Higher Levels Of Light Intensity Research Articles

Nutrient-efficient catfish-based aquaponics for producing lamb's lettuce at two light intensities.

Aquaponic systems are sustainable processes of managing water and nutrients for food production. An innovate nutrient-efficient catfish-based (Clarias gariepinus) aquaponics system was implemented for producing two cultivars of two leafy vegetables largely consumed worldwide: lamb's lettuce (Valerianella locusta var. Favor and Valerianella locusta var. de Hollande) and arugula (Eruca vesicaria var. sativa and Eruca sativa). Different growing treatments (4 × 2 factorial design) were applied to plants of each cultivar, grown at two light intensities (120 and 400 μmol m-2 s-1). During growth, several morphological characteristics (root length, plant height, leaf number, foliage diameter and biggest leaf length) were measured. At harvest, plants were weighed and examined qualitatively in terms of greenness and health status. Additionally, leaf extracts were obtained and used to determine total phenolic contents, antioxidant capacities, and levels of cytotoxicity to Caco-2 intestinal model cells. After a 5-week growth period, both lamb's lettuce cultivars presented high levels of greenness and health status, at both light intensities, particularly the var. de Hollande that also showed higher average performance in terms of plant morphology. In turn, arugula cultivars showed lower levels of greenness and health status, especially the cultivar E. vesicaria var. sativa submitted to direct sunlight during growth. In addition, plant specimens submitted to higher levels of light intensity showed higher contents in antioxidants/polyphenols. Cultivars with a higher content in antioxidants/polyphenols led to higher Caco-2 cell viability. For successful industrial implementation of the aquaponics technology, different and optimized acclimatizing conditions must be applied to different plant species and cultivars. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Komposisi dan Struktur Tumbuhan Bawah pada Habitat yang Diinvasi Tumbuhan Invasif di Kawasan Wisata Geopark Silokek Kabupaten Sijunjung

The Silokek Geopark area, Sijunjung Regency, is one of the tourist areas in West Sumatra Province which has a high level of biodiversity, which can be disrupted due to the presence of invasive plants. A study has been carried out which aims to determine the composition and structure of undergrowth in habitats invaded by weeds in the Silokek Geopark tourist area, Sijunjung Regency. This research was conducted from September to December 2022 using the quadratic method and plotting by purposive sampling with a plot size of 10 x 10 m with a sub-plot measuring 2 x 2 m. The composition of undergrowth in the habitat invaded by weeds found 24 families, 38 genera, 38 species, and 1049 individuals. Among the undergrowth found, there were 12 families, 20 genera, 20 species and 532 individuals of invasive plants with the dominant family being Asteraceae (30.41%), and the co-dominant family being Nephrolepidaceae and Poaceae with a percentage of 17 each. .83% and 11.63%. The highest important value index was in Nephrolepis biserrata (28.42%) and the lowest was in Musa acuminata (0.76%). The most dominant weed species was Mikania michranta with an IVI of 18.79%. The diversity index of the understorey plants in this area is categorized as high with a diversity index (H' = 3.24). Weed plant species are more successful in dominating open and disturbed areas with high levels of light intensity, gaps or wide gaps and forest edges can be utilized by invasive plant species to grow optimally.

Comparison of dynamic behavior between continuous- and discrete-time models of intraguild predation.

Intraguild predation is a common ecological phenomenon that manifests itself by the aggression of one predator by another to obtain a shared prey species. In this paper, we develop a discrete analog of a stoichiometric continuous-time intraguild predation model. We analyze the dynamics of the discrete-time model, such as boundedness and invariance, stability of equilibria, and features of ecological matrices. The dynamic behavior of the two models is compared and analyzed through numerical analysis. We observe the same coexistence region of populations and stoichiometric effects of food quality of the shared prey in both models. Obvious differences between the discrete- and continuous-time models can be observed with intermediate and high levels of light intensity. The multistability characteristics and the existence interval of chaos differ among the different time scale models. This study provides evidence of the importance of time scales on intraguild predation.

Variations in photosynthesis associated traits and grain yield of minor millets

Photosynthesis is one of the important processes, and understanding its variability can be one of the approaches to improve crop productivity. It is presumed that most of the minor millets have C4 type of photosynthetic carbon fixation. However, research on quantifying the variability in photosynthesis associated traits in minor millets is limited. Objectives of this study were to (1) quantify the variation in leaf anatomical, physiological and yield traits among the minor millets and (2) to assess whether photosynthesis associated traits had a relationship with grain yield in minor millet. The result indicated that finger millet, little millet, barnyard millet, proso millet, foxtail millet and kodo millet had C4 leaf anatomy, and among them, finger millet had an increased vascular bundle and bundle sheath cell size. Among the minor millets, at ambient light, temperature and CO2 levels, the photosynthetic rate, stomatal conductance, intrinsic water use efficiency, number of major and minor veins, and grain yield were higher in foxtail millet. The CO2 response curve indicates that proso millet had a higher photosynthetic rate at higher concentrations of CO2 than other minor millets. However, the light response curve suggests that foxtail millet had a higher photosynthetic rate at higher light intensity levels. Among the minor millets studied, there was no relationship between mean photosynthesis associated traits over different growth stages with grain yield.

In vivo Acclimatization Responses of Platycodon grandiflorum For. Duplex to Different Soil Types and Environmental Factors

This study aimed to evaluate the effects of soil types and environmental factors for optimum conditions of seedlings growth of the Platycodon grandiflorum for establishing the in vivo acclimatization system of regenerated plants derived from the in vitro culture. P. grandflorum seedlings were transferred to the in vivo condition and acclimatized under different soil types, light intensities, and various temperatures. Changes caused by environmental factors and soil types in plant growth viz. plant height, leaf width, leaf length, stem diameter, number of leaves, branches and nodes were recorded in this study. Among the nine types of soil, the best growth performances were obtained from the soil type SVP (Soil mixed with horticultural bed soil, vermiculite, and perlite @ 2:1:1). Seedlings of P. grandiflorum showed the best growth at higher levels of light intensity (60 μmol·m-2·s-1). In contrast, P. grandiflorum seedlings showed the best growth response at a moderate level of temperature (25°C). Collectively, the present study provides a better understanding of the responses of growth characteristics in P. grandiflorum seedlings exposed to various soil types, light intensities, and temperatures.

Effects of light intensity on photosynthetic capacity and light energy allocation in Panax notoginseng.

To explore the effects of light intensity on photosynthetic characteristics and light adaptation of the shade-demanding species Panax notoginseng, the responses of photosynthesis to photosynthetic photon flux density, CO2 and sunflecks in the two-year-old Panax notoginseng were investigated under different levels of light intensity (29.8%, 9.6%, 5.0%, 1.4% and 0.2% of full sunlight). Meanwhile, chlorophyll a fluorescence parameter and light energy partitioning were also recorded and calculated in the responsive process. P. notoginseng grown under 29.8% full sunlight (FL) had a lower apparent quantum yield (AQY), potential photochemical quantum yield (Fv/Fm) and potential photochemical activity (Fv/Fo), however, it had a higher maximum net photosynthetic rate (Pn max), maximum electron transport rate (Jmax), F/Fm', electron transport rate (ETR), photochemical quenching (qP) and the proportion of light energy allocated to photochemistry dissipation (ΦPS2), but the non-photochemical quenching (NPQ) was not the highest. There were no significant differences in Pn max, light compensation point (LCP), light saturation point (LSP), dark respiration rate (Rd) among 9.6%FL and 5.0% FL treatments, but these treatments had relatively higher values of NPQ, AQY, carboxylation efficiency (CE), maximum carboxylation rate (Vc max), Fv/Fm and Fv/Fo. In addition, the Pn max, CE, Vc max, Jmax, ETR,F/Fm', qP, NPQ and ΦPSII decreased with the decrease in light intensity from 5.0%FL to 0.2%FL, and the proportion of light energy allocated to fluorescent dissipation (Φf,d) were increased. Under 500 μmol·m-2·s-1 light-flecks inducting, the ΦPSⅡof P. notoginseng increased slowly with the extension of time except for the treatment of less than 5.0%FL, and under the circumstance of 1.4%FL and 0.2%FL, ΦPSⅡreached significantly a perfect result, moreover, Φf,dincreased rapidly. These results suggested that the enhancement in photosynthetic electron transport to use the light energy and the moderate photoinhibition of PS2 might avoid the irreversible oxidative damage of photosynthetic organization in P. notoginseng under high levels of light intensity. Moderate shading was beneficial to maintain its higher non-photochemical quenching ability. However, its photosynthetic capacity depressed and the proportion of light energy allocated to non-photochemical pathway increased obviously in excessive shading, and it easily caused a light oxidative damage.

Non-photochemical Quenching Plays a Key Role in Light Acclimation of Rice Plants Differing in Leaf Color

Non-photochemical quenching (NPQ) is an important photoprotective mechanism in rice; however, little is known regarding its role in the photosynthetic response of rice plants with differing in leaf color to different irradiances. In this study, two rice genotypes containing different chlorophyll contents, namely Zhefu802 (high chlorophyll) and Chl-8 (low chlorophyll), were subjected to moderate or high levels of light intensity at the 6-leaf stage. Chl-8 possessed a lower chlorophyll content and higher chlorophyll a:b ratio compared with Zhefu802, while Pn, Fv/Fm, and ΦPSII contents were higher in Chl-8. Further results indicated that no significant differences were observed in the activities of Rubisco, Mg2+-ATPase, and Ca2+-ATPase between these genotypes. This suggested that no significant difference in the capacity for CO2 assimilation exists between Zhe802 and Chl-8. Additionally, no significant differences in stomatal limitation were observed between the genotypes. Interestingly, higher NPQ and energy quenching (qE), as well as lower photoinhibitory quenching (qI) and production of reactive oxygen species (ROS) was observed in Chl-8 compared with Zhefu802 under both moderate and high light treatments. This indicated that NPQ could improve photosynthesis in rice under both moderate and high light intensities, particularly the latter, whereby NPQ alleviates photodamage by reducing ROS production. Both zeaxanthin content and the expression of PsbS1 were associated with the induction of NPQ under moderate light, while only zeaxanthin was associated with NPQ induction under high light. In summary, NPQ could improve photosynthesis in rice under moderate light and alleviate photodamage under high light via a decrease in ROS generation.

Prevalence and Incidence of Black Band Disease of Scleractinian Corals in the Kepulauan Seribu Region of Indonesia

Black band disease (BBD) is the oldest recognised disease associated with scleractinian corals. However, despite this, few BBD surveys have been conducted in the Indonesian archipelago, one of the world’s hot spots for coral diversity. In this study, we show that BBD was recorded in the reefs of Kepulauan Seribu, Indonesia, at the time of surveying. The disease was found to mainly infect corals of the genus Montipora. In some instances, upwards of 177 colonies (31.64%) were found to be infected at specific sites. Prevalence of the disease ranged from 0.31% to 31.64% of Montipora sp. colonies throughout the archipelago. Although BBD was found at all sites, lower frequencies were associated with sites closest to the mainland (17.99 km), as well as those that were furthest away (63.65 km). Despite there being no linear relationship between distance from major population centers and BBD incidence, high incidences of this disease were associated with sites characterized by higher levels of light intensity. Furthermore, surveys revealed that outbreaks peaked during the transitional period between the dry and rainy seasons. Therefore, we suggest that future surveys for disease prevalence in this region of Indonesia should focus on these transitory periods.

Functional ratios among leaf, xylem and phloem areas in branches change with shade tolerance, but not with local light conditions, across temperate tree species.

Leaf, xylem and phloem areas drive the water and carbon fluxes within branches and trees, but their mutual coordination is poorly understood. We test the hypothesis that xylem and phloem areas increase relative to leaf area when species are selected for, or branches are exposed to, higher levels of light intensity. Trees of 10 temperate, broadleaved and deciduous, tree species were selected. Fifty-centimetre-long branches were collected from shaded and exposed conditions at a height of 3-4m. We measured the total leaf area, xylem area, phloem area and leaf traits, as well as the area of the constituent cell types, for a stem section at the branch base. Xylem area:leaf area and phloem area:leaf area ratios did not differ consistently between sun and shade branches, but, as expected, they decreased with species' shade tolerance. Similar trends were observed for conductive cell areas in xylem and phloem. Trees of light-demanding species maintain higher water loss and carbon gain rates per leaf area by producing more xylem area and phloem area than shade-tolerant species. We call for more comparative branch studies as they provide an integrated biological perspective on functional traits and their role in the ecology of tree species.

Physiological characteristics of the primitive CO2 concentrating mechanism in PEPC transgenic rice

The relationship between carbon assimilation and high-level expression of the maize PEPC in PEPC transgenic rice was studied by comparison to that in the untransformed rice,japonica kitaake. Stomatal conductance and photosynthetic rates in PEPC transgenic rice were higher than those of untransformed rice, but the increase of stomatal conductance had no statistical correlation with that of photosynthetic rate. Under high levels of light intensity, the protein contents of PEPC and CA were increased significantly. Therefore the photosynthetic capacity was increased greatly (50%) with atmospheric CO(2) supply. While CO(2) release in leaf was reduced and the compensation point was lowered correspondingly under CO(2) free conditions. Treatment of the rice with the PEPC-specific inhibitor DCDP showed that overexpression of PEPC and enhancement of carbon assimilation were related to the stability of Fv/Fm. Labeling with(14)CO(2) for 20 s showed more(14)C was distributed to C(4) primary photosynthate asperate in PEPC transgenic rice, suggesting that there exists a limiting C(4) photosynthetic mechanism in leaves. These results suggest that the primitive CO(2) concentrating mechanism found in rice could be reproduced through metabolic engineering, and shed light on the physiological basis for transgenic breeding with high photosynthetic efficiency.

Method for analyzing series resistance and diode quality factors from field data Part II: Applications to crystalline silicon

The method described in a prior journal publication [1] is applied to the determination of module series resistance and diode quality factors for several crystalline silicon (c-Si) technology photovoltaic (PV) modules. This method makes use of the functional dependence of the slope of the current–voltage ( I– V) characteristics at open circuit ( R oc) against the reciprocal of the short-circuit current density ( J sc), from multiple I– V curves taken under variable illumination. It is shown that calculations of the series resistance for six modules yield values in the range 1.0–1.6 Ω-cm 2, expressed in unit-cell area terms. The derived values for the series resistance ( R s) determined from the data are investigated for their effect on the module fill factor (FF) values and their dependence at higher light intensity levels. The diode quality factors also derived from the same data are shown to be somewhat larger than those obtained from the more canonical method — slope of the fit of the open-circuit voltage ( V oc) versus logarithm of J sc. The differences between the two methods are explored within a two-diode model for c-Si. Deriving average values of diode quality factors for series-connected cells using either method is shown to exhibit problematic issues.

Survival of enteric bacteria in relation to simulated solar radiation and other environmental factors in marine waters

The survival rates of enteric bacteria (i.e. Escherichia coli and enterococci) exposed to a sunlight simulator were determined at two different depths of sea water in varying conditions of light intensity, turbidity, sewage content, degree of mixing and temperature under controlled laboratory conditions. The combined effect of these factors on bacterial die-off was evaluated by statistical analyses carried out on the experimental data obtained according to the central composite experimental design. The magnitude and the general character of the influence of the factors were determined. The variability of bacterial mortality due to the effect of light was shown to depend on the variability of the intensity of light and the other microenvironmental factors (i.e. turbidity, sewage content, and mixing) influencing the depth profile of the light intensity and bacterial concentration. All factors except temperature were found to exert a significant influence on bacterial die-off under light conditions. Higher rates of die-off were brought about by high levels of light intensity and mixing with low levels of turbidity and sewage content of the water. No appreciable difference was found between the survival capabilities of E. coli and enterococci on exposure to light.

Trends in Washington State's Apple Industry

Washington is the leading producer of apples in the United States. North-central and south-central Washington and the Columbia Basin are the major production regions within the state. The climate of these production regions is characterized by cold winters and hot, dry summers with high levels of light intensity. The principal varieties produced are still `Delicious', `Golden Delicious', and `Granny Smith'; however, `Fuji', `Gala', and `Braeburn' have been planted widely since 1988. Despite increasing levels of production and lower prices beginning in 1986, apple prices have recovered relatively well in recent years due to aggressive exports to southeast Asia and Mexico. Increased international competition has resulted in a trend towards higher-density orchards using dwarfing rootstock so that earlier production can be achieved. Evaluation of the performance of new varieties in Washington's climatic conditions has increased. Although not the focus of this article, several social and environmental issues are facing the Washington apple industry, including increasing restrictions on chemical usage, competition for a limited water resource, regulation of ground water quality, pending labor relations legislation, and increasing urbanization pressures.

Impossibility of acridine orange intercalation in nuclear DNA of the living cell

The ability of a “vital” dye, acridine orange (AO), to intercalate into the DNA of living cells was investigated by quantitative intensified fluorescence microscopy and digital imaging under various conditions of dye concentration, excitation light intensity, and ionic concentration. Our results demonstrate that the bulk of chromatin DNA is packed in a way that does not allow AO intercalation. At low dye concentrations and very low levels of light intensity, the only fluorescent structures observed inside the nucleus are the nucleoli. This nonpermissive state of the chromatin appears to be a characteristic feature of the nucleus in living cells. AO intercalation into DNA can be mediated by raising the nuclear Na + concentration. This was achieved here by using a cation carrier, monensin, a procedure which permits the avoidance of cell permeabilization. Furthermore, we show that the discharge of lysosomal enzymes in the living cell, via a targeted photodynamic reaction which occurs at high levels of light intensity, can also release the constraints which impede dye intercalation into nuclear DNA. In conclusion, studies carried out under conditions where intercalative dyes such as AO are able to stain the nuclear DNA have to be interpreted with caution and do not provide direct evidence on the structural state of native chromatin. The molecular origin of the absence of AO intercalation in chromatin of the living cell is discussed with regard to the restrained uncoiling of the double helix which is required for dye intercalation.

Habitat Exploration through Morphological Plasticity in Two Chalk Grassland Perennials

The results of previous workers suggest that rhizome lengths and the degree of rhizome branching in clonal perennial plants may change in response to environmental conditions, enabling plants to more efficiently capture unevenly distributed resources (so-called responses). Such components of plant growth were investigated in two rhizomatous graminoids of chalk grassland, Carex flacca and Brachypodium pinnatum. Mean rhizome length in Brachypodium was significantly smaller under high nutrient availability, but only when unshaded. Carex produced longer rhizomes under high light conditions, but showed no effects of nutrients. In both species, branching was greater under higher levels of light intensity, and with more favourable nutrient conditions. Shoots of both species increased in height in response to shading, but only shoots of Brachypodium responded to fertilization. As Carex does not produce shorter rhizomes under more favourable conditions, the foraging model is inapplicable to this species. Growth responses of Brachypodium were in better agreement with the foraging hypothesis. However, in this species the amount of endogenous variation in rhizome length and bud dynamics overrides the plastic changes in response to different resource supply.

Feeding responses of the horsefly, Tabanus nigrovittatus, to phagostimulants

ABSTRACT. Wild caught horseflies, Tabanus nigrovittatus Macq. (Diptera, Tabanidae), were presented solutions of 0.15 MNaCl at 37°C containing various concentrations of ATP, ADP, AMP, adenosine, phytic acid or 2,3‐diphosphoglycerate in an artificial feeding apparatus. The insects fed upward through a Para‐film M® membrane. ADP (ED50 35 μM) was more potent than ATP (ED50 112 μM) and AMP (ED50 382 mUM). All of these diets were deposited in the midgut, an indication that the flies were in the ‘blood feeding’ mode. Adenosine caused only 23% gorging at 1 mM. Phytic acid caused only 10% gorging at 1 mM and 2,3‐diphosphoglyceric acid had no activity at 0.6 mM. Flies would feed only in highly reflective cages under high levels of light intensity (1200–1500 lux) at the membrane surface.

Intracavity laser excitation of NCO fluorescence in an atmospheric pressure flame

Laser excited fluorescence of the NCO radical has been obtained using discrete prism selected lines of an argon ion laser pump source. To our knowledge this is the first time NCO fluorescence has been obtained in a flame environment. NCO was formed in a slightly rich atmospheric pressure CH4/N2O flame. This flame was placed inside the extended cavity of the argon laser to take advantage of the much higher light intensity levels. All of the available laser lines pump vibrational hot bands of the NCO A 2Σ+ ← X 2Π system. The 4658 Å line appears to be the most useful for probing NCO densities. This line pumps in the A 2Σ+(0,00,0) ← X 2Π (1,01,0) vibrational band. NCO is pumped to N′ = 31 by this line, probably via the Q231 transition although the R230 and P232 transitions could not be ruled out in the present analysis. The 4658 Å line was used to determine a relative NCO density profile through the reaction zone of a CH4/N2O flame. Profiles of C2, CN, and temperature were also obtained in this flame and are compared with the NCO profile. A lower limit of approximately 3×1014 cm−3 was placed on the peak NCO density in the flame. Attempts to find NCO or CN fluorescence in a CH4/air flame failed indicating probable differences in nitrogen chemistry for the two flames.

Light-induced reduction in excitation efficiency in the trp mutant of Drosophila.

In the transient receptor potential (trp) mutant of Drosophila, the receptor potential appears almost normal in response to a flash but quickly decays to baseline during prolonged illumination. Photometric and early receptor potential measurements of the pigment suggest that the pigment is normal and that the decay of the trp response during illumination does not arise from a reduction in the available photopigment molecules. However, there is reduction in pigment concentration with age. Light adaptation cannot account for the decay of the trp response during illumination: in normal Drosophila a dim background light shortens the latency and rise time of the response and also shifts the intensity response function (V-log I curve) to higher levels of light intensity with relatively little reduction in the maximal amplitude (Vmax) of response. In the trp mutant, a dim background light or short, strong adapting light paradoxically lengthens the latency and rise time of the response and substantially reduces Vmax without a pronounced shift of the V-log I curve along the I axis. The effect of adapting light on the latency and V-log I curve seen in trp are associated with a reduction in effective stimulus intensity (reduction in excitation efficiency) rather than with light adaptation. Removing extracellular Ca+2 reduces light adaptation in normal Drosophila, as evidenced by the appearance of "square" responses to strong illumination. In the trp mutant, removing extracellular Ca+2 does not prevent the decay of the response during illumination.

INTERMEDIATE PROCESSES IN PHOTOTRANSDUCTION: A STUDY IN DROSOPHILA MUTANTS

Abstract— A variety of procedures were used to modify the light response of Drosophila photoreceptors in order to find out if these manipulations produce effects that mimic some aspects of light adaptation. The ultimate goal of our approach is to use these experimental manipulations to dissect the different stages of the phototransduction process.The means which were used to modify the light response were as follows: (a) light adaptation of normal photoreceptors, (b) exposure of normal photoreceptors to various levels of CO2 (c) light adaptation of the trp Drosophila mutant in which the receptor potential decays to baseline during illumination, (d) exposure of the temperature sensitive norpAH52 mutant of Drosophila to elevated temperatures. Intensity‐response functions were obtained using intracellular and extracellular recordings. The maximal response amplitude (Vmax) was then plotted as a function of the light intensity (s̀) which evoked a response of half maximal amplitude. This plot was used to compare the effects of the procedures described above. Qualitatively all the manipulations had similar effects, they reduced Vmax and shifted s̀ to higher levels of light intensity, however, quantitatively the various effects were different.The finding that each experimental manipulation gave a different Vmax versus s̀ plot suggests that they affect different stages in phototransduction. We suggest that the slope of the Vmax versus a function can be interpreted in terms of an ordered cascade of events in phototransduction. This interpretation might give us a tool to distinguish between early and late stages in phototransduction.

DIURNAL BEHAVIOR AND BITING HABITS OF BLACK FLIES (DIPTERA: SIMULIIDAE) IN THE FORESTS OF QUEBEC

Studies in the region of Baie Comeau, Quebec, from 1954 to 1956, showed that black flies were most active in the morning 1 to 2 hours after dawn and in the evening [Formula: see text] to 1 hour before sunset. Flight activity appeared to depend on light intensity if the temperature was not below 45° F, the wind velocity not above 2 m.p.h., and the relative humidity not below 50%. In the morning, activity was greatest at higher levels of light intensity, i.e., 20 ft-c, than in the evening, 5 ft-c. Activity increased before thunderstorms and rain and the increase appeared related more to the change in light intensity than to changes in atmospheric pressure or humidity. At night, black flies moved to resting places in the tops of the trees, probably because of the more suitable light intensity at the higher levels just before dark. Oviposition commenced in the late afternoon and continued until dark except on overcast days, when it commenced in early afternoon. Simulium (Simulium) venustum Say bit man mainly on the back of the neck.