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PubMed1971

Spectral Distribution of Light in a Tobacco Canopy and Effects of End-of-Day Light Quality on Growth and Development.

Shifts in spectral distribution of light were determined within and below a canopy of field-grown burley tobacco (Nicotiana tabacum L. cv. Burley 21). The leaves transmitted much far red light relative to red and blue light. Thus, shaded leaves received more far red light, relative to red and blue, than was received by unshaded leaves. Under field conditions, tobacco plants within rows grew taller than did those at the west end of rows.Developmental effects of end-of-day red and far red light were studied in the controlled environment laboratory. Plants that received far red light last, each day, resembled plants shaded by other plants. The far red-irradiated plants developed longer internodes, were lighter green in color, and had thinner leaves than the red-irradiated ones. Plants of both treatments had the same number of leaves on the main axis. However, the red-irradiated plants developed branches from axils of lower leaves, while no branching occurred on plants that received far red radiation last each day.

Journal Article↗
PubMed2006

Growth and ethylene evolution by shade and sun ecotypes of Stellaria longipes in response to varied light quality and irradiance.

Plants growing in the shade receive both low light irradiance and light enriched in far red (FR) (i.e., light with a low red (R) to FR ratio). In an attempt to uncouple the R/FR ratio effects from light irradiance effects, we utilized Stellaria longipes because this species has two distinct natural population ecotypes, alpine (dwarf) and prairie (tall). The alpine population occupies the open, sun habitat. By contrast, the prairie population grows in the shade of other plants. Both 'sun' and 'shade' ecotypes responded with increased stem elongation responses under low irradiance, relative to growth under 'normal' irradiance, and this increased growth was proportionally similar. However, only the shade ecotype had increased shoot elongation in response to a low R/FR ratio. By contrast, the sun ecotype showed increased stem elongation in response to increasing R/FR ratio. Varying the R/FR ratios had no significant effect on ethylene evolution in either sun or shade ecotype. Under low irradiance, only the sun ecotype showed a significantly changed (decreased) ethylene evolution. We conclude that R/FR ratio and irradiance both regulate growth, and that irradiance can also influence ethylene evolution of the sun ecotype. By contrast, R/FR ratio and irradiance, while having profound influences on growth of the shade ecotype, do not appear to regulate these growth changes via effects on ethylene production.

Ethylenes↗
PubMed2004

Stomatal conductance of lettuce grown under or exposed to different light qualities.

BACKGROUND AND AIMS: The objective of this research was to examine the effects of differences in light spectrum on the stomatal conductance (Gs) and dry matter production of lettuce plants grown under a day/night cycle with different spectra, and also the effects on Gs of short-term exposure to different spectra. METHODS: Lettuce (Lactuca sativa) plants were grown with 6 h dark and 18 h light under four different spectra, red-blue (RB), red-blue-green (RBG), green (GF) and white (CWF), and Gs and plant growth were measured. KEY RESULTS AND CONCLUSIONS: Conductance of plants grown for 23 d under CWF rose rapidly on illumination to a maximum in the middle of the light period, then decreased again before the dark period when it was minimal. However, the maximum was smaller in plants grown under RB, RGB and GF. This demonstrates that spectral quality during growth affects the diurnal pattern of stomatal conductance. Although Gs was smaller in plants grown under RGB than CWF, dry mass accumulation was greater, suggesting that Gs did not limit carbon assimilation under these spectral conditions. Temporarily changing the spectral quality of the plants grown for 23 d under CWF, affected stomatal responses reversibly, confirming studies on epidermal strips. This study provides new information showing that Gs is responsive to spectral quality during growth and, in the short-term, is not directly coupled to dry matter accumulation.

Culture Media↗
PubMed2000

Cryptochrome nucleocytoplasmic distribution and gene expression are regulated by light quality in the fern Adiantum capillus-veneris.

Numerous cellular responses are reportedly regulated by blue light in gametophytes of lower plants; however, the molecular mechanisms of these responses are not known. Here, we report the isolation of two blue light photoreceptor genes, designated cryptochrome genes 4 and 5 (CRY4 and CRY5), from the fern Adiantum capillus-veneris. Because previously we identified three cryptochrome genes, this fern cryptochrome gene family of five members is the largest identified to date in plants. The deduced amino acid sequences of the five genes show remarkable similarities with previously identified cryptochromes as well as class I photolyases. Like the other plant cryptochromes, none of the cryptochromes of this fern possesses photolyase activity. RNA gel blot analysis and competitive polymerase chain reaction analysis indicate that the expression of the newly identified CRY4 and CRY5 genes is regulated by light and is under phytochrome control. The intracellular distribution of reporter beta-glucuronidase (GUS)-CRY fusion proteins indicates that GUS-CRY3 and GUS-CRY4 localize in fern gametophyte nuclei. The nuclear localization of GUS-CRY3 is regulated in a light-dependent manner. Together with our physiological knowledge, these results suggest that CRY3, CRY4, or both might be the photoreceptor that mediates inhibition of spore germination by blue light.

Amino Acid Sequence↗
PubMed1981

Effect of Light Quality on Stomatal Opening in Leaves of Xanthium strumarium L.

Flux response curves were determined at 16 wavelengths of light for the conductance for water vapor of the lower epidermis of detached leaves of Xanthium strumarium L. An action spectrum of stomatal opening resulted in which blue light (wavelengths between 430 and 460 nanometers) was nearly ten times more effective than red light (wavelengths between 630 and 680 nanometers) in producing a conductance of 15 centimoles per square meter per second. Stomata responded only slightly to green light. An action spectrum of stomatal responses to red light corresponded to that of CO(2) assimilation; the inhibitors of photosynthetic electron transport, cyanazine (2-chloro-4[1-cyano-1-methylethylamino]-6-ethylamino-s-triazine) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea, eliminated the response to red light. This indicates that light absorption by chlorophyll is the cause of stomatal sensitivity to red light. Determination of flux response curves on leaves in the normal position (upper epidermis facing the light) or in the inverted position (lower epidermis facing the light) led to the conclusion that the photoreceptors for blue as well as for red light are located on or near the surfaces of the leaves; presumably they are in the guard cells themselves.

Journal Article↗
PubMed1995

Effect of Vernalization, Photoperiod, and Light Quality on the Flowering Phenotype of Arabidopsis Plants Containing the FRIGIDA Gene.

We have compared the flowering response to vernalization, photoperiod, and far-red (FR) light of the Columbia (Col) and Landsberg erecta (Ler) ecotypes of Arabidopsis into which the flowering-time locus FRIGIDA (FRI) has been introgressed with that of the wild types Col, Ler, and San Feliu-2 (Sf-2). In the early-flowering parental ecotypes, Col and Ler, a large decrease in flowering time in response to vernalization was observed only under short-day conditions. However, Sf-2 and the Ler and Col genotypes containing FRI showed a strong response to vernalization when grown in either long days or short days. Although vernalization reduced the responsiveness to photoperiod, plants vernalized for more than 80 d still showed a slight photoperiod response. The effect of FRI on flowering was eliminated by 30 to 40 d of vernalization; subsequently, the response to vernalization in both long days and short days was the same in Col and Ler with or without FRI. FR-light enrichment accelerated flowering in all ecotypes and introgressed lines. However, the FR-light effect was most conspicuous in the FRI-containing plants. Saturation of the vernalization effect eliminated the effect of FR light on flowering, although vernalization did not eliminate the increase of petiole length in FR light.

Journal Article↗
PubMed1969

Effects of light quality on the circadian rhythm of leaf movement of a short-day-plant.

Studies were made of the effects of blue, green, red and far-red (FR) light on the circadian rhythm of leaf movement of Coleus blumei x C. frederici, a short day plant. Under continuous illumination with blue light, there was a significant lengthening of the period of the rhythm to about 24.0 hr, as compared to 22.5 hr in continuous darkness. Under continuous red light, the period length was significantly shortened to 20.5 hr. Under continuous green or FR, the period length was not significantly different from the dark control. It was observed that under continuous FR illumination, the leaves tended to oscillate in a more downward position. Eight-hr red light signals were effective in advancing the phase of the rhythm as compared to a control under continuous green light. Blue light signals were effective in delaying the phase of the rhythm. FR light signals were ineffective in producing either delay or advance phase shifts. Far-red light did not reverse the effects of either red or blue light signals. On the basis of these results it is suggested, that pigments which absorb blue or red light, rather than phytochrome, mediate the effect of light on the circadian rhythm of leaf movement.

Journal Article↗
PubMed2004

Involvement of cyanobacterial phytochromes in growth under different light qualities and quantities.

Inactivation of the genes for the cyanobacterial phytochromes cph1 and cph2 in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 affected the growth of the cells under certain light conditions. Differences in growth were detected by recording growth curves and in competition experiments. Mutation of cph1 and cph2 resulted in different effects. The cph1-mutant strains exhibited a reduced growth rate under far-red light (FRL), whereas the growth of the cph2-mutant strains was inhibited by red light (RL). The growth rate of a cph1- / cph2- double mutant was reduced under both RL and FRL. Furthermore, cph1-, cph2- as well as double-mutant strains showed impaired growth under high-light (HL) conditions. Acclimation of the photosynthetic apparatus of the mutants to RL, FRL and HL, as determined by pigment analysis, was similar to that of the wild type.

Bacterial Proteins↗
PubMed2000

Spectral light quality affects protein profile of Synechococcus sp. PCC 7942: a comparative 2-dimensional gel electrophoresis (2-DGE) analysis.

We report here a comparative analysis of the effect of blue (450 nm), red (660 nm), and white light (400-700 nm) on the protein profile of cyanobacteria Synechococcus sp. PCC 7942. In vivo labeling of cells with [(35)S] methionine and their subsequent analysis by two-dimensional gel electrophoresis (2-DGE) showed that eight polypeptides were unique to dark adapted cells, ten were blue light specific, and four were specifically induced in red light. The results show that Synechococcus sp. respond to various light treatments rapidly and synthesize new polypeptides in dark and blue/red light.

Bacterial Proteins↗
PubMed1994

Analysis of the parsley chalcone-synthase promoter in response to different light qualities.

We examined the chalcone synthase (chs) promoter from parsley [Petroselinum crispum Miller (A.W. Hill)] for the existence of separate promoter elements responsible for transcriptional activation of the chs gene by UV-B and by blue light. A combination of in-vivo foot-printing in parsley cells and light-induced transient expression assays with different chs promoter constructs in parsley protoplasts was used. Dark controls and blue-light-irradiated cells gave identical in-vivo footprints on the chs promoter. Pre-irradiation with blue light prior to a UV-B-light pulse is known to cause a shift in the timing of UV-B-light-induced increase in chs transcription rates. This shift was also manifested on the DNA template, since UV-B-light-induced in-vivo footprints in cells pretreated with blue light were detected earlier than in cells which had been irradiated with a UV-B-light pulse only. Although there was a clear shift in the timing of footprint appearance, the patterns of footprinting did not change. Light-induced transient-expression assays revealed that the shortest tested chs promoter which retained any light responsiveness, was sufficient for mediating both induction by UV light and the blue-light-mediated kinetic shift. These findings argue against a spatial separation of UV-B- and blue-light-responsive elements on the chs promoter. We interpret these data by postulating that the signal transduction pathways originating from the excitation of UV-B- and blue-light receptors merge at the chs promoter, or somewhere between light perception and protein-DNA interaction.

Acyltransferases↗
PubMed1977

Effect of light quality on the organization of photosynthetic electron transport chain of pea seedlings.

The activity of NADP and O(2) photoreduction by water is essentially higher in chloroplasts isolated from pea seedlings (Pisum sativum L.) grown under blue light as compared with that from plants grown under red light. In contrast, the photoreduction of NADP and O(2) with photosystem I only is practically the same or even lower in chloroplasts isolated from plants grown under blue light. The addition of plastocyanin does not affect the rate or the extent of NADP photoreduction by water in the chloroplasts isolated from plants grown under blue light, whereas it sharply activates NADP reduction in the chloroplasts isolated from plants grown under red light. The extent of the light-induced oxidation of cytochrome f is appreciably higher in chloroplasts isolated from plants grown under blue light. Cytochrome b(559) plays the predominant role in the oxidoreductive reactions of these chloroplasts. Furthermore, the fluorescence measurements indicate more effective transfer of excitation energy from chlorophyll to the photosystem II reaction center in chloroplasts isolated from plants grown under blue light.The data reported are interpreted in terms of differential rates of electron transport from water in the two chloroplast preparations.

Journal Article↗
PubMed1999

Shade-avoidance responses in two common coastal redwood forest species, Sequoia sempervirens (Taxodiaceae) and Satureja douglasii (Lamiaceae), occurring in various light quality environments.

Shade-avoidance responses were examined for two species common to the coastal redwood forest, Sequoia sempervirens and Satureja douglasii. Sequoia seedlings demonstrated a shade-avoidance response when given end-of-day far-red light by increased hypocotyl, epicotyl, and first-node extension, and greater total number of needles and reduced anthocyanin concentration. Thus, Sequoia seedlings respond as sun-adapted plants. Satureja has several leaf monoterpene chemotypes that occur in different light environments including the redwood forest, and the types responded differently to the light treatments. The pulegone type responded to end-of-day far-red light as a sun-adapted plant with significant extension growth, increased leaf area and chlorophyll, and reduced anthocyanin. The isomenthone type responded as a shade-tolerant plant and did not exhibit extension growth nor a change in other parameters with end-of-day far-red light. However, the carvone and bicyclic types had variable responses depending on the parameter studied, which indicated genetic variation for these traits.

Journal Article↗