Protein,fatty acid,and pigment content of <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> under different light regimes

The effects of irradiance and photoperiod on growth rates, chlorophyll a, β-carotene, total protein, and fatty acid content of Chlorella vulgaris were determined. The maximum growth rate (1.13 day⁻¹) was at 100 μmol photons m⁻² s⁻¹ and 16:8-h light/dark photoperiod. Chlorophyll a and β-carotene contents significantly differed under different light regimes with chlorophyll a content lower at high irradiance and longer light duration, while β-carotene showed the inverse trend. The total protein and fatty acid content also significantly differed in different light regimes; the maximum percentage of protein (46%) was at 100 μmol photons m⁻² s⁻¹ and 16:8 h photoperiod, and minimum (33%) was at 37.5 μmol photons m⁻² s⁻¹ and 8:16 h photoperiod; the total saturated fatty acids increased, while monounsaturated and polyunsaturated fatty acids decreased with increasing irradiance and light duration.     

<Emphasis Type="Italic">Petunia</Emphasis> × <Emphasis Type="Italic">hybrida</Emphasis> during transition to flowering as affected by light intensity and quality treatments

Petunia × hybrida was grown under high (H), medium (M) and low (L) light intensity [photoperiod; 16 h d⁻¹, photosynthetic photon flux density (PPFD); 360, 120 and 40 μmol m⁻² s⁻¹, respectively] as well as under end-of-day (EOD) red (R) and far-red (FR) light quality treatments [photoperiod; 14.5 h d⁻¹, PPFD; 30 μmol m⁻² s⁻¹ EOD; 15 min, Control (C) light; without EOD light treatment]. Shoot growth, leaf anatomical and photosynthetic responses as well as the responses of peroxidase (POD) isoforms and their specific activities following transition to flowering (1–6 weeks) were evaluated. Flower bud formation of Petunia × hybrida was achieved at the end of the 4th week for H light treatment and on the end of the 6th week for FR light treatment. No flower bud formation was noticed in the C and R light treatments. H and M light treatments induced lower chlorophyll (Chla, Chlb, Chla+b) concentrations in comparison to L light. On the other hand R and FR light chlorophyll content were similar to C light. Photosynthetic parameters [CO₂ assimilation rate (A), transpiration rate (E) and stomatal conductance (g _s) values] were higher in the H light treated plants in comparison to M and L light treated plants. A, E and g _s values of R and FR light were similar to C light plants. Leaf anatomy revealed that total leaf thickness, thickness of the contained tissues (epidermis, palisade and spongy parenchyma) and relative volume percentages of the leaf histological components were differently affected within the light intensity and the light quality treatments. POD specific activities increased from the 1st to the 6th week during transition to flowering. Native-PAGE analysis revealed the appearance of four anionic POD (A₁–A₄) isoforms in all light treatments. On the basis of the leaf anatomical, photosynthetic and plant morphological responses, the production of high quality Petunia × hybrida plants with optimal flowering times could be achieved through the control of both light intensity and light quality. The appearance of A₁ and A₂ anionic POD isoforms could be also used for successful scheduling under light treatments.     

Effects of light and temperature on the attachment and development of <Emphasis Type="BoldItalic">Gloiopeltis tenax</Emphasis> and <Emphasis Type="BoldItalic">Gloiopeltis furcata</Emphasis> tetraspores

Two 60-day experiments were conducted to study the influence of photon flux density (PFD) and temperature on the attachment and development of Gloiopeltis tenax and Gloiopeltis furcata tetraspores. In the first experiment, tetraspores of the two Gloiopeltis species were incubated at five temperature ranges (8°C, 12°C, 16°C, 20°C, 24°C) under a constant PFD of 80 μmol photons m⁻² s⁻¹ with a photoperiod of 12:12. In a second experiment, tetraspores were incubated under five PFD gradients (30, 55, 80, 105, 130 μmol photons m⁻² s⁻¹) at a constant temperature of 16°C with a photoperiod of 12:12. Maximum density of attached tetraspores was observed at 16°C for both species. Maximum per cent of spore germinating into disc was recorded at 12–16°C for G. tenax and 8–12°C for G. furcata. Maximum per cent of discs producing erect axes for G. tenax and G. furcata were recorded at 24°C and 20°C, respectively. Light had no significant effect on tetraspore attachment and developing into disc, but it affected the growth, sprouting and survival of its discs. Under 30–55 μmol photons m⁻² s⁻¹, the discs of the two species of Gloiopeltis did not form thallus until the end of the experiment. Optimum PFD range for G. tenax discs was 80–105 μmol photons m⁻² s⁻¹, whilst it was 80–130 μmol photons m⁻² s⁻¹ for G. furcata. Results presented in this study are expected to assist the progress of artificial seeding of Gloiopeltis.     

Optimal Light Regime for the Cultivation of Transgenic Laminaria japonica Gametophytes in a Bubble-column Bioreactor

Fluctuating light intensity had a more significant impact on growth of gametophytes of transgenic Laminaria japonica in a 2500 ml bubble-column bioreactor than constant light intensity. A fluctuating light intensity between 10 and 110 μE m⁻² s⁻¹, with a photoperiod of 14 h:10 h light:dark, was the best regime for growth giving 1430 mg biomass l⁻¹.     

Photon flux density and light quality induce changes in growth,stomatal development,photosynthesis and transpiration of <Emphasis Type="Italic">Withania Somnifera</Emphasis> (L.) Dunal. plantlets

The aim of the study was to establish whether the quantity and the quality of light affect growth and development of Withania somnifera plantlets. We have studied growth and histo-physiological parameters [stomatal characteristics, chloroplastic pigments concentrations, photosynthesis, and transpiration (E)] of W. somnifera plantlets regenerated under various light intensities, or monochromatic light or under a mixture of two colors of light in tissue culture conditions. Plantlets grown under a photon flux density (PFD) of 30 μmol m^-2 s^-1 showed greater growth and development than those raised under other PFDs. Chlorophylls and carotenoids, numbers of stomata, rate of photosynthesis (P_N) and transpiration (E), stomatal conductance (g_s), and water use efficiency (WUE) increased with increasing the PFD up to 60 μmol m^-2 s^-1. Light quality also affected plantlets growth and physiology. Highest growth was observed under fluorescent and in a mixture of blue and red light. Very few stomata were developed in any of the monochromatic light but under fluorescent or under a mixture of two colors stomatal numbers increased. Similarly, g_s, E, P_N, and WUE were also higher under fluorescent light and under a mixture of red and blue light. Regressional analysis showed a linear relationship between P_N (r ² = 70) and g_s and between E (r ² = 0.95) and g_s. In conclusion, both the quality and the quantity of light affect growth of plantlets, development of stomata and physiological responses differently depending on the intensity and the wavelength of light.     

Early development of germlings of <Emphasis Type="Italic">Sargassum thunbergii</Emphasis> (Fucales,Phaeophyta) under laboratory conditions

Morphology and culture studies on germlings of Sargassum thunbergii (Mertens et Roth) Kuntze were carried out under controlled laboratory conditions. Growth characteristics of these germlings grown under different temperatures (from 10 to 25°C), irradiances (from 9 to 88 μmol photons m⁻² s⁻¹), and under blue and white light conditions are described. The development of embryonic germlings follows the classic “8 nuclei 1 egg” type described for Sargassaceae. Fertilized eggs spent 5–6 h developing into multicellular germlings with abundant rhizoids after fertilization. Under conditions of 20°C, 44 μmol photons m⁻² s⁻¹ and photoperiod of 12 h, young germlings with one or two leaflets reached 2–3 mm in length after 8 weeks. Temperature variations (10, 15, 20, 25°C) under 88 μmol photons m⁻² s⁻¹ significantly influenced the growth rate within the first week, although this effect became less obvious after 8 weeks, especially at 15 and 20°C. Variation in germling growth was highly significant under different irradiances (9, 18, 44, 88 μmol photons m⁻² s⁻¹) at 25°C. Low temperature (10°C) reduced germling growth. Growth of germlings cultured under blue light was lower than in white light. Optimal growth of these germlings occurred at 25°C and 44 μmol photons m⁻² s⁻¹.     

Plant regeneration via somatic embryogenesis of <Emphasis Type="Italic">Camptotheca acuminata</Emphasis> in temporary immersion system (TIS)

The present study describes a protocol for plant regeneration via somatic embryogenesis in temporary immersion system (TIS) for Camptotheca acuminata. Somatic embryos were induced by culturing hypocotyl segments from 14-day-old in vitro grown C. acuminata seedlings in TIS. Hypocotyl segments were placed in culture vessels modified with a mechanical device to support the fixation of explants. Cultures were maintained under a 16 h photoperiod with a light intensity of 60 μmol m⁻² s⁻¹ PPF at 25 ± 1°C. After 16 weeks of incubation embryogenic calli were formed above the edge of the mechanical device in the basal Murashige and Skoog (MS) medium containing 35 g l⁻¹ sucrose and without hormonal supplementation. For plantlet regeneration, somatic embryos at cotyledonary stage were cultured in three different concentrations of 6-benzylamino-purine (0.5, 1.0 and 1.5 mg l⁻¹ BAP) and in plant growth regulator (PGR) free medium. In general, 0.5 mg l⁻¹ BAP was found to be the most effective concentration for growth and development of Camptotheca embryos in TIS. Conversion of somatic embryos into plantlets was also successfully achieved on sterile substrates moistened with 0.5 mg l⁻¹ BAP. Plantlets derived from cotyledonary embryos were rooted in vitro with 0.5 mg l⁻¹ indole-3-butyric acid (IBA) before transfer to ex vitro conditions.     

Effects of light, CO2 and humidity on carnation growth, hyperhydration and cuticular wax development in a mist reactor

Summary Plant survival ex vitro requires functioning stomata, adequate cuticular wax composition and deposition, and normal morphological development. Light intensity, CO₂ and relative humidity were altered inside an acoustic window mist reactor to study their effects on carnation (Dianthus caryophyllus) growth, stomata development, hyperhydration and epicuticular wax content. Increasing the light intensity from 65 to 145 μmol m⁻² s⁻¹ and enrichment of the gas phase with CO₂ (1350 ppm) reduced the number of hyperhydrated plants from 75 to 25% and increased the percentage dry weight of normal (healthy) plants from 17 to 25%. Lowering the relative humidity (≈70% RH) surrounding the plants during the mist-off phase for the last 2 wk of culture reduced the number of hyperhydrated plants from 70 to 9% and also increased the percentage of dry weight of normal plants from 16 to 25%. The stomata on plants grown in conditions of high light or low humidity had smaller apertures and appeared sunken when compared to stomata from plants grown in low light and high relative humidity. The epicuticular wax profiles of plants from the greenhouse or Magenta boxes showed a distinct shift in wax compounds with developmental age, plant type (hyperhydrated or normal), and type of box that was used (vented or not). In addition, very different wax profiles were observed from plants grown in reactors with altered CO₂ and light intensities.     

Changes in the condition of photosynthetic apparatus of a diatom alga <Emphasis Type="Italic">Thallassiosira weisflogii</Emphasis> during photoadaptation and photodamage

Two populations of a diatom alga Thallassiosira weisflogii were grown at photon flux densities (PFD) of 0.8 and 8 μmol/(m² s). For both diatom populations, the recovery of chlorophyll fluorescence parameters (F ₀, F _m, F _v/F _m, and NPQ) was monitored after nondestructive irradiation by visible light at PFD of 40 μmol/(m² s) and after high-intensity irradiation by visible light (1000–4000 μmol/(m² s)). The exposure of diatoms to PFD of 40 μmol/(m² s)—higher than PFD used for algal growth but still nondamaging to photosynthetic apparatus—induced nonphotochemical quenching (NPQ), which was stronger in algae grown at higher PFD (8 μmol/(m² s)) than in algae grown at low light. After irradiation with high-intensity light, the recovery of chlorophyll fluorescence parameters was more pronounced in algae grown at elevated PFD level. During short-term irradiation of diatoms with high-intensity visible light (1000 μmol/(m² s)), a stronger NPQ was observed in the culture adapted to high irradiance. After the treatment of algae with dithiothreitol (an inhibitor of carotenoid deepoxidase in the diadinoxanthin cycle) or NH₄Cl (an agent abolishing the proton gradient at thylakoid membranes), a short exposure of algae to PFD of 40 μmol/(m² s) induced hardly any nonphotochemical quenching. The results indicate the dominant contribution of xanthophyll cycle carotenoids to energy-dependent quenching.     

Marine Plankton Algae Grown with Light-Dark Cycles.

The diatoms Ditylum brightwellii and Nitzschia turgidula were grown in semi-continuous culture under various combinations of light intensity, temperature and daylength (photoperiod). Growth was strongly limited by light intensities below 0.03 cal/em². min in both species. Above this intensity, light saturation of growth was rapidly approached in Nitzschia but only gradually so in Ditylum. The growth rate in continuous light was never significantly higher than with 16 hours of light plus 8 hours of dark. In Ditylum, continuous light above 0.03 cal/cm². min caused a strong inhibition of growth at all temperatures. The chlorophyll concentration in the cells was greater the shorter the photopceriod. In cultures synchronised by different combinations of light intensity and photoperiod, cell division generally took place in the light. Synchrony was best under short photoperiods of bright light. Time courses are shown for chlorophyll synthesis and photosynthesis in synchronised cultures.     

Photoinhibition of photosynthesis in dwarf bean (Phaseolus vulgaris L.) leaves: effect of sink-limitations induced by changes in daily photon receipt

Bean (Phaseolus vulgaris L. cv. Long John) plants were grown with photoperiods of 6 and 16 h at constant photon flux density (PFD), giving a daily photon receipt (DPR) of 17 and 48 mol · m⁻² respectively. Vegetative growth was determined at regular intervals and diurnal whole-plant photosynthesis measured. Intact trifoliate leaves were exposed to photoinhibitory treatments at PFDs of 800 and 1400 μmol · m⁻² · s⁻¹ at temperatures of 14 and 20 °C, both in the absence and presence of the inhibitors chloramphenicol and dithiothreitol. Fluorescence and photon yields were determined at regular intervals throughout each treatment. Plants grown with photoperiods of 6 h had significantly lower growth rates than those grown with 16-h photoperiod but no difference in net photosynthetic rates or photon yields were found. Carbohydrate analyses confirmed short-day plants were strongly sink-limited. Long-day plants were slightly sink-limited, with a high proportion of starch in the leaves and reduced photosynthesis between 13 and 16 h. Plants grown in low DPR were more susceptible to photoinhibition, from sustained closure of some photosystem II reaction centres, than plants grown in high DPR. Capacity for thermal dissipation appeared dependent on PFD while photochemical capacity was more dependent on DPR. Received: 6 June 1997 / Accepted: 17 September 1997     

Effects of light intensity and nitrogen starvation on growth, total fatty acids and arachidonic acid in the green microalga Parietochloris incisa

The effects of light and nitrogen deficiency on biomass, fatty acid content and composition were studied in Parietochloris incisa, the unicellular freshwater chlorophyte accumulating very high amounts of arachidonic-acid-rich triacylglycerols. P. incisa cultures grown on complete nutrient medium and under high light (400 μmol photons m^{− 2} s⁻¹) showed the highest rate of growth in comparison to medium (200 μmol photons m⁻² s⁻¹) and low (35 μmol photons m⁻² s⁻¹) light intensity. Cultures grown under high light (on complete BG-11 medium) attained higher volumetric contents of total fatty acids and arachidonic acid due to greater increase in biomass. Nitrogen starvation brought about a strong increase in the arachidonic acid proportion of total fatty acids. Thus, adjustments to cultivation conditions could serve as an efficient tool for manipulation of yield and relative content of arachidonic acid in P. incisa. The significance of the changes in lipid metabolism for adaptation of P. incisa to high-light stress and nitrogen deficiency is also discussed.     

The impact of ozone fumigation and fertilization on chlorophyll fluorescence of birch leaves (Betula pendula)

 The impact of ozone fumigation on chlorophyll a fluorescence parameters and chlorophyll content of birch trees grown at high and low fertilization were studied for 6-, 8-, and 12-week old leaves. Fluorescence parameters were measured with a portable fluorometer with its fibre optics tightly inserted in a gas exchange cuvette at light intensities from 0 to 220 μmol photons m⁻² s⁻¹. Ozone caused significant changes of primary photosynthetic reactions: a decrease of the quantum yield of photosystem II and an increase of non-photochemical quenching. In all leaves a biphasic light response of non-photochemical quenching was observed. Ozone fumigation shifted the onset of the second phase from a PFD of about 60 μmol m⁻² s⁻¹ to about 30 μmol m⁻² s⁻¹. While the fertilizer concentration had no influence on this character, high fertilization supply of plants partially reduced O₃-induced damage. The light responses of Ft, Fm′ and NPQ observed in birch leaves grown in O₃-free air indicate the existence of at least two different processes governing energy conversion of the photosynthetic apparatus at PS II in the range of PFD 0–200 μmol photons m⁻² s⁻¹. The first phase was attributed to a rather slowly relaxing type of non-photochemical quenching, which, at least at low PFD, is thought to be related to a state 1–2 transition. The further changes of the fluorescence parameters studied at higher PFD might be explained by an increase of energy-dependent quenching, connected with the energization of the thylakoid membrane and zeaxanthin synthesis. A major effect of ozone treatment was a lowering of PS II quantum yield. This reflects a reduction of PS II electron transport and corresponds to the reduction of CO₂-fixation observed in ozonated leaves. Received: 24 September 1996 / Accepted: 27 January 1999     

<Emphasis Type="Italic">In vitro</Emphasis> culture of <Emphasis Type="Italic">Chrysanthemum</Emphasis> plantlets using light-emitting diodes

Effects of illumination spectrum on the morphogenesis of chrysanthemum plantlets (Chrysanthemum morifolium Ramat. ‘Ellen’) grown in vitro were studied using an illumination system consisting of four groups of light-emitting diodes (LEDs) in the following spectral regions: blue (450nm), red (640nm), red (660nm), and far-red (735nm). Taking into account all differences in shoot height, root length, and fresh and dry weight (FW and DW, respectively), observed while changing the total photon flux density (PFD), the optimal total PFD for growth of chrysanthemum plantlets in vitro was estimated. For 16 h photoperiod and typical fractions of the spectral components (14%, 50%, 28%, and 8%, respectively), the optimal total PFD was found to be 40 μmol m⁻² s⁻¹. Our study shows that the blue component in the illumination spectrum inhibits the plantlet extension and formation of roots and simultaneously increases the DW to FW ratio and content of photosynthetic pigments. We demonstrate photomorphogenetic effects in the blue region and its interaction with the fractional PFD of the far-red spectral component. Under constant fractional PFD of the blue component, the root number, length of roots and stems, and fresh weight of the plantlets have a correlated nonmonotonous dependence on the fractional PFD of the far-red component.     

Light-Dependency of Growth and Secondary Metabolite Production in the Captive Zooxanthellate Soft Coral Sinularia flexibilis

The branching zooxanthellate soft coral Sinularia flexibillis releases antimicrobial and toxic compounds with potential pharmaceutical importance. As photosynthesis by the symbiotic algae is vital to the host, the light-dependency of the coral, including its specific growth rate (μ day⁻¹) and the physiological response to a range of light intensities (10–1,000 μmol quanta m⁻² s⁻¹) was studied for 12 weeks. Although a range of irradiances from 100 to 400 μmol quanta m⁻² s⁻¹ was favorable for S. flexibilis, based on chlorophyll content, a light intensity around 100 μmol quanta m⁻² s⁻¹ was found to be optimal. The contents of both zooxanthellae and chlorophyll a were highest at 100 μmol quanta m⁻² s⁻¹. The specific budding rate showed almost the same pattern as the specific growth rate. The concentration of the terpene flexibilide, produced by this species, increased at high light intensities (200–600 μmol quanta m⁻² s⁻¹).     

Description of the individual growth of Daphnia magna (Crustacea: Cladocera) through the von Bertalanffy growth equation. Effect of photoperiod and temperature

Daphnia magna is a cladoceran used as a model organism in aquatic ecology and ecotoxicology studies. Because growth is a critical parameter to study the effect of environmental conditions on the development of zooplankters, the somatic growth of D. magna was measured here and described by the von Bertalanffy growth equation (VBGE), a mathematical model widely used in fisheries management. For this purpose, the effect of two temperatures (20 and 25°C) and two photoperiod conditions (12:12 and 16:8, light:dark) was assayed. Experiments began with neonate females and were finished when parthenogenetic females reached the age of 41 days; they were fed the microalga Ankistrodesmus falcatus (400,000 cell ml⁻¹, 12 mg l⁻¹, dry weight). According to the VBGE, maximal length (L _max) was inversely correlated with the growth rate (K). The highest L _max (6.45 mm) was for the females grown at 20°C with the 12:12 photoperiod, whereas the maximum growth rate (K = 0.182 ± 0.010) was for individuals grown at 25°C with the 12:12 photoperiod. The number of clutches during the studied period was significantly higher for females grown at 25°C, 12:12. Temperature affected the growth rate and the maximum size in D. magna; interaction of temperature with photoperiod was also noteworthy. The VBGE was a nifty way to assess the effects of the tested environmental factors.     

Light intensity determines the extent of mercury toxicity in the cyanobacterium Nostoc muscorum

The extent of mercury (Hg) toxicity in the heterocystous cyanobacterium Nostoc muscorum grown for 72 h in three different light intensities was tested for various physiological parameters viz. growth, pigment contents, photosynthesis, respiration, reactive oxygen species (ROS), malondialdehyde formation and antioxidants. A general reduction in growth and pigments, whole cell O₂-evolution, photosynthetic electron transport activities and ¹⁴CO₂-fixation was observed in a metal concentration–dependent manner, and this effect was more pronounced in high light (130 μmol photon m⁻² s⁻¹)–exposed cells as compared to low (10 μmol photon m⁻² s⁻¹) and normal (70 μmol photon m⁻² s⁻¹) light intensity–exposed cells; however, carotenoids and respiration showed reverse trend. Among photosynthetic electron transport activities, whole chain activity was found to be most sensitive in comparison with photosystem II (PS II) and photosystem I (PS I). Comparing the different photosynthetic processes, ¹⁴CO₂-fixation was most affected in cyanobacterial cells when exposed to Hg and different light intensities. After application of various exogenous electron donors, diphenyl carbazide was found to be more effective to restore PS II activity, suggesting that site of damage lies in between oxygen evolving complex and PS II. Level of oxidative stress (superoxide radical and lipid peroxidation) was maximum at 3.0 μM of Hg when coupled with high light intensity (except hydrogen peroxide). A dose-dependent increase in enzymatic antioxidants such as superoxide dismutase, peroxidase and catalase as well as non-enzymatic antioxidants such as proline, ascorbate, cysteine (except under high light intensity) and non-protein thiols [NP-SH] was observed, which further increased with the increase in light intensity. It was noticed that Hg intoxicates N. muscorum through ROS production, which is aggravated along with the increase in light intensity. Overall results suggest that the severity of the metal stress does increase with Hg concentrations but when coupled with light, it was the light intensity that determines the extent of Hg toxicity.     

Light colour influences the behaviour and stress physiology of captive tench (<Emphasis Type="Italic">Tinca tinca</Emphasis>)

Groups of juvenile tench (7.02 ± 0.28 g) were reared under four different light regimes; blue light, red light (80 Wm⁻² 12L:12D photoperiod) white light (912 ± 210 lux, 80 Wm⁻², 12L:12D photoperiod) and no light (0 lux) (0L:24D). Visibility of fish out of shelters was used as an indicator of activity and was monitored by video recording. Blood plasma cortisol concentrations were also measured. Fish under blue or white light were significantly less active during the photophase than those under red or no light (P < 0.01). Red light produced similar activity patterns to fish receiving 24 h darkness. Plasma cortisol concentrations were also significantly influenced (P < 0.05) with the fish under white light having the highest plasma cortisol concentration (317 ± 62 ng cm⁻³) compared to fish in the dark treatment (106 ± 36 ng cm⁻³). Thus, the provision of coloured light filters increases activity in juvenile tench and may reduce their intrinsic stress level.     

Effect of light-emitting diodes on growth and morphogenesis of upland cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) plantlets in vitro

The objective of this study was to determine the effects of different light-emitting diode (LED) light sources on the growth of upland cotton (Gossypium hirsutum L.) plantlets. Shoot bud apex cuttings of upland cotton (1.0 cm) were transplanted on Murashige and Skoog (MS) basal medium supplemented with 0.1 mg/l 6-benzyladenine (BA) and 0.5 mg/l naphthalene acetic acid (NAA) and cultured in vitro for 45 days. They were exposed to 50 μmol m⁻² s⁻¹ photosynthetic photon flux (PPF) and a 12-h photoperiod under six different lights: fluorescent lamp (CON), monochromatic blue LED (B), three blue and red LED mixtures (B:R = 3:1, 1:1, 1:3) and monochromatic red LED (R). The effects of the six light sources on growth and morphogenesis of upland cotton plantlets grown in vitro were investigated. Fresh weight, dry weight, stem length and second internode length were greatest in plantlets cultured under the B:R = 1:1 blue and red LED light, followed by blue LED light, and they were lowest in plantlets cultured under a fluorescent lamp. Chlorophyll content, leaf thickness, palisade tissue length, leaf and stomata area were highest in plantlets cultured under blue LED light. Root activity, sucrose, starch and soluble sugar contents were highest in plantlets cultured under red LED light. Our results showed that larger, healthier plantlets and a greater biomass of upland cotton were produced in the presence of red LED supplemented with a quantity of blue LED light. Blue and red LED (B:R = 1:1) was the most suitable light for the growth of upland cotton plantlets in vitro, and it may be used as alternative light source for an upland cotton culture system.     

Effects of temperature,photosynthetic photon flux density,photoperiod and O<Subscript>2</Subscript> and CO<Subscript>2</Subscript> concentrations on growth rates of the symbiotic dinoflagellate, <Emphasis Type="Italic">Amphidinium</Emphasis> sp.

Symbiotic dinoflagellates of the species Amphidinium are expected to be pharmaceutically useful microalgae because they produce antitumor macrolides. A microalgae production system with a large number of cells at a high density has been developed for the efficient production of macrolide compounds. In the present study, the effects of culture conditions on the cellular growth rate of dinoflagellates were investigated to determine the optimum culture conditions for obtaining high yields of microalgae. Amphidinium species was cultured under conditions with six temperature levels (21–35°C), six levels of photosynthetic photon flux density (15–70 μmol photons m⁻² s⁻¹), three levels of CO₂ concentration (0.02–0.1%), and three levels of O₂ concentration (0.2–21%). The number of cells cultured in a certain volume of solution was monitored microscopically and the cellular growth rate was expressed as the specific growth rate. The maximum specific growth rate was 0.022 h⁻¹ at a temperature of 26°C and O₂ concentration of 5%, and the specific growth rate was saturated at a CO₂ concentration of 0.05%, a photosynthetic photon flux density of 35 μmol photons m⁻² s⁻¹ and a photoperiod of 12 h day⁻¹ upon increasing each environmental parameter. The results demonstrate that Amphidinium species can multiply efficiently under conditions of relatively low light intensity and low O₂ concentration.