Cultivation of Euglena gracilis on Residues from a Food Industry

The economic red macroalga Gracilaria lemaneiformis was selected to study light intensity effects on its grow th,photosynthesis,effective quantum efficiencies( Yield) and pigments contents in aerated and non-aerated cultures. Three different light intensities w ere as follow s: 50 μmol /( m2· s)( low light intensity),100 μmol /( m2·s)( moderate light intensity),and 200 μmol/( m2·s)( high light intensity). The results show ed that the highest grow th rate of G. lemaneiformis w as observed w hen alga w as treated w ith moderate light intensity,and too low or too high light intensity inhibited its grow th. The relative grow th rates of aerated cultured algae,under the low light intensity,moderate light intensity and high light intensity,w ere increased by 26. 85%,31. 82% and 40. 56%,respectively. In aerated culture,the photosynthetic rate and the photosynthetic efficiency of alga treated w ith low light intensity increased by 8. 14% and 4. 26%,and the respiration rate of alga under high light intensity decreased by 20. 70%,and Yield increased by 44. 16%. The results suggested that reduced grow th w as mainly due to the limited photosynthesis in case of low light intensity,or could be ascribed to the increased respiration in case of high light intensity. Aerated culture could relieve the negative effect on the grow th rate of alga as a result of for low light or high light intensity.

Effects of gluconate on biomass improvement and light stress tolerance of Haematococcus pluvialis in mixotrophic culture

In order to evaluate the response of two soybean cultivars (032 and BP) to cold stress [control (28°C) and cold stress (5°C)] at two light intensity levels [normal light (8000 lux) or low light (2000 lux) intensity], an experiment was done in a factorial arrangement based on completely randomized design with three replicates under greenhouse conditions. The results clearly showed that leaf number and chlorophyll a and ab contents in soybean seedlings have a tendency to decrease (31, 17 and 14 %, respectively) by cold stress while stem diameter markedly increased (up to 15) as compared to those grown under control conditions. Cold stress reduced nodes number, plant height and chlorophyll content (SPAD value) in two light intensities, however, this effect is more noticeable at low light intensity for nod numbers (31%) and plant height (56%) and at high light intensity for SPAD value (21%). Cold stress also significantly suppressed plant height in both cultivars (52% in 032 and 47% in BP). Where light intensity increased from 2000 to 8000 lux, 032 plants exhibited slightly increase in stem diameter and chlorophyll b while BP plants exhibited 9 and 21% decrease , respectively. In conclusion, cold stress in either 2000 or 8000 lux could adversely affect morphological parameters of soybean plants, however, the rate of damage increased at low light intensity.

Leaf mesostructure, photochemical activity, and chloroplast photophosphorylation (PP) in the fourth true leaf of 28-day-old Chinese cabbage (Brassica chinensis L.) plants were investigated. Plants were grown under a light source based on red (650 nm) and blue (470 nm) light-emitting diodes (LED) with red/blue photon flux ratio of 7: 1 and under illumination with high-pressure sodium lamp (HPSL) at photon flux densities of 391 ± 24 μmol/(m2 s) (“normal irradiance”) and 107 ± 9 μmol/(m2 s) (“low irradiance”) in photosynthetically active range. At normal irradiance, the leaf area in plants grown under HPSL was twofold higher than in LED-illuminated plants; other parameters of leaf mesostructure were little affected by spectral quality of incident light. The lowering of growth irradiance reduced the majority of leaf mesostructure parameters in plants grown under illumination with HPSL, whereas in LED-illuminated plants the lowered irradiance reduced only specific leaf weight but increased the leaf thickness and dimensions of mesophyll cells and chloroplasts. The photochemical activity of isolated chloroplasts was almost independent of growth irradiance and light spectral quality. Light quality and intensity used for plant growing had a considerable impact on PP in chloroplasts. At normal light intensity, the highest activity of noncyclic PP in chloroplasts was observed for plants grown under HPSL; at low light intensity the highest rates of PP were noted for plants grown under LED. The P/2e− ratio, which characterizes the degree of PP coupling to electron transport in the chloroplast electron transport chain, showed a similar pattern. Thus, the narrow-band spectrum of the light source had little influence on leaf mesostructure and electron transport rates. However, this spectrum significantly affected the chloroplast PP activity. The PP patterns at low and normal light intensities were opposite for plants grown under LED and HPSL light sources. We suppose that growing plants under LED array at normal light intensity disturbed the chloroplast coupling system, thus preventing the effective use of light energy for ATP synthesis. At low light intensity, chloroplast PP activity was significantly higher under LED illumination, but plant growth was suppressed because of impaired adaptation to low light intensity.

Two types with regard to adaptation to different light intensities are described: tbe Chlorella type and the Cyclotella type. The Chlorella type is mostly found among the green algae, the Cyclotella type among the diatoms. The Chlorella type adapts to a new light intensity mainly by changing the pigment content. Therefore the cells adapted to a high light intensity have a lower chlorophyll a content per cell than cells adapted to a low light intensity. Light saturation is mostly rather low for cells adapted to low light intensities. The light-saturated rate of photosynthesisist mostly lower for cells adapted to a high light intensity than for cells adapted to a low light intensity. The actual photosynthesis is not much higher at a high light intensity than at a low one. The actual photosynthesis is the photosynthesis at the light intensity where the cells are grown. - The Cyclotella type adapts only by changing the light-saturated rate. The chlorophyll content is the same in cells grown at low and high light intensities. Light saturation for cells grown at a low light intensity is rather high. The light-saturated rate is much higher in the case examined at the high light intensity than at the low one. The actual photosynthesis is considerably higher for cells grown at the high light intensities than for cells grown at low light intensities.- The two adaptation types are not sharply separated since transition types occur.

Effects of C5 organic carbon and light on growth and cell activity of Haematococcus pluvialis under mixotrophic conditions

Small sea urchins Strongylocentrotus intermedius (1–2 cm of test diameter) are exposed to different environments of light intensities after being reseeded to the sea bottom. With little information available about the behavioral responses of S. intermedius to different light intensities in the environment, we carried out an investigation on how S. intermedius is affected by three light intensity environments in terms of phototaxis, foraging and righting behaviors. They were no light (zero lx), low light intensity (24–209 lx) and high light intensity (252–2,280 lx). Light intensity had obvious different effects on phototaxis. In low light intensity, sea urchins moved more and spent significantly more time at the higher intensity (69–209 lx) (P = 0.046). S. intermedius in high light intensity, in contrast, spent significantly more time at lower intensity (252–690 lx) (P = 0.005). Unexpectedly, no significant difference of movement (average velocity and total distance covered) was found among the three light intensities (P > 0.05). Foraging behavior of S. intermedius was significantly different among the light intensities. In the no light environment, only three of ten S. intermedius found food within 7 min. In low light intensity, nine of 10 sea urchins showed successful foraging behavior to the food placed at 209 lx, which was significantly higher than the ratio of the number (two of 10) when food was placed at 24 lx (P = 0.005). In the high light intensity, in contrast, significantly less sea urchins (three of 10) found food placed at the higher light intensity (2,280 lx) compared with the lower light intensity (252 lx) (10/10, P = 0.003). Furthermore, S. intermedius showed significantly longer righting response time in the high light intensity compared with both no light (P = 0.001) and low light intensity (P = 0.031). No significant difference was found in righting behavior between no light and low light intensity (P = 0.892). The present study indicates that light intensity significantly affects phototaxis, foraging and righting behaviors of S. intermedius and that ~200 lx might be the appropriate light intensity for reseeding small S. intermedius.

Multilayer vertical production systems using sole-source (SS) light-emitting diodes (LEDs) can be an alternative to more traditional methods of microgreens production. One significant benefit of using LEDs is the ability to select light qualities that have beneficial impacts on plant morphology and the synthesis of health-promoting phytochemicals. Therefore, the objective of this study was to quantify the impacts of SS LEDs of different light qualities and intensities on the phytochemical content of brassica ( Brassica sp.) microgreens. Specifically, phytochemical measurements included 1) total anthocyanins, 2) total and individual carotenoids, 3) total and individual chlorophylls, and 4) total phenolics. Kohlrabi ( Brassica oleracea var. gongylodes ), mustard ( Brassica juncea ‘Garnet Giant’), and mizuna ( Brassica rapa var. japonica ) were grown in hydroponic tray systems placed on multilayer shelves in a walk-in growth chamber. A daily light integral (DLI) of 6, 12, or 18 mol·m −2 ·d −1 was achieved from SS LED arrays with light ratios (percent) of red:blue 87:13 (R 87 :B 13 ), red:far-red:blue 84:7:9 (R 84 :FR 7 :B 9 ), or red:green:blue 74:18:8 (R 74 :G 18 :B 8 ) with a total photon flux from 400 to 800 nm of 105, 210, or 315 µmol·m −2 ·s –1 for 16 hours, respectively. Phytochemical measurements were collected using spectrophotometry and high-performance liquid chromatography (HPLC). Regardless of light quality, total carotenoids were significantly lower under increasing light intensities for mizuna and mustard microgreens. In addition, light quality affected total integrated chlorophyll with higher values observed under the light ratio of R 87 :B 13 compared with R 84 :FR 7 :B 9 and R 74 :G 18 :B 8 for kohlrabi and mustard microgreens, respectively. For kohlrabi, with increasing light intensities, the total concentration of anthocyanins was greater compared with those grown under lower light intensities. In addition, for kohlrabi, the light ratios of R 87 :B 13 or R 84 :FR 7 :B 9 produced significantly higher anthocyanin concentrations compared with the light ratio of R 74 :G 18 :B 8 under a light intensity of 315 µmol·m −2 ·s −1 . Light quality also influenced the total phenolic concentration of kohlrabi microgreens, with significantly greater levels for the light ratio of R 84 :FR 7 :B 9 compared with R 74 :G 18 :B 8 under a light intensity of 105 µmol·m −2 ·s −1 . However, the impact of light intensity on total phenolic concentration of kohlrabi was not significant. The results from this study provide further insight into the selection of light qualities and intensities using SS LEDs to achieve preferred phytochemical content of brassica microgreens.

Synergistic effects of temperature and light intensity on growth and physiological performance in Chaetoceros calcitrans

The aim of this study was to investigate the effects of light intensity and enhanced nitrogen supply on the growth and photosynthesis of the green-tide macroalga, Ulva prolifera. Thalli of U. prolifera were grown in natural or NH (4) (+) -enriched seawater under two different light intensities for 7 days, and then the growth rate, pigmentation, and photosynthetic performance of the thalli were evaluated. The results show that the relative growth rate (RGR) was markedly higher under the high light level than under the low light level. Enrichment with NH (4) (+) enhanced the RGR under high light intensity, but did not affect RGR under low light intensity. In low light conditions, NH (4) (+) -enrichment resulted in a marked decrease in the maximal photosynthetic rate (P (m)) and the maximum carbon fixation rate (V (max)), but it did not affect the half saturation constant for carbon (K (0.5)) or the ratio of V (max) to K (0.5), which reflects the carbon acquisition efficiency. In high light conditions, P (m), K (0.5), and the dark respiration rate (R (d)) increased under NH (4) (+) enrichment, but V (max) and the V (max) / K (0.5) ratio decreased. Regardless of the light intensity, NH (4) (+) -enrichment did not affect the apparent photosynthetic efficiency (alpha), which reflects the ability of the alga to use light energy at low light levels. Under both low and high light intensities, the chlorophyll a (Chl a), chlorophyll b (Chl b), and carotenoids (Car) contents in thalli were higher in NH (4) (+) -enriched than in natural seawater, except that there was a decrease in the Chl b content of thalli in NH (4) (+) -enriched seawater under low light intensity. Therefore, NH (4) (+) enrichment improved the growth and photosynthetic performance of U. prolifera under high light intensity, but not under low light intensity. We discuss the possible mechanisms underlying these physiological responses.

Various environmental factors not only affect plant growth and physiological responses individually but also interact with each other. To examine the impact of light intensity on the drought responses of sweet basil, plants were subjected to maintenance of two substrate volumetric water contents (VWC) using a sensor-based automated irrigation system under two distinct light intensities. The VWC threshold was set to either a dry (0.2 m3·m−3) or sufficiently wet condition (0.6 m3·m−3) under low (170 μmol·m−2·s−1) or high light intensities (500 μmol·m−2·s−1). The growth and physiological responses of sweet basil (Ocimum basilicum L.) were observed over 21 days in the four treatment groups, where the combination of two environmental factors was analyzed. Under high light intensity, sweet basil showed lower Fv/Fm and quantum yield of PSII, compared to that under low light intensity, regardless of drought treatment. Fourteen days after drought treatment under high light intensity, stomatal conductance and the photosynthetic rate significantly reduced. Whereas plants under low light intensity showed similar stomatal conductance and photosynthetic rates regardless of drought treatment. Assessment of shoot and root dry weights revealed that plant growth decline caused by drought was more pronounced under high light intensity than under low light intensity. Thus, sweet basil showed significant declines in growth and physiological responses owing to drought only under high light intensity; no significant changes were observed under low light intensity.

It is already known that light quality and intensity have major influences on the growth, etiolation, germination, and morphology of many plant species, but there is limited information about the effect of wavelength and light intensity on nutrient absorption by plants. Therefore, this study was established to evaluate the plant growth, stomata formation, chlorophyll index, and absorption of macro- and micronutrients by common bean plants under six light treatments. The experimental design was completely randomized and consisted of six treatments: strong blue (blue LED at high light intensity); weak blue (blue LED at low light intensity); strong red (red LED at high light intensity); weak red (red LED at low light intensity; pink (combined red + blue LED), and white (combined red + white led). The stomatal density (stomata mm−2); the SPAD index; plant height (cm); root length (cm); plant dry weight (g); root dry weight (g); and the concentrations of N, S, K, Mg, Ca, B, Zn, Mn, and Fe on leaf analysis were influenced by all treatments. We found that plant photomorphogenesis is controlled not only by the wavelength, but also by the light intensity. Etiolation was observed in bean plants under blue light at low intensity, but when the same wavelength had more intensity, the etiolation did not happen, and the plant height was the same as plants under multichromatic lights (pink and white light). The smallest plants showed the largest roots, some of the highest chlorophyll contents, and some of the highest stomatal densities, and consequently, the highest dry weight, under white LED, showing that the multichromatic light at high intensity resulted in better conditions for the plants in carbon fixation. The effect of blue light on plant morphology is intensity-dependent. Plants under multichromatic light tend to have lower concentrations of N, K, Mg, and Cu in their leaves, but the final amount of these nutrients absorbed is higher because of the higher dry weight of these plants. Plants under blue light at high intensity tended to have lower concentrations of N, Cu, B, and Zn when compared to the same wavelength at low intensity, and their dry weight was not different from plants grown under pink light. New studies are needed to understand how and on what occasions intense blue light can replace red light in plant physiology.

Predation by Neoseiulus cucumeris on western flower thrips, and its oviposition on greenhouse cucumber under winter vs. summer conditions in a temperate climate

CO2 uptake and various leaf parameters were examined including photosynthetic pigment content (chlorophyll a, b, and total carotenoids), fresh/dry weight, percentage of water content, gram dry weight/area, and total plantlet leaf areas of an aseptically cultured clone of red raspberry (Rubus idaeus L.) incubated at 5 light intensities, from 2 to 6 klx. Cultured plantlets demonstrated relatively low levels of CO2 uptake, averaging 2.5 mg CO2 dm–2hr–1 and rarely exceeding 4 mg CO2 dm–2 hr–1 at saturating light intensities. Pigment content was higher in plantlets incubated at lower light intensities (2 to 4 klx). Cultures incubated at 3 klx were evaluated both at the time of transfer to soil and 1 month later. Plantlet leaves retained from culture could be distinguished from new leaves by tagging all plantlet leaves prior to soil transfer; both were assessed separately 1 month after transplantation. Leaves retained from culture, 30% of the total leaf area of transplants, contributed less than 10% of the CO2 uptake at 3 klx. These leaves accounted for 10% to 30% of the total leaf area at higher light intensities but were net respirers. There was an increase in dry matter accumulation at 6 and 9 klx in these tagged leaves, but not at 3 klx. Continued accumulation of dry matter by the tagged leaves can be only at the expense of photosynthetic activity of the newly formed leaves. New leaves of transplants had a greater dry matter accumulation at 9 klx and a pigment content greater than the tagged leaves. Their pigment content was similar to that of young, control plant leaves. Transplants were capable of uptake rates of 5–7 mg CO2 dm–2 hr–1 or 50% of field control rates. The photosynthetic contribution of the leaves from culture was small or negative. The first new leaves formed in soil were transitional with intermediate capability. Acclimatization to the soil environment was time dependent and required the production of new leaves initiated in the new environment.

The newly described phototrophic dinoflagellate Alexandrium pohangense, APPH1409, fed only on the dinoflagellate Margalefidinium polykrikoides among 16 potential algal prey species tested. To explore the ecophysiology of A. pohangense, its growth and ingestion rates with and without added M. polykrikoides prey were determined as a function of light intensity (0–346 µmol photons m−2 s−1) and temperature (10–35 °C). Both the autotrophic and mixotrophic growth rates of A. pohangense fed on M. polykrikoides were significantly affected by light intensity. In the darkness, A. pohangense did not grow under either mixotrophic or phototrophic conditions. The compensation light intensity for the growth of A. pohangense under mixotrophic conditions (2.7 µmol photons m−2 s−1) was lower than that under autotrophic conditions (11.7 µmol photons m−2 s−1). Growth inhibition due to light stress did not occur at the tested light intensities. A. pohangense grew between 15 and 30 °C, but did not grow at 10 °C or ≥ 32 °C. Both the autotrophic and mixotrophic growth rates of A. pohangense fed on M. polykrikoides were also significantly affected by temperature. At the same light intensity or temperature, the mixotrophic growth rate of A. pohangense was generally considerably greater than the autotrophic growth rate, with a few exceptions. Therefore, light intensity, water temperature, and prey accessibility may affect the population dynamics of this species.