Light Of Different Qualities Research Articles

Investigating the Physiological and Molecular Responses of Solanum lycopersicum hp Mutants to Light of Different Quality for Biotechnological Applications.

The effect of the light of different spectral compositions, white fluorescent light (WFL), red light (RL, 660 nm), blue light (BL, 450 nm), green light (GL, 525 nm), and white LED light (WL, 450 + 580 nm), on the physiological parameters of Solanum lycopersicum 3005 hp-2 (defective for a DET1 gene) and 4012 hp-1w; 3538 hp-1; 0279 hp-1.2 (defective for a DDB1a gene) photomorphogenetic mutants was studied. The parameters of the primary photochemical processes of photosynthesis, photosynthetic and transpiration rates, the antioxidant capacity of low-molecular weight antioxidants, the content of the total phenolic compounds, including flavonoids, and the expression of the genes involved in light signaling and biosynthesis of secondary metabolites were determined. Under BL, the 3005 hp-2 mutant showed the highest nonenzymatic antioxidant activity, which occurred to a greater extent due to the increase in flavonoid content. At the same time, under BL, the number of secretory trichomes on the surface of the leaves of all mutants increased equally. This suggests the accumulation of flavonoids inside leaf cells rather than in trichomes on the leaf surface. The data obtained indicate the possibility of using the hp-2 mutant for biotechnology to increase its nutritional value by enhancing the content of flavonoids and other antioxidants by modulating the spectral composition of light.

Light quality as a driver of photosynthetic apparatus development.

Light provides energy for photosynthesis and also acts as an important environmental signal. During their evolution, plants acquired sophisticated sensory systems for light perception and light-dependent regulation of their growth and development in accordance with the local light environment. Under natural conditions, plants adapted by using their light sensors to finely distinguish direct sunlight and dark in the soil, deep grey shade under the upper soil layer or litter, green shade under the canopy and even lateral green reflectance from neighbours. Light perception also allows plants to evaluate in detail the weather, time of day, day length and thus the season. However, in artificial lighting conditions, plants are confronted with fundamentally different lighting conditions. The advent of new light sources - light-emitting diodes (LEDs), which emit narrow-band light - allows growing plants with light of different spectral bands or their combinations. This sets the task of finding out how light of different quality affects the development and functioning of plants, and in particular, their photosynthetic apparatus (PSA), which is one of the basic processes determining plant yield. In this review, we briefly describe how plants perceive environment light signals by their five families of photoreceptors and by the PSA as a particular light sensor, and how they use this information to form their PSA under artificial narrow-band LED-based lighting of different spectral composition. We consider light regulation of the biosynthesis of photosynthetic pigments, photosynthetic complexes and chloroplast ATP synthase function, PSA photoprotection mechanisms, carbon assimilation reactions and stomatal development and function.

Influence of Light of Different Spectral Compositions on the Growth, Photosynthesis, and Expression of Light-Dependent Genes of Scots Pine Seedlings.

Varying the spectral composition of light is one of the ways to accelerate the growth of conifers under artificial conditions for the development of technologies and to obtain sustainable seedlings required to preserve the existing areas of forests. We studied the influence of light of different quality on the growth, gas exchange, fluorescence indices of Chl a, and expression of key light-dependent genes of Pinus sylvestris L. seedlings. It was shown that in plants growing under red light (RL), the biomass of needles and root system increased by more than two and three times, respectively, compared with those of the white fluorescent light (WFL) control. At the same time, the rates of photosynthesis and respiration in RL and blue light (BL) plants were lower than those of blue red light (BRL) plants, and the difference between the rates of photosynthesis and respiration, which characterizes the carbon balance, was maximum under RL. RL influenced the number of xylem cells, activated the expression of genes involved in the transduction of cytokinin (Histidine-containing phosphotransfer 1, HPT1, Type-A Response Regulators, RR-A) and auxin (Auxin-induced protein 1, Aux/IAA) signals, and reduced the expression of the gene encoding the transcription factor phytochrome-interacting factor 3 (PIF3). It was suggested that RL-induced activation of key genes of cytokinin and auxin signaling might indicate a phytochrome-dependent change in cytokinins and auxins activity.

Chlorophyll fluorescence parameters to assess utilization of excitation energy in photosystem II independently of changes in leaf absorption

Measurement of Pulse-Amplitude-Modulated (PAM) chlorophyll a fluorescence is widely used method for obtaining information on the functional state of photosystem II (PSII). Recently, it has been shown that some of long-established fluorescence parameters must be interpreted with caution, when the light-induced chloroplast movements occur. In our work we have analyzed the effect of chloroplast movements on these parameters. We have derived new parameters that are independent of the change in PSII absorption occurring during measurement. To verify whether there is a need for new parameters or the difference between the parameters commonly used and the newly derived ones is insignificant, we conducted an experiment with Arabidopsis thaliana wild type plants and its phot1 phot2 mutant defective in chloroplast movement. Plants were exposed to light of different qualities (450, 470, 550 or 660 nm) and quantities (100, 400 or 1200 μmol m−2 s−1) for up to 40 min. Since the blue light-induced chloroplast avoidance reaction is a photoprotective mechanism, we expected that phot1 phot2 mutant will compensate the lack of this mechanism by increasing non-photochemical quenching. However, using the light at both 450 and 470 nm, the calculation of commonly used parameter, ΦNPQ (quantum yield of regulated light-induced thermal energy dissipation in PSII) based on Hendrickson et al. [L. Hendrickson, R.T. Furbank, W.S. Chow, Photosynth. Res. 82 (2004) 73–81] showed the opposite. On the other hand, the results obtained using our newly proposed formulae to determine quantum yield of PSII thermal energy dissipation were in line with our assumption. Thus, the experimental data showed that some formulae of fluorescence parameters are dependent on the change in PSII absorption and need to be interpreted carefully. On the contrary, the formulae introduced by us can remove the effect of changes in PSII absorption that occur during measurement, without additional measurements, and give the real estimate of light-induced non-photochemical quenching.

Analysis of c-di-GMP Levels Synthesized by a Photoreceptor Protein in Response to Different Light Qualities Using an In Vitro Enzymatic Assay.

Diguanylate cyclases are enzymes that use two GTP molecules to produce one molecule cyclic dimeric guanosine monophosphate (c-di-GMP). This cyclic dinucleotide is an ubiquitous prokaryotic second messenger that controls a variety of cell functions. Several proteins have been described which contain a photoreceptor domain fused to a diguanylate cyclase. The cyanobacterial light sensor Cph2 is responsible for the blue-light induced synthesis of c-di-GMP in Synechocystis sp. PCC 6803. Here, we provide a detailed protocol for an in vitro enzymatic assay with a purified photoreceptor protein using light as the crucial reaction parameter for c-di-GMP synthesis. The assay is accomplished under continuous illumination with light of different quality with inactivation of the enzyme by heat denaturation. Analytics are performed using HPLC-UV.

Acclimation of Haslea ostrearia to light of different spectral qualities – confirmation of `chromatic adaptation' in diatoms

The marine diatom Haslea ostrearia was cultured under light of different qualities, white (WL), blue (BL), green (GL), yellow (YL), red (RL), and far-red (FRL) and at two irradiance levels, low and high (20 and 100 μmol photons m −2 s −1, respectively). The effects of the different light regimes were studied on growth, pigment content, and photosynthesis, estimated by the modulated fluorescence of chlorophyll, as relative electron transport rate (rETR). For all the light qualities studied, growth rates were higher at high irradiance. Compared to the corresponding WL controls, growth was higher in BL and lower in YL at low irradiance, and lower in YL and GL at high irradiance. Except for YL, almost all the pigment contents of the cells were lower at high irradiance. At low irradiance, cell pigment contents (chlorophyll a and c, fucoxanthin) and pigment ratios (in function of chlorophyll a) were lower in YL, RL, and FRL. Whatever the irradiance level, the maximum PSII quantum efficiency ( F v/ F m) remained almost constant for WL, BL, and GL. Other fluorescence parameters (photochemical quenching, rETR max, and α, the maximum light utilization coefficient) were lower in GL, YL, RL, and FRL, at low irradiance. Although not statistically significant, BL caused an increase in these fluorescence parameters. These findings are interpreted as evidence that inverse chromatic acclimation occurs in diatoms.

Soybean Photoperiod‐Sensitivity Loci Respond Differentially to Light Quality

Soybean [Glycine max (L.) Merr.] genotypes have been identified that show differential sensitivity to light quality. The use of different lamp types emitting light of different quality changed flowering responses to long days. The objective of this study was to investigate the flowering response of three photoperiod‐sensitivity loci to long days of various light qualities. ‘Harosoy’ near‐isogenic lines were grown under 20‐h‐long days of different light qualities, as measured by the bichromatic ratio of red to far‐red quanta (R:FR), and under light quality gradients. Generally, the photoperiodic response was greater, i.e., later flowering, with decreased R:FR. The El allele was most sensitive to light quality and required an R:FR approximating that of natural daylight for response to long days. The E3 allele was the least sensitive, and the E4 allele showed intermediate sensitivity to light quality. The earliest‐flowering near‐isogenic line (e1 e3 e4), previously found to be insensitive to long day length, showed sensitivity to long days of low R:FR light. Long days of high R:FR light were not effective in delaying flowering for some genotypes. Sensing the R:FR ratio is the function of phytochrome in light‐grown plants. The three loci studied in this work responded differentially to changes in R:FR, suggesting either a close relationship between soybean E alleles and phytochrome or the possibility that some photoperiod‐sensitivity loci are part of the phytochrome family of genes.

Arabidopsis rbcS Genes Are Differentially Regulated by Light

Individual members of the Arabidopsis thaliana ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit (rbcS) gene family are differentially regulated by light of different qualities. In 10-d-old etiolated seedlings, the expression of only three of the four genes is under inductive phytochrome control. rbcS mRNA levels reach a maximum (3- to 5-fold higher than the dark level) about 6 h after a red light pulse, but the rate of decay differs among the genes. Moreover, rbcS 2B requires a higher fluence for induction. At early stages of development, rbcS 1A, 2B, and 3B are highly expressed in the dark and cannot be further induced by red light, indicating a developmental component in the overall regulatory mechanism. Continuous light experiments indicate that high-irradiance responses may play a role in the induction of at least three of the four rbcS genes. Under conditions of phytochrome saturation, rbcS 1A is insensitive to blue light pulses, whereas among the three B locus genes, at least rbcS 3B appears to respond to a blue-light photoreceptor. These results add to the data suggesting that individual members of rbcS gene families in higher plants may be subject to a variety of differing regulatory mechanisms.

Ribulose bisphosphate carboxylase capacity and chlorophyll content in developing seedlings of Chenopodium rubrum L. growing under light of different qualities and fluence rates

In order to evaluate the aclimation of Chenopodium seedlings to different quantum fluence rates of R and BL, kinetics of Rubisco capacity, Chl content and chloroplast structure were studied. Under monochromatic light photoreceptors are stimulated selectively and their influence on biosynthetis capacities during chloroplast development can be studied.R irradiations saturate Rubisco capacity even at the lowest quantum fluence rates applied, whereas Chl a+b synthesis depends strongly upon fluence rate of R. Under BL irradiations, both Rubisco capacity and Chl content are fluence rate dependent. R irradiations favour Chl b synthesis relative to Chl a, whereas under BL Chl a content is high relative to Chl b. Under R irradiation Pfr is the main photoreceptor involved in regulation of Rubisco capacity whereas under BL a specific BL absorbing photoreceptor may control the response. From the fluence rate dependency under BL irradiations it is concluded that the blue region of the day light spectrum may be the sensor for monitoring fluence rate and causing the characteristic changes in shade and high/low WL adaptation with respect to Rubisco levels in Chenopodium.

Cell expansion in the filamentous gametophyte of the fernOnoclea sensibilis L.

Filamentous gametophytes of the fernO. sensibilis were exposed to paired combinations of light of different qualities, hormones and cations in the attempt to elucidate the underlying processes that regulate cell expansion. Simultaneous treatments with high-pH buffers or the auxin antagonistp-chlorophenoxyisobutyric acid abolished blue-light-mediated expansion but did not influence growth in red light. In contrast, the red-light response was preferentially altered by the ethylene absorbant KMnO4 or the Ca(2+) chelator ethyleneglycol-bis(β-aminoethyl ether) N,N'-tetraacetic acid. The Ca(2+) ionophore A23187 caused a significant reduction in cell expansion under both blue and red irradiation. A marked promotion of expansion was mediated by high concentrations of indole-3-acetic acid, but this effect was dependent on the presence of low-pH buffers. The ethylene-generating agent 2-chloroethylphosphonic acid decreased the magnitudes of both photoresponses; this inhibition was further enhanced by high Ca(2+) concentrations. These findings and those with other plants are interpreted in terms of two independent control mechanisms for cell expansion: 1) a blue light photoreceptor-auxin-hydrogen ion system, and 2) a phytochrome-ethylene-calcium ion system.

PHOTOCONTROL OF STOMATAL MOVEMENTS

Summary1. Opening in light is a feature common to the majority of functional stomata, but the current argument is against the traditional view that light is the principal environmental promoter of opening, because stomata can open in the dark in response to CO2 removal and/or temperature increase. In this review, evidence is provided that light is more efficient and effective than other physical factors in both producing and maintaining wide opening. However, light acts on stomata both directly and indirectly, in conjunction with changes in, for example, CO2 balance, water regime and temperature of the leaf tissue.2. Three general categories of light effects on stomata are recognized: (a) photosynthetic effects driven by metabolic processes, induced or enhanced by light, (b) hydrophotic effects mediating through light‐induced changes in epidermal turgor, and (c) photothermal effects arising from light‐dependent changes in leaf temperature.3. Photosynthetic effects involve both CO2 depletion, and starch mobilization, malate synthesis, H+ extrusion, and accumulation of K+ and C1‐ in guard cells; these processes are triggered by light of different qualities: (a) Both blue and red light are involved in photosynthetic CO2 fixation, utilizing energy from photosynthetic light reaction(s), which provides C precursors for synthesis of stornatal starch. (b) Blue light, but not red, enhances starch mobilization, PEP carboxylase activity and respiration. Accordingly, blue light is postulated to enhance hydrolysis of stornatal starch providing C3 precursors for malate synthesis via PEP‐fixation of endogenous CO2; the active extrusion of H+, derived from malate, is coupled with K+ influx to guard cells. Malate and C1‐ are competitive anions, for K+, and one begins to play a progressively more important role as the other becomes limiting; in intact leaves, however, malate plays a more decisive role. These processes are driven by the energy from blue‐light‐enhanced respiration. (c) Both photosynthetic fixation and PEP carboxylation act as CO2 sensors, but the exact role of CO2 in the stornatal mechanism has yet to be determined.4. Hydrophotic and photothermal effects facilitate guard cell expansion by releasing epidermal pressure through enhanced evaporative water loss, and are, therefore, indirect effects of light; photothermal effects may also contribute to metabolic processes outlined in paragraph 3.5. Stomatal closure in the dark accompanies starch synthesis, malate reduction, efflux of K+ and C1‐ from guard cells, and accumulation of CO2 in substomatal cavities. Malate may be converted to starch via C2 compounds. Guard cells release K+ and C1‐ into apoplastic space, from which they are removed by neighbouring cells. The entry of K+ into neighbouring cells is supposed to be coupled with H+ extrusion. These processes are dependent on respiratory energy.6. The differential abaxial and adaxial stomatal light responses are related to inherent metabolic differences between the two epidermes, but the biochemical basis is not known.

INFLUENCE ON VISION OF EXTREMELY LOW FREQUENCY ELECTROMAGNETIC FIELDS

The strong electric currents used for heating purposes in welding and steel industries set up related magnetic fields (generally 0.1--10 mT and 50 Hz). Such fields 10--50 Hz, 0--40 mT) were used to induce visual light phenomena, magnetophosphenes. Threshold values for magnetophosphenes were determined as a function of magnetic field frequency as well as colour and intensity of the background illumination. A typical sensitivity maximum was found at 20--25 Hz. Differences between volunteers with normal colour vision and colour defective ones were observed. The frog retina was exposed to the same type of fields. Retinal activity, induced by the fields, was registered from the ganglion cell layer by means of microelectrode technique. The results indicate that magnetophosphenes are generated in the retina and in the same channels that are normally propagating signals induced by light of different qualities. The findings may be of guidance when formulating threshold limit values for extremely low frequency electromagnetic fields in industry.

Der Einfluß von Licht verschiedener Wellenlänge auf die Akkumulation und den Umsatz von Anthocyan-3-monoglucosiden in isolierten Petalen von Petunia hybrida

Summary The influence of different light qualities: far-red, red, blue, and dark on the accumulation and the turnover of the 3-monoglucosides of delphinidin, petunidin, and malvidin was studied in isolated petals of the delphinidin-genotype (L. M. ff K.) of Petunia hybrida by feeding and by pulse labelling experiments using acetate-2-14C. Radioactivity is randomly incorporated into the anthocyanins which differ only in the B-ring methylation pattern (fig. 1). The aim of the study was to see whether there is a specific influence of light of different qualities on the anthocyanin composition of the isolated petals, i.e. whether changes occur in the relative proportions of these anthocyanin-3-monoglucosides due to the light quality. Furthermore, by studying the turnover, it was attempted to elucidate whether the light control of anthocyanin accumulation is mediated by the regulation of synthesis alone or by the regulation of both synthesis and turnover. Since the physiological behaviour of the buds differs with the time of harvest and the age of the plants, the bud-half technique was employed. The buds were symmetrically bisected. In each experiment one half of the bud halves, chosen to serve as a reference, was given a standard red light treatment. The physiologically equivalent other corresponding half of the bud-halves received the experimental treatment. Tests showed that during the incubation period anthocyanin accumulation can be considered to be proceeding normally. The anthocyanin content of the lower half of the bud is highest at the beginning of bud development, then it stays constant. Later on, a distribution gradient is built up in the bud with the anthocyanin content increasing and becoming highest in the upper quarter of the petals. Malvidin-3-monoglucoside shows the steepest gradient, delphinidin-3-monoglucoside the smoothest. Independent thereof, the accumulation in the different parts is linear with bud length (fig. 2). In red light, concluded from a comparison of experiments run in white fluorescent light and dark (Steiner 1971) and the experiments in red and dark (table 5), the anthocyanin composition seems to be influenced in the same manner as in white fluorescent light. In far-red light compared to red no differences are observed in the anthocyanin composition (table 3). In blue light compared to red the malvidin-3-monoglucoside accumulation remains unchanged. However, the petunidin- and particularly the delphinidin-3-monoglucoside accumulation is markedly increased, thus leading to a specific change in the anthocyanin composition (table 4). In the dark compared to red the accumulation of delphinidin- and petunidin-3-monogluco-side seems to be unchanged. However, the accumulation of malvidin-3-monoglucoside is reduced (table 5). Thus, in the dark a similar change in the anthocyanin composition is observed as in blue light, though for an entirely different reason. In red light, concluded from a comparison of experiments in white fluorescent light and dark (Steiner 1971) and the experiments in red and dark (table 11), the turnover of the 3-monoglucosides on a relative basis seems to be similar to that found in white fluorescent light. In far-red light compared to red no differences could be observed with respect to the turnover of all 3-monoglucosides (table 9). In blue light compared to red the turnover of all 3-monoglucosides is unspecifically increased (table 10). In the dark compared to red no differences are found in the turnover of delphinidin- and petunidin-3-monoglucoside, but the turnover of malvidin-3-monoglucoside is higher in the dark than in red (table 11). The data clearly show that the light controlled linear accumulation of the anthocyanin-3-monoglucosides in isolated petals of Petunia is without exception the result of synthesis and turnover. Due to the specific light quality the rate of synthesis as well as the rate of turnover can differ for each of the 3-monoglucosides. Hence, the anthocyanin composition of the petals can change. Yet, a similar anthocyanin composition may, on the other hand, be the result of a different accumulation regulation. A simple hypothesis is given proposing a reasonable regulation model fitting the data. Red and far-red light show the same effect on the anthocyanin composition. Blue light specifically alters this composition. Accordingly, anthocyanin composition in Petunia belongs to those photomorphogenic responses in which blue light action is prominent.

Coupling of ion transport in green cells ofAtriplex spongiosa leaves to energy sources in the light and in the dark

The coupling of ion transport to energy sources in the light and in the dark in green cells ofAtriplex spongiosa leaves was investigated using light of different qualities, an inhibitor of electron transport (dichlorophenyl dimethyl urea), and an uncoupler (p-CF3O-carbonyl cyanide phenylhydrazone). Two different mechanisms of ion uptake were, distinguished. (1) A light-dependent Cl(-) pump which is linked to light-dependent K(+) uptake. The energy for this pump is probably derived from photosynthetic electron transport or from nicotinamide adenine dinucleotide phosphate, reduced form. This mechanism is dichlorophenyl dimethyl urea-sensitive and enhanced by uncouplers. (2) A mechanism independent of light, which operates at the same rate in the light and in the dark. This mechanism is sensitive to uncouplers. It is probably aK-Na exchange mechanism since K(+) and Cl(-) uptake and a small net uptake of H(+) are balanced by Na(+) loss.

Flower Formation in Kalanchoë blossfeldiana by Very Short Photoperiods under Light of Different Quality

Kalanchoe blossfeldiana—a typical short-day plant—can be induced to flower by daily light periods as short as 1 min or even 1 sec of sunlight or incandescent light, provided many such cycles are given1,2; controls kept in continuous darkness remain vegetative if the temperature is maintained at 17° C or higher2,3.