Pn Values Research Articles

Photosynthetic Physiological Basis of Forage Mass Stability in a Progeny of Rhizome-Rooted ‘Qingshui’ Medicago sativa L.

Rhizome-rooted alfalfa (Medicago sativa L.) is an excellent forage for establishing grazing and ecological grasslands, requiring a high and stable yield. Studying the genetic and physiological basis of stable expression of biomass traits is essential for improving production performance in rhizome-rooted alfalfa. We analyzed forage mass and photosynthetic physiological indices of the improved progenies (RSA−01, RSA−02, and RSA−03), parental “Qingshui” (CK1), and “WL168” (CK2) at ages one and five years and their relationships, then revealed heterotic stability. Moreover, we explored the effects of interannual dynamics and genetic differences on tested indices. The results revealed compared with the forage mass of CK1, RSA−03 at ages one and five years increased by 22.17% and 19.72%, respectively, while RSA−01 and RSA−02 varied from 1.40% to 8.65%, indicating obvious heterosis in forage mass of RSA−03. At one year of age, Gs value, Car content and SS content of RSA−03 were higher than those of CK1; SS content of RSA−03 were higher than those of CK2 and RSA−02; Ci, Gs and Tr values of RSA−03 were higher than those of RSA−01. At five years of age, Pn, Gs, and WUE values, and Sta content of RSA−03 were higher than those of CK1; Ci value and Suc content of RSA−03 were higher than those of CK2; Car content and Gs value of RSA−03 were higher than those of other progenies. The forage mass; Chl(a/b) ratio; Pn, Gs, and WUE values; Suc content of RSA−03 at age five years were higher than those at age one year by 9.99%–44.24%. Through path analysis, Gs and NSC were direct factors affecting forage mass at age one year, and both Pn and SP affected forage mass indirectly through Gs; Gs and Chl(a+b) were direct factors affecting forage mass at age five years, and SS affected forage mass indirectly through Gs. Interestingly, Chlb, Chl(a/b), Pn, Tr, Gs, Ci, Suc, SP, and SS were more influenced by age than genetics, while the opposite was true for Car and Sta. Accordingly, RSA−03 showed obvious and stable heterosis in forage mass and photosynthetic physiology, recommending the establishment of grazing pastures and ecological vegetation.

Effects of Nutrition and Light Quality on the Growth of Southern Highbush Blueberry (Vaccinium corymbosum L.) in an Advanced Plant Factory with Artificial Lighting (PFAL)

A plant factory is a highly developed product system that can produce higher yields and better quality plants under controlled conditions. However, knowledge of blueberry cultivation in plant factories is limited. This study established an advanced plant factory with artificial lighting (PFAL) and investigated the effects of nutrition supply and light qualities on the growth performance of blueberries. Different nutrition treatments affected the vegetative growth of blueberries in PFAL, especially the new shoot length and number. Exogenous fertilization significantly promoted the uptake of N, P, and K elements, and a nutrition solution with N:P:K = 2:1:1 was suggested to be superior for blueberries in PFAL. Red light facilitated vegetative growth to some degree, and the blue light was conducive to increased chlorophyll and anthocyanin content. The Pn value was significantly enhanced under 60% red plus 40% blue light. Combining red and blue light is more beneficial to blueberry growth and might be a preferential strategy in PFAL. This study is the first to investigate the growth performance of blueberries cultivated in PFAL, which can provide an important theoretical database for blueberry cultivation in a plant factory with artificial lighting.

Responses of the Leaf Water Physiology and Yield of Grapevine via Different Irrigation Strategies in Extremely Arid Areas

The contradiction between water supply and demand has become increasingly prominent due to the large agricultural water consumption and low irrigation water use efficiency (IWUE) in the extremely arid area of Xinjiang, which needs to be solved by efficient irrigation. In this study, the effects of different irrigation levels (the lower and upper limits of irrigation (LULI) were 50–80%, 60–90%, and 70–100% of the field capacity (FC), respectively) under two irrigation methods (root zone irrigation (RZI) and furrow irrigation (FI)) on the photosynthetic physiology and yield of grape were analyzed to explore suitable irrigation schemes in extremely arid areas. The results show that the diurnal variation curve of the net photosynthetic rate (Pn) of grape leaves in the extreme arid region was not sensitive to the response of irrigation methods. However, RZI could improve the apparent quantum efficiency and maximum photosynthetic rate by 60.00% and 31.25%, respectively, reduce the light compensation point by 17.91%, and alleviate the photosynthetic lunch break phenomenon. Under FI, the physiological indexes of leaves increased with the increase in the LULI, while the Pn and SPAD values were the largest under RZI when the LULI was 60–90% of FC. The daily average Pn value of T2 in 2021 and 2022 ranged from 12.93 to 17.77 μmol·m−2·s−1. Compared with FI, RZI significantly improved the leaf water potential, Pn, and SPAD values by increasing the soil water content (SWC) of the 40–80 cm soil layer by 5.04–8.80%, which increased the yield by 6.86–18.67%. The results show that the yield and water use efficiency reached the peak when the LULI was 60–90% of FC under RZI, which could provide theoretical support for efficient irrigation of vineyards in extremely arid areas.

Estimation of the net photosynthetic rate for waterlogged winter wheat based on digital image technology

AbstractThe net photosynthetic rate (Pn) is one of the important indicators to measure photosynthetic capacity of crops. Therefore, it is critically important to find real‐time methods for accurately estimating Pn of winter wheat (Triticum aestivum L.). This information could provide guidance on the management of waterlogging stress. To explore the optimal monitoring method for Pn of winter wheat under waterlogging stress, the correlations between Pn and 16 characteristic image indices were analyzed in irrigated and drained microplot experiments. Then, based on the indices values, Pn was estimated using the multiple linear regression (MLR), support vector machine (SVM), backpropagation neural network (BP), and random forest (RF) models, which were constructed based on the optimal monitoring image indices. Water logging when compared to no waterlogged wheat had similar Pn values <6 days. After 12 days, waterlogged wheat plants had a lower Pn value than in no waterlogged plants. All indices were correlated with the Pn (p < 0.05), and Pn estimation accuracy was lower at the winter wheat flowering and complete ripeness periods than at the milky and waxy ripe maturity periods. Based on the results of the models tested, the RF model had higher R2 (0.904) values than the other models. These findings suggest that machine learning models could be used to accurately predict Pn, and the random forest algorithm was the best.

Photosynthesis, Respiration, and Thermal Energy Dissipation in Leaves of Two Phenotypes of Plantago media L. under Environmental Conditions

The ability to maintain the balance between the absorbed light energy and energy used in photosynthesis is a key factor of plant adaptation to variable environmental conditions. In this work, diurnal variations in photosynthesis, respiration, thermal energy dissipation, and the activity of the antioxidant system were studied in hoary plantain (Plantago media L.) growing on an open slope (sun plants) and under natural shading in the herbage (shade plants). The highest leaves net photosynthetic rate (Pn) was observed early in the morning and amounted to 2.6 and 9.2 μmol CO2/m2 s in shade and sun plants, respectively. In the daytime, the Pn values of sun plants decreased significantly (threefold) along with the decrease in stomatal conductance; changes of both parameters developed concurrently with the increase in insolation and air temperature. The Pn changes in leaves of shade plants were less pronounced and weakly dependent on stomatal conductance. The leaves of shade plants contained comparatively high amounts of soluble carbohydrates, whereas the sun plant leaves accumulated larger amounts of starch. In the daytime, nonphotochemical quenching (NPQ) of chlorophyll a fluorescence in photosystem II of sun plant leaves could be as large as 2.6 rel. units, which was four- to fivefold higher than NPQ in shade plants. In leaves of sun plants in the morning and evening hours, the ratio of cytochrome pathway (CP) and the alternative (AP) respiratory pathways was approximately 1.0, whereas this ratio decreased to 0.4 during the day, synchronously with an increase in NPQ. The CP/AP ratio in shade plant leaves remained constant throughout the diurnal cycle and equaled 1.4, indicating a comparatively high energy efficiency of respiration in shaded plants growing under the grass canopy. The leaves of sun plants featured an increased content of superoxide anion radical and hydrogen peroxide as well as the elevated activity of antioxidant enzymes (superoxide dismutase, guaiacol peroxidase) that control the accumulation of reactive oxygen species. The results emphasize the importance of coordinated changes in energy-dissipating processes and the activity of the antioxidant system for maintaining the energy and redox balance in phototrophic tissues during long-term adaptation of plants to environmental conditions, excessive insolation in particular.

N Addition Mitigates Water Stress via Different Photosynthesis and Water Traits for Three Native Plant Species in the Qinghai–Tibet Plateau

Reseeding with native plants to rebuild alpine meadow has become a popular way of ecological restoration. However, the harsh environment poses a great challenge to the establishment of native plants due to poor management of water and nutrients. How water–fertilizer interaction influences dominant grass species is still unclear, and reasonable water and fertilizer conditions are still not determined. Our results showed that addition of nitrogen could mitigate the photosynthetic and water-use traits caused by water stress, i.e., a reduction in Pn and water use results from fewer and thinner leaves, weak stomatal traits, etc. Compared to the control, the peak Pn values of Poa crymophila, Festuca coelestis, and Stipa purpurea increased significantly (71.2%, 108.4%, and 25.4%, respectively). Under drought stress, Pn tended to decrease due to reduced stomatal conductance (Gs). However, appropriate fertilization buffered against Pn decreases by altering the stomatal size and regulating the Gs. Based on reduced water consumption, the water-use efficiency of P. crymophila and F. coelestis decreased whereas that of S. purpurea increased. WHFH for P. crymophila and F. coelestis and WHFL for S. purpurea growth were suitable for the alpine region. WHFH for P. crymophila and F. coelestis and WHFL for S. purpurea were suitable for their establishment in the alpine region. A reasonable water–fertilizer combination could effectively reduce the risk of establishment failure in ecological restoration.

Effect of Phytochrome Deficiency on Photosynthesis, Light-Related Genes Expression and Flavonoid Accumulation in Solanum lycopersicum under Red and Blue Light.

The effect of red (RL, 660 nm) and blue (BL, 450 nm) light on phy mutant tomato plants was studied. The rates of photosynthesis (Pn) and transpiration, the efficiency of the primary photochemical processes of photosynthesis, the contents of flavonoids and phenolic compounds, the low-molecular-weight antioxidant capacity (Trolox equivalent antioxidant capacity (TEAC)) of leaf extracts, and the expression of light-dependent genes were evaluated. Under RL, BL, and white fluorescent light (WFL), the Pn values decreased in the order: WT > phyb2 > phyaphyb2 > phyaphyb1phyb2, except for the Pn in phyb2 on BL. Phyb2 also had a larger number of stomata under BL and, as a result, it reached maximum transpiration. The noticeable accumulation of flavonoids and phenolic compounds was observed only in the phyb2 and phyaphyb2 mutants upon irradiation with BL, which agrees with the increased TEAC in the leaf extracts. We suggest that the increased antioxidant activity under PHYB2 deficiency and the maintenance of high photosynthesis under BL are based on an increase in the expression of the early signaling transcription factors genes BBX, HY5. The largest decrease in the content of flavonoids and TEAC was manifested with a deficiency in PHYB1, which is probably the key to maintaining the antioxidant status in BL plants.

Optimizing Nitrogen, Phosphorus, and Potassium Fertilization Rates for Fruit Performance of Chinese Cherry (Prunus pseudocerasus Lindl.)

ABSTRACT Attempts had been made to optimize nitrogen (N), phosphorus (P) and potassium (K) fertilization rates for increased fruit performance of Chinese cherry (Prunus pseudocerasus Lindl.). This study was conducted using a randomized block design (RBD) consisting of three factors and four levels, totaling to 14 treatments with each treatment repeated in triplicate. The results illustrated that the fertilization application increased the trunk, leaf, crown and new shoot growth, however, the optimal combination of N, P, and K (NPK) fertilization for growth varied among different parts of the young tree. Moreover, the fruit weight and size, internal quality, and fruit set rate (FSR) were positively affected by fertilization. Specifically, the no. 12 treatment (0.3 kg N + 0.4 kg P + 0.2 kg K) contained the optimal NPK combination for enhanced fruit size and cherry fruit set. Similarly, although the treatment is not the maximum of NPK concentration, the no. 12 treatment for mean daily values of Pn (MDVP) and the NPK concentration in leaf was significantly higher compared to other treatments. Additionally, Pearson’s correlation analysis suggests that the FSR was positively and significantly correlated with fruit weight (FW), fruit vertical diameter (FVD) and the soluble sugars (SS) in fruit. In general, the no. 12 treatment was the optimal NPK fertilization rates for young tree growth, fruit quality of Chinese cherry (Prunus pseudocerasus Lindl.) in the Karst region of southwest China.

Effects of Different Concentrations of Micro-Nano Bubbles on Grain Yield and Nitrogen Absorption and Utilization of Double Cropping Rice in South China

Micro-nano bubble (MNB) irrigation can effectively improve the hypoxia stress caused by conventional irrigation and shows great potential in plant development, yield improvement, and saving of water and fertilizer, and has been recognized as a new and high-efficiency technology in crop planting. However, former research on MNB concentration had no clear segmentation, and other MNB concentrations can achieve better or worse effects. This remains to be further explored in order to explore the optimal concentration of MNBs for the yield and nitrogen absorption and utilization of the double cropping rice. With early rice Ganxin203 and late rice WufengyouT025 as the experimental cultivars, the effects of MNBs on growth, yield, and nitrogen absorption and utilization of the potted double cropping rice were analyzed by setting three concentrations of MNBs (LM, low concentration; MM, middle concentration; HM, high concentration), compared with the ordinary running water (CK). Compared with CK, grain yield of the early rice under the MNB treatment increased by 4.84~10.95% and the late rice increased by 6.10~14.31%. It was found that the higher the concentration of the MNBs, the higher the yield of the rice. This is due to that the MNBs improved the tiller-bearing rate, increased the SPAD and Pn values of the flag leaves in the whole growth period, slowed down the drop of the leaf SPAD and Pn from heading stage to maturity, increased the number of the adventitious roots, improved the α-NA oxidation of the root, and simultaneously promoted the nitrogen accumulation, absorption, and utilization. The HM treatment obtained the best benefits, and the effect of the MNBs on the late rice was better than the early rice.

Photosynthesis, Nitrogen Allocation, Non-Structural Carbohydrate Allocation, and C:N:P Stoichiometry of Ulmus elongata Seedlings Exposed to Different Light Intensities.

The leaf photosynthetic capacity, leaf N partitioning, non-structural carbohydrate content, C, N, and P contents of endangered U. elongata seedlings exposed to different light intensities were compared in this study. The most favorable light condition for the survival and growth of U. elongata seedlings in the present study was 100% full sunlight, as this induced higher Pn, PNUE, PC, PR, PB, and NSC content relative to shade-treated seedlings. PNUE, PR, PC, and PB in U. elongata seedling leaves decreased under 40% and 10% full sunlight, while PL increased, indicating that shade increased the light capture efficiency of photosystem (PS) II but decreased electron transfer from PSII to PSI. Furthermore, leaf N content increased with shade intensity, revealing an adaptive strategy for poor light environments. Additionally, the smallest leaf biomass, Pn, WUE, and CE values and C:N and C:P ratios in stems and leaves were observed under 10% full sunlight. These results indicate that seedlings growing under 40% full sunlight will benefit U. elongata conservation.

Water status and thermal response of lime trees to irrigation and shade screen

Most lime trees are cultivated under open-field conditions. However, in the Mediterranean area some growers use shade screen to protect their orchards against abiotic and biotic stresses, inducing changes in the plant’s surrounding microclimate that could affect its water status. This field experiment focuses on the effect of shade screen (high density polyethylene white net with 76% light transmission) and irrigation on plant and soil water status of Bearss lime trees. Two irrigation treatments were applied during the summer-autumn to open-field and shaded lime trees: irrigated (control) and non-irrigated (stress). Volumetric soil water content (θv), air temperature (Ta) and canopy temperature (Tc) were real-time monitored and several derived thermal indices were calculated. Stem water potential (Ψstem) and leaf gas exchange: net photosynthesis (Pn) and stomatal conductance (gs) were measured on representative days. Withholding irrigation caused a gradual decline in soil and plant water status. θv decreased from the outset in the non-irrigated treatments, showing breaking point connecting the rapid and the slower soil drying processes. Significant differences in Ψstem, and gs values were observed between controls and stressed trees 15 days after stress initiation. During early stages of water stress, lime trees cultivated in open-field showed lower values of soil and plant water status than those grown in shaded conditions. However, at the end of stress period, similar values were noted for both cropping systems, pointing to severe water deficit. Tc and Tc-Ta values reflected the current lime tree water status. The soil water content sensors anticipated the plant water stress situation respect to thermal ones. The higher θv, Ψstem, gs, Pn and Tc values registered in shaded lime trees revealed that shading allowed better soil-plant water status and a 12-day window of opportunity to respond to the imposed soil water deficits. Threshold thermal-based values are proposed for precise irrigation management of lime trees in open-field and shaded conditions.

Aluminum uptake, translocation, physiological changes, and overall growth inhibition in rice genotypes (Oryza sativa) at vegetative stage.

Aluminum (Al) contamination in acidic soil is a major problem in paddy field, causing grain yield loss, especially in central plains of Thailand. The objective of this study was to assess Al content in the root tissues, its translocation to the leaves, and Al toxicity in three genotypes of rice, RD35 (local acidic-tolerant), Azucena (positive-check Al-tolerant), and IR64 (high yielding) under 0 (control) or 1mM AlCl3 (Al toxicity) at pH 4.5. Al content in the root tissues of rice cv. RD35 under 1mM AlCl3 was peaked at 4.18mgg‒1 DW and significantly translocated to leaf tissues (0.35mgg‒1 DW), leading to reduced leaf greenness (SPAD) (by 44.9% over the control) and declined net photosynthetic rate (Pn) (by 54.5% over the control). In contrast, Al level in cvs. Azucena and IR64 was restricted in the roots (2.12mgg‒1 DW) with low amount of translocation in the leaf tissues (0.26mgg‒1 DW), resulting in maintained values of SPAD and Pn. In cv. RD35, root and shoot traits including root length, root fresh weight, shoot height, shoot fresh weight, and shoot dry weight in 1mM Al treatment were significantly dropped by > 35% over the control, whereas these parameters in cvs. Azucena and IR64 were retained. Based on the results, RD35 rice genotype was identified as Al sensitive as it demonstrated Al toxicity in both aboveground and belowground parts, whereas Azucena and IR64 were found tolerant to 1mM Al as they demonstrated storage of Al in the root tissues to reduce toxicity in the leaf tissues. The study suggests that root traits, shoot attributes, chlorophyll degradation, and photosynthetic reduction can be successfully employed for the screening of Al-tolerant genotypes in rice breeding programs.

Effects of Different Tillage Measures on Soil Temperature and Humidity and Photosynthetic Capacity of Soybean

In this study, we investigated the effects of different tillage measures on soil environment and soybean yield. We chose a combination of eight tillage treatments using Heihe 43 as the test variety in order to correlate the yield with tillage practices. Our study design involved tilling and rototilling as primary treatments in combination with the following secondary treatment methods: advance deep loosening, advance cultivation, conventional deep loosening, and conventional cultivation. We investigated the effects of the above tillage treatments on soil physicochemical properties and soil biological activity. We also analyzed how tillage treatments impacted the morphology, photosynthetic characteristics, and yield of soybean. Our results indicated that tilling was more beneficial than rototilling in terms of increase in soil water content; the water content at the seedling stage increased from 5.80% to 17.13% in the 0–5 cm soil layer which was subjected to tilling. Under tilling conditions, the Pn, Tr, and Gs values of soybean plants were higher compared to those of soybean cultivated in soil subjected to rototilling. However, Ci values of soybean were higher in rototilled soil. In 2018, we observed an increase in the number of pods and grains per plant in PT1 and PT2 of tilling compared to that of RT1 and RT2 of rototilling. PT1 and PT2 showed a percentage increase of 9.12% and 7.33%, respectively. T1 and T2 both increased the number of pods and grains per plant of soybean under the same tillage conditions, which in turn increased the yield.

Systemic periostin is associated with larger infarct size and worse clinical outcomes in patients with acute coronary syndromes and periodontal disease

Abstract Funding Acknowledgements Type of funding sources: None. Background Periodontal disease (PD) is associated with increased inflammation, which can contribute to atheromatous plaque rupture and consequent acute coronary syndrome (ACS). Periostin (Pn) is a new biomarker associated with inflammation, being involved in the complex process of myocardial recovery after an ACS; however, the association between Pn, other inflammatory biomarkers and concomitant PD in patients with ACS has not been elucidated so far. Purpose the aim of this study was to investigate the link between serum levels of Pn, other systemic inflammatory biomarkers and their impact on the clinical evolution following an ACS. Methods this was an observational prospective study in which 92 patients with ACS and concomitant PD were enrolled. Patients were divided into two groups, according to the median value of Pn which was 30,63 ng/ ml: group 1 included 46 patients with low Pn level and group 2 included 46 patients with high Pn level. Inflammatory status was investigated using serum levels of C reactive protein (CRP), interleukin 6 (IL6), endothelial/ intravascular adhesion molecules (VCAM/ICAM), P-selectin, matrixmetalloproteases (MMP9), Albumin (Ab), Apolipoprotein B (ApoB), alkaline phosphatase (AF) and sST2. For Ab, CRP, and AF the values were recorded at baseline and on day 7. Results Patients with high Pn levels presented more frequent STEMI type myocardial infarction (p=0.0004), heart failure (p=0.002) and a longer duration of hospitalization (p=0.008) and stay in the intensive coronary care unit (p=0.004). They also expressed significantly higher levels of MMP 9 (201 ± 69,37pg/ml vs 132,7 ± 112,2 pg/ml, p = 0.003), Ab (4,08 ±0,34 mg/dl vs 3,08 ± 1,46 mg/dl p=0.02), and AF at baseline at day 7 (53,84 ± 16,2 vs 47,36 ± 16,36 UI/l p=0.022; 58,73 ± 29,91 vs 42,56 ± 16,42 UI/l, p=0.0001). Patients in group 2 had also higher levels of triglycerides (p=0.02) and LDL cholesterol (p=0.0008), as well as a higher amount of myocardial necrosis, as expressed by total creatine kinase (p=0.0004) and CK-MB (p=0.0096). However, serum levels of CRP at baseline (9,2 ± 12,87 mg/ dl vs 26,61 ± 25,59 mg/dl, p=0.0009) and at day 7 (19,25 ± 26,77 mg/dl vs 31,84 ± 29,4 mg/dl, p=0.043) were significantly lower in group 2. Conclusions In patients with ACS and PD, increased systemic levels of circulating Pn indicate a larger myocardial infarction and worse clinical outcomes, being also associated with increased levels of matrixmetalloproteases, involved in the myocardial repair.

Is Lymph Node Dissection Necessary During Radical Nephroureterectomy for Clinically Node-Negative Upper Tract Urothelial Carcinoma? A Multi-Institutional Study.

PurposeThis study aimed to compare the oncological outcomes of patients with upper tract urothelial carcinoma (UTUC) without clinical lymph node metastasis (cN0) undergoing lymph node dissection (LND) during radical nephroureterectomy (NU).MethodsFrom the updated data of the Taiwan UTUC Collaboration Group, a total of 2726 UTUC patients were identified. We only include patients with ≥ pT2 stage and enrolled 658 patients. The Kaplan–Meier estimator and Cox proportional hazards model were used to analyze overall survival (OS), cancer-specific survival (CSS), disease-free survival (DFS), and bladder recurrence-free survival (BRFS) in LND (+) and LND (−) groups.ResultsA total of 658 patients were included and 463 patients without receiving LND and 195 patients receiving LND. From both univariate and multivariate survival analysis, there are no significant difference between LND (+) and LND (-) group in survival rate. In LND (+) group, 18.5% patients have pathological LN metastasis. After analyzing pN+ subgroup, it revealed worse CSS (p = 0.010) and DFS (p < 0.001) compared with pN0 patients.ConclusionsWe found no significant survival benefit related to LND in cN0 stage, ≥ pT2 stage UTUC, irrespective of the number of LNs removed, although pN+ affected cancer prognosis. However, from the result of pN (+) subgroup of LND (+) cohort analysis, it may be reasonable to not perform LND in patients with cT2N0 stage due to low positive predictive value of pN (+). In addition, performing LND may be considered for ureter cancer, which tends to cause lymphatic and hematogenous tumor spreading. Further large prospective studies are needed to validate our findings.

Effect of Integrated Organic–Inorganic Amendments on Leaf Physiological and Grain Starch Viscosity (Rapid Visco-Analyzer Profile) Characteristics of Rice and Ultisols Soil Quality

Current farming systems are highly reliant on chemical fertilizers (CF), which negatively affect soil health, the environment, and crop productivity. Substituting organic fertilizer for chemical fertilizer (CF) is an important agricultural practice that improves soil health and crop productivity and is eco-friendly. To explore the effects of organic fertilizer in the form of cattle manure (CM) or poultry manure (PM) combined with CF on soil properties, leaf physiological traits, and grain physiochemical characteristics of rice, a 2-year field experiment was conducted in a dual cropping system with six treatments: Neg-CF (no N fertilizer control), Pos-CF (100% CF), High-CM (60% CM + 40% CF), Low-CM (30% CM + 70% CF), High-PM (60% PM + 40% CF), and Low-PM (30% PM + 70% CF). The results exhibited that the adding of organic manure significantly improved soil chemical traits such as soil organic C (SOC), total N (TN), and available N (AN). Similarly, applying the combined fertilizer led to significant increases in the leaf net photosynthetic rate (Pn), SPAD values, and rice grain nutritional and cooking characteristics according to Rapid Visco-Analyzer (RVA) profile. Average increases in SOC, TN, Pn, starch content (SC), and amylose content (AC) were 16%, 12%, 9%, 7%, 9%, and 12%, respectively, across the year in the Low-PM compared to the Pos-CF treatment. Moreover, the manure amendments significantly altered the RVA profile attributes, including peak viscosity, tough viscosity, final viscosity, and the setback and pasting temperatures compared to Pos-CF. Linear regression analysis revealed that SOC and TN were positively associated with leaf Pn and SPAD values. Further, leaf Pn and SPAD were positively correlated with rice grain SC and AC. The correlation heat map analyses revealed a positive correlation in the RVA profile between the soil properties and leaf physiological traits. These correlation analyses showed that the increase in soil chemical traits and leaf physiological activities played a significant role in higher rice grain nutritional and cooking quality. Overall, the findings of this study show that the integrated use of organic fertilizers and CF in rice fields enhances soil functionality and the quality of rice on a sustainable basis.

Iron effect on symbiotic efficiency of horse gram

Four horse gram Rhizobium (HGR) strains HGR-4, 6, 13 and 25 grown under different concentrations of Iron (Fe) were inoculated individually to horse gram plants. These plant sets were screened for their net photosynthetic rate (PN), pod formation and symbiotic efficiency. Horse gram plants inoculated with the strain HGR-4 have shown high PN values at 100 µg g-1 of Fe. The number of pods formed were maximum upon inoculation with HGR-4 at 300 µg g-1 of Fe. Nodulation was maximum with the prior inoculation of the strains HGR-6, 13 and 25 at 500 µg g-1 of Fe. Leghaemoglobin content was maximum on inoculation with HGR-6, 13 and 25 at 300 µg g-1 of Fe. This study demonstrated that the horse gram plants associated with rhizobia, besides having nitrogen fixing capacity also have shown Fe stress tolerance and the ability to remove Fe from soils. Hence, the study confirms the ability of HGR-4, HGR-6, HGR-13 and HGR-25 isolates of Rhizobium to have tolerance of the metal Fe at the plant nodule during pot experiments. Therefore these isolates could be suggested for cultivation of horse gram plants in Fe contaminated soils. These findings imply that horse gram-rhizobia symbiosis is an essential element of plant adaptation to metal stress. Key words: Iron, rhizobia, metal tolerance, symbiotic efficiency

Photosynthetic and growth characteristics of apple and soybean in an intercropping system under different mulch and irrigation regimes in the Loess Plateau of China

The shortage of and intense competition for water and light are the main factors restricting the productivity of agroforestry systems in the Loess Plateau of western Shanxi, China. The combination of soil mulch and irrigation in agroforestry systems can regulate the interspecific relationships and increase the productivity of the component crops. However, the effects of mulch and irrigation regimes on the photosynthetic physiological characteristics of the agroforestry system and its synergistic mechanisms are still unclear. A 3-year experiment with two factors, mulch and irrigation, was conducted to investigate the effects of different mulch practices and irrigation levels on the photosynthetic characteristics, growth indices, and interspecific relationships of a fruit tree-crop intercropping system. An apple–soybean intercropping system was selected as the research object, and two mulch types [straw mulch (M1) and plastic mulch (M2)] and four maximum irrigation levels [no irrigation (W0), 55% (W1), 70% (W2), and 85% (W3) field capacity (Fc)] were tested. No mulch together with no irrigation was the control treatment (CK). The results showed that there was no photosynthetic siesta phenomenon in the intercropping system, and the daily variations of the net photosynthetic rate (Pn) and transpiration rate (Tr) were unimodal. The mean values for Pn, Tr, and leaf photosynthetic efficiency (PUE) of the apple and soybean under the M2 treatment were generally higher than under the M1 treatment, whereas Tr and PUE increased as the amount of irrigation increased. In 2017–2018, the maximum mean Pn values for both apple and soybean were observed under the M2W2 treatment, whereas in 2019, they were observed under the M2W3 treatment. The Pn, Tr, and leaf intrinsic water use efficiency (WUEi) of soybean correlated positively with the distance from the trees, whereas PUE correlated negatively with it. Mulch and water replenishment increased apple shoot growth and the height, leaf area index, and yield of soybean, especially under plastic mulch. A principal components analysis found that the M2W2 treatment had the highest comprehensive benefits in 2017–2018, whereas in 2019, the highest were achieved with the M2W3 treatment. Therefore, to optimize the photosynthetic efficiency and yield of the apple–soybean intercropping system in the loess region of western Shanxi, we suggest a combination of plastic mulch and maximum irrigation of 70% Fc in normal years, but maximum irrigation should be increased to 85% Fc in dry years.

Salt interferences to metabolite accumulation, flavonoid biosynthesis and photosynthetic activity in Tetrastigma hemsleyanum

This work mainly investigated the interferences of NaCl treatment to major metabolite accumulation, individual flavonoid biosynthesis and photosynthetic activity in Tetrastigma hemsleyanum. The results showed that the accumulation of phenolic acids, steroids and polysaccharides in T. hemsleyanum was significantly enhanced after the treatment of 50 or 100 mM NaCl for 12 days, and after 150 mM NaCl treatment for 3 days, the total content of flavonoids reached the highest value of 219.5 μg·g‐1−1 and was higher by 3.8 times in comparison with the control (CK). In addition, the salt stress would generally enhance the reaction selectivity of Path II (RPSII) to produce flavonol derivatives (Rut, IsoQ, Km3rut, Ast, Qu, Km) and reduce the reaction selectivity of Path I (RPSI) to produce flavone derivatives (IsoO, Or, Ap), and after the treatment of 150 mM NaCl for 3 days, the RPSII and the RPSI reached the highest level of 0.785 and the lowest level of 0.215, respectively. Moreover, salt stress demonstrated significant and diverse effects on photosynthetic characteristics of T. hemsleyanum. Compared with CK, the values of Pn, Cond, Tr, Fv/Fm, Y(Ⅱ) and qP increased first and then declined with increasing NaCl concentration and stress time, and the highest level of Pn, Fv/Fm and Y(II)occurred after 50 mM NaCl treatment. These findings clearly showed that 50 mM NaCl treatment results in favorable changes in photosynthesis and secondary metabolites accumulation in T. hemsleyanum.

Assessment of leaf photosynthetic performances and bioaccumulation of trace metals by lettuce leaves and strawberry fruits amended with sewage sludge: Which possible re-use in agriculture?

Sewage sludge (SS) is the by-product of wastewater treatment. SS can be used to improve soil fertility thanks to its nitrogen and phosphorus contents. However, crop plants grown on SS amended soils could represent a risk for human health due to the possible high content of trace metals provided by SS. Thus, the present work aimed to investigate the possible effects of SS amendment (used at 10 and 20% of the weight of soil) on the leaf photosynthesis of two different pot-grown crop species: Lactuca sativa as a leafy vegetable and Fragaria x ananassa as a fruit species. Moreover, an assessment of the potential trace metal bioaccumulation in lettuce leaves and strawberry fruits was also performed. The results showed that SS amendments increased Pn and gs values in leaves of both species thanks to the nutrients provided by SS supplementation, also resulting in a higher leaf biomass of lettuce SS-plants compared to relative controls. SS added at 10% to lettuce plants turned out to be the best compromise between plant growth and sensitivity to trace metals contained in SS. Lettuce leaves accumulated higher amount of Cu, Zn and Hg, while strawberry fruits accumulated more Zn and Hg than relative controls. However, the reported values of trace metals were lower than the Reg. CE 1881/2006 and FAO/WHO threshold values, except for the Cu content in lettuce leaves treated with SS-20%. The results highlighted that for lettuce and strawberry plants, SS amendment could be a good agronomic practice to increase plant growth and productivity in potted plants.