rows), and CK (sole cropping of soybean, with 70 cm rows spacing). Results showed that the photosynthetically active radiation transmittances of soybean canopy at V5 stage under A2 treatment (31.1%) were considerably higher than those under A1 (8.7%) treatment, and the red-to-far-red ratio was reduced significantly under A1 (0.7) and A2 (1.0) treatments compared with those under CK (1.2). By contrast with CK, stem diameter, total aboveground biomass, chlorophyll content and net photosynthetic rate decreased significantly except plant height under A1 and A2. The thickness of palisade tissue and spongy tissue of soybean leaf under A1 and A2 were significantly reduced at V5 stage compared with CK. The leaf thicknesses under A1 and A2 were lower than those in CK by 39.5% and 18.2%, respectively. At the R1 stage of soybean (after maize harvest), the soybean plant height, stem biomass, leaf biomass and petiole biomass under A1 and A2 treatments were still significantly lower than those under CK, but no significant differences were observed in Chl a/b, Pn, epidermis thickness and spongy tissue thickness of soybean leaves in A2 compared with CK. In addition, the soybean yields (g plant-1) under A1 and A2 were 54.69% and 16.83% lower than those in CK, respectively. These findings suggested that soybean plants can regulate its morphological characteristics and leaf anatomical structures under different light environments.

This study aimed to evaluate the hypoglycemic effect of Zanthoxylum alkylamides and explore the potential mechanism in streptozotocin (STZ)-induced diabetic rats. Diabetic rats were orally treated with 3, 6, and 9 mg per kg bw alkylamides daily for 28 days. As the alkylamide dose increased, the relative weights of the liver and kidney, fasting blood glucose, and fructosamine levels were significantly decreased. The alkylamides also significantly increased the body weight and improved the oral glucose tolerance of the rats. Likewise, the alkylamides significantly increased the levels of liver and muscle glycogen and plasma insulin. These substances further alleviated the histopathological changes in the pancreas of the diabetic rats. The beneficial effects of high-dose alkylamides showed a comparable activity to the anti-diabetic drug glibenclamide. Western blot and real-time PCR results revealed that the alkylamide treatment significantly decreased the expression levels of the key enzymes (phosphoenolpyruvate caboxykinase and glucose-6-phosphatase) involved in gluconeogenesis and increased the glycolysis enzyme (glucokinase) in the liver, and enhanced the expression levels of pancreatic duodenal homeobox-1, glucokinase, and glucose transporter 2 in the pancreas. In addition, it was also observed that the alkylamides, unlike glibenclamide, increased the transient receptor potential cation channel subfamily V member 1 and decreased cannabinoid receptor 1 expressions in the liver and pancreas. Therefore, alkylamides can prevent STZ-induced hyperglycemia by altering the expression levels of the genes related to glucose metabolism and by ameliorating pancreatic dysfunction.