High Light Intensity Conditions Research Articles

Effect of light intensity on the survival of European spiny lobster (Palinurus elephas) larvae reared in aquaculture system

Light plays a crucial role in the growth, development, and survival of aquatic organisms. To evaluate the survival of European spiny lobster (Palinurus elephas) larvae in relation to different light intensities (26, 359, and 910 lux, equivalent to 0.35, 4.74, and 12.29 μmol·m−2·s−1, respectively), this study monitored the survival rates of reared spiny lobster from the early instar phyllosoma stages to their metamorphosis into the puerulus stage (111 days after hatching) at the three light intensities. The newly hatched larvae were cultured in 65-L Kreisel tanks with 200 individuals each (three replicates per treatment, i.e., light intensity). Phyllosoma stages I to III larvae showed no significant differences in survival rates under different light intensities. However, light intensity did have a significant impact on the survival rates of phyllosoma stages IV and V as well as the metamorphosis of phyllosoma VI into puerulus. The highest survival rates were observed under high and medium light intensity conditions. At the end of the experiment, the highest mean survival rate for stage VI, the metamorphosis into the puerulus stage, was 42.0 ± 2.52 % under high light intensity. These survival rates for reared pueruli were 84 times higher than those achieved in previous studies. The present study results show promise for the successful implementation of commercial scale rearing protocols for European spiny lobster and have implications for the design of crustacean larvae culture systems.

Microalgae Haemococcus pluvialis, Cultured in OHM Medium under Stressful Conditions: Phenolic Content and Antioxidant Capacity

Haematococcus pluvialis, a unicellular green microalgae, is able to accumulate the large amounts of astaxathin under stress conditions. Nutritional factors such as nitrate or phosphate and light intensity play an important role in the growth, accumulation of phenolic compounds and antioxidant capacity microalgae H. pluvialis. In this study, H. pluvialis was cultured under three conditions of stress, nutrient depletion, denitrification of nitrate and addition of NPK fertilizer, and natural light in OHM medium to investigate the phenolic content and antioxidant capacity of the biomass of H. pluvialis microalgae. The results showed that, under denitrification of nitrate and addition of NPK fertilizer, the phenolic content reached a high value (8.054 µg gallic acid/g) and there was no significant difference with the two conditions of nutrient depletion (4.115 µg gallic acid/g) and natural light (4.707 µg gallic acid/g) (p<0.05). However, no differences were found between the antioxidant capacity under denitrification of nitrate and addition of NPK fertilizer (51.390%) and natural light (52.301%) (p=0.552) that were higher than nutrient depletion (45.257%) (p<0.05). Thus, under the stress conditions of nitrate depletion and high light intensity, H. pluvialis has the ability to synthesize and accumulate high amounts of bioactive compounds and microalgae biomass can be applied in dietary supplement and cosmeticeuticals.

The content of phenols and activity of polyphenol oxidase in the hametophyte of dominant mosses in forest ecosystems of the Ukrainian Roztochia

Bryophytes are indicators of the state of forest ecosystems. Dominant species of forest mosses are sensitive to the influence of abiotic factors and demonstrate adaptive reactions different from vascular plants, which are decisive for the prediction of changes in the natural environment. We have analyzed the changes in the content of water-soluble phenols and the activity of polyphenol oxidase n the hametophyte of dominant epigean forest mosses depending on changes in the intensity of insolation, the water and temperature regime of soils and air in experimental localities of forest ecosystems of the Ukrainian Roztochia. The highest content of water-soluble phenolic compounds was found in the resistant mosses Polytrichum formosum and Atrichum undulatum on the territory of protected beech forest under conditions of low light intensity and sufficient humidity of local vegetation. The maximum indicators of the content of phenolic compounds were found in A. undulatum (199.5±9.8 μg/g of dry matter mass), and the lowest – in Plagiomnium affine (54.7±2.6 μg/g of dry matter mass) that is sensitive to changes in the ecological conditions of local vegetation in all studied areas. A significant decrease in the content of phenolic compounds in areas of disturbed ecosystems may indicate the active participation of phenols in the adaptation of mosses to the effects of high light intensity, elevated temperatures and moisture deficit. The highest indicators of polyphenol oxidase activity were determined in P. affine (120.4±6.1 relative units/g of dry matter mass*s) and P. formosum (41.8±2.1 relative units/g of dry matter mass*s) from local vegetation under unfavorable conditions on the territory of stationary recreation. A direct correlation between the content of phenolic compounds and the activity of polyphenol oxidase was not established. The higher activity of this enzyme under conditions of high light intensity than in shaded local plants may indicate a relationship between polyphenol oxidase and photosynthesis. An increase in the activity of polyphenol oxidase contributes to the significant formation of quinones, which, accumulating in cell walls, reduce the processes of lipid peroxidation, regulate their permeability and ensure better moisture storage in the moss turfs.

Performance Evaluation of New Table Grape Varieties under High Light Intensity Conditions Based on the Photosynthetic and Chlorophyll Fluorescence Characteristics

The evaluation of photosynthetic characteristics of plants is important for the success rate of germplasm introduction. To select grape varieties with higher adaptability and trait performance, this experiment is aimed at evaluating and comparing the photosynthetic indices, chlorophyll fluorescence parameters, photosynthetic pigment content, and leaf characteristics of five Chinese hybrid varieties. The results showed that under high light intensity stress, the leaf growth of ‘Ruidu Cuixia’ was most affected and its specific leaf weight was the lowest, while ‘Jing Hongbao’ had the highest chlorophyll content. The maximum net photosynthetic rate (Pnmax), maximum light quantum yield (Fv/Fm), and apparent quantum efficiency (AQE) were different among varieties. It was reported that the ‘Ruidu Zaohong’ variety had the highest Pnmax. ‘Ruidu Wuheyi’ was found to have the highest Fv/Fm, while the highest AQE was recorded for ‘Ruidu Cuixia’, with intercellular CO2 concentration (Ci) and stomatal conductance (gs) at 292.56 μmol·mol−1, 766.56 mmol·m−2·s−1, and 66.8 μmol·m−2·s−1, respectively. The indices of ABS/CSm, TRo/CSm, and DIo/CSm were significantly different among varieties, and these indices of ‘Ruidu Zaohong’ were the highest. Pn was positively correlated with Ci and Tr, gs were positively correlated with Fv and TRo/CSm. The specific leaf area was negatively correlated with Fv/Fm and ΦDIo. The results of the principal component analysis and TOPSIS comprehensive evaluation showed that ‘Jing Hongbao’ and ‘Ruidu Cuixia’ performed best. Overall, the measurement of the photosynthetic characteristics of the plants during the growing period provided valuable data for the varietal introduction strategies. The better photosynthetic performance of ‘Jing Hongbao’ and ‘Ruidu Cuixia’ indicates more adaptability to the long day, high light intensity, and the high-temperature climate of Xinjiang.

Palliative Effects of Kaolin on Citrus Plants Under Controlled Stress Conditions of High Temperature and High Light Intensity

Under field conditions high temperatures are usually associated to high light intensity for periods of time that are getting longer because of global warming caused by climate change. These adverse conditions lead to significant reductions in yield and fruit quality in crops of great economic relevance such as citrus. In this work, the effect of high temperatures and high light intensity occurring alone or simultaneously has been studied in Carrizo citrange plants, a citrus genotype widely used as a rootstock, and the mitigating effect of kaolin (KL) evaluated. The combined stress conditions affected the plants in a unique manner at both, physiological and hormonal regulation levels, different to the effects of each individual stress. KL alleviated the deleterious effect of combined stress in different ways: (i) reducing leaf damage and abscission, (ii) improving physiological and gas exchange parameters, (iii) decreasing foliar proline content, (iv) increasing chlorophyll content, (v) preventing carotenoid degradation, and (vi) modulating levels of hormones and their precursors involved in plant responses to stress [abscisic acid (ABA), salicylic acid (SA), cinnamic acid (CA), indole-3-acetic acid (IAA), jasmonic acid (JA) and 12-oxophytodienoic acid (OPDA)].

Disinfection By-Products Formation from Chlor(am)ination of Algal Organic Matter of Chlorella sorokiniana.

Eutrophication in water reservoirs releases algal organic matter (AOM), which is an important precursor of disinfection by-products (DBPs) formed during water treatment. Chlorella sorokiniana is a microalgae which flourishes under conditions of high light intensity and temperature, thus its prevalence in algal blooms is expected to increase with climate change. However, Chlorella sorokiniana AOM has not been previously investigated as a DBP precursor. In this context, this study evaluated the effect of AOM concentration, humic acid (HA), and pH on DBP formation from chlor(am)ination of AOM Chlorella sorokiniana. DBP yields determined by linear regression for trichloromethane (TCM) and chloral hydrate (CH) were 57.9 and 46.0 µg·mg DOC-1 in chlorination, while the TCM, CH, dichloroacetonitrile (DCAN), 1,1,1-trichloropropanone (1,1,1-TCP), and chloropicrin (CPN) concentrations were 33.6, 29.8, 16.7, 2.1, and 1.2 µg·mg DOC-1 in chloramination. Chloramination reduced the formation of TCM and CH but increased CPN, DCAN, and 1,1,1-TCP yields. AOM Chlorella sorokiniana showed a higher DBP formation than 9 of 11 algae species previously investigated in the literature. At basic pH, the concentration of TCM increased while the concentration of other DBP classes decreased. Bromide was effectively incorporated into the AOM structure and high values of bromine incorporation factor were found for THM (1.81-1.89) and HAN (1.32) at 1.5 mg Br·L-1. Empirical models predicted successfully the formation of THM and HAN (R2 > 0.86). The bromide concentration had more impact in the model on the DBP formation than AOM and HA. These results provide the first insights into the DBP formation from AOM chlor(am)ination of Chlorella sorokiniana.

Larger responses of trees’ leaf senescence to cooling than warming: Results from a climate manipulation experiment

Global warming generally delays autumn leaf senescence, which affects carbon and water cycles of terrestrial ecosystem and exerts feedbacks on the climate system. Nevertheless, several regions in the Northern Hemisphere have experienced autumn cooling since the start of the 21st century. Whether cooling affects leaf senescence to the same extent as warming is currently unclear. In this study, we conducted a manipulative experiment with warming or cooling treatments imposed during summer and autumn on saplings of ginkgo and oak to investigate the effects of seasonal warming and cooling on leaf senescence. In addition, two light intensity and photoperiod treatments were applied to study their interactive effects with temperature on leaf senescence. We found that the temperature sensitivity of leaf senescence (ST) was significantly larger in autumn (5.4–6.4 days ℃−1) than in summer (0.6–2.4 days ℃−1). Interestingly, cooling had a larger effect on leaf senescence than warming, with a significantly higher ST under cooling (1.7–3.5 days ℃−1 in summer and 8.5–11.6 days ℃−1 in autumn) than under warming (0.8–1.0 days ℃−1 and 0.3–1.8 days ℃−1). Furthermore, higher light intensity significantly decreased the temperature sensitivity of leaf senescence especially in autumn, i.e. ST was 3.8 and 6.1 days ℃−1 under high light intensity condition, but the ST was 8.2 and 8.0 days ℃−1 under low light intensity, for ginkgo and oak, respectively. Our results suggest unequal effects of cooling and warming on leaf senescence, and radiation affects the leaf senescence processes by altering its temperature sensitivity. These findings enrich our understanding of leaf senescence and could be integrated into the ecosystem models to improve their performance.

Characteristics of a New Halotolerant Arctic Strain of Carotenogenic Microalga <i>Halochlorella rubescens</i> NAMSU SBB-20

Green microalgae capable of accumulating secondary carotenoids are the most important objects of biotechnology, and the search for new strains with unique properties, in particular, those adapted to growth at low temperatures and high salinity in the environment, is an urgent task. The NAMSU SBB-20 microalga strain was isolated from an algal-bacterial biofilm found on the coast of the White Sea in the littoral zone of the Solovetsky Archipelago. Identification of the strain showed its belonging to the species Halochlorella rubescens P.J.L.Dangeard. The species H. rubescens was first described for the White Sea. Under conditions of high light intensity, ultrastructural changes in cells are shown, among which destruction of the photosynthetic apparatus and the formation of cytoplasmic and chloroplast lipid inclusions are noted. It was shown that the culture of the NAMSU SBB-20 strain is capable of acquiring an orange color under unfavorable growth conditions. An assessment was made of the effect of the composition of the medium and the intensity of illumination on the pigment composition of the algae. The highest absolute values of the accumulation of carotenoids were noted during cultivation in light with an intensity of 150 mol PAR quanta/m2/s on BG-11 media containing no source of phosphorus (15.66 0.18 mg/L) or nitrogen (15.95 0.56 mg/L). The described strain has a biotechnological potential due to the initial halotolerance and the accumulation of high values of secondary carotenoids in the biomass.

Responses of photosynthesis and chlorophyll fluorescence during light induction in different seedling ages of Mahonia oiwakensis

BackgroundThe aim of this study was to determine the actual state of the photosynthetic apparatus and exhibit distinguishable differences in the chlorophyll fluorescence (ChlF) components in different seedling ages of M. oiwakensis plants subjected to different light intensity (LI). Potted 6-month-old greenhouse seedlings and field collected 2.4-year-old seedlings with 5 cm heights were selected and randomly separated into seven groups for photosynthesis measurements illuminated with 50, 100 (assigned as low LI), 300, 500, 1,000 (as moderate LI), 1,500 and 2,000 (as high LI) μmol m–2 s–1 photosynthetic photon flux density (PPFD) treatments.Resultsn 6-month-old seedlings, as LI increased from 50 to 2,000 PPFD, the values of non-photochemical quenching and photo-inhibitory quenching (qI) increased but potential quantum efficiency of PSII (Fv/Fm) and photochemical efficiency of photosystem II (ΦPSII) values decreased. High electron transport rate and percentage of actual PSII efficiency by Fv/Fm values were observed in 2.4-year-old seedlings at high LI conditions. Furthermore, higher ΦPSII was detected under low LI conditions, with lower energy-dependent quenching (qE) and qI values and photo-inhibition % decreased as well. However, qE and qI increased as ΦPSII decreased and photo-inhibition% increased under high LI treatments.ConclusionsThese results could be useful for predicting the changes in growth and distribution of Mahonia species grown in controlled environments and open fields with various combinations of varying light illuminations, and ecological monitoring of their restoration and habitat creation is important for provenance conservation and helps to formulate better conservation strategies for the seedlings.

Suppression of the HOS1 Gene Affects the Level of ROS Depending on Light and Cold.

The E3 ubiquitin-protein ligase HOS1 is an important integrator of temperature information and developmental processes. HOS1 is a negative regulator of plant cold tolerance, and silencing HOS1 leads to increased cold tolerance. In the present work, we studied ROS levels in hos1Cas9Arabidopsis thaliana plants, in which the HOS1 gene was silenced by disruption of the open reading frame via CRISPR/Cas9 technology. Confocal imaging of intracellular reactive oxygen species (ROS) showed that the hos1 mutation moderately increased levels of ROS under both low and high light (HL) conditions, but wild-type (WT) and hos1Cas9 plants exhibited similar ROS levels in the dark. Visualization of single cells did not reveal differences in the intracellular distribution of ROS between WT and hos1Cas9 plants. The hos1Cas9 plants contained a high basal level of ascorbic acid, maintained a normal balance between reduced and oxidized glutathione (GSH and GSSG), and generated a strong antioxidant defense response against paraquat under HL conditions. Under cold exposure, the hos1 mutation decreased the ROS level and substantially increased the expression of the ascorbate peroxidase genes Apx1 and Apx2. When plants were pre-exposed to cold and further exposed to HL, the expression of the NADPH oxidase genes RbohD and RbohF was increased in the hos1Cas9 plants but not in WT plants. hos1-mediated changes in the level of ROS are cold-dependent and cold-independent, which implies different levels of regulation. Our data indicate that HOS1 is required to maintain ROS homeostasis not only under cold conditions, but also under conditions of both low and high light intensity. It is likely that HOS1 prevents the overinduction of defense mechanisms to balance growth.

Enhanced astaxanthin production of Haematococcus pluvialis strains induced salt and high light resistance with gamma irradiation

This study was conducted to increase the productivity of biomass that contains high astaxanthin content by developing a mutant Haematococcus pluvialis strain with strong environmental tolerance. H. pluvialis has a low cell-growth rate and is vulnerable to stressors such as salinity or light intensity, which may hinder large-scale commercial cultivation. A mutant M5 strain selected through 5000-Gy gamma irradiation showed improved biomass and astaxanthin production under high-salinity and high-light intensity conditions. With enhanced SOD activity and overexpressed astaxanthin biosynthesis genes (lyc, crtR-b, bkt2), M5 demonstrated an increase in biomass and astaxanthin productivity by 86.70 % and 66.15 %, respectively compared to those of untreated cells. Also, the omega-3 content of M5 increased by 149.44 % under 40 mM CaCl2 compared to the untreated cells. Finally, even when subjected to high-intensity light irradiation for the whole life cycle, the biomass and astaxanthin concentration increased by 84.99 % and 241 %, respectively, compared to the wild-type cells.

Production of volatile organic iodine compounds by the marine cyanobacterium Calothrix parasitica under different light intensities

Volatile organic iodine compounds (VOICs) that exist in the marine environment, such as diiodomethane (CH2I2), chloroiodomethane (CH2ClI), and bromoiodomethane (CH2BrI), are known to transport iodine from the ocean to the atmosphere. These VOICs play important roles in various atmospheric chemistry processes, such as ozone decomposition. So far, marine phytoplankton such as diatoms and chlorarachniophytes have been reported to produce these VOICs in the culture experiments. In this study, we examined the production of VOICs by the marine cyanobacterium Calothrix parasitica NIES-267 (axenic) cultured at 24 °C for several weeks. The effect of light intensity on the production of VOICs was also studied by irradiating the culture medium of C. parasitica with light at intensities of 60, 90, and 120 μmol photons m−2 s−1. In addition, incubation experiments with 13CH2I2 added to the culture medium were performed to evaluate the decrease of 13CH2I2 due to photolysis during incubation. The concentrations of VOICs in the culture medium were measured using a purge-and-trap gas chromatograph-mass spectrometer. The concentrations of VOICs in the culture medium increased during the exponential or stationary phase at each light intensity. During the exponential phase, the chlorophyll a-normalized production rates of CH2ClI and CH2BrI increased with increasing light intensity from 60 to 120 μmol photons m−2 s−1, while the chlorophyll a-normalized maximum production rate of CH2I2 was found to be 28 pmol (μg chlorophyll a) −1 d−1 at 90 μmol photons m−2 s−1. During the incubation period, 13CH2I2 was photodegraded by about 17% at 120 μmol photons m−2 s−1. The relative production rates were CH2I2 > CH2ClI > CH2BrI for all light conditions, and the relative amount of CH2I2 tended to decrease under high light intensity conditions (120 μmol photons m−2 s−1). These results suggest that the cyanobacterium C. parasitica could be one of the significant sources of VOICs such as CH2I2 in the marine environment, and that light intensity would be an important factor in estimating VOICs emissions from marine cyanobacteria.

De Novo Assembly and Annotation of Microalga Tetradesmus obliquus Transcriptome

Tetradesmus obliquus is a unicellular green microalga and considered as a potential source for biotechnological production of pigments such as lutein. No genome-related data is available for T. obliquus that would increase the ability to develop new approaches in biotechnological applications. We present the first transcriptome data for T. obliquus. The aim of this study is to provide a comprehensive transcriptome annotation and identification of conserved genes involved in lutein pigment biosynthesis in Tetradesmus obliquus cells by analyzing pooled RNA-Seq data. Next-Generation Sequencing was applied for the pooled cDNAs library prepared by combining the cell cultures collected from samples exposed to dark and high light intensity conditions. Transcripts were assembled by the de novo assembly approach. Trinotate software was used for functional annotation of assembled transcripts. We also carried out BLAST analysis comparing the transcriptome data against known lutein biosynthesis genes. The 49.15% of the assembled sequences were functionally annotated, providing a total of 21490 unigenes. Our data also revealed the transcript sequences for ten conserved genes required for lutein biosynthesis. The data produced in this study can be used for molecular approaches in biotechnological applications related to T. obliquus, such as increasing the yield of pigment production.

Characteristics of Vacuolar Inclusions in Coelastrella rubescens Namsu R1 Green Microalgae Cells in Low- and High-Intensity Light

Coelastrella rubescens Kaufnerová & Eliás (Chlorophyceae) is a green, single-celled algae that lives in the terrestrial-air environment. Under stress conditions, its cells go into a state characterized by low photosynthetic activity and high content of reserve lipids and secondary carotenoids. For the first time, a comparative morphological, ultrastructural, and elemental analysis of vacuolar inclusions in the C. rubescens NAMSU R1 strain when cultivated on a mineral medium under conditions of low and high (causing stress) light intensity. Microalgae cells stained with the fluorescent dye DAPI showed signs of the presence of polyphosphates. Polarization microscopy in cells of C. rubescens has identified structures capable of refracting polarized light, which is typical of crystals. Cell analysis of C. rubescens with the transmission electron microscopy (TEM) method revealed the presence of various vacuoles with heterogeneous contents (autophagic bodies, crystalloids, and rounded globules of inhomogeneous electron density). With the exception of autophagic bodies noted in cells only in bright light, these inclusions were characteristic of microalgae cells, regardless of the intensity of illumination. The elemental composition of vacuolar inclusions was characterized by TEM in combination with energy-dispersive X-ray spectroscopy: the predominant content of nitrogen, phosphorus, or both elements simultaneously was established in them. The potential physiological role of C. rubescens vacuolar inclusions is discussed.

Optimal Growth Conditions for Azolla pinnata R. Brown: Impacts of Light Intensity, Nitrogen Addition, pH Control, and Humidity

Nitrogen pollution from agriculture is a major challenge facing our society today. Biological nitrogen fixation is key to combat the damage that is caused by synthetic nitrogen. Azolla spp. are ideal candidates for fast nitrogen fixation. This study aimed to investigate the optimal growth conditions for Azolla pinnata R. Brown. The growth conditions that were investigated included the growth medium type and strength, light intensity, the presence/absence of nitrogen in the medium, pH control, and humidity. Higher light intensities increased plant growth by 32%, on average. The highest humidity (90%) yielded higher growth rate values than lower humidity values (60% and 75%). The presence of nitrogen in the medium had no significant effect on the growth rate of the plants. pH control was critical under the fast growth conditions of high light intensity and high humidity, and it reduced algal growth (from visual observation). The optimal growth rate that was achieved was 0.321 day−1, with a doubling time of 2.16 days. This was achieved by using a 15% strength of the Hoagland solution, high light intensity (20,000 lx), nitrogen present in the medium, and pH control at 90% humidity. These optimised conditions could offer an improvement to the existing phytoremediation systems of Azolla pinnata and aid in the fight against synthetic nitrogen pollution.

Monitoring of growth and biochemical composition of Dunaliella salina and Dunaliella polymorpha in different photobioreactors

In this study, the isolation of green algae were collected from two different stations of Aegean Sea and Seyfe Lake. The molecular identification of Dunaliella species using their 18S ribosomal DNA genes were sequenced and investigated with the BLAST program in the NCBI database. After the morphological and molecular identification, two different Dunaliella species were deposited in Ege University Microalgae Culture Collection. D. salina and D. polymorpha cells were firstly produce in both bubble column to monitor the growth profiles and then the species were cultivated in bubble column and stirred column photobioreactors (PBRs) under both high light intensity and different mixing conditions to investigate the total protein, carbohydrate, lipids and carotenoid concentrations. Moreover, this study aims to evaluate the production of β-carotene using two different PBRs. As a result of this study, D. salina in stirred PBR obtained the highest lipid (334.79 ±0.02 mg/L), total carotenoid (96.7 ±0.02 mg/L), and β-carotene content (21.18 ±0.03 µg/mL), while the maximum dry cell mass of 0.906 g/L was reached by D. polymorpha in bubble column PBR. The aim of this study was to investigate the nutritional values and β-carotene content of Dunaliella salina and D. polymorpha isolated from Turkey.

The difficulty of estimating the electron transport rate at photosystem I.

It is still a controversial issue how the electron transport reaction is carried out around photosystem I (PSI) in the photosynthetic electron transport chain. The measurable component in PSI is the oxidized P700, the reaction center chlorophyll in PSI, as the absorbance changes at 820-830nm. Previously, the quantum yield at PSI [Y(I)] has been estimated as the existence probability of the photo-oxidizable P700 by applying the saturated-pulse illumination (SP; 10,000-20,000µmol photons m-2s-1). The electron transport rate (ETR) at PSI has been estimated from the Y(I) value, which was larger than the reaction rate at PSII, evaluated as the quantum yield of PSII, especially under stress-conditions such as CO2-limited and high light intensity conditions. Therefore, it has been considered that the extra electron flow at PSI was enhanced at the stress condition and played an important role in dealing with the excessive light energy. However, some pieces of evidence were reported that the excessive electron flow at PSI would be ignorable from other aspects. In the present research, we confirmed that the Y(I) value estimated by the SP method could be easily misestimated by the limitation of the electron donation to PSI. Moreover, we estimated the quantitative turnover rate of P700+ by the light-to-dark transition. However, the turnover rate of P700 was much slower than the ETR at PSII. It is still hard to quantitatively estimate the ETR at PSI by the current techniques.

Effects of two water regimes on morphological traits, nutritive value and physiology of three Bituminaria bituminosa varieties from the Canary Islands

AbstractMorphological traits, nutritive values and physiological responses to two different water regimes of three Bituminaria bituminosa varieties: var. albomarginata, var. crassiuscula and var. bituminosa were evaluated in a greenhouse experiment. Two water regimes were imposed for 63 days; well‐watered (WW) plants and deficit‐watered (DW) plants, both starting from a high soil water content (dripping point). The three varieties showed similar aerial biomass reduction under reduced watering, 50% for var. albomarginata, 51% for var. bituminosa and 43% for var. crassiuscula. Var. Albomarginata showed lower shoot biomass under both water regimes than var. bituminosa (56.2% in WW plants and 55.2% in DW plants) and var. crassiuscula (52% in WW plants and 57.8% in DW plants). This lower shoot biomass could be attributed to the high initial soil water content imposed in this experiment, affecting early development. This hypothesis is supported by the lower root biomass production of var. albomarginata and its distribution. The DW treatment of this experiment was not sufficiently restrictive to cause morphological modifications, whilst of the forage quality variables analysed, only ash was affected. Var. crassiuscula and var. albomarginata had a lower specific leaf area (239 cm2 g‐1 and 235 cm2 g‐1, respectively) than var. bituminosa (352 cm2 g‐1), which might represent an important adaptation to high light intensity and temperature conditions. The values of stem mass fraction (SMF) and leaf mass fraction (LMF) for var. crassiuscula (SMF = 0.36 and LMF = 0.28) and var. albomarginata (SMF = 0.35 and LMF = 0.36) indicated better forage aptitude of these varieties than var. bituminosa (SMF = 0.50 and LMF = 0.19). All varieties showed good values of crude protein and digestibility, although important differences were found between leaf and stem. According to the studied morphological, nutritional and physiological traits, var. albomarginata showed the best aptitude for being introduced as permanent grasslands in some Mediterranean farming systems. However, the possible susceptibility of var. albomarginata to high water content in the soil could limit its introduction. These results help to inform the potential use of these three Canarian B. bituminosa varieties to improve Mediterranean rainfed grasslands of extensive farming systems.

High Productivity of Eicosapentaenoic Acid and Fucoxanthin by a Marine Diatom Chaetoceros gracilis in a Semi-Continuous Culture.

Significantly high eicosapentaenoic acid (EPA) and fucoxanthin contents with high production rate were achieved in semi continuous culture of marine diatom. Effects of dilution rate on the production of biomass and high value biocompounds such as EPA and fucoxanthin were evaluated in semi-continuous cultures of Chaetoceros gracilis under high light condition. Cellular dry weight increased at lower dilution rate and higher light intensity conditions, and cell size strongly affected EPA and fucoxanthin contents. The smaller microalgae cells showed significantly higher (p < 0.05) value of 17.1 mg g-dw–1 fucoxanthin and 41.5% EPA content per total fatty acid compared to those observed in the larger cells. Chaetoceros gracilis can accumulate relatively higher EPA and fucoxanthin than those reported previously. In addition, maintenance of small cell size by supplying sufficient nutrients and light energy can be the key for the increase production of valuable biocompounds in C. gracilis.

Analysis of β-d-glucan biosynthetic genes in oat reveals glucan synthesis regulation by light.

Oat (Avena sativa) has human health benefits when consumed as a whole-grain food, attributed to the high content of (1,3;1,4)-β-d-glucan (mixed-linkage glucan [MLG]), but little is known about the synthase genes and synthesis mechanism of MLG polysaccharides in this species. The concentration of oat MLGs under different light intensities was measured by a standard enzymatic approach and further verified by immunoelectron microscopy. The effect of light intensity on MLG synthase genes was examined by RT-qPCR and western blot analyses. The pattern of expression directed by the promoter of the oat MLG synthase gene was also investigated by histochemical β-glucuronidase (GUS) analysis. The oat orthologues of genes implicated in the synthesis of MLG in other cereals, including cellulose synthase-like (Csl) F, H and J gene families, were defined. Transcript profiling of these genes across oat tissues indicated that AsCslF6 transcripts dominated. Under high light intensities, the expression of AsCslF6, a major isoform of the MLG synthase genes, increased to >30 % of the dark growth control. The amount of MLG in oat rose from 0.07 to 1.06 % with increased light intensity. Histochemical tests showed that the AsCslF6 gene promoter preferentially directs GUS expression under high light intensity conditions. Oat MLG synthesis is regulated by light. High light intensity upregulates the expression of the MLG synthase AsCslF6 gene, leading to an increase in the amount of MLG in oat leaves.