Effects of thinning on the understory light environment of different stands and the photosynthetic performance and growth of the reforestation species Phoebe bournei

Light levels determine regeneration in stands and a key concern is how to regulate the light environment of different stand types to the requirements of the understory.In this study,we selected three stands typical in south China(a Cryptomeria japonica plantation,a Quercus acutissima plantation,and a mixed stand of both)and three thinning intensities to determine the best understory light environ-ment for 3-year-old Phoebe bournei seedlings.The canopy structure,understory light environment,and photosynthe-sis and growth indicators were assessed following thin-ning.Thinning improved canopy structure and understory light availability of each stand;species composition was the reason for differences in the understory light environ-ment.Under the same thinning intensity,the mixed stand had the greatest light radiation and most balanced spectral composition.P.bournei photosynthesis and growth were closely related to the light environment;all three stands required heavy thinning to create an effective and sustained understory light environment.In a suitable understory light environment,the efficiency of light interception,absorption,and use by seedlings was enhanced,resulting in a higher carbon assimilation the main limiting factor was stomatal conductance.As a shade-avoidance signal,red/far-red radia-tion is a critical factor driving changes in photosynthesis and growth of P.bournei seedlings,and a reduction increased light absorption and use capacity and height:diameter ratios.The growth advantage transformed from diameter to height,enabling seedlings to access more light.Our findings suggest that the regeneration of shade-tolerant species such as P.bournei could be enhanced if a targeted approach to thinning based on stand type was adopted.

Heterogeneous population distribution enhances resistance to wheat lodging by optimizing the light environment

Lodging is still the key factor that limits continuous increases in wheat yields today,because the mechanical strength of culms is reduced due to low-light stress in populations under high-yield cultivation.The mechanical properties of the culm are mainly determined by lignin,which is affected by the light environment.However,little is known about whether the light environment can be sufficiently improved by changing the population distribution to inhibit culm lodging.Therefore,in this study,we used the wheat cultivar“Xinong 979”to establish a low-density homogeneous distribution treatment(LD),high-density homogeneous distribution treatment(HD),and high-density heterogeneous distribution treatment(HD-h)to study the regulatory effects and mechanism responsible for differences in the lodging resistance of wheat culms under different population distributions.Compared with LD,HD significantly reduced the light transmittance in the middle and basal layers of the canopy,the net photosynthetic rate in the middle and lower leaves of plants,the accumulation of lignin in the culm,and the breaking resistance of the culm,and thus the lodging index values increased significantly,with lodging rates of 67.5%in 2020–2021 and 59.3%in 2021–2022.Under HD-h,the light transmittance and other indicators in the middle and basal canopy layers were significantly higher than those under HD,and the lodging index decreased to the point that no lodging occurred.Compared with LD,the activities of phenylalanine ammonia-Lyase(PAL),4-coumarate:coenzyme A ligase(4CL),catechol-O-methyltransferase(COMT),and cinnamyl-alcohol dehydrogenase(CAD)in the lignin synthesis pathway were significantly reduced in the culms under HD during the critical period for culm formation,and the relative expression levels of TaPAL,Ta4CL,TaCOMT,and TaCAD were significantly downregulated.However,the activities of lignin synthesis-related enzymes and their gene expression levels were significantly increased under HD-h compared with HD.A partial least squares path modeling analysis found significant positive effects between the canopy light environment,the photosynthetic capacity of the middle and lower leaves of plants,lignin synthesis and accumulation,and lodging resistance in the culms.Thus,under conventional high-density planting,the risk of wheat lodging was significantly higher.Accordingly,the canopy light environment can be optimized by changing the heterogeneity of the population distribution to improve the photosynthetic capacity of the middle and lower leaves of plants,promote lignin accumulation in the culm,and enhance lodging resistance in wheat.These findings provide a basis for understanding the mechanism responsible for the lower mechanical strength of the culm under high-yield wheat cultivation,and a theoretical basis and for developing technical measures to enhance lodging resistance.

Research on color image matching method based on feature point compensation in dark light environment

Image matching refers to the process of matching two or more images obtained at different time,different sensors or different conditions through a large number of feature points in the image.At present,image matching is widely used in target recognition and tracking,indoor positioning and navigation.Local features missing,however,often occurs in color images taken in dark light,making the extracted feature points greatly reduced in number,so as to affect image matching and even fail the target recognition.An unsharp masking(USM)based denoising model is established and a local adaptive enhancement algorithm is proposed to achieve feature point compensation by strengthening local features of the dark image in order to increase amount of image information effectively.Fast library for approximate nearest neighbors(FLANN)and random sample consensus(RANSAC)are image matching algorithms.Experimental results show that the number of effective feature points obtained by the proposed algorithm from images in dark light environment is increased,and the accuracy of image matching can be improved obviously.

Tempo-Spatial Variations in Stomatal Conductance, Aperture and Density of Ligustrum sinense Acclimated to Different Light Environments

There was heterogeneous distribution in stomatal conductance (g-s) and stomatal aperture for both high- and low-light leaves of Ligustrum sinense Lour. in four designated positions within a leaf. Linear or exponential or polynomial relationships between g-s and stomatal aperture were found when regression of g-s and stomatal aperture was established. Statistical analysis revealed that the relationship between g-s and stomatal aperture for high-light leaves was more significant than that of low-light leaves. A linear relationship between g-s and stomatal aperture existed in both positions 1 and 3 for both high- and low-light leaves. The stomatal density of the low-light leaves was much lower than that of the high-light leaves. The sensitivity of stomata to changing environment for high-light leaves was higher than that for low-light leaves, which may also relate to the higher stomatal density for the high-light leaves.

Photosynthetic Gas Exchange and Leaflet Movement of Robinia pseudoacacia in Relation to Changing Light Environments

On the sunny days, there were little diurnal changes in both azimuth and directional angle for either sun_ or shade_leaflet. However, there existed a significant diurnal change in midrib angle that reflected movements regarding evasion of light stress around noon hours. On the cloudy day, a very little diurnal difference was found in azimuth, directional and midrib angle. It is suggested that changing light environment is the main factor for inducing leaflet movement of Robinia pseudoacacia , and the rhythmical movement does not attribute to the leaflet movement. Leaf orientation control test showed that the photosynthetic rate ( Pn ), stomatal conductance ( g s ) and transpiration ( Tr ) of the artificial fixed_leaflets were significantly lower than that of control_leaflets. And the leaf temperature ( Tl ) of the fixed leaflets significantly exceeded that of control_leaflets, which may attribute to the significant difference of light interception between the fixed and control_leaflets. The light_dependent leaflet movement is the morphological adjustment of maintaining optimal physiological status.

Systemic regulation of photosynthetic function in maize plants at graining stage under a vertically heterogeneous light environment

To cope with a highly heterogeneous light environment,photosynthesis in plants can be regulated systemically.Currently,the majority of studies are carried out with various plants during the vegetative growth period.As the reproductive sink improves photosynthesis,we wondered how photosynthesis is systemically regulated at the reproductive stage under a vertically heterogeneous light environment in the field.Therefore,changes of light intensity within canopy,chlorophyll content,gas exchange,and chlorophyll a fluorescence transient were carefully investigated at the graining stage of maize under various planting densities.In this study,a high planting density of maize drastically reduced the light intensities in the lower canopy,and increased the difference in vertical light distribution within the canopy.With the increase of vertical heterogeneity,chlorophyll content,light-saturated photosynthetic rate and the quantum yield of electron transport in the ear leaf(EL) and the fourth leaf below the ear(FLBE) were decreased gradually,and the ranges of declines in these parameters were larger at FLBE than those at EL.Leaves in the lower canopy were shaded artificially to further test these results.Partial shading(PS) resulted in a vertically heterogeneous light environment and enhanced the differences in photosynthetic characteristics between EL and FLBE.Removing the tassel and top leaves(RTL) not only improved the vertical light distribution within the canopy,but also reduced the differences in photosynthetic characteristics between the two leaves.Taken together,these results demonstrated that maize plants could enhance the vertical heterogeneity of their photosynthetic function to adapt to their light environment;slight changes of the photosynthetic function in EL at the graining stage under a vertically heterogeneous light environment indicated that the systemic regulation of photosynthesis is weak at the graining stage.

Prediction of Photosynthetic Carbon Assimilation Rate of Individual Rice Leaves under Changes in Light Environment Using BLSTM-Augmented LSTM

A model to predict photosynthetic carbon assimilation rate(A)with high accuracy is important for forecasting crop yield and productivity.Long short-term memory(LSTM),a neural network suitable for time-series data,enables prediction with high accuracy but requires mesophyll variables.In addition,for practical use,it is desirable to have a technique that can predict A from easily available information.In this study,we propose a BLSTM augmented LSTM(BALSTM)model,which utilizes bi-directional LSTM(BLSTM)to indirectly reproduce the mesophyll variables required for LSTM.The most significant feature of the proposed model is that its hybrid architecture uses only three relatively easy-to-collect external environmental variables—photosynthetic photon flux density(Q_(in)),ambient CO_(2) concentration(C_(a)),and temperature(T_(air))—to generate mesophyll CO_(2) concentration(C_(i))and stomatal conductance to water vapor(g_(sw))as intermediate outputs.Then,A is predicted by applying the obtained intermediate outputs to the learning model.Accordingly,in this study,1)BALSTM(Q_(in),C_(a),T_(air))had a significantly higher A prediction accuracy than LSTM(Q_(in),C_(a),T_(air))in case of using only Q_(in),C_(a),and T_(air);2)BALSTMC_(i),g_(sw),which had C_(i) and g_(sw) as intermediate products,had the highest A prediction accuracy compared with other candidates;and 3)for samples where LSTM(Q_(in),C_(a),T_(air))had poor prediction accuracy,BALSTMC_(i),g_(sw)(Q_(in),C_(a),T_(air))clearly improved the results.However,it was found that incorrect predictions may be formed when certain factors are not reflected in the data(e.g.,timing,cultivar,and growth stage)or when the training data distribution that accounts for these factors differs from the predicted data distribution.Therefore,a robust model should be constructed in the future to improve the prediction accuracy of A by conducting gasexchange measurements(including a wide range of external environmental values)and by increasing the number of training data samples.

Responses of fractal dimensions of Picea koraiensis seedlings to different light environments

The changes of fractal dimension ofPicea koraiensis seedlings under different light intensities in natural secondary forests was studied. The results showed that with the change of light environment, crown characters ofPicea koraiensis seedlings exhibited a greater plastic in lateral number, lateral increment, lateral dry weight, and specific leaf area. The range of calculated fractal dimensions of seedling crowns was confined between 2.5728 and 2.1036, but maximum of fractal dimension achieved in term moderate shading and in extreme low light conditions fractal dimension was least.

Approach to the Zoning and Management for the Function of Light Environment

Light pollution becomes more and more serious, but the study on this field is far from enough. In this paper, light environment is defined as light-free area, dark area, intermediate sight area, and bright area. In addition, it is marked with index value by index system, which includes average brightness, brightness evenness, glare index, and background brightness.

Characteristics of office lighting energy consumption and its impact on air conditioning energy consumption

The energy consumption of office buildings has increased sharply since the 21st century with the increasing ur-banization coverage.At this stage,the energy consumption of office buildings in China mainly comes from air conditioning and lighting.This paper obtains the regression equation of natural lighting illumination and radi-ant heat gain under different curtain conditions through experiments and simulations,and gives the theoretical calculation process of curtain regulation of office thermal and light environment and energy consumption.DeST and Ecotect software were used to analyze the thermal and light environment and energy consumption of the office.The results show that setting curtains in the room can effectively improve the indoor thermal light en-vironment,the higher the transmittance of curtains the lower the lighting energy consumption,the higher the number of high temperature hours of natural room temperature and the greater the radiant heat gain.The room with thick curtains has the lowest energy consumption for air conditioning in summer,followed by the room with thin curtains,and the room without curtains has the highest energy consumption for air conditioning.The room without curtains has the lowest energy consumption for artificial lighting,the room with thin curtains has the second lowest,and the room with thick curtains has the highest electricity consumption for artificial lighting.The air conditioning energy consumption accounts for the main building energy consumption,followed by the lighting energy consumption.After setting curtains in the office,the air conditioning energy consumption caused by the solar radiation heat entering the room through the exterior windows is smaller than the lighting energy consumption caused by artificial lighting.Therefore,the installation of internal shading with moderate trans-mittance and good thermal insulation performance can make the energy saving of lighting and air conditioning energy consumption reach the optimal value.

Influences of open-central canopy on photosynthetic parameters and fruit quality of apples(Malus×domestica)in the Loess Plateau of China

Although open-central canopy(OCC)is popular in apple(Malus×domestica)orchards in Loess Plateau of China,its relevant photosynthetic mechanisms have not been elucidated.In this study,changes in photosynthetically active radiation(PAR),gas exchange,chlorophyll fluorescence quenching and fruit quality in apple trees were measured in OCC and compared with those in the conventional condensed round and large canopy(RLC).Results showed that light intercepted at different orientations was 44%higher by OCC than that by RLC.The improved light environment within OCC remarkably increased leaf maximum net photosynthetic rate(Pnmax)and significantly decreased stomatal limitation.Under high light,the ratio of photorespiratory rate to gross photosynthetic rate(Pr/Pg)in OCC was higher than that in RLC.Moreover,reversible component in non-photochemical quenching(r(qE))was increased,while irreversible component(r(qI))was decreased in OCC than in RLC.As a result,the fruit quality in OCC was greatly boosted as evidenced by the significantly increased single fruit weight,fruit flesh firmness and fruit soluble solid contents and the sharply decreased fruit titratable acid contents.PAR intercepted by the canopy and the fruit soluble solid contents,leaf Pnmaxor single fruit weight were positively correlated,while PAR or Pnmaxwas negatively correlated with the fruit titratable acid contents.Accordingly,the improved crown light environment and the enhanced leaf photosynthetic performance and photoprotective capacity in OCC led to the boosted fruit quality.

Influence of lighting environment on social preferences in sticklebacks from two different photic habitats.I.mate preferences of wild-caught females

Ultraviolet(UV)A signals(320-400 nm)are important in mate choice in numerous species.The sensitivity for UV signals is not only assumed to be costly,but also expected to be a function of the prevailing ecological conditions.Generally,those signals are favored by selection that efficiently reach the receiver.A decisive factor for color signaling is the lighting environment,especially in aquatic habitats,as the visibility of signals,and thus costs and benefits,are instantaneously influenced by it.Although ecological aspects of color signal evolution are relatively well-studied,there is little data on specific effects of environmental UV-light conditions on signaling at these shorter wavelengths.We studied wild-caught gravid female 3-spined sticklebacks Gasterosteus aculeatus of 2 photic habitat types(tea-stained and clear-water lakes),possessing great variation in their UV transmission.In 2 treatments,tea-stained and clear-water,preferences for males viewed under UV-present(UV-1-)and UV-absent(UV-)conditions were tested.A preference for males under UV+conditions was found for females from both habitat types,thus stressing the significance of UV signals in stickleback's mate choice decisions.However,females from both habitat types showed the most pronounced preferences for males under UV-h conditions under clear-water test conditions.Moreover,reflectance measurements revealed that the carotenoid-based orange-red breeding coloration in wild-caught males of both habitat types differed significantly in color intensity(higher in clear-water males)and hue(more red shifted in clear-water males)while no significant differences in UV coloration were found.The differential reflection patterns in longer wavelengths suggest that sticklebacks of both habitat types have adapted to the respective water conditions.Adaptations of UV signals in a sexual context to ambient light conditions in both behavior and coloration seem less evident.

Biomass allocation and assimilation efficiency of natural Tilia amurensis samplings in response to different light regimes

Biomass allocation and assimilation efficiency of natural Amour linden (Tilia amurensis) samplings in different light regimes were analyzed in the paper. The results showed that shoot increment of samplings in gap was the highest and that of samplings under canopy was the least. Samplings in gap expressed apical dominance strongly but samplings in full sun and under canopy behaved intensive branching. Lateral competition or moderate shading was favored to bole construction. The patters of biomass allocation of samplings in different light environment were rather similar. The biomass translocated to stem was more than that to other organs, and about one half of photosynthate was used to support leaf turn over. On the contrary, photosynthates of samplings in full sun were mostly consumed in leaves bearing and energy balancing. The carbon assimilation for leaves of samplings in gap was the most efficient, and more carbons were fixed and translocated to non-photosynthetic organs, especially to stemwood.

Influence of ambient water coloration on habitat and conspecific choice in the female Lake Malawi cichlid, Metriaclima zebra

Female cichlid fish living in African great lakes are known to have sensory systems that are adapted to ambient light environments.These sen-sory system adaptations are hypothesized to have influenced the evolution of the diverse male nuptial coloration.In rock-dwelling Lake Malawi mbuna cichlids,however,the extent to which ambient light environments influence female sensory systems and potentially associated male nuptial coloration remains unknown.Yet,the ubiquitous blue flank coloration and UV reflection of male mbuna cichlids suggest the potential impacts of the blue-shifted ambient light environment on these cichlid's visual perception and male nuptial coloration in the shallow water depth in Lake Malawi.In the present study,we explored whether and how the sensory bias of females influences intersexual communication in the mbuna cichlid,Metriaclima zebra.A series of choice experiments in various light environments showed that M.zebra females (1)have a pref-erence for the blue-shifted light environment,(2)prefer to interact with males in blue-shifted light environments,(3)do not show a preference between dominant and subordinate males in full-spectrum,long-wavelength filtered,and short-wavelength filtered light environments,and (4)show a"reversed"preference for subordinate males in the UV-filtered light environment.These results suggest that the visual perception of M.zebra females may be biased to the ambient light spectra in their natural habitat by local adaptation and that this sensory bias may influence the evolution of blueand UV reflectivepatterns in male nuptial coloration.

Performance analysis of ghost imaging lidar in background light environment

The effect of background light on the imaging quality of three typical ghost imaging(GI) lidar systems(namely narrow pulsed GI lidar, heterodyne GI lidar, and pulse-compression GI lidar via coherent detection) is investigated. By computing the signal-to-noise ratio(SNR) of fluctuation-correlation GI, our analytical results, which are backed up by numerical simulations, demonstrate that pulse-compression GI lidar via coherent detection has the strongest capacity against background light, whereas the reconstruction quality of narrow pulsed GI lidar is the most vulnerable to background light. The relationship between the peak SNR of the reconstruction image andσ(namely, the signal power to background power ratio) for the three GI lidar systems is also presented, and theresults accord with the curve of SNR-σ.

Environment-dependent attack rates of cryptic and aposematic butterflies

Many organisms have evolved adaptive coloration that reduces their risk of predation. Cryptic colo- ration reduces the likelihood of detection/recognition by potential predators, while warning or aposematic coloration advertises unprofitability and thereby reduces the likelihood of attack. Although some studies show that aposematic coloration functions better at decreasing attack rate than crypsis, recent work has suggested and demonstrated that crypsis and aposematism are both successful strategies for avoiding predation. Furthermore, the visual environment （e.g., ambient lighting, background） affects the ability for predators to detect prey. We investigated these 2 related hypoth- eses using 2 well-known visually aposematic species of Heliconius butterflies, which occupy differ- ent habitats （open-canopy vs. closed-canopy）, and one palatable, cryptic, generalist species Junonia coenia. We tested if the differently colored butterflies differ in attack rates by placing plasti- cine models of each of the 3 species in 2 different tropical habitats where the butterflies naturally occur： disturbed, open-canopy habitat and forested, closed-canopy habitat. The cryptic model had fewer attacks than one of the aposematic models. Predation rates differed between the 2 habitats, with the open habitat having much higher predation. However, we did not find an interaction between species and habitat type, which is perplexing due to the different aposematic phenotypes naturally occurring in different habitats. Our findings suggest that during the Panamanian dry sea- son avian predation on perched butterflies is not a leading cause in habitat segregation between the 2 aposematic species and demonstrate that cryptically colored animals at rest may be better than aposematic prey at avoiding avian attacks in certain environments.

Adaptive stray-light compensation in dynamic multi-projection mapping

Projection-based mixed reality is an effective tool to create immersive visualizations on real-world objects. Its wide range of applications includes art installations, education, stage shows, and advertising. In this work, we enhance a multi-projector system for dynamic projection mapping by handling various physical stray-light effects: interreflection,projector black-level, and environmental light in real time for dynamic scenes. We show how all these effects can be efficiently simulated and accounted for at runtime, resulting in significantly improved projection mapping results. By adding a global optimization step,we can further increase the dynamic range of the projection.

Anthocyanin accumulation in juvenile Schima superba leaves is a growth trade-off by consuming energy for adaptation to high light during summer

Aims Anthocyanin accumulation is the main factor underlying why young plant leaves turn red,and plant growth follows the principle of maximizing the economic efficiency of energy.There is a need to verify the role of young plant leaves turning red and confirm whether anthocyanin accumulation overconsumes the energy of the plant.Methods We compared the different pigment contents,antioxidant capaci-ties,leaf mass per area,photosynthetic characteristics,dark res-piration rates,light compensation points(LCPs)and electron flow distribution of young and mature Schima superba leaves grown under full sunlight and 30%full sunlight conditions.We then exam-ined the correlations between anthocyanins and total antioxidant capacity,photosynthetic pigments,dark respiration rates,LCPs by using linear regression.Finally,we analyzed Pearson correlation coefficients and used principal component analysis to evaluate the interactions of these functional indicators.Important Findings The young leaves of S.superba accumulated anthocyanins in full sunlight but not in 30%full sunlight.Anthocyanins substantially con-tributed to the total antioxidant capacity(accounting for 33.29%)in juvenile S.superba leaves.Young leaves containing more anthocyanin accumulated less reactive oxygen species after high light(HL)treat-ment.However,juvenile leaves accumulating anthocyanins showed 56.97%higher dark respiration rates,24.79%higher LCPs and 5.32%higher allocations of electron flow to photorespiration and lower organic substance accumulation than did those without anthocyanins.These results suggest that young S.superba leaves must consume more energy to accumulate anthocyanins to adapt to HL environments.Therefore,plants sacrifice growth rate to ensure survival,which is a trade-off for their ability to respond to external environments.