Chlorophyll Fluorescence Intensity Research Articles

Identification of the CsFtsH genes from Camellia sinensis reveals its potential role in leaf color phenotype

The filamentation temperature-sensitive H (FtsH) metalloprotease participates in the chloroplast photosystem II (PSII) repair cycle, playing a crucial role in regulating leaf coloration. However, the evolutionary history and biological function of the FtsH family in albino tea plants are still unknown. In this study, 35 CsFtsH members, including 7 CsFtsH-like (CsFtsHi1-CsFtsHi7) proteins, mapping onto 11 chromosomes in 6 subgroups, were identified in the ‘Shuchazao2′ tea genome, and their exon/intron structure, domain characteristics, collinearity, protein interaction network, and secondary structure were comprehensively analyzed. Furthermore, real-time fluorescence quantitative PCR (RT-qPCR) analysis revealed that the expression levels of CsFtsH1/2/5/8 were significantly positively correlated with the leaf color of tea plants. The subcellular localization revealed that they were located in the chloroplast. The transgenic Arabidopsis has demonstrated that CsFtsH2 and CsFtsH5 could restore the chlorophyll content and chlorophyll fluorescence intensity in var1 and var2 mutants, respectively. Moreover, protein–protein interactions have confirmed that CsFtsH1 with CsFtsH5, and CsFtsH2 with CsFtsH8 could form a hetero-comples and function in chloroplasts. In summary, this study aims to not only increase the understanding of the underlying molecular mechanisms of CsFtsH but also to provide a solid and detailed theoretical foundation for the breeding of albino tea plant varieties.

Characteristics of the photosynthetic activity of corn using different drugs under stress

Goal. To study under controlled conditions the effect of hormonal preparations based on humus extracts and anti-stress stimulants with a high content of amino acids and biologically active substances on the development of corn under conditions of stress, as well as their effect on the photosynthetic activity of plants.
 Methods. The research was carried out in a climatic chamber (a room with adjustable control of temperature, daylight and air humidity) of the Ukrainian research plant quarantine station of the Institute of Plant Protection of the National Academy of Sciences. Photosynthetic activity was measured using a portable fluorometer «Floratest». During the growing season, two foliar feedings were carried out in the phase of development of corn VVSN 12, the first application of drugs during the growing season — VVSN 13, — the second application of drugs during the vegetation period — VVSN 14.
 Results. The analysis of the induction curves of chlorophyll fluorescence and the indicators of the maximum background fluorescence showed a difference between the plants that were under soil moisture of 70% and 50% RH. When corn plants were in a state close to stress for a long time, the difference between the curves of chlorophyll fluorescence intensity between the two controls increased. The use of the studied drugs provided the finding of the indicator of the maximum value of fluorescence induction above the dry control in all variants of the experiment. Best results provided: preparation B (high concentrated suspension for nutrition and plant stress decreasing based upon the humus extract. They contented N — 150 g/l, K2O — 300 g/l, Mg — 30 g/l, metal cations in В, Cu, Fe, Mn and Zn with additional adhesive effects and surfactant), at rate of application 0.5 and 0.25 l/ha; Axofol (high concentrated suspension from extract of brown algae Ascophyllum nodosum with microelements, B — 38.1 g/l, Mn — 10.2 g/l, Zn — 6.4 g/l) at rate of application 1.0 and 0.5 l/ha.
 Conclusions. As the time of corn plants being in a state close to stress increases, the difference between the curve of chlorophyll fluorescence intensity in the wet control and the dry control increases. The use of the studied drugs provided the finding of the indicator of the maximum value of fluorescence induction above the dry control in all variants of the experiment. The use of the researched preparations in conditions of soil moisture of 50% ensured the improvement of vegetation indicators of plants.

Effects of Xanthomonas campestris pv. campestris on the photosynthesis of cabbage in the early stage of infection

Cabbage is one of the most important cruciferous vegetables. Black rot, caused by Xanthomonas campestris pv. campestris (Xcc) seriously affects cabbage production; therefore, it is important to study the resistance mechanism to black rot in cabbage. In this study, cabbage photosynthetic physiology changes in the early stages of Xcc infection were analyzed using physiological index determination and transcriptome analysis. The results showed that the Xcc infection can lead the chlorophyll degradation and decreased the net photosynthetic rate (Pn), and the decrease in Pn was mainly due to non-stomatal factors. In addition, the maximum photosynthetic efficiency (Fv/Fm), actual photosynthetic efficiency of photosystem II (PSII) gradually decreased, and the OJIP curve tended to be flat, indicating that Xcc infection reduced the activity of the PSII reaction center and affected the chlorophyll fluorescence intensity. Moreover, the primary photochemical reaction of cabbage leaves was damaged, and electron transfer on the PSII receptor side was inhibited after Xcc infection. NADP-GAPDH and FBPase activities in the Calvin cycle decreased after Xcc invasion. Using transcriptome analysis, 173, 77, 63, and 53 differentially expressed genes (DEGs) were enriched in "carbon metabolism", "photosynthesis", "carbon fixation in photosynthetic organisms", and "metabolism of porphyrins and chlorophyll" metabolic processes, respectively. These results suggest that Xcc infection affects cabbage photosynthesis via multiple pathways. Our results provide a theoretical basis for further research on black rot-resistant breeding and cabbage resistance mechanisms.

Adaptation of gooseberry varieties to the changed agro-climatic conditions of Kyiv Polissia

In connection with global warming, the study of plant adaptation to climate change, resistance to lack of moisture and high temperatures becomes relevant. Meteorological and phenological observations prove that a change in temperature conditions leads to an earlier start of vegetation and a lengthening of the growing season in all investigated gooseberry varieties. To assess the functional state of the photosynthetic apparatus of plants, a minimally invasive instrumental method of determining the intensity of chlorophyll fluorescence in plant leaves, adapted to work on the domestic photofluorimeter "Floratest", was used. Based on the results of the analysis of the parameters of the chlorophyll fluorescence induction curves (Fo, Fpl, Fmax, Ft) and the comparison of the coefficients for these values (Kpl, K1, K2), it was established that Fo and Kpl are the most informative. A strong correlation dependence of the indicator of the background level of fluorescence at the time of full opening of the shutter (Fo) was established. The value of Fо correlates positively with indicators of the moisture regime, negatively – with temperature indicators. Correlations between the fluorescence growth index and the variable (Kpl) showed the opposite: the largest positive correlation was observed with mean maximum temperature, the smallest with precipitation. On the basis of mathematical analysis and modeling of the obtained FIC curves and indicators of agro-climatic conditions, the values of the maximum temperature and the minimum amount of precipitation, which are critical for the functioning of the gooseberry photosynthetic apparatus, were determined. Such a study makes it possible to evaluate the course of photochemical reactions associated with the work of plant photosystems according to standard coefficients of photochemical activity, which have already been tested in numerous works of domestic researchers on a wide range of agricultural crops.

Characterization of Chlorophyll Fluorescence and Antioxidant Defense Parameters of Two Gracilariopsis lemaneiformis Strains under Different Temperatures.

In this study, two Gracilariopsis lemaneiformis strains-the wild type and a green-pigmented mutant-were cultured at three temperatures (8, 20, and 30 °C) for 7 days to explore their temperature tolerance using photosynthetic performance and antioxidant defense parameters. When the two strains of G. lemaneiformis were separately cultured at 30 °C, the fast chlorophyll fluorescence intensity of the wild type decreased, whereas the green mutant showed no significant change. The decrease in the performance index on absorption basis value under heat stress was lower in the green mutant than in the wild type. In addition, the green mutant had stronger antioxidant activity at 30 °C. Furthermore, a greater decrease in the values of maximum photochemical quantum yield and performance index on an absorption basis in the green mutant indicated that it had a greater degree of inhibition of photosynthetic performance under low temperatures. However, the green mutant produced less reactive oxygen species under low temperatures, suggesting that the antioxidant potential of the green mutant might be higher. In conclusion, the green mutant exhibited heat tolerance and could recover from low-temperature damage; therefore, it has the potential for large-scale cultivation.

Impacts of Chlorine on the Change of Chlorophyll Fluorescence Spectrum to Phaeodactylum tricornutum

Chlorine-containing disinfectants have been widely used all over the world to prevent COVID-19. However, little is known about the potential risk of chlorine-containing disinfectants in the marine environment. Phaeodactylum tricornutum (P. tricornutum) is a typical marine economic diatom, often used as an effective biomarker in ecotoxicology research. Here, the present study has investigated the effect of different effective chlorine concentrations on photosynthesis of P. tricornutum by chlorophyll fluorescence spectroscopy. Results have demonstrated that chlorine exposure promoted the chlorophyll fluorescence intensity at initial stage (24 h), suggesting that a large amount of energy is emitted in the form of fluorescence. However, the chlorophyll fluorescence intensity could not be detected under the high effective chlorine concentrations (6.7 × 10−3, 1.0 × 10−2, 1.3 × 10−2 and 1.7 × 10−2 mg L−1) after 48 h, indicating that the chlorine had high toxicity leading to the death of microalgae. In addition, the emission spectra of P. tricornutum were determined to contain two distinct fluorescence peaks representing the core antenna of photosystem II (685 nm) and the photosystem I complexes (710 nm) in the control group. The fluorescence emission peak value at 685 nm is significantly lower than the peak value at 710 nm in the control group, whereas chlorine treatments were opposite. It can be concluded that microalgae can regulate the distribution of excitation energy between the two photosystems to ensure that algae can utilize light energy. The result also found that the peak position of fluorescence emission spectra has a blue shift in all of NaClO treatments. The fluorescence intensity of microalgae excited at 467 nm was lower than that at 439 nm in chlorine treatments, illustrating chlorophyll b antenna was more easily damaged than chlorophyll a antenna. Our findings are providing new insights into the changing mechanism of chlorophyll fluorescence on P. tricornutum under chlorine stress and valuable data for risk assessment of marine environments.

Analysis of Fast Fluorescence Kinetics of a Single Cyanobacterium Trapped in an Optical Microcavity.

Photosynthesis is one the most important biological processes on earth, producing life-giving oxygen, and is the basis for a large variety of plant products. Measurable properties of photosynthesis provide information about its biophysical state, and in turn, the physiological conditions of a photoautotrophic organism. For instance, the chlorophyll fluorescence intensity of an intact photosystem is not constant as in the case of a single fluorescent dye in solution but shows temporal changes related to the quantum yield of the photosystem. Commercial photosystem analyzers already use the fluorescence kinetics characteristics of photosystems to infer the viability of organisms under investigation. Here, we provide a novel approach based on an optical Fabry-Pérot microcavity that enables the readout of photosynthetic properties and activity for an individual cyanobacterium. This approach offers a completely new dimension of information, which would normally be lost due to averaging in ensemble measurements obtained from a large population of bacteria.

Non-Destructive Monitoring of Ripening Process of the Underutilized Fruit Kadam Using Laser-Induced Fluorescence and Confocal Micro Raman Spectroscopy

Underutilized fruits like kadam are bio-reserves of numerous biochemical and minerals and have the potential to be used as food alternatives and supplements to fulfill the needs of malnourished populations. The production of quality fruits needs monitoring throughout the growth and ripening in order to build consumer and industry confidence. The nondestructive optical spectroscopic techniques have immense potential to monitor the growth and ripening indices of the fruits. Hence, this study explores the potential of laser-induced fluorescence and confocal micro Raman spectroscopy for the reliable and cost effective monitoring of growth and ripening of kadam fruits. The analysis of the laser-induced fluorescence measurements reveals that the ripening of the kadam fruits may be monitored by analyzing the fluorescence emission of chlorophyll and carotenoids. The decrease in the intensity of chlorophyll fluorescence accompanied by the increase in the intensity of the carotenoid bands is the characteristic fluorescence signature associated with the ripening of the kadam fruits. Hence, upon the ripening of the fruits, the concentration of chlorophyll decreases considerably with the accumulation of carotenoids. This fact is further complimented by confocal micro Raman measurements, which show that as the fruit ripens, the intensity of carotenoid bands increases dramatically. The observed spectral features may be used by the horticulture scientists and nutritionists to monitor the growth, maturity, and ripening of underutilized fruits like kadam in order to maximize the quality and minimize postharvest losses.

Combined contributions of carotenoids and chlorophylls in two-photon spectra of photosynthetic pigment-protein complexes-A new way to quantify carotenoid dark state to chlorophyll energy transfer?

Transitions into the first excited state of carotenoids, Car S1, are optically forbidden in conventional one-photon excitation (OPE) but are possible via two-photon excitation (TPE). This can be used to quantify the amount of Car S1 to Chlorophyll (Chl) energy transfer in pigment-protein complexes and plants by observing the chlorophyll fluorescence intensity after TPE in comparison to the intensity observed after direct chlorophyll OPE. A parameter, ΦCoupling Car S1-Chl, can be derived that directly reflects relative differences or changes in the Car S1 → Chl energy transfer of different pigment-protein complexes and even living plants. However, very careful calibrations are necessary to ensure similar OPE and TPE excitation probabilities and transition energies. In plants, the exact same sample spot must be observed at the same time. All this is experimentally quite demanding. ΦCoupling Car S1-Chl also corrects intrinsically for direct chlorophyll TPE caused by larger chlorophyll excesses in the complexes, but recently it turned out that in certain TPE wavelengths ranges, its contribution can be quite large. Fortunately, this finding opens also the possibility of determining ΦCoupling Car S1-Chl in a much easier way by directly comparing values in TPE spectra observed at wavelengths that are either more dominated by Cars or Chls. This avoids tedious comparisons of OPE and TPE experiments and potentially allows measurement at even only two TPE wavelengths. Here, we explored this new approach to determine ΦCoupling Car S1-Chl directly from single TPE spectra and present first examples using known experimental spectra from Cars, Chl a, Chl b, LHC II, and PS 1.

High throughput analysis of leaf chlorophyll content in sorghum using RGB, hyperspectral, and fluorescence imaging and sensor fusion

BackgroundLeaf chlorophyll content plays an important role in indicating plant stresses and nutrient status. Traditional approaches for the quantification of chlorophyll content mainly include acetone ethanol extraction, spectrophotometry and high-performance liquid chromatography. Such destructive methods based on laboratory procedures are time consuming, expensive, and not suitable for high-throughput analysis. High throughput imaging techniques are now widely used for non-destructive analysis of plant phenotypic traits. In this study three imaging modules (RGB, hyperspectral, and fluorescence imaging) were, separately and in combination, used to estimate chlorophyll content of sorghum plants in a greenhouse environment. Color features, spectral indices, and chlorophyll fluorescence intensity were extracted from these three types of images, and multiple linear regression models and PLSR (partial least squares regression) models were built to predict leaf chlorophyll content (measured by a handheld leaf chlorophyll meter) from the image features.ResultsThe models with a single color feature from RGB images predicted chlorophyll content with R2 ranging from 0.67 to 0.88. The models using the three spectral indices extracted from hyperspectral images (Ration Vegetation Index, Normalized Difference Vegetation Index, and Modified Chlorophyll Absorption Ratio Index) predicted chlorophyll content with R2 ranging from 0.77 to 0.78. The model using the fluorescence intensity extracted from fluorescence images predicted chlorophyll content with R2 of 0.79. The PLSR model that involved all the image features extracted from the three different imaging modules exhibited the best performance for predicting chlorophyll content, with R2 of 0.90. It was also found that inclusion of SLW (Specific Leaf Weight) into the image-based models further improved the chlorophyll prediction accuracy.ConclusionAll three imaging modules (RGB, hyperspectral, and fluorescence) tested in our study alone could estimate chlorophyll content of sorghum plants reasonably well. Fusing image features from different imaging modules with PLSR modeling significantly improved the predictive performance. Image-based phenotyping could provide a rapid and non-destructive approach for estimating chlorophyll content in sorghum.

Effects of sodium hypochlorite treatment on the chlorophyll fluorescence in photosystem II of microalgae

Chlorophyll fluorescence-based method shows great potentials for on-site assessing the vitality of algae in treated ship's ballast water. However, there is very limited information on the mechanism of chlorophyll fluorescence in photosystem II (PSII) after the NaClO treatment. In this paper, the effects of NaClO treatments with five concentrations (0.01, 0.04, 0.08, 0.12 and 0.15 mg/L) and treating periods (6, 24 and 48 h) on the chlorophyll fluorescence kinetics and spectra of Chlorella vulgaris (C. vulgaris) and Platymonas helgolandica (P. helgolandica) were investigated. Experimental results showed that both exposure time and dose were important factors that affect the toxicity of NaClO to microalgae. Further analyses showed that the maximum photochemical quantum yield of PSII, photochemical quenching and yield decreased rapidly with the increase in NaClO concentrations in the range of 0.04 mg/L to 0.15 mg/L, suggesting that NaClO seriously inhibited PSII reaction centers of algae. In addition, the maxima value of fluorescence at excitation wavelength still appeared near 437 nm and 468 nm under NaClO stress, pointing to the pigments for fluorescence produced by algae were mainly chlorophyll a and chlorophyll b antenna. As compared to chlorophyll a, the relative fluorescence intensity of chlorophyll b decreased significantly in the all of NaClO treatments. According to the fluorescence emission spectra, treatment of NaClO resulted in a shift of the maximum peak of C. vulgaris and P. helgolandica from 685.2 nm to 681.9 nm and 685.2 nm to 680.5 within 6 h, respectively. This indicates that the structure of antenna light-absorbing pigments of PSII changed under NaClO stress. These results revealed that the chlorophyll fluorescence mechanism in PSII of damaged microalgae occurred variation, which was important for the reliable application of on-site analysis of ballast water indicator based on chlorophyll fluorescence detection.

Solar-induced chlorophyll fluorescence intensity has a significant correlation with negative air ion release in forest canopy

Forest vegetation is an essential source of negative air ion (NAI) and influencing factor of the process. A number of studies have focused on the temporal and spatial changes of NAI in different forest communities and their relationship with meteorological factors; however, there is no literature on the relationship between solar-induced chlorophyll fluorescence intensity (SIF) and NAI, and quantitative research on relationship between NAI and photosynthesis of forest vegetation is comparatively limited. In this study, we investigated the dynamic changes NAI, SIF, and meteorological parameters in canopy during the growing season by using a flux tower at the sites Xiaolangdi and Minquan in a warm-temperate monsoon climate zone from June to September of 2019 and 2020. Results showed that the canopy NAI, SIF, and photosynthetically active radiation (PAR) showed significant diurnal and seasonal dynamic change characteristics, and that the changes in the observed indicators at different times were significantly different. The seasonal change characteristics of canopy NAI and SIF were relatively similar, and canopy SIF could accurately capture the dynamic changes of NAI. Additionally, the NAI–SIF relationship was increasingly significant at higher PAR levels, and the coefficient of determination (R2) of the two sites reached 0.652 and 0.570. It showed that when vegetation photosynthesis was fully activated, the dynamic change process of the canopy NAI provided a more robust correlation and more accurate estimation in the vegetation's main growth stage, thus demonstrating the reliability of SIF as an indicator for tracking NAI seasonal changes. In the future, automatic, continuous SIF observations could provide reliable understanding of the photosynthetic characteristics of terrestrial ecosystems, thereby quantifying the contribution potential of forest to NAI application in ground-based optical measurement and airborne and satellite remote sensing. This provides a working foundation for direct assessment of spatial and temporal distribution patterns of global seasonal NAI.

Assessment of the effect of heavy metal salts on the photosynthetic activity of aquatic plants

The status of the photosynthetic pigments in the aquatic plants Lemna minor L. and Elodea canadensis Michx. under the action of Ni2+, Co2+, Cu2+ and Pb2+ acetate in concentrations 5.00, 2.50, 1.25, 0.62, 0.31, 0.15, 0.07, and 0.03 mg/L was assessed by changes in the fluorescence intensity of chlorophyll a and b and their ratio. It was established that nickel acetate in original solutions in all the above concentrations caused an increase in the fluorescence intensity of chlorophylls a and b in L. minor in relation to the control while the lead salt suppressed it. Co2+ acetate inhibits the fluorescence of chlorophyll a with concentrations in the initial solutions of 0.03 to 0.15 and 2.50 mg/L and that of chlorophyll b at all concentrations, except 0.62, 1.25 and 2.50 mg/L. For E. canadensis it was found that the salts of all metals at all concentrations caused a reduction of the fluorescence intensity of chlorophyll a relative to the control and increased it in the case of chlorophyll b. The exception is the effect of copper and lead acetates with a concentration of 1.25 mg/L, when the fluorescence intensity of chlorophyll b is maintained at the control level. The presence of Ni2+, Co2+, Cu2+, and Pb2+ acetates in all concentrations in the culture medium influences the quantitative and qualitative characteristics of chlorophyll a and b, which indicates a violation of the photosynthesis process. Our data on the change in the chlorophyll a / b ratio leads to a conclusion about degradation of chlorophyll a relative to chlorophyll b after the effect of heavy metals.

Effects of Combined Nitrogen Deficient and Mixotrophic (+Glucose) Culture on the Lipid Accumulation of Parachlorella Kessleri TY

The combustion explosion of ordinary diesel is a global environmental problem. Green microalgae, which do not cause eutrophication, are a raw material that can be used to clean biodiesel. To increase lipid productivity, this study used a nitrogen deficient & mixotrophic (+Glucose) culture of lipid-producing microalgae Parachlorella kessleri TY from Shanxi Province, China. To examine the growth of P. kessleri TY, we measured dry weight, chlorophyll content, and chlorophyll fluorescence intensity under different culture conditions, in addition to the contents of neutral lipids, total lipids, and fatty acids, to examine its lipid accumulation ability. Cells were cultured in autotrophic, nitrogen deficient, mixotrophic (+Glucose), and nitrogen deficient & mixotrophic (+Glucose) conditions for 7 days. We found the growth of P. kessleri TY under nitrogen deficient & mixotrophic conditions was higher than that under the autotrophic and nitrogen deficient conditions, but lower than that under the mixotrophic (+Glucose) conditions. However, its lipid accumulation ability was significantly higher than that of control cultures. In conclusion, P. kessleri TY cultured under nitrogen-deficient and mixotrophic (+Glucose) conditions has significant lipid production capacity. Our results provide a theoretical basis for the use of microalgae as a raw material in the production of biodiesel, and promote the application of P. kessleri TY in large-scale production.

Droplet-based microfluidic screening and sorting of microalgal populations for strain engineering applications

The application of microfluidic technologies to microalgal research is particularly appealing since these approaches allow the precise control of the extracellular environment and offer a high-throughput approach to studying dynamic cellular processes. To expand the portfolio of applications, here we present a droplet-based microfluidic method for analysis and screening of Phaeodactylum tricornutum and Nannochloropsis gaditana, which can be integrated into a genetic transformation workflow. Following encapsulation of single cells in picolitre-sized droplets, fluorescence signals arising from each cell can be used to assess its phenotypic state. In this work, the chlorophyll fluorescence intensity of each cell was quantified and used to identify populations of P. tricornutum cells grown in different light conditions. Further, individual P. tricornutum or N. gaditana cells engineered to express green fluorescent protein were distinguished and sorted from wild-type cells. This has been exploited as a rapid screen for transformed cells within a population, bypassing a major bottleneck in algal transformation workflows and offering an alternative strategy for the identification of genetically modified strains.

Biosensing the Presence of Metal Nanoparticles by Spectrally- and Time-Resolved Endogenous Fluorescence in Water Moss Fontinalis antipyretica

Pollution by heavy metals represents a significant environmental burden. We employed confocal microscopy with spectral detection and fluorescence lifetime imaging (FLIM) to evaluate the effect of nanoparticles (NPs) from various metals (Zinc, Nickel, Cobalt, Copper) on endogenous fluorescence of Fontinalis antipyretica moss. Short term (3–5 day) exposure to NPs, designed and fabricated by direct synthesis using femtosecond laser ablation in water, was studied. The green flavonoid and/or lignin endogenous fluorescence peaking between 500 and 560 nm was found to be increased by Zn and significantly reduced by Cu. The overall red chlorophyll fluorescence intensity with a maximum of 680 nm remained largely unchanged after exposure to Ni and Zn, but was decreased in the presence of Co and completely abolished by Cu. All NPs but Zn induced changes in the fluorescence lifetimes, demonstrating increased sensitivity of this parameter to environmental pollution. Gathered data indicate fast responsiveness of the endogenous fluorescence in the Fontinalis antipyretica moss to the presence of heavy metals that can thus potentially serve as a biosensing tool for monitoring environmental pollution in the moss natural environment.

Experimental Study of the Quantitative Impact of Flow Turbulence on Algal Growth

Flow turbulence has been widely accepted as one of the essential factors affecting phytoplankton growth. In this study, laboratory cultures of Microcystis aeruginosa in beakers were carried out under different turbulent conditions to identify the quantitative relationship between the algal growth rate and the turbulent intensity. The turbulent intensity (represented by energy dissipation rate, ε) was simulated with the software FLUENT. Daily measurement of the two parameters (algal biomass and chlorophyll-a concentration) was carried out during the experimental period to represent the algal growth rate. Meanwhile, the rates of photosynthetic oxygen evolution and chlorophyll fluorescence intensity were calculated to investigate the photosynthetic efficiency. The results indicated that the growth rate of Microcystis aeruginosa became higher in the turbulent environment than in the still water environment under the designed experimental conditions. The peak growth rate of Microcystis aeruginosa occurred when ε was 6.44 × 10−2 m2/s3, over which the rate declined, probably due to unfavorable impacts of strong turbulence. In comparison, the maximum rate of photosynthetic oxygen evolution occurred when ε was 0.19 m2/s3. Based on the findings of this study, an exponential function was proposed in order to incorporate the effect of flow turbulence into the existing algal growth models, which usually just consider the impacts of nutrient availability, illumination, and temperature.

Induced mutagenesis for improving water stress tolerance in durum wheat (Triticumturgidum L. subsp. durum)

Over the Water deficit is considered to be one of the most important limiting factors for crop productivity worldwide. Thus, it is important to use water resources more efficiently. One of the ways to conserve water and respond to the climate change is by using appropriate crop species and cultivars, notably which have low requirements for water.Chemical mutagens have contributed immensely to the development of a wide range of genetic variability and the improvement of several crop plants, including durum wheat. This study has the aim of understanding the effect of water stress on some morpho-physiological parameters and identifying tolerant lines to water stress from an EMS-mutated population in durum wheat. The results, under moderate (T1) and severe (T2) conditions of water stress,show the positive effect of mutagenesis on the population resulting in tolerantmutated linesto water deficit. Compared to the non-mutated, 32.15% of lines have a higher specific leaf weight; 57.14% of lines have a better ability to maintain a high water content and 75% of all lines demonstrate a very high intensity of chlorophyll fluorescence .In sum, this study has revealed the improvement of water stress tolerance in some induced durum wheat mutants.

Measurement of airborne algal mortality rates due to heat shock treatment

Green and/or black soiling on building facades worldwide is caused by airborne algae, which has strong drought tolerance and grows in the atmosphere. Poikilohydric plants such as algae and lichens have high heat resistance under dry conditions and high thermo-sensitivity under wet conditions. However, there have been no studies of heat shock treatments against airborne algae adhering to surfaces. This study investigated the relationship between heat shock conditions (treatment temperature and duration and the water content of algae) and algal mortality. Algae collected from the exterior wall of a building were heat-treated in a laboratory, and their chlorophyll fluorescence intensity was measured. The following results were obtained: (a) higher treatment temperature and longer treatment time increased the rate of algal death, (b) the survival rate of heat-treated dry algae was higher than that of wet algae and recovered after the treatment, and (c) the effects of continuous and intermittent heat shock were similar, and algal mortality increased with the total treatment time. It was concluded that the airborne algae died after heat shock treatment at 35 °C for 24 h and at 40 °C after 6 h under wet conditions. Algae from an exterior concrete wall were heat-treated in a wet condition, and algal death was confirmed by the decrease in surface L* values and a color change from green to yellow.

Photochemical analysis for selection of stress tolerant plant

This electronic document is a “live” template and already defin This study was carried out to selection of abiotic stress tolerant plant species of sixty-eight plant species at Hantaek Botanical Garden in Korean using photochemical analysis. Many abiotic stresses have led to a decline in agricultural productivity and the disappearance of ecologically important plant species. Chlorophyll a fluorescence is a powerful tool to measure environmental stress response in plants. The polyphasic OJIP fluorescence transient was used to evaluate the behavior of Photosystem II (PSII) and Photosystem I (PSI) during the entire experiment period (from July to August). The photochemical reaction showed higher maximal chlorophyll fluorescence (Fp) intensity under heat and wet stress in forty-one plant species. In twenty seven plant species, chlorophyll fluorescence intensity showed a significant decrease.
 In wet stress, the fluorescence parameters related with electron transport on PSII and PSI reduced over twenty percent. As a result of the identifying under heat and wet stress, energy dissipation per reaction center (DIo/RC) was heavily affected.
 It was clearly indicated that the connectivity between photosynthetic PSII and PSI, i.e. electron transport, was far effective in the selection of stress tolerant plants.