Exotic plantations differ in "nursing" an understory invader: A probe into invasional meltdown.

Forest plantations most likely promote exotic plant invasion. Using an in situ monitoring method, this study investigated the traits correlated with growth and reproduction of an understory invader, Phytolacca americana L., and ecological factors including understory irradiance, soil stoichiometry and microbial patterns associated with these traits in different exotic plantations of Robinia pseudoacacia L. and Pinus thunbergii Parl. at Mount Lao, Qingdao, China. We found that the traits of P. americana underneath the R. pseudoacacia stand might be situated at the fast side of the trait economic spectrum. The R. pseudoacacia stand appeared to "nurse" P. americana. Furthermore, we intended to explain the nurse effects of R. pseudoacacia stands by examining their ecological factors. First, the R. pseudoacacia stand created understory light attenuation, which matched the sciophilous feature of P. americana. Second, the soil beneath the R. pseudoacacia stand might benefit P. americana more since the soil has greater resource availability. Third, a higher microbial diversity was found in the soil derived from P. americana underneath the R. pseudoacacia stand. A greater abundance of plant pathogens was detected in the soil derived from P. americana in the R. pseudoacacia stand, while more abundant mycorrhizal fungi were detected in the P. thunbergii stand. We speculate that plant pathogens can defend P. americana from aggression from other understory competitors. The mycorrhizal fungi in the P. thunbergii stand might benefit P. americana while simultaneously benefiting other understory plants. Intensive competition from other plants might interfere with P. americana. The potential relationships between plant performance and ecological factors may explain the invasion mechanism of P. americana. The present study provides a novel insight on the facilitative effects of exotic tree plantation on an exotic herb through the modification of soil biota, with implications for the biocontrol of invasive species and forest management and conservation.

Diurnal predators in dim light: the ability of mantids to prey for supper.

Many insects rely heavily on visual cues in foraging and other life activities. Mantids are insect predators that usually ambush prey. The sophisticated visual system of mantids allows them to spot, track, and strike at prey with high accuracy. Mantids are categorized as diurnal animals in most cases, while our field observations suggested that they were active in foraging both day and night. Therefore, we hypothesize that predation in dim light is possible for mantids, while mantids are unable to capture prey in complete darkness. In this study, we experimentally examined whether different light conditions could affect the predation success and efficiency of mantid nymphs and adults, Hierodula chinensis Werner (Mantodea: Mantidae), through behavioral observations. Individual mantids were placed in individual chambers in complete darkness, simulated moonlight (0.1 lux), or simulated dusk (50 lux) conditions and were allowed to forage for prey items for 10 min. Our observations showed no evidence that H. chinensis could capture any prey in complete deprivation of light. The proportion of nymphs with successful predation in simulated moonlight was 50% higher than that in complete darkness and 45.83% lower than that in simulated dusk. The proportion of adults with successful predation in simulated moonlight was 42.11% higher than that in complete darkness and 57.89% lower than that in simulated dusk. Overall, the results provide new insights into the behavioral ecology of diurnal predators at night, with potential association with moonlight, starlight, and light pollution.

Asymbiotic Seed Germination and In Vitro Seedling Development of the Endangered Orchid Species Cypripedium guttatum.

Cypripedium guttatum is a highly restricted terrestrial orchid that faces increasing endangerment owing to its habitat destruction and illegal collection. Compared to epiphytic orchids, terrestrial orchids such as C. guttatum have harder seed coats and more demanding in vitro germination conditions. This study aimed to develop an effective in vitro propagation system for C. guttatum to aid in its conservation. Seeds from mature capsules were subjected to various conditions, including sterilization using 1% sodium hypochlorite (NaOCl) and different light conditions, culture media, hormones, and organic supplements, to assess germination and early seedling development in vitro. Sterilization with 1% NaOCl significantly improved the germination rate, especially under dark conditions. Germination initiation occurred at 2 and 3 months in orchid seed sowing medium (OSM) and Murashige and Skoog (MS) medium, respectively. The addition of 1 mg/L naphthaleneacetic acid (NAA) further enhanced germination. However, the inclusion of organic supplements, such as apple and banana homogenates, in the culture medium led to substantial growth inhibition after 12 months. Notably, orchid maintenance medium (OMM) without organic additives proved to be the most suitable for seedling growth. The results of this study show that sterilization, appropriate light, and optimal NAA concentrations are beneficial for seed germination.

Effect of changing mesopic and photopic light conditions on visual functions.

AIM: To determine the effects of change in light conditions on refractive error and visual functions including visual acuity, stereopsis and contrast sensitivity. METHODS: This cross-sectional study was conducted in the optometry clinic of the Shahid Beheshti School of Rehabilitation on 48 students in 2021-2022. All of them had eye health and normal visual function and could have refractive errors or not. Light intensity of 4 lx was considered equivalent to photopic light condition and light intensity of 1 lx was considered to be equivalent to mesopic light condition. The amount of refractive error was checked by auto refractometer and its changes in mesopic light condition were subjectively measured. Also, visual acuity, stereopsis and contrast sensitivity (in five spatial frequencies of 1.5, 3, 6, 12, and 18 cycles per degree), were measured first in photopic light condition and then in mesopic light condition, by Snellen control vision chart, stereo butterfly test and the M&S technology monitor test respectively. RESULTS: In the 48 student subjects with an average age of 22.69±3.56y, mean of refractive error as sphere equivalent, visual acuity and stereopsis were -1.25±1.74 diopters, 0 logMAR, 44.37±13.03 seconds of arc, respectively in photopic light condition while in mesopic light was equal to -1.56±1.75 diopters, 0.12±0.09 logMAR and 50.62±33.35 seconds of arc, respectively. The mean of contrast sensitivity measured at spatial frequencies of 1.5, 3, 6, 12, and 18 cycles per degree in photopic condition was equal to 2.38±0.04, 2.37±0.07, 2.04±0.21, 1.27±0.32, 0.82±0.27 logarithm of contrast sensitivity, respectively and in mesopic lighting condition was equal to 2.34±0.12, 2.30±0.16, 1.84±0.28, 1.02±0.28, 0.63±0.24 logarithm of contrast sensitivity, respectively. Statistical analysis showed a significant difference between the two lighting conditions in all evaluated variables [refractive error (P<0.001), visual acuity (P<0.001), stereopsis (P=0.008) and contrast sensitivity (P<0.001)]. CONCLUSION: The refractive error of the student subjects in mesopic light condition change towards myopia, and its amount is clinically significant. Also, the examination and comparison of the factors of visual acuity, stereopsis and contrast sensitivity in these two lighting conditions show that the decrease in brightness level to the mesopic level causes a decrease in the aforementioned visual functions.

Effects of clonal integration and nutrient availability on the growth of Glechoma longituba under heterogenous light conditions.

Introduction: Clonal integration of connected ramets within clones is an important ecological advantage. In this study, we tested the hypothesis that the effects of clonal integration on performance of donor and recipient ramets when one resource is heterogeneous can be influenced by the availability of another resource of donor ramets. Methods: We conducted a greenhouse experiment on the widespread, perennial herb Glechoma longituba. Clonal fragments consisting of pairs of connected ramets were grown for seven weeks. The younger, apical ramets were exposed under 30% or 100% light condition and the older, basal ramets were treated with three levels of nutrients. The connections between ramets were either severed or left intact. 30% light condition negatively affected the growth of apical ramets, basal ramets and the whole fragments. Results: Clonal integration significantly increased the growth of apical ramets, but decreased the growth of the basal ramets. Medium and high level nutrient availability of basal ramets significantly increased the growth of apical ramets, basal ramets and the whole fragments. At the high nutrient level, the reduction in growth of basal ramets from clonal integration was decreased, but the growth responses of apical ramets and the whole fragments to clonal integration were not influenced by nutrient availability. Conclusion: The results suggested that clonal integration was benefit to the growth of apical ramets of Glechoma longituba but at the cost of reducing the growth of basal ramets. Although the high nutrient level could reduce the cost that clonal integration brought to the unshaded basal ramets, but could not increase the benefit that clonal integration brought to the shaded apical ramets and whole fragment.

Imaging iridotrabecular contact in angle closure.

Background: With ultrasound biomicroscopy (UBM), radial scans are taken by using a typical ciliary process, to show the details of the iridocorneal angle, the anterior surface of the ciliary body, and its relation to the posterior iris. Appositional closure represents potentially reversible contact between the peripheral iris and trabecular meshwork. The appositional closure can further be classified according to the configuration of iridotrabecular contact (ITC). UBM can be performed in dark and light conditions, which has been shown to be useful for detecting changes in iridocorneal angle configuration associated with dark and light. Purpose: To image ITC configuration in appositional angle closure and also image iridocorneal angle in dark and bright light room illumination. Synopsis: UBM demonstrates two types of ITC configuration in appositional closure which are, B-type and S-type. It can also demonstrate the presence of sinus of Mapstone in S-type of ITC. Highlights: UBM allows imaging of dynamic changes in the iris and shows that the degree of appositional angle closure is a dynamic process that can change rapidly depending on the lighting conditions. Video link: https://youtu.be/tgN4SLyx6wQ.

The interaction of salinity and light regime modulates photosynthetic pigment content in edible halophytes in greenhouse and indoor farming.

Given its limited land and water use and the changing climate conditions, indoor farming of halophytes has a high potential to contribute significantly to global agriculture in the future. Notably, indoor farming and classical greenhouse cultivation differ in their light regime between artificial and solar lighting, which can influence plant metabolism, but how this affects the cultivation of halophytes has not yet been investigated. To address this question, we studied the yield and content of abscisic acid, carotenoids, and chlorophylls as well as chloride of three halophyte species (Cochlearia officinalis, Atriplex hortensis, and Salicornia europaea) differing in their salt tolerance mechanisms and following four salt treatments (no salt to 600 mM of NaCl) in two light regimes (greenhouse/indoor farming). In particular, salt treatment had a strong influence on chloride accumulation which is only slightly modified by the light regime. Moreover, fresh and dry mass was influenced by the light regime and salinity. Pigments exhibited different responses to salt treatment and light regime, reflecting their differing functions in the photosynthetic apparatus. We conclude that the interaction of light regime and salt treatment modulates the content of photosynthetic pigments. Our study highlights the potential applications of the cultivation of halophytes for indoor farming and underlines that it is a promising production system, which provides food alternatives for future diets.

Egg rejection based on egg size recognition as a specific strategy against parasitic cuckoos.

In the coevolutionary interactions between avian brood parasites and their hosts, egg recognition based on color and/or pattern is a common and effective defense to counter parasitism. However, for egg recognition based on size, only a few studies have found affirmative results, and they do not provide unambiguous evidence that egg size recognition in hosts has evolved as an important and specific anti-parasite adaptation against parasite eggs. We studied the brood parasite system between the Asian emerald cuckoo Chrysococcyx maculatus and its host, the chestnut-crowned warbler Phylloscopus castaniceps. The cuckoo parasitizes the warbler using non-mimetic and larger eggs at a parasitism rate of 12.9%. The warbler nests used in this experiment were built in a dark environment with the nest illuminance near 0 lux. Experiments with 2 types of model eggs with colors and patterns resembling cuckoo eggs of different sizes (cuckoo egg size or host egg size) showed that the warblers were able to reject 63.6% of cuckoo model eggs under these dim light conditions. However, model eggs with the same color and pattern similar to the warbler egg size were always accepted. This study provides strong evidence supporting the theory that egg size recognition can be evolved in hosts as a specific anti-parasite adaptation against cuckoos. We suggest that the egg size recognition of the warbler is an outcome of the tradeoff between the costs of violating the parental investment rule and suffering cuckoo parasitism.

Long-time behavior of swimming Euglena gracilis in a heterogenous light environment.

The cell motion of Euglena gracilis in homogeneous and heterogeneous light environments was analyzed. Homogeneous and heterogeneous environments were prepared, with only a red color or with a red circle surrounded by brighter white regions, respectively. In a heterogeneous environment, the cells move into the red circle. Swimming orbits at 1/25 s intervals for 120 s were analyzed. The speed distribution of the 1 s-averaged cell orbits in a homogeneous environment was different from that in a heterogeneous environment, where the faster swimming fraction was enhanced. The relationship between speed and curvature radius was analyzed using a joint histogram. Histograms for short timescale motion, constructed by 1 s-averaged orbits, suggest that the cell swimming curves are not biased, while those for long timescale motion, constructed by 10 s-averaged orbits, suggest that the cell swimming curves are biased in the clockwise direction. Furthermore, the curvature radius determines the speed, which does not seem to depend on the light environment. The mean squared displacement in a heterogeneous environment is larger than that in a homogeneous environment on a 1 s timescale. These results will be the basis for constructing a model for the long-time behavior of photomovement for light differences.

High relative humidity improves leaf burn resistance in flowering Chinese cabbage seedlings cultured in a closed plant factory.

Plant factories that ensure the annual production of vegetable crops have sparked much attention. In the present study, thirty types of common vegetable crops from 25 species and eight families, were grown in a multi-layer hydroponic system in a closed-type plant factory to evaluate the adaptive performance. A total of 20 vegetable crops, belonging to 14 species and 4 families, unexpectedly exhibited different degrees of leaf margin necrosis in lower leaves firstly, then the upper leaves gradually. We defined this new physiological disorder as "leaf burn". It occurred more commonly and severely in cruciferous leafy vegetables. Two different light intensities (150 and 105 µmol m-2 s-1 photosynthetic photon flux density (PPFD)), three photoperiod conditions (12, 10 and 8 h d-1) and two canopy relative air humidity (RH) (70% and 90% RH) were set to evaluate the suppression effects on leaf burn occurrence in two commercial flowering Chinese cabbage cultivars ('Sijiu' and 'Chixin'), the special cruciferous vegetable in South China. We discovered that changing light conditions did not fully suppress leaf burn occurrence in the cultivar 'Sijiu', though lower light intensity and shorter photoperiod partly did. Interestingly, the occurrence of leaf burn was completely restrained by an increased canopy RH from 70% to 90%. Specifically, the low RH-treated seedlings occurred varying degree of leaf burn symptoms, along with rapidly decreased water potential in leaves, while the high RH treatment significantly lessened the drop in leaf water potential, together with increased photosynthetic pigment contents, net photosynthetic rate, stomatal conductance and transpiration rate, decreased leaf stomatal aperture and density, and thus reduced the incidence of leaf burn in 'Sijiu' and 'Chixin', from 28.89% and 18.52% to zero, respectively. Taken together, high canopy RH may favor maintaining leaf water potential and improving photosynthesis performance, jointly regulating leaf burn incidence and plant growth.

Joint Effect of Heavy Vehicles and Diminished Light Conditions on Paediatric Pedestrian Injuries in Backover Crashes: A UK Population-Based Study.

Backover crashes cause considerable injuries especially among young children. Prior research on backover crashes has not assessed the joint effect of heavy vehicles and diminished light conditions on injuries. By analysing the United Kingdom STATS19 crash dataset from 1991 to 2020, this study focused on backover crashes involving paediatric cyclists or pedestrians aged ≤17 years and other motorised vehicles. By estimating the adjusted odds ratio (AOR) of multiple logistic regression models, pedestrians appeared to have 82.3% (95% CI: 1.78-1.85) higher risks of sustaining killed or serious injuries (KSIs) than cyclists. In addition, casualties involved in backover crashes with heavy vehicles were 39.3% (95% CI: 1.35-1.42) more likely to sustain KSIs than those involved in crashes with personal cars. The joint effect of heavy vehicles and diminished light conditions was associated with a 71% increased probability of sustaining KSIs (AOR = 1.71; 95% CI: 1.60-1.83). Other significant joint effects included young children (aged 0 to 5 years) as pedestrian (AOR = 1.92; 95% CI: 1.87-1.97), in diminished light conditions (AOR = 1.23; 95% CI: 1.15-1.31), and with heavy vehicle (AOR = 1.37; 95% CI: 1.28-1.47).

Effects of automatic emergency braking systems on pedestrian crash risk.

OBJECTIVE: Automatic emergency braking (AEB) that detects pedestrians has great potential to reduce pedestrian crashes. The objective of this study was to examine its effects on real-world police-reported crashes. METHODS: Two methods were used to assess the effects of pedestrian-detecting AEB on pedestrian crash risk. Vehicles with and without the system were examined on models where it was an optional feature. Poisson regression was used to estimate the effects of AEB on pedestrian crash rates per insured vehicle year, and quasi-induced exposure using logistic regression compared involvement in pedestrian crashes to a system-irrelevant crash type. RESULTS: AEB with pedestrian detection was associated with significant reductions of 25%-27% in pedestrian crash risk and 29%-30% in pedestrian injury crash risk. However, there was not evidence that that the system was effective in dark conditions without street lighting, at speed limits of 50 mph or greater, or while the AEB-equipped vehicle was turning. CONCLUSIONS: Pedestrian-detecting AEB is reducing pedestrian crashes, but its effectiveness could be even greater. For the system to make meaningful reductions in pedestrian fatalities, it is crucial for it to work well in dark and high-speed conditions. Other proven interventions to reduce pedestrian crashes under challenging circumstances, such as improved headlights and roadway-based countermeasures, should continue to be implemented in conjunction with use of AEB to prevent pedestrian crashes most effectively.

Influence of Luminosity on Functional Attributes of Quesnelia quesneliana (Brongn.) L.B.Sm. / Influência da Luminosidade nos Atributos Funcionais em Quesnelia quesneliana (Brongn.) L.B.Sm.

Quesnelia quesneliana is an endemic species from Brazil with restricted distribution in restinga areas and has been suffering from changes in its habitat. This study aimed to evaluate the influence of light on the morpho-anatomy and pigment content of Q. quesneliana. The samples were collected in the Liberdade neighborhood in São Mateus, Espírito Santo State, Brazil, which is impacted by anthropization. The influence of light was tested comparing individuals completely exposed to it and individuals under shade. For a morphobiometric analysis, 150 individuals were measured for each light condition, and for pigment determination, 10 leaves were used for each light condition. For anatomical analysis, samples were fixed in 50% FAA and transferred to 70 % ethanol solution after 48 hours. Cross sections were made on roots and stems, and transverse and paradermal sections on leaves. It was concluded that individuals exposed to light are smaller, with higher carotenoid content, while shaded individuals are larger, with more succulent and darker leaves due to greater accumulation of chlorophyll. Anatomically, the individual's structure is similar.

Quesnelia quesneliana é endêmica do Brasil com distribuição restrita nas áreas de restinga e vem sofrendo com alterações no seu habitat. O trabalho objetivou avaliar a influência da luminosidade na morfoanatomia e conteúdo de pigmentos foliares de Q. quesneliana. As amostras foram coletadas no bairro Liberdade em São Mateus, Estado do Espírito Santo, Brasil, que sofre com ações antrópicas. A influência das condições de luminosidade foi testada comparando indivíduos completamente expostos à luminosidade e à sombra. Para as análises morfobiométricas foram mensurados 150 indivíduos por condição luminosa, e para a determinação de pigmentos, foram utilizadas 10 folhas por condição luminosa. Para a análise anatômica, as amostras foram armazenadas em FAA 50 para fixação e transferidas para etanol 50% após 48 horas. Foram realizadas secções transversais em raízes e caules, e secções transversais e paradérmicas em folhas. Conclui-se que os indivíduos expostos a luminosidade são menores, com maior teor de carotenoides, enquanto os indivíduos sombreados são maiores, com folhas mais suculentas e escuras devido ao maior acúmulo de clorofila. Anatomicamente, a estrutura dos indivíduos é similar.

Insights into Gene Regulation of Jasmonate-Induced Whole-Plant Senescence of Tobacco under Non-Starvation Conditions.

Jasmonate (JA)-induced plant senescence has been mainly studied with a dark/starvation-promoted system using detached leaves; yet, the induction of whole-plant senescence by JA remains largely unclear. This work reports the finding of a JA-induced whole-plant senescence of tobacco under light/non-starvation conditions and the investigation of underlying regulations. Methyl jasmonate (MeJA) treatment induces the whole-plant senescence of tobacco in a light-intensity-dependent manner, which is suppressed by silencing of NtCOI1 that encodes the receptor protein of JA-Ile (the bioactive derivative of JA). MeJA treatment could induce the senescence-specific cysteine protease gene SAG12 and another cysteine protease gene SAG-L1 to high expression levels in the detached leaf patches under dark conditions but failed to induce their expression in tobacco whole plants under light conditions. Furthermore, MeJA attenuates the RuBisCo activase (RCA) level in the detached leaves but has no effect on this protein in the whole plant under light conditions. A genome-wide transcriptional assay also supports the presence of a differential regulatory pattern of senescence-related genes during MeJA-induced whole-plant senescence under non-starvation conditions and results in the finding of a chlorophylase activity increase in this process. We also observed that the MeJA-induced senescence of tobacco whole plants is reversible, which is accompanied by a structural change of chloroplasts. This work provides novel insights into JA-induced plant senescence under non-starvation conditions and is helpful to dissect the JA-synchronized process of whole-plant senescence.

Light and competition alter leaf stoichiometry of introduced species and native mangrove species.

Ecological stoichiometry is the study of the balance of ecosystem energy and nutrient cycling, especially carbon (C), nitrogen (N), and phosphorus (P). C, N, and P are the key elements for plant growth and metabolism. Systematic research on leaf stoichiometry in mangrove forest ecosystems is still lacking. To understand the leaf stoichiometry of introduced species and native species in mangrove forests, we selected four species (one introduced species, Sonneratia apetala, and three native species, Avicennia marina, Aegiceras corniculatum, and Kandelia obovate) and measured leaf C, N, and P contents under different light conditions. The results showed that there were significant negative scaling relationships of leaf C versus N and C versus P but positive scaling relationships of leaf N versus P in the four mangrove species. Light and competition had significant effects on leaf stoichiometry, especially under the full light condition. S. apetala influenced leaf elements in a mixture with native species. Interspecific competition reduced leaf N and P contents in A. corniculatum and K. obovate but increased leaf N and P contents in A. marina. Leaf N and P contents of the four species showed similar responses to both intraspecific and interspecific competition. The ratio of leaf C:N:P (108:11:1) in the mangrove forests was lower than that in other ecosystems, and species with a higher growth rate had a higher leaf P content and lower N:P ratio, supporting the growth rate hypothesis. Leaf N:P was 11.04, indicating that there was N limitation in the mangrove forests. This systematic research of leaf stoichiometry of mangrove forests improves our understanding of mangrove growth and nutrient use strategies in response to different environmental stresses.

Demosaicing of RGBW Color Filter Array Based on Rank Minimization with Colorization Constraint.

Recently, the white (w) channel has been incorporated in various forms into color filter arrays (CFAs). The advantage of using the W channel is that W pixels have less noise than RGB pixels; therefore, under low-light conditions, pixels with high fidelity can be obtained. However, RGBW CFAs normally suffer from spatial resolution degradation due to a smaller number of color pixels than in RGB CFAs. Therefore, even though the reconstructed colors have higher sensitivity, which results in larger CPSNR values, there are some color aliasing artifacts due to a low resolution. In this paper, we propose a rank minimization-based color interpolation method with a colorization constraint for the RGBW format with a large number of W pixels. The rank minimization can achieve a broad interpolation and preserve the structure in the image, and it thereby eliminates the color artifacts. However, the colors fade from this global process. Therefore, we further incorporate a colorization constraint into the rank minimization process for better reproduction of the colors. Experimental results show that the images can be reconstructed well even from noisy pattern images obtained under low-light conditions.

Gene Expression Analysis of Zeaxanthin Epoxidase from the Marine Microalga Dunaliella tertiolecta in Response to Light/Dark Cycle and Salinity.

Zeaxanthin is an important pigment in the photo-protection mechanism of microalgae. However, zeaxanthin epoxidase, an enzyme involved in the accumulation and conversion of zeaxanthin, has not been extensively studied in microalgae. In this work, we report the expression pattern of zeaxanthin epoxidase in Dunaliella tertiolecta (DtZEP) at different light and diverse salinity conditions. To confirm the responsiveness to light conditions, the ZEP expression pattern was investigated in photoperiodic (16 h of light and 8 h of dark) and continuous (24 h of light and 0 h of dark) light conditions. mRNA expression levels in photoperiodic conditions fluctuated along with the light/dark cycle, whereas those in continuous light remained unchanged. In varying salinity conditions, the highest mRNA and protein levels were detected in cells cultured in 1.5 M NaCl, and ZEP expression levels in cells shifted from 0.6 M NaCl to 1.5 M NaCl increased gradually. These results show that mRNA expression of DtZEP responds rapidly to the light/dark cycle or increased salinity, whereas changes in protein synthesis do not occur within a short period. Taken together, we show that DtZEP gene expression responds rapidly to light irradiation and hyperosmotic stress. In addition, ZEP expression patterns in light or salinity conditions are similar to those of higher plants, even though the habitat of D. tertiolecta is different.

Targeted proteome analysis of microalgae under high-light conditions by optimized protein extraction of photosynthetic organisms.

Cell disruption and protein solubilization protocols for the relative quantification of individual subunits in photosystems were developed for photosynthetic organisms including cyanobacterium Synechocystis sp. PCC 6803, green-algae Chlamydomonas reinhardtii, and seed plant Arabidopsis thaliana. The optimal methods for the disruption of Chlamydomonas, Synechocystis, and Arabidopsis cells were sonication, microbeads (Φ approximately 0.1 mm), and large beads (Φ = 5.0 mm), respectively. Extraction of the total proteins exceeded 90% using each optimal cell disruption method. Solubilization efficiency of membrane proteins was improved by the phase transfer surfactant (PTS) method. Ninety seven and 114 proteins from Chlamydomonas and Synechocystis, respectively, including membrane proteins such as photosystem proteins, ATP synthase, and NADH dehydrogenase, were successfully analyzed by nano-liquid chromatography tandem mass spectrometry. These results also indicated the improved efficiency of solubilization and trypsin digestion using PTS buffer. The results of the relative quantitative evaluation of photosystem subunits in Chlamydomonas and Synechocystis grown under high-light conditions were consistent with those of previous studies. Thus, the optimal cell disruption and PTS methods allow for comprehensive relative quantitative proteome analysis of photosynthetic organisms. Additionally, NdhD1 and NdhF1, which are NDH-1 subunit homologs, were increased under high-light conditions, suggesting that the NDH-1L complex, including NdhD1 and NdhF1, is increased under high-light conditions. The relative quantitative proteome analysis of individual subunits indicates the diverse functions of NDH-1 protein.

[Effects of temporal and spatial variation of canopy structures and light conditions on population characteristics of Fargesia decurvata.] / å† å±‚ç»“æž„å’Œå ‰çŽ¯å¢ƒçš„æ—¶ç©ºå˜åŒ–å¯¹ç´«è€³ç®­ç«¹ç§ç¾¤ç‰¹å¾çš„å½±å“.

The canopy structures and light conditions and the population characteristics of Fargesia decurvata, a dominant understory species, were investigated in three typical communities, i.e., deciduous broad-leaved forest, evergreen and deciduous broad-leaved mixed forest, evergreen broad-leaved forest. The results showed that with the succession from deciduous broad-leaved forest to evergreen and deciduous broad-leaved mixed forest and to evergreen broad-leaved forest, the Shannon index, Simpson index and Pielou index were increased, suggesting that the development of communities in Jinfo Mountains tended to be stable. Moreover, canopy structures were significantly changed, in that the canopy openness and mean leaf angle decreased, leaf area index increased, and canopy extinction ability enhanced, resulting in the decrease of light intensity under the canopy. The upper canopy was the main contributor for canopy closure, with the crown depth and crown area of canopy being the two main influencing factors. Moreover, canopy structures were significantly correlated with light conditions in the forest, with the greatest influence on the diffuse solar radiation. With the growth season coming, canopy openness and understory light conditions were decreased, while leaf area index increased, and their maximum values appeared in June or July in the three forest types. The maximum and minimum value of mean leaf angle appeared in spring and summer, respectively. Clonal growth of F. decurvata was closely related to canopy structures and light conditions. In evergreen and deciduous broad-leaved mixed forest with moderate light, F. decurvata grew best, with high and thick ramets, high ramet density (29.69±1.68 ind·m-2) and high ability to expand rhizomes. In deciduous broad-leaved forest, the strong light condition caused the reduction of soil water might have effects on the growth of F. decurvata. However, in the evergreen broad-leaved forest with low light condition, ramets of F. decurvata tended to be short and thin, with low ramet density (5.80±1.16 ind·m-2) and the clonal expansion ability. Those results suggested that forest succession would change canopy structures and understory light conditions. Low understory light conditions prohibited the regeneration and development of F. decurvata population.

[Simulation on photosynthetic light-responses of leaves of Quercus variabilis and Robinia pseudoacacia under different light conditions.] / ä¸åŒå ‰çŽ¯å¢ƒä¸‹æ “çš®æ Žå’Œåˆºæ§å¶ç‰‡å ‰åˆå ‰å“åº”æ¨¡æ‹Ÿ.

Photosynthesis can reflect the responses of plants to environmental changes. In this study, photosynthetic light-response curves were measured by the Li-6400XT photosynthetic system in Quercus variabilis and Robinia pseudoacacia plantations in Xiaolangdi Forest Ecosystem Research Station. Photosynthetic light-response curves were fitted by Ye model. The differences of photosynthetic parameters between inner and margin forests were examined. Stomatal conductance (gs) light-response curve were fitted using the mechanism model of gs coupled with a modified model of light-response of photosynthesis. The light-response characteristics of gs were investigated. Net photosynthetic rates (Pn) of Q. variabilis in the inner forest was higher than that in the margin. The initial light efficiency (Α) was 12.4% more in the inner forest than that in the margin in July and August when photosynthetically active radiation was less than 200 Μmol·m-2·s-1. The ability to capture and utilize weak light of Q. variabilis leaves in the inner forest was obviously higher than that in the margin. When photosynthetically active radiation was higher than 200 Μmol·m-2·s-1, Pn of Q. variabilis leaves in the margin forest was larger than that in the inner. Under weak light conditions (0-200 Μmol·m-2·s-1), Pn of R. pseudoacacia in the inner forest was higher than that in the margin. Pn of R. pseudoacacia in the inner forest was less than that in the margin when light intensity was higher than 200 Μmol·m-2·s-1. The dark respiration rate (Rd) and light compensation point (Ic) in the inner forest were 50.0% and 42.8% lower than those in the margin. The less Rd and Ic of the inner forest could reduce carbon loss and adapt to low photosynthetic rate. The stomatal conductance light-response of R. pseudoacacia in the inner forest significantly differed from that in the margin. The leaves of Q. variabilis and R. pseudoacacia had strong adaptability to the changes of light condition. The values of maximum net photosynthetic rate (Pn max) and Α of Q. variabilis leaves were mainly controlled by gs, and Rd and Ic were primarily affected by air temperature. Pn max and Α of R. pseudoacacia leaves had significant positive correlation with air temperature. The Ic and the light saturation point (Is) were remarkably correlated with leaf saturation vapor pressure deficit.