Effect of Low Light on the Characteristics of Photosynthesis and Chlorophyll a Fluorescence During Leaf Development of Sweet Pepper

Low light stress is one of the main limiting factors which influence the production of sweet pepper under protected cultivation in China. In this experiment, two genotypes of sweet pepper, ShY （low light-tolerant genotype） and 20078 （low light-sensitive genotype）, were used to study the effects of low light （photosynthetic photon flux density, PPFD was 75- 100 umol m-2 s-1, control 450-500 umol m-2 s-1） on photosynthesis during leaf development. The result indicated that under low light chlorophyll content, net photosynthetic rate （PN）, photosynthetic apparent quantum efficiency （Фi） and carboxylation efficiency （CE） of sweet pepper leaves increased gradually and decreased after reaching the maximum levels. The time to reach the peak values for all the above parameters was delayed, whereas the light compensation point （LCP） decreased gradually along with leaf expansion. The decrease in maximum quantum yield of PS II （Fv/Fm） was not observed at any stages of the leaf development under low light condition, but the actual PS II efficiency under irradiance （ФPS II） was lower accompanied by an increased non-photochemical quenching （NPQ） in young and/or old leaves compared with mature leaves. The antenna thermal dissipation （D） was a main way of heat dissipation when young leaves received excessive light energy, while the decline in photosynthetic function in senescence leaf was mostly owing to the decrease in carbon assimilation capacity, followed by a significantly increased allocation of excessive energy （Ex）. Compared with 20078, ShY could maintain higher PN, ФPS II and lower QA reduction state for a longer time during leaf development. Thus, in ShY photosynthetic efficiency and the activity of electron transport of PS II were not significantly affected due to low light stress.

Effects of Low Light on Agronomic and Physiological Characteristics of Rice Including Grain Yield and Quality

Light intensity is one of the most important environmental factors that determine the basic characteristics of rice development. However, continuously cloudy weather or rainfall, especially during the grain-filling stage, induces a significant loss in yield and results in poor grain quality. Stress caused by low light often creates severe meteorological disasters in some rice-growing regions worldwide. This review was based on our previous research and related research regarding the effects of low light on rice growth, yield and quality as well as the formation of grain, and mainly reviewed the physiological metabolism of rice plants, including characteristics of photosynthesis, activities of antioxidant enzymes in rice leaves and key enzymes involved in starch synthesis in grains, as well as the translocations of carbohydrate and nitrogen. These characteristics include various grain yield and rice quality components （milling and appearance as well as cooking, eating and nutritional qualities） under different rates of shading imposed at the vegetative or reproductive stages of rice plants. Furthermore, we discussed why grain yield and quality are reduced under the low light environment. Next, we summarized the need for future research that emphasizes methods can effectively improve rice grain yield and quality under low light stress. These research findings can provide a beneficial reference for rice cultivation management and breeding program in low light environments.

Low Light Stress Down-Regulated Rubisco Gene Expression and Photosynthetic Capacity During Cucumber (Cucumis sativus L.) Leaf Development

Low light stress is one of the most important factors affecting photosynthesis and growth in winter production of cucumber （Cucumis sativus L.） in solar greenhouses in northern China. Here, two genotypes of cucumber （Deltastar and Jinyan 2） are used to determine the effect of low light stress on Rubisco expression and photosynthesis of leaves from emergence to senescence. During leaf development, the net photosynthetic rate （PN）, stomatal conductance （gs）, Rubisco initial activity and activation state, transcript levels of rbcL and rbcS, and the abundance of rbcL and rbcS DNA in these two genotypes increase rapidly to reach maximum in 10-20 d, and then decrease gradually. Meanwhile, the actual photosystem II efficiency （OpSll） of cucumber leaves slowly increased in the early leaf developing stages, but it declined quickly in leaf senescent stages, accompanied by an increased non-photochemical quenching （NPQ）. Moreover, PN, gs, initial Rubisco activity, and abundance of protein, mRNA and DNA of Rubisco subunits of leaves grown under 100 μmol m^-2 s^-1 are lower, and require more time to reach their maxima than those grown under 600 μmol m^-2 s^-1 during leaf development. All these results suggest that lower photosynthetic capacity of cucumber leaves from emergence to senescence under low light stress is probably due to down-regulated Rubisco gene expression in transcript and protein levels, and decreased initial and total activity as well as activation state of Rubisco. Deltastar performs better than Jinyan 2 under low light stress.

The Physiologic Reaction of Cucumber to Low Temperature and Low Light Intensity

The dynamics of chlorophyll content, leaf area and photosynthesis of cucumber seedlings were studied under sole stress of two low temperatures and low light intensity as well as combined stresses of low light intensity and the two low temperatures. The results showed that low light intensity reduced sensitivity of cucumber to low temperature and improved chlorophyll content, leaf area and chlorophyll fluorescence quantum yield. The photosynthesis rate was reduced under low light intensity. The intensity of light played the leading role in growth of cucumber under the low temperature condition, while the low temperature played the leading role under the critical low temperature condition. There were differences in reaction to light and temperature among different varieties. The tolerance to low temperature and low light intensity was not always synergetic for the same cucumber variety.

Photosynthetic Characteristics and Ultrastructure of Chloroplast of Cucumber Under Low Light Density in Solar-Greenhouse

The photosynthetic characteristics and ultrastructure of chloroplast of cucumber in solar-greenhouse were studied. The result showed that the photosynthetic rate (Pn), photosyntheticability (A350), carboxylation efficiency, light saturation point and light compensation pointall declined remarkably under low light density, indicating that the photosynthetic characteristicsof cucumber were closely related to light environment. Under low light density, the minimalfluorescence (Fo), alterable fluorescence (Fv), photochemical efficiency of PSⅡ(Fv/Fm), steadyfluorescence in light (Fs), maximal fluorescence (Fm) and actual efficiency of PSⅡ(φPSⅡ)etcincreased, indicating that the photochemical activity and efficiency for solar energy transformationenhanced, thus the light proportion used to electron transport also increased. The chlorophylla, b, a/b and carotenoid of shading leaves decreased. However, the depressed extent of Chl a andChl a/b were obviously larger than that of Chl b. The number of chloroplast and starch grainin cucumber leaves descended, but that of grana and lamella increased as a shaded result. Thesize of chloroplast and starch grain of shading leaves minished.

Effects of Acetylsalicylic Acid and Calcium Chloride on Photosynthetic Apparatus and Reactive Oxygen-Scavenging Enzymes in Chrysanthemum Under Low Temperature Stress with Low Light

The effects of acetylsalicylic acid （ASA）, CaCl2, and ASA ＋ CaCl2 on the photosynthetic apparatus and antioxidant enzyme activities were investigated in chrysanthemum Jinba （a cut flower cultivar） under low temperature stress with low light （TL stress） （16/12℃, day/night, PFD 100 μmol m^-2 s-1）. The results showed that under TL stress, the net photosynthesis rate （Pn）, carboxylation efficiency （CE）, apparent quantum yield （AQY）, maximal photochemical efficiency （Fv/Fm） of PSII, quantum yield of PSII electron transport （ФPSII）, and photochemical quenching （qP） of the chrysanthemum leaves in all treatments were significantly decreased, but the decreases were alleviated by ASA, CaCl2, and ASA ＋ CaCl2 treatments compared with the controls. The alleviating effect of ASA ＋ CaCI2 was better than either ASA or CaCl2 single treatment. Moreover, the ASA ＋ CaCl2 treatment highly improved the chlorophyll content, relatively improved the number and size of chloroplast and starch grain in the leaves of chrysanthemum plants compared with ASA and CaCl2 treatments. It was indicated that ASA and/or CaCI2 could regulate the photosynthetic functions in the leaves of chrysanthemum plants to enhance the resistance against TL stress. On the other hand, reduction in relative conductance rate implied that ASA and/ or CaCl2 could protect from membrane injury in leaves of chrysanthemum plants. The activities of SOD, POD, and CAT in the treated leaves of chrysanthemum were increased as compared with the controls. It was suggested that ASA and/or CaCl2 had positive regulation effects on the defence enzyme activities in chrysanthemum leaves which could protect the photosynthetic apparatus to a certain degree under the TL stress. In brief, the treatment of ASA together with CaCl2 was better for chrysanthemum plants to adapt TL stress than single ASA or CaCl2 treatments.

Low Light During Grain Filling Stage Deteriorates Rice Cooking Quality, but not Nutritional Value

To investigate the effect of low light （LL, 50% natural light） during grain filling （GF） stage on rice transamination, amino acid （AA） accumulation, nutritional value, and cooking quality in three different rice genotypes, transaminase activities and AA levels in grains during GF stage and the traits that significantly affected rice quality （physical appearance, cooking quality, and nutritional value） were analyzed. LL did not disturb transamination in rice grains during GF stage, as minimal impact was found on alanine and aspartate transaminase activities. Nevertheless, most AAs in caryopses, including lysine and threonine, increased in response to LL, except for sulfur-containing AAs. These results suggest that AA metabolism and accumulation in rice grains were rarely suppressed by LL during GF stage. Rice nutritional ingredients at harvest, such as major protein components including glutelin and most important essential amino acids （EAAs） including lysine and threonine, increased significantly in response to LL, whereas most protein and EAA ratios were rarely affected. However, LL markedly affected physical appearance of rice grains by reducing brown rice rate, milled rice rate, and 1000-grain weight and increasing the chalkiness rate. In addition, cooking qualities decreased in response to LL, while breakdown values and amylose levels decreased and setback values increased. We concluded that LL during GF stage decreased the cooking quality of rice, but could potentially improve the nutritional value of rice.

Effective Dose Screening of Low Level Red Light in Different Cell Indexes

The low level red light irradiation dose that produced positive response on different cell indexes was selected through experiments.In fibroblast detection model,the low level red light irradiation dose that had positive response to the four indicators of mitochondrial membrane potential,ATP release,cell migration and collagen synthesis was screened.The experimental results showed that low level red light with a irradiation dose of 2 J/cm^(2) had a positive response to the above four indexes in fibroblast.The test model on fibroblast was later transferred to dermal papilla cells for further experimental verification.The results showed that low level red light with a irradiation dose of 2 J/cm^(2) also had a positive response to the four indicators of dermal papilla cells,namely,mitochondrial membrane potential,ATP release,cell proliferation rate and collagen synthesis.It is proved that the low level red light with a irradiation dose of 2 J/cm^(2) could improve the mitochondrial function,cell migration and collagen synthesis of fibroblast and dermal papilla cell,thus providing energy for cell activities,improving cell repair ability and cell anti-aging ability.

Low-Light Enhancer for UAV Night Tracking Based on Zero-DCE++

Unmanned aerial vehicle (UAV) target tracking tasks can currently be successfully completed in daytime situations with enough lighting, but they are unable to do so in nighttime scenes with inadequate lighting, poor contrast, and low signal-to-noise ratio. This letter presents an enhanced low-light enhancer for UAV nighttime tracking based on Zero-DCE++ due to its ad-vantages of low processing cost and quick inference. We developed a light-weight UCBAM capable of integrating channel information and spatial features and offered a fully considered curve projection model in light of the low signal-to-noise ratio of night scenes. This method significantly improved the tracking performance of the UAV tracker in night situations when tested on the public UAVDark135 and compared to other cutting-edge low-light enhancers. By applying our work to different trackers, this search shows how broadly applicable it is.

Three‐terminal perovskite/integratedbackcontactsilicon tandem solar cells under low light intensity conditions

The current climate and energy crisis urgently needs solar cells with efficiencies above the 29% single junction efficiency bottleneck.Silicon/perovskite tandem solar cells are a solution,which is attracting much attention.While silicon/perovskite tandem cells in 2-terminal and 4-terminal configurations are well documented,the three-terminal concept is still in its infancy.It has significant advantages under low light intensities as opposed to concentrated sunlight,which is the critical factor in designing tandem solar cells for low-cost terrestrial applications.This study pre-sents novel studies of the sub-cell performance of the first three-terminal perovskite/silicon selective band offset barrier tandem solar cells fabricated in an ongoing research project.This study focuses on short circuit current and operating voltages of the subcells under light intensities of one sun and below.Lifetime studies show that the perovskite bulk carrier lifetime is insensitive to illumination,while the silicon cell's lifetime decreases with decreasing light intensity.The combination of perovskite and silicon in the 3T perovskite-silicon tandem therefore reduces the sensitivity of V_(OC) to light intensity and maintains a relatively higher V_(OC) down to low light intensities,whereas silicon single-junction cells show a marked decrease.This technological advantage is proposed as a novel advantage of three-terminal perovkite/silicon solar cells for low light intensities of one sun or less.

Low lighting image enhancement using local maximum color value prior

We study the problem of low lighting image en- hancement. Previous enhancement methods for images un- der low lighting conditions usually fail to consider the factor of image degradation during image formation. As a result, the lost contrast could not be recovered after enhancement. This paper will adaptively recover the contrast and adjust the exposure for low lighting images. Our first contribution is the modeling of image degradation in low lighting con- ditions. Then, the local maximum color value prior is pro- posed, i.e., in most regions of well exposed images, the lo- cal maximum color value of a pixel will be very high. By combining the image degradation model and local maximum color value prior, we propose to recover the un-degraded im- ages under low lighting conditions. Last, an adaptive expo- sure adjustment module is proposed to obtain the final result. We show that our approach enables better enhancement com- paring with popular image editing tools and academic algo- rithms.

Contributions of DPOR at Low Light Intensity to Chlorophyll Biosynthesis and Growth in the Synechocystis sp. PCC 6803

The chlL gene encoding one component of light-independent (dark) protochlorophyllide oxido reductase (DPOR) was deleted in cyanobacterium Synechocystis sp. PCC 6803 (S.6803). The resulting chlL- mutant lost DPOR activity. No significant differences of chlorophyll (Chl) content and growth rate were observed between the wild and the mutant strains grown at 50 mE·m2·s1 light intensity for photomixtrophic and photoautotrophic growth. However, differences were observed at 1 mE·m2·s1 light intensity. For photomixtrophic growth, the mutant Chl content was 50% of the wild content with continuous light and 35.7% of the wild content with a 10 h light/ 14 h dark cycle. For photoautotriphic growth, the mutant Chl level was 76.3% of the wild content with continuous light and 63.2% with a 10 h light/ 14 h dark cycle. The results indicate that DPOR contributes to Chl synthesis and increases the growth rate in cyanobacteria phototrophically cultured at 1mE·m2·s1 light intensity. In contrast, the photosynthetic capacity on a per-cell basis of the mutant is 5% higher than that of the wild strain with continuous light and 27% higher than that of the wild strain with a 10 h light/14 h dark cycle at 1 mE·m2·s1 light intensity for photoautotrophic growth. With the low Chl content, the cyanobacteria have the ability to improve their photosynthetic capacity by decreasing the ratio of PSI to PSII by unknown morphological or physiological means.

Novel Frame Shift and Integral Technique for Enhancing Low-Light-Level Moving Images

A novel frame shift and integral technique for the enhancement of low light level moving image sequence is introduced. According to the technique, motion parameters of target are measured by algorithm based on difference processing. To obtain spatial relativity, images are shifted according to the motion parameters. As a result, the processing of integral and average can be applied to images that have been shifted. The technique of frame shift and integral that includes the algorithm of motion parameter determination is discussed, experiments with low light level moving image sequences are also described. The experiment results show the effectiveness and the robustness of the parameter determination algorithm, and the improvement in the signal-to-noise ratio （SNR） of low light level moving images.

The electromagnetically induced transparency in the Y-type four-level atom system at low light levels

In this paper a Y-type four-level atom interacting with external fields system is investigated. It is shown that increasing the control field can reduce the probe absorption, the electromagnetically induced transparency (EIT) and gain can be obtained if the parameters are taken appropriately. An interesting phenomenon is found that the system appears to be probe gain in a large region if the external fields Rabi phases are taken appropriately, too.

Low driving voltage in an organic light-emitting diode using MoO_3/NPB multiple quantum well structure in a hole transport layer

The driving voltage of an organic light-emitting diode（OLED） is lowered by employing molybdenum trioxide（MoO3）/N,N＇-bis（naphthalene-1-yl）-N,N＇-bis（phe-nyl）-benzidine（NPB） multiple quantum well（MQW） structure in the hole transport layer.For the device with double quantum well（DQW） structure of ITO/[MoO3（2.5 nm）/NPB（20 nm）]2/Alq3（50 nm）/LiF（0.8 nm）/Al（120 nm）],the turn-on voltage is reduced to 2.8 V,which is lowered by 0.4 V compared with that of the control device（without MQW structures）,and the driving voltage is 5.6 V,which is reduced by 1 V compared with that of the control device at the 1000 cd/m2.In this work,the enhancement of the injection and transport ability for holes could reduce the driving voltage for the device with MQW structure,which is attributed not only to the reduced energy barrier between ITO and NPB,but also to the forming charge transfer complex between MoO3 and NPB induced by the interfacial doping effect of MoO3.

The new finding of Neogene marine low-resistivity light oil field in the western part of Pearl River Mouth Basin

Based on the new finding of Wenchang L low-resistivity light oil field, the finding process, reservoir characteristics and pool-forming pattern were studied. The oil-rock correlation, neritic reservoir type, hydrocarbon conduct system and dominant migration and accumulation direction,and new techniques were discussed. The results showed that large amount of hydrocarbon generated by shallow lacustrine mudstone and shale of Eocene Wenchang formation could migrate from sag to Qionghai uplift distantly; neritic shoal-bar reservoir have developed in the 1st member of Zhujiang formation, dip-sag faults and regional good marine sandstone layers of the 1st and the 2nd member of Zhujiang formation have constituted hydrocarbon conduct system in Qionghai uplift; the late fault system which were controlled by Dongsha tectonic movement constructed the connection between lower hydrocarbon and upper neritic shoal-bar reservoir. Therefore, the pool-forming pattern with "vertical migration and accumulation, secondary structure-lithology-dominated" was proposed. Finally the enlightenment of explorating new findings was discussed.

Catalytic performance and kinetics of Au/γ-Al_2O_3 catalysts for low-temperature combustion of light alcohols

Au/γ-Al2O3 catalysts were prepared by deposition-precipitation method for the catalytic combustion of low concentration alcohol streams(methanol,ethanol,iso-propanol and n-propanol).The catalysts were characterized by X-ray photoelectron spectroscopy(XPS),X-ray diffractometry(XRD) and energy dispersive X-ray micro analysis(EDS) techniques.The XPS results showed that there was only Au0 on the surface of catalysts.The XRD patterns showed that Au was presumably highly dispersed over γ-Al2O3.The temperatures for complete conversion of methanol,ethanol,iso-propanol and n-propanol with concentration of 2.0 g/m3 were 60,155,170 and 137 ℃,respectively,but they were completely mineralized into CO2 and H2O at 60,220,260 and 217 ℃ respectively over the optimized catalyst.The activity of the catalyst was stable in 130 h.The kinetics for the catalytic methanol elimination followed quasi-first order reaction expressed as r=0.652 8c0+0.084 2.The value of apparent activation energy is 54.7 kJ/mol in the range of reaction temperature.

THE SPATIOTEMPORAL CHARACTERISTICS OF LIGHT RAIN DAYS AND LOW CLOUD COVER UNDER HEAVY POLLUTION OVER SOUTH CHINA

By using the data set of light rain days and low cloud cover at 51 stations in South China(SC), and the method of linear regression and correlative analysis, we analyze the spatiotemporal characteristics of the light rain days and low cloud cover including annual variation and long-term seasonal change. The results are as follows:(1) The trends of light rain days and low cloud cover over SC are opposite(light rain days tended to decrease and low cloud cover tended to increase in the past 46 years). The value distributed in east is higher than that in west, and coastal area higher than inland area.(2) The regression coefficients of light rain days and low cloud cover during 1960-2005 are4.88 d/10 years and 1.14%/10 years respectively, which had all passed the 0.001 significance level.(3) Variations of light rain days are relatively small in spring and summer, but their contributions are larger for annual value than that of autumn and winter.(4) There are two regions with large values of aerosol optical depth(AOD), which distribute in central and southern Guangxi and Pearl River Delta(PRD) of Guangdong, and the value of AOD in PRD is up to 0.7.The aerosol index distributed in coastal area is higher than in the inland area, which is similar to the light rain days and low cloud cover over SC. Aerosol indexes in SC kept increasing with fluctuation during the past 27 years. The GDP of the three provinces in SC increased obviously during the past 28 years, especially in Guangdong, which exhibited that there is simultaneous correlation between light rain days with the variables of low cloud cover and release of aerosols over SC during 1960 to 2005.

低光照下的无人机异物检测与定位

为解决无人机在低光照环境下的巡检过程中,不能对场景中的异物进行识别与定位,导致后续智能算法无法获得环境语义信息的问题.本文提出一种将ORB-SLAM2算法与适用于低光照目标检测改进的YOLOv5模型进行信息融合的方法.首先,通过RGB-D相机自采集低光照数据集进行深度学习训练及融合算法验证.然后,结合关键帧信息、目标检测模块的输出结果以及相机的固有信息完成目标像素坐标提取.最后,通过关键帧信息和像素坐标完成目标物体相对世界坐标系的位置解算.本文实现了低光照环境下目标物体较为准确的识别和目标物体在世界坐标系中分米级的定位,为低光照环境下无人机智能巡检提供了一种有效的解决方案.