Search

This study aimed to investigate the impact of low-temperature (LT) stress during the jointing stage on three most representative wheat varieties in the Huang-Huai-Hai region: “Shannong 38” (a robust winter wheat variety), “Jimai 22” (a semi-winter wheat variety), and “Zhenmai 12” (a weak winter wheat variety). The objective was to explain the sensitivity and change thresholds of various physiological and yield indicators of three winter wheat varieties to low temperatures during the jointing stage and to construct an index for the grading of LT disasters during the jointing stage using principal component analysis. Controlled environment experiments were conducted using an artificial climate chamber during the jointing stage of winter wheat. Five daily minimum temperature treatments were applied, namely (T1, −6 °C); (T2, −3 °C); (T3, 0 °C); (T4, 3 °C); (T5, 6 °C); and control (CK, 8 °C). The duration of treatments was divided into three levels: (D1: 2 days), (D2: 4 days), and (D3: 6 days). It was found that the photosynthetic parameters and chlorophyll content showed a decreasing trend with the increase in the degree of LT stress. The activities of protective enzymes and endogenous hormones increased during the early stages of LT stress or at relatively high temperatures. However, they decreased significantly with an increase in LT stress. Among the varieties, “Zhenmai 12” exhibited a yield reduction rate exceeding 10% under 3 °C LT stress for more than 4 days and a yield reduction rate exceeding 20% under 0 °C LT stress for more than 6 days. “Jimai 22” showed a yield reduction rate exceeding 10% under 3 °C LT stress lasting more than 2 days, and a yield reduction rate exceeding 20% under −3 °C LT stress lasting more than 4 days. “Shannong 38” experienced a yield reduction rate exceeding 10% under 0 °C LT stress lasting more than 4 days and a yield reduction rate exceeding 20% under −6 °C LT stress lasting more than 6 days. Principal component analysis (PCA) conducted on all trait indicators of the three winter wheat varieties revealed that “Zhenmai 12” experienced mild LT stress at 6 °C for 2 days, moderate LT stress at 0 °C for 6 days, and severe LT stress at −3 °C for 6 days. “Jimai 22” experienced mild LT stress under 6 °C for 6 days, moderate LT stress under 0 °C for 4 days, and severe LT stress under −6 °C for 2 days. “Shannong 38” experienced mild LT stress under 3 °C for 4 days, moderate LT stress under 0 °C for 4 days, and severe LT stress under −6 °C for 6 days.

To study the effects of long-term and short-term high temperature stress and recovery on the physiological functions and appearance quality of chrysanthemums, a controlled experiment with chrysanthemums was conducted. The treatments were 25 °C for 3 days (T1D3), 25 °C for 9 days (T1D9), 41 °C for 3 days (T2D3) and 41°C for 9 days (T2D9). The results indicated that there is no significant difference between the T1D3 and T1D9 groups. Conversely, the total chlorophyll content (Chl), net photosynthetic rate (PN), and maximum quantum yield of Photosystem II (PSII) (FV/FM) under T2D3 and T2D9 decreased by 27.07%, 43.30%, 5.62%, and 44.85%, 68.22%, 8.29%, respectively. The JIP-test results showed that the T2D9-stressed plants had a lower efficiency and functional antenna size, and a higher activity of the reaction centre than T2D3. The contents of malondialdehyde, soluble protein and proline increased by 3.67 nmol/g FM, 298.75 μg/g, and 192.99 μg/g, and the antioxidant enzymes activities were inhibited significantly under T2D9. After the stress was relieved, Chl, PN, and FV/FM under T2D3 recovered to the same level as T1D3, while T2D9 did not. Furthermore, the diameter of the flowers in T2D3 showed no significant difference with the chrysanthemums under T1D3. However, the plants in T2D9 recovered poorly. Both the diameter of the flowers and the anthocyanin under T2D9 reduced significantly comparing with T1D9, indicating that the damage in the chrysanthemum seedlings caused by long-term high temperature was irreversible.

High relative humidity (RH) and high temperature are expected more frequently due to climate change, and can severely affect the growth of chrysanthemums. In order to analyze the interactive effects of RH and high temperature on the photosynthetic performance of chrysanthemum, a completely randomized block experiment was conducted with three factors, namely temperature (Day/night temperature, 35°C/18°C, 38°C/18°C, 41°C/18°C), RH (Whole day RH, 50%, 70%, 90%), and treatment duration (3d, 6d, 9d). The control (CK) temperature was 28°C/18°C and RH was 50%. The results showed that with the increase of temperature, the apparent quantum efficiency (AQE), maximum net photosynthetic rate (Pn-max), net photosynthetic rate (Pn), transpiration rate (Tr), water use efficiency (WUE), maximal recorded fluorescence intensity (Fm), PSII maximal photochemical efficiency (Fv/Fm), absorption flux per cross section (ABS/CSm), trapped energy flux per cross section (TRo/CSm), electron transport flux per cross section (ETo/CSm) and photosynthetic pigment content of leaves significantly decreased, the minimal recorded fluorescence intensity (Fo), fluorescence intensity at point J of the OJIP curve (Fj) and non-photochemical quenching per cross section (DIo/CSm) significantly increased, the fluorescence difference kinetics of the OJ phase of chrysanthemum leaves showed K-bands. Pn, AQE, Fm, Fv, Fv/Fm, ABS/CSm, TRo/CSm, ETo/CSm and photosynthetic pigment content were higher at 70% RH than the other two RH conditions. The dominant factor causing the decrease of Pn in leaves was stomatal limitation at 35°C,38°C, three RH conditions, 3d and 6d, but non-stomatal limitation at 41°C and 9d. There was an interaction between temperature and RH, with a significant impact on Pn. The temperature had the greatest impact on Pn, followed by RH. This study confirms that heat stress severely affects the photosynthesis of chrysanthemum leaves, and when the temperature reaches or exceeds 35°C, adjusting the RH to 70% can effectively reduce the impact of heat stress on chrysanthemum photosynthesis.

This paper proposes a special disconnector for surge protector (SPD) with the ability to pass large pulse currents under multiple pulses, which has been verified to solve the problem of SPD fire and combustion under multiple pulses in engineering applications. The safety problem caused by the lightning strike failure of SPD has always been a difficult research point in low-voltage power distribution systems, especially the failure mechanism under multi-pulse lightning strike is still unclear. In this paper, the multi-pulse lightning generator is used to simulate the multi-pulse lightning current to carry out the SPD lightning impulse test. The results show that the SPD will have short-circuit breakdown and fire and combustion under multi-pulse lightning strikes, mainly because the continuous pulses will generate energy superposition, and the built-in disconnector and external disconnector fuses and circuit breakers cannot effectively cooperate with the SPD, and there is a protection blind spot. As a result, the SPD cannot be quickly detached at the moment of a short circuit. Based on the thermal effect of multi-pulse lightning strikes, a multi-pulse SPD special disconnector is designed, which can effectively solve the problem of lightning strike ignition of SPD under multi-pulse lightning strikes, and is of great significance to the lightning protection safety of low-voltage power distribution systems.

IntroductionEnvironmental temperature and nitrogen (N) fertilizer are two important factors affecting the sugar and organic acid content of tomato fruit. N is an essential nutrient element for plant growth and development, and plays a key role in regulating plant growth, fruit quality and stress response. However, the comparative effect of different N fertilizer levels on the accumulation of soluble sugar and organic acid in tomato young fruit under high temperature stress and its mechanism are still unknown.MethodsThree N fertilizer levels (N1, N2, N3) combined with two temperatures (28/18°C, CK; 35/25°C, HT) were used to study the effects of N fertilizer, HT and their interaction on the soluble sugar and organic acid components, content, metabolic enzyme activity and the expression level of key genes in tomato young fruit, revealing how N fertilizer affects the sugar and organic acid metabolism of tomato young fruit under HT at physiological and molecular levels.ResultsThe content of soluble sugar and organic acid in tomato young fruit under HT exposure was increased by appropriate N fertilizer (N1) treatment, which was due to the accumulation of glucose, fructose, citric acid and malic acid. High N (N3) and HT exposure had a negative impact on soluble sugar and reduce sugar accumulation. Further studies showed that due to the up-regulation of the expression of sucrose metabolizing enzyme genes (CWINV2, HK2, SPS, PK) and sucrose transporter (SUT1, SUT4, SWEETs) in tomato, N fertilizer increased the accumulation of soluble sugar by improving the sucrose metabolism, absorption intensity and sucrose transport of fruit under HT exposure. Due to the increase of PEPC gene expression, N fertilizer increased the accumulation of citric acid and malic acid by improving the TCA cycle of fruit under HT exposure.DiscussionNitrogen fertilizer can improve the heat tolerance of tomato young fruits by improving sugar metabolism under HT exposure. The results can provide theoretical support for the correct application of N fertilizer to improve the quality of tomato fruit under HT exposure.

This study was conducted to investigate the effects of nitrogen application on growth, photosynthetic performance, nitrogen metabolism activities, and fruit quality of tomato plants under high-temperature (HT) stress. Three levels of daily minimum/daily maximum temperature were adopted during the flowering and fruiting stage, namely control (CK; 18°C/28°C), sub-high temperature (SHT; 25°C/35°C), and high-temperature (HT; 30°C/40°C) stress. The levels of nitrogen (urea, 46% N) were set as 0 (N1), 125 (N2), 187.5 (N3), 250 (N4), and 312.5 (N5) kg hm2, respectively, and the duration lasted for 5 days (short-term). HT stress inhibited the growth, yield, and fruit quality of tomato plants. Interestingly, short-term SHT stress improved growth and yield via higher photosynthetic efficiency and nitrogen metabolism whereas fruit quality was reduced. Appropriate nitrogen application can enhance the high-temperature stress tolerance of tomato plants. The maximum net photosynthetic rate (PNmax), stomatal conductance (gs), stomatal limit value (LS), water-use efficiency (WUE), nitrate reductase (NR), glutamine synthetase (GS), soluble protein, and free amino acids were the highest in N3, N3, and N2, respectively, for CK, SHT, and HT stress, whereas carbon dioxide concentration (Ci), was the lowest. In addition, maximum SPAD value, plant morphology, yield, Vitamin C, soluble sugar, lycopene, and soluble solids occurred at N3-N4, N3-N4, and N2-N3, respectively, for CK, SHT, and HT stress. Based on the principal component analysis and comprehensive evaluation, we found that the optimum nitrogen application for tomato growth, yield, and fruit quality was 230.23 kg hm2 (N3-N4), 230.02 kg hm2 (N3-N4), and 115.32 kg hm2 (N2), respectively, at CK, SHT, and HT stress. Results revealed that the high yield and good fruit quality of tomato plants at high temperatures can be maintained by higher photosynthesis, nitrogen efficiency, and nutrients with moderate nitrogen.

Drought is a major stress that restricts the growth and development of winter wheat (Triticum aestivum L.), and recovery after drought is the key to coping with adversity. So, we used a meta-analysis to quantitatively evaluate the responses of winter wheat to drought stress and rewatering and investigated the differences caused by several moderators (e.g., stress intensity, treatment durations, growth stages, planting methods, and experimental areas). The results show that drought can cause many negative effects on winter wheat. However, in most cases, rewatering can offset these adverse effects. Winter wheat under short-term or mild stress was less affected, and rewatering can restore it to the control level. Net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (gs) are sensitive to environmental water change. Drought reduced the quantum yield of electron transport (ΦPSII), with insignificant effects on the efficiency of PSII (Fv/Fm). Additionally, the responses to drought and rewatering also varied with different growth stages. The regreening stage and the anthesis-filling stage are both critical water management periods. Rewatering after the jointing stage had no significant effect on leaf area (LA) and plant height (PH). The drought tolerance and recovery ability of field-grown wheat were better than those of pot-grown wheat. Winter wheat planted on the Loess Plateau was less affected than that on the Huang-Huai-Hai Plain and the Middle–Lower Yangtze Plain. Overall, different moderators may lead to different degrees of responsiveness of wheat to drought stress and postdrought rewatering. This study provides a reference for winter wheat to cope with drought stress and a useful guidance to wheat breeding programs.

To study the impact of nitrogen application on the photosynthetic structure and photosystem activity of tomato (Lycopersicon esculentum Mill.) leaves during the recovery stage after heat stress, the OJIP curve and JIP parameters were determined through a control experiment in an artificial climate chamber. The tomato variety was “Jinfen No. 1”. Four day/night temperature levels (25 °C/15 °C as control CKT; 30 °C/20 °C, lightly high-temperature LHT; 35 °C/25 °C, moderate high-temperature MHT; 40 °C/30 °C, severe high-temperature SHT) were set for a duration of 7 days. Five nitrogen supply levels (N1–N5: 0, 1.3, 1.95, 2.6 and 3.75 g/plant, respectively; 2.6 g/plant is the recommended nitrogen application rate, CKTN4) were applied. The results showed that the O, K, J, I and P phases on the chlorophyll a fluorescence curve were significantly affected by different nitrogen treatments in heat stress recovery. Compared with CKT, with the increase in nitrogen supply, the fluorescence intensity of SHTN2-SHTN5 treatment increased significantly at P, I and J phases, while that of MHTN1-MHTN4 treatment decreased. The fluorescence intensity of SHTN5 and SHTN3 increased by 13.27% and 10.10% in the P phase, 13.52% and 12.1% in the I phase and 20.16% and 26.18% in the J phase, respectively. There were highly significant differences (p < 0.01) in the impact of high temperatures and nitrogen levels on the fluorescence parameters. On the 1st day after short-term heat stress, N had no significant effect on Fv/FM, Fv, Fo and FM; however, their interaction was significant (p < 0.05). On the 8th day, there were no significant interaction effects between HT and N for Fv/Fo, ABS/RC and DIo/RC. Fv/Fo proved to be sensitive to the application of both high temperatures and nitrogen. Under all five nitrogen applications, temperature played a significant role in increasing DIo/RC, especially for N2 and N3. The results indicated that decreasing the nitrogen application under SHT resulted in a higher number of active RCs and an increased value of specific energy flux (ABS/RC, TRo/RC and DIo/RC), indicating the enhanced ability of RC to reduce plastoquinone. The study provides a reference for the diagnosis of nitrogen nutrition under high-temperature stress using chlorophyll fluorescence methods.

To investigate the effects of low-temperature (LT) stress on photosynthetic properties and senescence characteristics of winter wheat leaves during the jointing stage, an environmental temperature control experiment was designed at Nanjing University of Information Science and Technology in 2023, using Triticum aestivum L. cv. “Ji Mai 22” as the test material. Four different temperature levels were set: 18 °C/8 °C (daily maximum/daily minimum temperature; CK), 13 °C/3 °C, 10 °C/0 °C, and 7 °C/3 °C. The duration of each treatment was 2, 4, and 6 days, respectively. The experimental findings reveal that the changes in physiological parameters of winter wheat leaves under low-temperature stress treatments are nonlinear. Under the 3 °C LT treatment, the photosynthetic parameters and endogenous hormone levels of wheat leaves significantly decrease after 6 days of stress. Under the 0 °C LT treatment, the photosynthetic parameters, leaf pigment content, and endogenous hormones of wheat decrease significantly, while under the −3 °C LT treatment, all the parameters of winter wheat leaves show a significant decline. Generally, the “Ji Mai22” wheat cultivar has a lower growth temperature limit of −3 °C during the jointing stage.

Heat stress is a major constraint for plant production, and evapotranspiration is highly linked to plant production. However, the response mechanism of evapotranspiration to heat stress remains unclear. Here, we investigated the effects of heat stress during two main growth stages on transpiration and evapotranspiration of gerbera. Two levels of day/night temperature were adopted during the vegetative growth stage (VG) and the flowering bud differentiation stage (FBD), namely control (CK; 28/18 °C) and heat stress (HS; 38/28°C) levels. The duration of HS was set as 5, 10, 15, and 20 days, respectively. At the beginning of HS, hourly transpiration was mainly inhibited near noon. With continuation of HS, the duration and extent of inhibition of hourly transpiration increased. Daily transpiration rate was also markedly reduced by HS during the VG (18.9%-31.8%) and FBD (12.1%-20.3%) stages compared to CK. The decrease in the daily transpiration rate was greater for longer duration of heat stress. This reduction of transpiration was the main contributor to stomatal limitation at the beginning of HS, while additional inhibition of root activity, leaf area, and root biomass occurred under long-term HS. The daily transpiration rate could not recover after the end of HS (so-called recovery phase), except when HS lasted 5 days during the VG stage. Interestingly, daily evapotranspiration during HS was substantially increased during the VG (12.6%-24.5%) and FBD (8.4%-17.6%) stages as a result of more increased evaporation (100%-115%) than reduced transpiration. However, during the recovery phase, the daily evapotranspiration was markedly decreased at the VG (11.2%-22.7%) and FBD (11.1%-19.2%) stages. Hence, we suggest that disproportionate variation of transpiration and evaporation during HS, especially at the recovery phase, should be considered in various evapotranspiration models and climate scenarios projections.

The collection of many environmental pollutants from road dust is harmful to living things and their surroundings. Previous studies have confirmed that road dust affects plant pigmentation, pollination, and biochemical properties. However, there are no comprehensive studies on multi-level dust pollution levels and multifaceted physiological properties of plants, and more importantly, there are no studies on atmospheric dust pollution monitors. In this experiment, the effect of road dust on the morphology and biochemistry of Salvia guaranitica St.Hil.was investigated by simulated deposition of different amounts of dust, and the changes of their physiological morphology under different pollution levels were also explored. A control group CK (0.00 g/plant), four experimental groups S1 (0.015 g/plant), S2 (0.030 g/plant), S3 (0.045 g/plant) and S4 (0.060 g/plant) were sprayed with the same dust samples every other day for 30 days. It was found that after 30 days of dust exposure, different degrees of morphological changes and damage occurred in Salvia. The different pollution levels also resulted in different degrees of biochemical characteristics of Salvia. With the increase of pollution, chlorophyll content, photosynthetic and evaporation rates decreased significantly, but the activity of SOD and the content of MDA increased significantly in different experimental groups. Especially, the experiments also revealed that severe road dust pollution caused damage and deformation to stomata, as well as a significant reduction in stomatal and glandular density. In addition, the regression curves of the different physiological responses of Salvia to road dust can be used as a preliminary basis for plant monitoring of dust pollution degrees, thus provided a scientific basis for the use of plant biomonitors in the field of pollution biology.

Chilling injury can adversely affect strawberry bud differentiation, pollen vitality, fruit yield, and quality. Photosynthesis is a fundamental process that sustains plant life. However, different strawberry varieties exhibit varying levels of cold adaptability. Quantitatively evaluating the physiological activity of the photosynthetic system under low-temperature chilling injury remains a challenge. In this study, we investigated the effects of different levels of chilling stress on twenty photosynthetic fluorescence parameters in strawberry plants, using short-day strawberry variety “Toyonoka” and day-neutral variety “Selva” as representatives. Three dynamic chilling treatment levels (20/10 °C, 15/5 °C, and 10/0 °C) and three durations (3 days, 6 days, and 9 days) were applied to each variety. WUE, LCP, Y(II), qN, SIFO2-B and rSIFO2-B were selected as crucial indicators of strawberry photosynthetic physiological activity. Subsequently, we constructed a comprehensive score to assess the strawberry photosynthetic system under chilling injury and established a hyperspectral inversion model for stress quantification. The results indicate that the short-day strawberry “Toyonoka” exhibited a recovery effect under continuous 20/10 °C treatment, while the day-neutral variety “Selva” experienced progressively worsening stress levels across all temperature groups, with stress severity higher than that in “Toyonoka”. The BPNN model for the comprehensive assessment of the strawberry photosynthetic system under chilling injury showed optimal performance. It achieved a stress level prediction accuracy of 71.25% in 80 validation samples, with an R2 of 0.682 when fitted to actual results. This study provides scientific insights for the application of canopy remote sensing diagnostics of strawberry photosynthetic physiological chilling injury in practical agricultural production.

Plenty of studies have demonstrated that DIF has an effect on the fruit growth. To study the effects of day and night temperature differences on the strawberry sugar quality, an experiment using climate chambers was conducted. Five different differences between the day and night temperatures (DIF) were set, which were 6 °C (28 °C/22 °C, day/night temperature), 8 °C (29 °C/21 °C), 10 °C (30 °C/20 °C), 12 °C (31 °C/19 °C), 14 °C (32 °C/18 °C). The results showed the following indices peaked with a DIF of 12 °C, including the photosynthesis rate, glucose content, fructose content, sucrose content, soluble sugar content and sugar metabolic enzyme activity. The respiration rate increased with the DIF during the day and decreased with the DIF at night. The root dry weight peaked at a DIF of 10 °C, the stolon dry weight peaked at a DIF of 8 °C and the leaf dry weight peaked at a DIF of 6 °C; however, the fruit dry weight reached maximum values at a DIF of 12 °C. The Grey correlation analysis showed that the most important factor in our experiment affecting the fructose content was the sucrose phosphate synthase; however, for the sucrose, glucose, and soluble sugars, the most important factor was the photosynthesis. We found that a DIF of 12 °C (31 °C/19 °C, day/night temperature) was the most suitable for strawberry growth, especially for the sugar content accumulation.

High temperatures have become a severe factor limiting growth and yield for tomatoes (Lycopersicon esculentum Mill.) due to unfavorable, above-optimum temperatures. Temperature and nitrogen application were the main regulatory factors in tomato plant cultivation. This research was undertaken to evaluate the effects of nitrogen application and high temperature on tomato morphology, dry matter accumulation and distribution, root vitality and nitrogen content of the above ground. Tomato variety “Jinfen No. 1” was planted and exposed to 4 day/night temperature levels (25 °C/15 °C as control CKT; 30 °C/20 °C, lightly high-temperature LHT; 35 °C/25 °C, moderate high-temperature MHT; 40 °C/30 °C, severe high temperature SHT) for 7 days after five nitrogen supply levels (N1–N5: 0, 1.3, 1.95, 2.6 and 3.75 g/plant, respectively; 2.6 g/plant is the recommended nitrogen-application rate, as control CKTN4). Within conditions, there was an extremely significant difference (p < 0.01) in all tomato plant parameters and an extremely significant interaction (p < 0.01) between high temperatures and nitrogen supply levels, except for plant height sampling on the 1st day in the recovery period. Dry matter accumulation decreased, and the accumulation rate slowed down. Dry matter accumulation under low nitrogen treatment was higher than in high nitrogen treatment. The proportion of dry matter in leaves decreased, the proportion of dry matter in stems increased and the difference in dry matter accumulation and proportion of dry matter between different nitrogen treatments decreased. Under LHT, the root activity of the tomato was increased under all nitrogen levels, while under MHT and SHT, high nitrogen and low nitrogen supply significantly inhibited root activity. Lightly high-temperature stress can increase root activity, and LHTN4 can increase by 5.15% compared with CKTN4. Appropriate nitrogen application can alleviate the damage caused by high-temperature stress on tomato plants and enhance the resistance of tomato plants, while excessive nitrogen application will aggravate the damage degree of tomato plants. In this study, the optimal nitrogen application rates under CKT-SHT treatment were 2.6, 2.6, 1.95 and 1.3 g/plant, respectively.

During the early growth stage of plants, low temperatures can alter cell permeability, reduce photosynthetic capacity, and have adverse effects on crop growth, development, and yield. Different strawberry cultivars have varying cold tolerance. In this study, we investigated the changes in cell permeability and photosynthetic activity of short-day and long-day types of strawberry cultivars under varying degrees of low-temperature stress, and evaluated the extent of cellular damage using photosynthetic and chlorophyll fluorescence parameters. The experiment utilized short-day strawberry cultivars ‘Toyonoka’ and ‘Red Face’, and long-day strawberry cultivars ‘Selva’ and ‘Sweet Charlie’ seedlings. Low-temperature treatments were set at −20, −15, −10, −5, 0, 5, and 10 °C for 12 h. The research demonstrated that short-day strawberries had greater tolerance to low temperatures, and all four strawberry cultivars began to experience low-temperature stress when the temperature was below 5 °C. A temperature range of 0 to −10 °C played a crucial role in causing severe cold damage to the strawberries. The low-temperature stress levels were constructed based on electrolyte leakage, with photosynthetic physiological characteristics serving as references. The study proves that the photosynthetic and chlorophyll fluorescence parameters can serve as effective probes for diagnosing low-temperature stress in strawberry seedlings, and their combination provides higher accuracy in identifying stress levels than any single type of parameter.

Because of their relatively simple structures, plastic greenhouses in southern China have poor resistance to adverse external weather conditions. Adverse meteorological condition inside the greenhouse is one of the main limiting factors for facility crop production in southern China. Among them, high temperature and high humidity (HTHH) often co-occurred in greenhouses, inducing great losses. Tomatoes (Lycopersicon esculentum Mill.) are grown under protected environment worldwide. Here, characteristics of HTHH inside plastic greenhouses in southern China were analyzed and tomato was chosen as the sample facility crop to study the effects of HTHH. Daily maximum temperature and average relative humidity (RH) inside plastic greenhouses were simulated using the extreme learning machine (ELM) method to identify HTHH events. The results showed that the plastic greenhouse HTHH events mainly occurred from June to September in southern China, especially in the southernmost region. During 1990 and 2019, the occurrence times and accumulative days of the HTHH events showed a downward trend at 0.3 times/decade and 2.6 days/decade, respectively, which is mainly due to their reduction in July. HTHH affected the growth of tomato, in which high temperature plays a more important role than high RH. Days of flower bud differentiation was more sensitive to HTHH stress than other physiological indexes of tomato. With the increase of the return period of HTHH events, the corresponding losses of physiological indexes of tomato increased, except for the western region, where HTHH events rarely occurred. The results in this study could provide guidance for production and layout of greenhouse-grown tomato, and the research approach can also be applied to other greenhouse-grown crops and meteorological disasters.

High temperature and high relative humidity (RH) are one of the most serious agricultural meteorological disasters that limit the production capacity of agricultural facilities. However, little information is available on the precise interaction between these factors on tomato growth. The objectives of this study were to determine the effect of high temperature under different RH levels on tomato growth and endogenous hormones and to determine the optimal RH for tomato seedling growth under high temperature environment. Two high temperature (38/18 °C, 41/18 °C) and three relative humidity (50 ± 5%, 70 ± 5%, 90 ± 5%) orthogonal experiments were conducted, with 28/18 °C, 50 ± 5% (CK) as control. The results showed that the dry matter accumulation of tomato plants under high temperature environment was significantly lower than that of CK. At 38 °C, the dry matter accumulation with 70% relative humidity was not significantly different from that of CK; at 41 °C, dry matter accumulation with 70% and 90% relative air humidity was significantly greater than that of 50%. The concentrations of soluble sugar and free amino acids in all organs in high temperature-treated plants were significantly higher than that in CK. As relative humidity increased, soluble sugar concentrations of each organ decreased, and the free amino acid concentrations increased. Cytokinin (ZT) and indole acetic acid (IAA) concentrations in tomato buds were significantly lower than in CK under high temperature conditions. The lower the RH, the lower the content of ZT and IAA. The gibberellin (GA3) and abscisic acid (ABA) concentrations were higher than in CK under high temperatures. GA3 concentrations decreased and ABA concentrations were augmented with increased humidity. The differences of tomato seedling growth indices and apical bud endogenous hormone concentrations between RHs under high temperature conditions were significant. Raising RH to 70% or higher under high temperature conditions could be beneficial to the growth of tomato plants. The results contribute to a better understanding of the interactions between microclimate parameters inside a Venlo-type glass greenhouse environment, in a specific climate condition, and their effects on the growth of tomato.

With the formulation of United Nations Convention on the Law of the Sea, marine pollution has received widespread attention from various countries. Green navigation is an important requirement for route planning, in which energy consumption is its primary focus. Ships are affected by complex marine meteorological environments, so it is difficult to plan a reasonable route. Some methods have been proposed to solve this problem, but there are some shortcomings, such as no consideration of the effect of wind direction, wind speed and wave. To solve this problem, we introduce a meta-heuristic whale optimization algorithm (WOA), which helps ships find a low-energy-consumption and safe route in a large-scale complex marine environment. The results of our simulation experiments indicate that WOA is more competitive than other state-of-the-art algorithms for route planning.

With the expansion of cucumber cultivation, many growers continue to experience extreme weather and environmental issues. This study aimed to examine and model the effects of low temperature (LT) and poor light (PL) stresses on cucumber growth. The experiment was designed as an orthogonal experiment that analyzed temperature, light, and duration. The daily maximum/minimum temperatures of the experiment were set as per the following four levels: 13 °C/3 °C, 16 °C/6 °C, 19 °C/9 °C, 22 °C/12 °C, and the control at 28 °C/18 °C. The light was divided into two levels: 200 μmol∙m−2∙s−1 and 400 μmol∙m−2∙s−1, with 800 μmol∙m−2∙s−1 as the control. Treatment duration was set at 2, 5, 8, and 11 days. Stress with different LT, PL, and duration was expressed using the stress effect (0–1), which decreased with an increase in stress level. Meanwhile, treatment with a temperature of 3 °C and light of 400 μmol∙m−2∙s−1 for 11 days had the smallest effect on stress, which was only 67% of that of the control following 50 days of recovery, and had the most severe effect on cucumber growth. The proportion of dry weight allocated to leaves and stems decreased with increasing low temperatures and poor light stress, but the proportion allocated to fruit increased. The highest percentage of fruit distribution was found in the treatment with temperature of 9 °C, light of 200μmol∙m−2∙s−1, and 11 days duration, being 3.57 times higher than the control. In order to better investigate the effects of LT and PL stress on cucumber growth, light and temperature effect (LTE), growing degree days (GDD), and product of thermal effectiveness and PAR (TEP) models were developed based on temperature and light. The root mean square error (RMSE) of the LTE model was found to be 4.214 g∙plant−1, 36.3% of that of the GDD model and 78.8% of that of the TEP model, better simulating the above-ground dry weight of cucumber plants.

Abstract Background The modification effect of leaching fraction (LF) on the physiological responses of plants to irrigation water salinity (ECiw) remains unknown. Here, leaf gas exchange, photosynthetic light–response and CO2–response curves, and total carbon (C) and nitrogen (N) accumulation in hot pepper leaves were investigated under three ECiw levels (0.9, 4.7 and 7.0 dS m− 1) and two LFs treatments (0.17 and 0.29). Results Leaf stomatal conductance was more sensitive to ECiw than the net photosynthesis rate, leading to higher intrinsic water use efficiency (WUE) in higher ECiw, whereas the LF did not affect the intrinsic WUE. Carbon isotope discrimination was inhibited by ECiw, but was not affected by LF. ECiw reduced the carboxylation efficiency, photosynthetic capacity, photorespiration rate, apparent quantum yield of CO2 and irradiance–saturated rate of gross photosynthesis; however, LF did not influence any of these responses. Total C and N accumulation in plants leaves was markedly increased with either decreasing ECiw or increasing LF. Conclusions The present study shows that higher ECiw depressed leaf gas exchange, photosynthesis capacity and total C and N accumulation in leaves, but enhanced intrinsic WUE. Somewhat surprisingly, higher LF did not affect the intrinsic WUE but enhanced the total C and N accumulation in leaves.

Nodes in a wireless sensor network are normally constrained by hardware and environmental conditions and face challenges of reduced computing capabilities and system security vulnerabilities. This fact calls for special requirements for network protocol design, security assessment models, and energy-efficient algorithms. Data aggregation is an effective energy conservation technique, which removes redundant information from the data aggregated from neighbor sensor nodes. How to further improve the effectiveness of data aggregation plays an important role in improving data collection accuracy and reducing the overall network energy consumption. Unfortunately, sensor nodes are normally deployed in an open environment and thus are subject to various attacks conducted by adversaries. Consequently, data aggregation brings new challenges to wireless sensor network security. In this article, we propose a novel secure data aggregation solution based on autoregressive integrated moving average model, a time series analysis technique, to prevent private data from being learned by adversaries. We leverage the autoregressive integrated moving average model to predict the data volume in sensor nodes, and update and synchronize the model as needed. The experimental results demonstrate that our model provides accurate predictions and that, compared with competing methods, our solution achieves better security, lower computation and communication costs, and better flexibility.

Abstract We investigated whether leaching fraction (LF) is able to modify the effects of irrigation water salinity (ECiw) on evapotranspiration (ET). We conducted an experiment with a completely randomized block design using five levels of ECiw and two LFs. Results showed that the electrical conductivity of drainage water (ECdw) in an LF of 0.29 was considerably higher during the 21–36 days after transplanting (DAT), and considerably lower after 50 DAT than in an LF of 0.17. The hourly, nighttime, daily, cumulative and seasonal ET all decreased considerably as a result of an increase in the ECiw. The daily ET started to be considerably higher in the LF of 0.29 than in the LF of 0.17 from 65 DAT. Compared with the LF of 0.17, the seasonal ET in the LF of 0.29 under various ECiw levels increased by 4.8%–8.7%. The Maas and Hoffman and van Genuchten and Hoffman models both corresponded well with the measured relative seasonal ET and the LF had no marked effects on these model parameters. Collectively, an increase in the level of ECiw always decreased the ET substantially. An increase in the LF increased the ET considerably, but there was a time lag.

Global mean temperature is expected to significantly increase by the end of the twenty-first century and could have dramatic impacts on a plant's growth, physiology, and ecosystem processes. Temperature manipulative experiments have been conducted to understand the responsive pattern of plant ecophysiology to climate warming. However, it remains unknown how different methodology used in these experiments will affect plants ecophysiological responses to warming. We conducted a comprehensive meta-analysis of the warming manipulative studies to synthesize the ecophysiological traits responses to warming treatment of different intensities, durations, and conducted for different species and under different experimental settings. The results indicated that warming enhanced leaf dark respiration (Rd) and specific leaf area (SLA) but decreased net photosynthetic rate (Anet) and leaf nitrogen content (LN). The positive and negative effects of warming on Rd and Anet were greater for C4 species than C3 species, respectively. The negative effect of warming treatment on Anet and LN and the positive effect on Rd were more evident under >1 year warming treatment. Negative effects of warming were more evident for plants grown at

Expressway toll station is listed by lightning protection experts as one of the five difficult problems in the field of international lightning protection. So far, the direct lightning protection of the expressway toll station is mainly based on the electrical geometry model-rolling ball method. Lightning rod or lightning belt is installed on the high pole lamp of the toll square and the ceiling of the toll island as a flash catching device to intercept lightning. The lightning rod is a section of metal conductor with the tip. From the process of the connection between up leader generated by the lightning rod and down leader of lightning, the lightning rod has the ability to attract the lightning rod, and can prevent lightning strike of the protected objects within a certain range. From the perspective of lightning protection methods and means, lightning protection plays an interception role against lightning discharge, also called interceptor. A large number of practice has proved that the lightning rod plays an important role in protecting the building structure from lightning damage. With the development of electronic information society, the limitations of lightning rod are more and more prominent, resulting in more and more lightning strike accidents. In 2019, China invented a new flash connection device-lightning interceptor that can overcome the limitations of lightning rod and has applied it on expressways, which has achieved remarkable results. In this paper, the physical parameters of lightning receiving process by the lightning interceptor and the lightning rod are compared, and the solution to prevent direct lightning strike at expressway toll station is proposed. [ABSTRACT FROM AUTHOR]