Influence Of Different Light Intensities Research Articles

Varying levels of natural light intensity affect the phyto-biochemical compounds, antioxidant indices and genes involved in the monoterpene biosynthetic pathway of Origanum majorana L.

BackgroundLight is a critical environmental factor in plants, encompassing two vital aspects: intensity and quality. To assess the influence of different light intensities on Origanum majorana L., pots containing the herb were subjected to four levels of light intensity: 20, 50, 70, and 100% natural light. After a 60-day treatment period, the plants were evaluated for metabolite production, including total sugar content, protein, dry weight, antioxidant indices, expression of monoterpenes biosynthesis genes, and essential oil compounds. The experimental design followed a randomized complete blocks format, and statistical analysis of variance was conducted.ResultsThe results indicated a correlation between increased light intensity and elevated total sugar and protein content, which contributed to improved plant dry weight. The highest levels of hydrogen peroxide and malondialdehyde (MDA) were observed under 100% light intensity. Catalase and superoxide dismutase enzymes exhibited increased activity, with a 4.23-fold and 2.14-fold increase, respectively, under full light. In contrast, peroxidase and polyphenol oxidase enzyme activities decreased by 3.29-fold and 3.24-fold, respectively. As light intensity increases, the expression level of the 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) gene increases. However, beyond a light intensity of 70%, the DXR gene expression level decreased. Furthermore, the expression levels of the cytochrome P450 genes CYP71D178 and CYP71D179 exhibited an increasing trend in response to elevated light intensity. Essential oil content increased from 0.02 to 0.5% until reaching 70% light intensity. However, with further increases in light intensity, the essential oil content decreased by 54 to 0.23%.ConclusionsThese findings emphasize the importance of balancing plant growth promotion and stress management under different light conditions. The research suggests that sweet marjoram plants thrive best in unshaded open spaces, resulting in maximum biomass. However, essential oil production decreases under the same conditions. For farmers in areas with an average light intensity of approximately 1700 µmol m−2s−1, it is recommended to cultivate sweet marjoram in shade-free fields to optimize biomass and essential oil production. Towards the end of the growth cycle, it is advisable to use shades that allow 70% of light to pass through. The specific duration of shade implementation can be further explored in future research.

Maltese Coastline Never Sleeps: The Effects of Artificial Light at Night (ALAN) on the Local Infralittoral Assemblages—A Case Study

Aside from the most notorious threats, the Mediterranean Sea faces novel and poorly explored impacts from artificial light at night (ALAN), which influences natural light–dark cycles and affects marine ecosystems. This study investigates the impact of ALAN on coastal infralittoral assemblages in Malta, where such effects remain unexplored. Using Baited Remote Underwater Videos (BRUVs), we examined the influence of different light intensities on species assemblages and behaviour at two sites: a light-polluted harbour and a darker reef area. Our findings reveal significant differences in fish community composition between light treatments and habitats. Among the 23,955 individuals recorded across multiple taxa, Boops boops accounted for 80% of observations. From our results, light intensity had a more substantial impact on community structure than habitat type, with species-specific responses to light. Predatory species such as Trachurus trachurus displayed increased activity under high-intensity white light, while Apogon imberbis and Serranus scriba were more abundant under red light, irrespective of habitat. These results underscore the role of ALAN in altering marine community dynamics and emphasise the need for sustainable management strategies to mitigate its impact on the biodiversity of the Mediterranean. This study provides initial empirical evidence of ALAN’s effects in Maltese waters, contributing to broader efforts to understand and manage light pollution in marine ecosystems.

Influence of different light intensities during the day on the motor activity in adolescents

This study investigates the impact of varying light intensities throughout the day on motor activity levels in adolescent girls aged between 14-16, who are students at a boarding school. The study lasted for three weeks, with each week consisting of four days. During this period, participants experienced three different lighting conditions from 07:00 to 18:00. These conditions included: standard light intensity in real-life settings, wearing blue-blocking glasses, and spending at least 1.5 hours outdoors daily for natural light exposure. The aim was to understand how modern lighting sources can replace natural lighting and to assess the influence of the lighting spectrum on the daily rhythms of motor activity. Restriction of blue light led to an increase in the average daily level (MESOR) of the intensity of movements denoted by HPIM (High Proportional Integrative Measures), as well as a decrease in the amplitude of the circadian rhythm ZCM (Zero Crossing Mode). This confirms the important role of blue light during the daytime as a Zeitgeber of the circadian rhythm. When adolescents spent at least 1.5 hours outside, mostly in the afternoon, the acrophases of ZCM’s 24-hour rhythm shifted half an hour later.

INTERAKCJA POMIĘDZY INTENSYWNOŚCIĄ ŚWIATŁA A STRESEM SUSZY I ICH WPŁYW NA WZROST SIEWEK PSZENICY

In this paper, wheat seedlings were exposed to different levels of photon flux density (PFD) and drought stress. Seedlings of the wheat cv. Goplana were cultivated in controlled conditions in a miniphytotrone and exposed to three different photosynthetic photon flux densities (400, 800, and 1200 μmol⋅m−2⋅s−1) and drought stress (a water potential of −0.6 MPa). The Hoagland’s solution-treat- ed seedlings served as a control. The fresh and dry matter of the overground parts and roots, rela- tive chlorophyll concentration, electrical conductivity and chlorophyll fluorescence parameters were measured. Drought stress decreased the biomass of wheat seedlings, cv. Goplana. Higher intensities of photosynthetically active irradiation stimulated biomass growth both under control conditions and under drought stress. Drought and higher PFD intensity resulted in a decrease in chlorophyll content. Only the highest light intensity, together with drought stress, negatively affected the structure of cell membranes, increasing their permeability. Both of the applied stress factors did not cause significant changes in the values of the determined parameters of chlorophyll fluorescence in the leaves of wheat seedlings. These results suggest that the increase in light intensity has a mobilising effect on the plant, stimulating the development of biomass both under control conditions and under drought stress. No changes in the values of chlorophyll fluorescence parameters under the influence of different light intensities and drought stress may indicate that there were no significant disturbances in the course of the light phase of photosynthesis in the leaves of the tested seedlings.

Effect of light intensity on negative air ion under phytotron control.

Negative air ion (NAI) is an important index for measuring air quality and has been widely recognized to be influenced by photosynthesis processes. However, vegetation type and light intensity are also known to impact NAI, contributing to significant uncertainties in the relationship between light and NAI. In this paper, we selected Pinus bungeana, Platycladus orientalis and Buxus sinica as research subjects and obtained their NAI, light intensity, and meteorological data through synchronous observation under the relatively stable condition of the phytotron. We analyzed the change characteristics of NAI and the difference of NAI production ability in needle and broadleaf vegetation under different light intensities. Finally, we determined the relationship and underlying mechanism governing light intensity and NAI using diverse tree species. The results showed that the influence of light on NAI was significant. In the environment without vegetation, the influence of different light intensities on NAI was not significant, and the mean NAI concentration was 310 ions·cm-3. Conversely, in the presence of vegetation, NAI showed a "single-peak" trend with increasing light intensity. The NAI concentration of the three tree species was significantly higher than under different light intensities when vegetation was not present. The NAI promoting ability of P. bungeana was the highest (675 ions·cm-3), followed by P. orientalis (478 ions·cm-3) and B. sinica (430 ions·cm-3), which increased by 117.5%, 53.9% and 38.6% compared to the environment without vegetation. The NAI growth rate was significantly different between needle and broadleaf vegetation based on the specific tridimensional green biomass. Additionally, the NAI growth rates of P. bungeana and P. orientalis were 647 and 295 ions·cm-3·m-3, respectively, which were 3.06 and 1.39 times that of B. sinica (211 ions·cm-3·m-3). The piecewise equation fitting effect of NAI and light intensity was better for different tree species, the determination coefficients (R2) of P. bungeana, P. orientalis and B. sinica were 0.926, 0.916 and 0.880, and the root mean square errors (RMSE) were 7.157, 6.008 and 5.389 ion·cm-3, respectively. Altogether, our study provides a theoretical basis as well as technical support for the construction of healthy vegetation stands, the selection of preferred tree species, and the optimization of vegetation models, and promotes air quality and the provision of ecosystem functions and services.

Influence of light intensity and photoperiod on the pigment and, lipid production of Dunaliella tertiolecta and Nannochloropsis oculata under three different culture medium

Microalgal biomass has the ability to store huge amount of triacylglycerides as fatty ester methyl esters (FAME) and carotenoids which has made algae as potential candidate for biorefinery approach. Essential fatty acid such as palmitic acid, stearic acid, arachidonic acid and eicospentanoic acid have been produced which are known for their various applications. The present study was aimed to evaluate the influence of different light intensities (120 and 250 μE/m2/s) and photoperiod (16:8h and 13:11h light/dark cycle) on the production of lipid, biomass and lutein. Dunaliella tertiolecta and Nannochloropsis oculata was grown for 23 days in F/2, sea salt media (SSM, Distilled water (DW) and SSM (natural seawater media,NSW) under two different light intensities and photoperiod regimes at 25 ᵒC. SSM (NSW) showed maximum accumulation of lipid in D.tertiolecta (34.56 mg/L/d). SSM (DW)- biomass showed 1.5 times higher lutein productivity of 0.253 mg/L/d under 13:11h light/dark cycle at 250 μE/m2/s compared to same medium under 16:8h light/dark cycles at 120 μE/m2/s. Where as in N.oculata, F/2 biomass showed higher lipid and lutein productivity of 15.69 and 0.279 mg/L/d, respectively The laboratory scale cultivation parameters and related media cost showed the suitability of different culture media adaptation to large scale production.

Influence of Light Intensity and Spectrum on Duckweed Growth and Proteins in a Small-Scale, Re-Circulating Indoor Vertical Farm.

Duckweeds can be potentially used in human and animal nutrition, biotechnology or wastewater treatment. To cultivate large quantities of a defined product quality, a standardized production process is needed. A small-scale, re-circulating indoor vertical farm (IVF) with artificial lighting and a nutrient control and dosing system was used for this purpose. The influence of different light intensities (50, 100 and 150 µmol m−2 s−1) and spectral distributions (red/blue ratios: 70/30, 50/50 and 30/70%) on relative growth rate (RGR), crude protein content (CPC), relative protein yield (RPY) and chlorophyll a of the duckweed species Lemna minor and Wolffiella hyalina were investigated. Increasing light intensity increased RGR (by 67% and 76%) and RPY (by 50% and 89%) and decreased chlorophyll a (by 27% and 32%) for L. minor and W. hyalina, respectively. The spectral distributions had no significant impact on any investigated parameter. Wolffiella hyalina achieved higher values in all investigated parameters compared to L. minor. This investigation proved the successful cultivation of duckweed in a small-scale, re-circulating IVF with artificial lighting.

光强对4种鸭跖草科植物生长和光合特性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 光强对4种鸭跖草科植物生长和光合特性的影响 DOI: 10.5846/stxb202009202445 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2018YFD1000406）；中央高校基本科研业务费专项资助基金（2572017EA04）；中央高校基本科研业务费专项资金项目（2572017BA08） Effects of light intensity on the growth and photosynthetic characteristics of four Commelinaceae plants Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探究4种鸭跖草科植物对不同光环境的适应能力，以紫鸭跖草、花叶水竹草、吊竹梅、绿叶水竹草4种植物为试验材料，利用遮光网设置5种光强梯度（分别为自然光强的100%、75%、50%、25%、5%），研究不同光强对4种植物生长和光合特性的影响。结果表明：随光强的减弱，4种植物的叶面积、比叶面积、株高、叶片夹角显著增加，但紫鸭跖草在5%自然光强下叶面积显著降低，同时降低的光强显著降低了4种植物叶片的上下表皮厚度和叶片厚度，以及紫鸭跖草、花叶水竹草和绿叶水竹草的栅栏组织厚度、花叶水竹草和绿叶水竹草的海绵组织厚度，但4种植物的栅栏组织和海绵组织比未发生显著变化。紫鸭跖草和花叶水竹草的Chl a、Chl b和Chl （a+b）含量随光强的降低呈先升后降趋势，而吊竹梅和绿叶水竹草的Chl a、Chl b和Chl（a+b）含量则显著升高。与100%自然光强和5%自然光强相比，4种植物在25%-75%自然光强下，能保持高的气孔开度、净光合速率、气孔导度、胞间二氧化碳浓度和蒸腾速率。研究表明，4种鸭跖草科植物具有较强的光适应性，可以通过调整植株形态、叶片解剖结构、光合色素含量、气孔开度和导度的方式在弱光环境中（25%-75%自然光强）增强对光的捕获和利用能力，保持较高的净光合速率，从而保证植株体在弱光环境中进行正常的生命活动。 Abstract:In this research, four Commelinaceae plants (Commelina purpurea, Tradescantia zebrina, Tradescantia flurnuensis ‘Variegata’, and Tradescantia flurnuensis ‘Vairidia’) were used as experimental materials to explore the influence of different light intensities on the growth and photosynthetic characteristics. Shading nets of different densities were used to create five light environments with 100%, 75%, 50%, 25%, and 5% of natural light intensity, respectively. The results indicated that the leaf area, specific leaf area, plant height, and leaf angle of the four plants increased significantly with the decrease of light intensity, but the leaf area of Commelina purpurea was significantly reduced in the 5% natural light intensity. Simultaneously, the reduction of light intensity significantly reduced the upper and lower epidermis and leaf thickness of the four plant leaves, as well as the thickness of the palisade tissue of Commelina purpurea, Tradescantia zebrina and Tradescantia flurnuensis ‘Vairidia’, the thickness of the sponge tissue of Tradescantia zebrina and Tradescantia flurnuensis ‘Vairidia’, but the ratio of palisade and sponge tissue of the four plants did not change significantly. The contents of Chl a, Chl b and Chl (a+b) in Commelina purpurea and Tradescantia zebrina increased first and then decreased with the decrease of light intensity. The contents of Chl a, Chl b and Chl (a+b) in Tradescantia flurnuensis ‘Variegata’ and Tradescantia flurnuensis ‘Vairidia’ increased significantly. Compared with 100% natural light intensity and 5% natural light intensity, the four plants can maintain high stomata opening, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and transpiration rate under 25%-75% natural light intensity. In summary, to ensure the normal growth without restriction in low-light environment, the considerable light adaptability of the four Commelinaceae plants can be generated in diverse ways by adjusting the plant morphology, leaf anatomical structure, photosynthetic pigment content, stomata opening and conduction to capture and use light efficiently, maintain a relatively high net photosynthetic rate in low light environments (25%-75% natural light intensity). 参考文献 相似文献 引证文献

English

This study investigated the influence of different light intensities on the early growth of Jatropha  curcas seedlings. Forty (40) seedlings were randomly selected from the germinated seedlings in the nursery and arrayed under four different treatments (0, 20, 40 and 60% light intensity). The amount of light being received by each of the seedlings was regulated, using constructed wooden box covered with wire gauze (1 mm in size) and measured with photometer. The results on seedlings germination under different light intensity revealed that, the highest mean height (29.2±1.94 cm) was observed in seedlings covered with 60% wire gauze, while the least mean height (27.0±1.24 cm) was observed in the seedlings placed under control treatment (0% wire gauze). Also the highest mean seedlings girth (2.69 ± 0.15 mm) was observed in seedlings not restricted with light intensity (0% wire gauze), while, the least mean girth (2.27±0.08 mm) was found in seedlings restricted with 60% light intensity. The average number of leaves in the four treatments ranges between 6 and 7. The result on analysis of variance (ANOVA) conducted shows a significant effects (P<0.05) of light intensity on J. curcas seedlings girth and number of leaves, while, the seedlings height shows no significant difference (P>0.05). Conclusively, the finding has shown that, J. curcas seedlings required light for its survival, but at varying intensity, and it was noticed that the thicker the light regulator (wire gauze), the lower the amount of light being absorbed by the seedlings. Key words: Jatropha seedling, light intensity, wire gauze, influence survival.

Influence of different light intensities on specific leaf weight, stomatal density photosynthesis and seed yield in soybean

The availability of low light intensity due to shading is the critical factor in determining soybean yield in intercropping system. An experiment was conducted to search genotypes tolerant to low light intensity, which can be better grown for intercropping system. The objective of this study was to determine the influence of different light regimes (35%, 50%, 75% of normal light and normal light) on physiological traits such as specific leaf weight, stomatal density, photosynthesis, total biomass and seed yield of soybean genotypes. Different shading conditions were created using shading net of 35, 50 and 75% to cut the natural solar radiation received by plants to identify genotypes tolerant to low light intensity. One set of plants was also grown under natural conditions without any shading net. Significant negative effect of low light intensity was observed on specific leaf weight, stomatal density and photosynthesis in soybean genotypes. Among the shading conditions, the average seed yield was maximum (31.5 g/pl) in plants grown under control condition. When plants were grown under 35% shading net the seed yield was declined by 37% (20.0 g/pl). However, severe reduction to the extent of 64 and 76% was observed when plants were grown under shading net of 50% (11.2 g/pl) and 75% (7.7 g/pl), respectively as compared to plants grown under control condition. Therefore, the effects of shade on crops should be considered when trying to increase the productivity of an intercropping system.

Effects of light intensity, light quality, and illumination period on cell growth, TFA accumulation, and DHA production in Crypthecodinium sp. SUN

Crypthecodinium strains are ideal candidates for DHA production. In a previous study, light was found to be efficient in inducing total fatty acid accumulation in Crypthecodinium sp. SUN. In order to further analyze the light-inducing behavior of this microalga, experiments were conducted to elucidate the influence of different light intensities, light qualities, and illumination periods on DHA production. The results showed that an irradiance of 30 μmol photons m−2 s−1 was most suitable for DHA production. Compared to red light and blue light, green light was more efficient in elevating the total fatty acid content in the cells. It was also found that illumination at the first 24 h promoted cell growth, whereas it favored total fatty acid accumulation only during 48–96 h. This is the first systematic investigation of the influence of light on total fatty acid accumulation and DHA production in Crypthecodinium sp. SUN, providing a solid foundation for further research on DHA production.

Abundance of Secreted Proteins of Trichoderma reesei Is Regulated by Light of Different Intensities.

In Trichoderma reesei light is an important factor in the regulation of glycoside hydrolase gene expression. We therefore investigated the influence of different light intensities on cellulase activity and protein secretion. Differentially secreted proteins in light and darkness as identified by mass spectrometry included members of different glycoside hydrolase families, such as CBH1, Cel3A, Cel61B, XYN2, and XYN4. Several of the associated genes showed light-dependent regulation on the transcript level. Deletion of the photoreceptor genes blr1 and blr2 resulted in a diminished difference of protein abundance between light and darkness. The amount of secreted proteins including that of the major exo-acting beta-1,4-glucanases CBH1 and CBH2 was generally lower in light-grown cultures than in darkness. In contrast, cbh1 transcript levels increased with increasing light intensity from 700 to 2,000 lux but dopped at high light intensity (5,000 lux). In the photoreceptor mutants Δblr1 and Δblr2 cellulase activity in light was reduced compared to activity in darkness, showing a discrepancy between transcript levels and secreted cellulase activity. Furthermore, evaluation of different light sensitivities revealed an increased light tolerance with respect to cellulase expression of QM9414 compared to its parental strain QM6a. Investigation of one of the differentially expressed proteins between light and darkness, CLF1, revealed its function as a factor involved in regulation of secreted protease activity. T. reesei secretes a different set of proteins in light compared to darkness, this difference being mainly due to the function of the major known photoreceptors. Moreover, cellulase regulation is adjusted to light intensity and improved light tolerance was correlated with increased cellulase production. Our findings further support the hypothesis of a light intensity dependent post-transcriptional regulation of cellulase gene expression in T. reesei.

Modified Photobioreactor for Biofixation of Carbon Dioxide by Chlorella vulgaris at Different Light Intensities

AbstractThe performance of a modified bioreactor inside a light enclosure for carbon dioxide biofixation by Chlorella vulgaris was investigated. The influence of different light intensities on the CO2 biofixation and biomass production rates was evaluated. The results showed that the photon flux available to the microalgal cultures can be a key issue in optimizing the microalgae photobioreactor performance, particularly at high cell concentrations. Although the optimal pH values for C. vulgaris are in the range of 6–8, cell growth can take place even at pH 4 and 10. Batch microalgae cultivation in the photobioreactor was used to investigate the effect of different light intensities. The maximum biomass concentration of 1.83 g L−1 was obtained at a light intensity of 100 μmol m−2s−1 and under aeration with 2 L min−1 of 2 % CO2‐enriched air.

Influence of Different Light Intensities on Growth, Survival and Hatchling Success in the Mosquitofish Gambusia affinis

In this study, we examined growth, survival and reproductive success of the viviparous fish Gambusia affinis exposed to different light intensities. The specific growth and survival rates were significantly lower in fish exposed to low light intensity (1250 lx) compared to those of controls, whereas these parameters were not significantly different in fish maintained at moderate (2900 lx) and high (4050 lx) light intensities. The condition factor was good in control fish compared to those kept in artificial light. Maximum numbers of early and late stage embryos were found in the abdominal cavity of fish exposed to moderate and high intensity light respectively. However, highest number of juveniles was recorded from fish maintained at high intensity light. These results suggest that low intensity light affects growth and survival rate, but hatchling success is maximized at high illumination condition in G. affinis.

Efeito do sombreamento na anatomia foliar de plantas jovens de andiroba (Carapa guianensis Aubl.)

A capacidade de utilização da luz varia entre as espécies, e o sucesso de cada indivíduo depende de suas respostas morfoanatômicas. Este estudo avaliou a influência de diferentes intensidades luminosas sobre a anatomia foliar de mudas de Carapa guianensis Aubl. Folhas sadias do segundo e terceiro nós foram coletadas de plantas jovens desenvolvidas em quatro níveis de sombreamento: 30%, 50%, 70% e 0% (pleno sol), durante oito meses de experimento. Análises anatômicas foram feitas sob Microscopia Óptica (MO), a partir de lâminas temporárias e permanentes e sob Microscopia Eletrônica de Varredura (MEV). A densidade estomática não apresentou diferenças significativas. As dimensões estomáticas e a espessura dos tecidos da lâmina foliar foram maiores com o aumento da intensidade luminosa. C. guianensis apresenta plasticidade anatômica, possibilitando a sobrevivência na floresta sob distintas condições luminosas.

Study of the senescence process in primary leaves of sunflower (Helianthus annuus L.) plants under two different light intensities

Different parameters that vary during leaf development may be affected by light intensity. To study the influence of different light intensities on primary leaf senescence, sunflower (Helianthus annuus L.) plants were grown for 50 days under two photon flux density (PFD) conditions, namely high irradiance (HI) at 350 μmol(photon) m-2 s-1 and low irradiance (LI) at 125 μmol(photon) m-2 s-1. Plants grown under HI exhibited greater specific leaf mass referred to dry mass, leaf area and soluble protein at the beginning of the leaf development. This might have resulted from the increased CO2 fixation rate observed in HI plants, during early development of primary leaves. Chlorophyll a and b contents in HI plants were lower than in LI plants in young leaves. By contrast, the carotenoid content was significantly higher in HI plants. Glucose concentration increased with the leaf age in both treatments (HI and LI), while the starch content decreased sharply in HI plants, but only slightly in LI plants. Glucose contents were higher in HI plants than in LI plants; the differences were statistically significant (p<0.05) mainly at the beginning of the leaf senescence. On the other hand, starch contents were higher in HI plants than in LI plants, throughout the whole leaf development period. Nitrate reductase (NR) activity decreased with leaf ageing in both treatments. However, the NR activation state was higher during early leaf development and decreased more markedly in senescent leaves in plants grown under HI. GS activity also decreased during sunflower leaf ageing under both PFD conditions, but HI plants showed higher GS activities than LI plants. Aminating and deaminating activities of glutamate dehydrogenase (GDH) peaked at 50 days (senescent leaves). GDH deaminating activity increased 5-fold during the leaf development in HI plants, but only 2-fold in LI plants. The plants grown under HI exhibited considerable oxidative stress in vivo during the leaf senescence, as revealed by the substantial H2O2 accumulation and the sharply decrease in the antioxidant enzymes, catalase and ascorbate peroxidase, in comparison with LI plants. Probably, systemic signals triggered by a high PFD caused early senescence and diminished oxidative protection in primary leaves of sunflower plants as a result.

Growth and Flowering Performance of Potted Gerbera, Gerbera Jamesonii L. Under Different Light Intensity

The influence of different light intensities (L0: full sunlight; L1: reduced sunlight; L2: 60% reduced sunlight) showed significant variations on growth and flower characteristics. Forty per cent reduced sunlight was more effective on growth and flower production than 60% reduced or in full sunlight. Tallest and thickest peduncles were produced (28.5 and 1.7 cm, respectively) with L1, similarly bigger flowers (6.0 cm diameter) were also found with L1 in comparison to L0 and L2. The maximum number of flowers per plant (15.6) was found from L1 and lowest (11.9) from L2.DOI: http://dx.doi.org/10.3329/jbas.v36i2.12965Journal of Bangladesh Academy of Sciences, Vol. 36, No. 2, 213-220, 2012

δ13C and δ15N in tissue of coral polyps and epilithic algae inhabiting damaged coral colonies under the influence of different light intensities

Studies were performed of the carbon and nitrogen stable isotope (δ13C and δ15N) composition (δ13C and δ15N) of the corals Porites cylindrica and P. lutea (5 years after damaging the colonies by the bleaching events) and of epilithic algae settled onto damaged areas of coral colonies. Coral polyps and three epilithic algal communities (‘red algal turf, green algal turf and red calcified crusts’) were sampled along the boundary between communities of coral polyps and algal colonizers from differently illuminated habitats from 2 to 90% of incident surface photosynthetically active radiation (PAR0). It was found that communities with a predominance of red algae significantly differed from communities with a predominance of green algae in δ13C but not in δ15N values. An influence of habitat irradiance was found only for communities of coral polyps for δ13C and δ15N values: under bright light (70–90% PAR0) polyp tissues of both coral species were significantly enriched in heavy carbon isotopes and insignificantly in nitrogen isotopes (δ13C values difference ~4‰) relative to tissues of corals under lower light 15–50% PAR0. On the basis of these results we assumed that differences in light intensities in the habitat ranging from 15 to 90% PAR0 do not influence on accessibility of the main carbon and nitrogen sources for corals and algae, and exchange by these elements between organisms. We also assumed that the relative enrichment in the heavy carbon isotopes of coral tissues in high light is a result of decreased isotope fractionation (or the absence of fractionation in photosynthesis of their zooxanthellae).

Acclimation effect on fatty acids of the coral Montipora digitata and its symbiotic algae

Lipids play a key role in thermal and photo-acclimation processes, yet they are often neglected in stress studies. We investigated the influence of different light intensities and an increase of temperature on the fatty acid composition of the coral Montipora digitata and its symbiotic algae (i.e., zooxanthellae). Coral branches were subjected to 3 different light intensities (7, 30 and 95% sea surface photosynthetic active radiation) in filtered seawater for 35 days. Fatty acids as methyl esters were determined using gas chromatography (GC) and verified by GC-mass spectrometry. Different light intensities, but only in combination with increased temperature, significantly affected the fatty acid composition of the coral host and zooxanthellae. Temperature and light intensity increases caused reductions in the proportion of polyunsaturated fatty acids in both the host and symbionts. Most changes occurred in the host coral, which suggests that the host is more susceptible to environmental change than the symbiont, or that the host shields the symbionts from environmental change.

Influence of different light intensities on the content of diosgenin, lipids, carotenoids and fatty acids in leaves of Dioscorea zingiberensis.

Cultivation of the climbing plant Dioscorea zingiberensis at a light intensity of 100 microE. m(-2) sec(-1) yields three different phenotypes. Most of the plants grow as green phenotype (DzW). Two further forms differ in their leaf shape and leaf color. Whereas one type exhibits a more pointed leaf shape in the upper part of the plant with leaves appearing yellow-green with white stripes or hatchings (DzY), the other type shows a more round leaf shape with an intensive yellow-green color (DzT). These three plant types differ in their diosgenin content not only in their rhizomes but also in the chloroplasts. In the rhizomes the diosgenin content in the green form is 0.4%, in the DzY-form 0.6% and in the DzT-form even 1.3% of the dry weight. Furthermore, even in chloroplasts of the green DzW-form and of the DzY-form the presence of diosgenin was demonstrated. It occurs there as the epimeric form yamogenin. The DzT-form contains no yamogenin in its chloroplasts. Besides this, these plant forms differ in their chlorophyll and carotenoid content and in their fatty acid composition. Carotenoids increase from 1.3% of total lipids in the green phenotype to 3.3% in the DzY- and to 4.2% in the DzT-form. This increase refers to beta-carotene as well as to lutein and neoxanthin. The chlorophyll content in the green type is 8.1% and lower in the DzY-form with 7%. The highest chlorophyll content is found in the DzT-form with 12%. Fatty acids in the DzY-form and in the DzT-form have a more unsaturated character than in the green phenotype. The content of the monoenoic acid trans-hexadecenoic acid is considerably lower in both phenotypes when compared to the green phenotype. In both phenotypes the quantity of fatty acids with 16 carbon atoms is reduced, whereas fatty acids with 18 carbon atoms occur in higher concentration. Cultivation of the green phenotype (DzW) at the three light intensities of 10, 100 and 270 microE x m(-2) x sec(-1) leads to changes of the diosgenin content in rhizomes, to an increase of leaf dry weight, to a reduction of the grana structure in chloroplasts and therewith to a decrease of the chlorophyll content. The total lipid content is highest under the cultivation at 100 microE x m(-2) x sec(-1) and reduced by 30% at 10 and 270 microE x m(-2) x sec(-1). Carotenoids, however, are highest in shaded plants (10 microE x m(-2) x sec(-1)) and plants grown under high light conditions of 270 microE x m(-2) x sec(-1). At 100 microE x m(-2) x sec(-1) a decrease of saturated fatty acids is observed in comparison to plants grown under shaded conditions.