Die Wirkung von blauem und rotem Licht auf die Synthese ribosomaler RNA bei Chlorella

In autotrophic cultures of Chlorella pyrenoidosa (strain 211-8b) incorporation of tritiated guanosine and uridine into ribosomal RNA is stimulated by light. Blue light of wavelengths around 457 nm is considerably more effective than red light around 679 nm (5·10^-10 Einstein cm^-2sec^-1 for both). This effect can be demonstrated for young daughter cells (at the end of the dark period) and for older cells (at the end of the light period). It is shown to depend on a regulation of rRNA-synthesis. The blue light dependent enhancement of incorporation is more pronounced in the cytoplasmic rRNA (25 and 18 s) than in the chloroplast rRNA (23 and 16 s). Blue light of low intensity (1·10^-10 Einstein cm^-2sec^-1) has nearly the same effectivity as the fivefold intensity, whereas red light of equal quantum fluxes enhances incorporation only slightly compared with the dark control. The blue light dependent enhancement of rRNA-synthesis continues in the following darkness in contrary to that caused by red light. This enhancement is also found in DCMU-poisened cultures. In contrast to this, in red light in presence of DCMU, incorporation into rRNA is nearly the same as in dark. It is concluded that the regulation of rRNA-synthesis in red light is closely connected to complete photosynthesis, while in blue light an additional regulation takes place independent of photosynthesis.     

Influence of light quality on the ribosomal RNA levels inWolffia arrhiza: Comparison of phosphate and magnesium limited chemostat populations

Wolffia arrhiza (L.) Wimm. was grown axenically in the chemostat under white luminescent light (photon fluence rate 23 ujnol m^-2 s^-1) and phosphate or magnesium limitation (0.075 and 0.01 jxmol 1^-1, respectively). Aliquots (1 g fresh mass) were taken from the continuous cultures and were irradiated for 1 h with either white light (control) or monochromatic blue (453 nm) or red (654 nm) light. The amount of [5^-3H]-uridine incorporated into cytosolic and chloroplastic rRNAs during these exposures was estimated and following results were obtained: In phosphate limited plants rod light considerably reduced and blue light slightly increased label incorporation as compared with the control. Moreover, in red light, chloroplast incorporation is relatively more slowed down than that in the cytosolic compartment (34 % as compared to 59 % of the control). In blue light the enhancement is approximately equal in both compartments. In magnesium limited plants incorporation under both blue and red light is moderately slower as compared with the control. In both cases also the retardation is slightly greater in the chloroplast than in the cytoplasm. The results suggest that rRNA metabolism is controlled by light quality as well as by mineral nutrition.     

STIMULATION OF LIGHT-SATURATED PHOTOSYNTHESIS IN LAMINARIA (PHAEOPHYTA) BY BLUE LIGHT1

The light-saturated rate of photosynthesis in blue light was 50-100% higher than that in red light for young sporophytes of Laminaria digitata (Huds.) Lamour., although photosynthetic rates were slightly higher in red than in blue light at low irradiances. Short exposures to low irradiances (e.g. 2 min at 20 μmol · m^?2· s^?1) of blue light also stimulated the subsequent photosynthesis of Laminaria sporophytes in saturating irradiances of red light but had little effect on photosynthesis in low irradiances of red light. The full stimulatory effect of short exposures to blue light was observed within 5 min of the blue treatment and persisted for at least 15 min in red light or in darkness. Thereafter, the effect began to decline, but some stimulation was still detectable 45 min after the blue treatment. The degree of stimulation was proportional to the logarithm of the photon exposure to blue light over the range 0.15-2.4 mmol · m^?2, and the effectiveness of an exposure to 0.6 mmol · m^?2at different wavelengths was high at 402-475 nm (with a peak at 460-475 nm) but declined sharply at 475-497 nm and was minimal at 544-701 nm. Blue light appears, therefore, to exert a direct effect on the dark reaction of photosynthesis in brown algae, possibly by activating carbon-fixing enzymes or by stimulating the uptake or transport of inorganic carbon in the plants.     

Der Einfluss von Farblicht auf Wachstum und Zusammensetzung Pflanzlicher Gewebekulturen

Summary The growth of green cultures of callus tissue from Nicotiana tabacum var. Samsun is stimulated by light. To determine whether the increase in growth is caused by photosynthesis or by a blue light dependent increase of protein synthesis, a comparative study was made of the effect which blue and red light have on the growth and the composition of tobacco tissue. It is shown that the growth stimulation by light depends on the chlorophyll content of the tissues. Starting with chlorophyll-free tissue the cultures begin to grow faster in blue light only after they become visibly green. On the other hand, the growth of green tissue in red light decreases as soon as the chlorophyll content under this condition becomes less. There are no differences in the rate of growth of green tissues cultivated in blue and in red light of approximately the same flow of quanta; in both cases the cultures grow better than the controls in the dark. Furthermore there are no differences between the protein and carbohydrate content of tissues grown in blue or red light and in the dark. There is, however, a small but significant difference between the total nitrogen of green tissue and that of chlorophyll-free tissue which is due to a higher amount of soluble nitrogen in the green tissue. From these results it is concluded that the light dependent growth stimulation is caused by photosynthesis. As shown by a light dependent ¹⁴CO₂ incorporation in which sucrose is the main product, the green cells are able to fix CO₂ photosynthetically. However, the rate of photosynthesis in the tissue cultures is small and does not balance the respiration. It seems very unlikely, therefore, that the formation of carbohydrates by photosynthesis is responsible for the observed growth increase.     

Photoperiod and light quality effects on rate of dark respiration and on photosynthetic capacity in developing seedlings of Chenopodium rubrum

Development and acclimation of energy transduction were studied in seedlings of Chenopodium rubrum L. ecotype selection 184 (50° 10' N; 105° 35' W) in response to photomorphogenic and photoperiodic treatments. Dark respiration and photosynthetic capacity [nmol O₂ (pair of cotyledons)⁻¹ h⁻¹] were measured with an oxygen electrode. Changes in chloroplast ultrastructure were analyzed concomitantly. After germination, seedlings were grown at constant temperature either in darkness or in continuous light (white, red, far-red and blue) or were subjected to diurnal cycles of light/dark or changes in light quality. Dark respiration was low in far-red light treated seedlings. In red light treated seedlings dark respiration was high and the mean value did not depend on fluence rate or photoperiod. Blue light stimulated transitorily and modulated dark respiration in photoperiodic cycles. Photosynthetic capacity was reduced by far-red light and increased by red light. In response to blue light photosynthetic capacity increased, with indications of a requirement for continuous energy input. Phytochrome and a separate blue light receptor seemed to be involved. In continuous red light a clear cut circadian rhythm of dark respiration was observed. Blue light had a specific effect on chloroplast structure.     

Potentiation of photosynthetic oxygen evolution in red light by small quantities of monochromatic blue light

Growth of the giant unicellular green alga, Acetabularia crenulata, stops in red light of broad spectral composition, but can be restored by the addition of small quantities of blue light. Long-term records of O₂ evolution indicate that the photosynthesis of Acetabularia responds in a parallel manner to blue light. Cells photosynthesizing at a light-limited rate in white light were given red light at an intensity that served to match or somewhat increase the instantaneous rate of O₂ production. A rapid decline in the rate commenced within 15 minutes and continued for 2 hours or more until it had fallen to 20 to 40% of the initial level. Very small doses of violet or blue radiation (<10⁻⁸ Einstein/cm²) then affected a complete, though temporary, restoration of the original rate of photosynthesis. Responses began after a lag of 4 to 5 minutes, regardless of their magnitude, and in the most favorable instances persisted 4 to 6 hours after the stimulus. Blue light treatments were effective as flashes as brief as 2.5 seconds, given simultaneously or in sequence with the red measuring light, or as low-intensity continuous irradiations. Blue-light induction of the response was stable over at least 5 minutes of darkness. After a suitable red-light pretreatment, 2 other algae, Chlamydomonas reinhardi and Fucus vesiculosus, were shown to respond similarly to low-intensity irradiations with blue or blue-green light.     

蓝光诱导的胶孢炭疽菌(Colletotrichum gloeosporioides)类胡萝卜素积累

胶孢炭疽菌(Colletotrichumgloeosporioides)为一种丝状真菌,蓝光照射可诱导类胡萝卜素的积累。光镜下观察表明,蓝光可诱导胶孢炭疽菌菌丝积累色素颗粒,而黑暗和红光处理却无此现象。类胡萝卜素的积累受蓝光光照强度的影响。28℃且蓝光为6.5μmol.m-2.s-1时,类胡萝卜素积累量可随光照时间延长呈增长趋势,在第5天达到最高峰为71.8μg/g FW,随后含量下降。此外,胶孢炭疽菌在黑暗中预培养的时间也影响蓝光的诱导反应。     

Photocontrol of Growth, and of Anthocyanin and Chlorogenic Acid Production in Cultured Callus Tissues of Haplopappus gracilis

Cultures of dark-grown Haplopappus callus (strain AI) were exposedto continuous blue, green, red, far-red, and white light for33 days at energy levels of approximately 10 J m^-2s^-1. Growthwas suppressed in all but far-red. Blue had the greatest suppressiveeffect, green the least; red and white were about equally effective.Mean cell generation times were increased from 8–8 days(dark control) to 12.5 days in red light and 20.5 days in blue.There was a slight increase in mean wet weight per cell in bluelight but a slight decrease in red, whereas there was almosta twofold increase in mean dry weight per cell in blue and littlechange in red. In contrast, far-red stimulated growth; the meancell generation time was reduced to 6–5 days and therewas little change in wet or dry weight per cell. Anthocyanin synthesis was promoted by all wavebands except far-red.Blue had the greatest effect, then white, red, and green inthat order. In blue light the pigments accumulated rapidly,but only during the early stages of culture. The maximum amountper cell was attained after 7 days and thereafter the valuesdeclined. In red, however, the pigments accumulated relativelyslowly, and the maximum cell content was not attained until22 days; the amount attained was less than half that attainedin blue light. Initially, the ratio of cyanidine-3-glucosideto cyanidine-3-rutinoside exceeded 5.0 in blue light, but theratio fell to almost unity with time. This probably reflecteda rapid initial synthesis of the glucoside accompanied by asteady conversion to the rutinoside. Blue light was also more effective than red in acceleratingchlorogenic acid production. The response to blue light occurredafter the initial rise in anthocyanins and continued for therest of the culture period. The data are discussed in relation to similar high-energy photoresponsesreported for intact systems.     

光质对植物光合作用的调控及其机理

光合作用是植物生长发育的基础.光质对植物光合作用的调控主要包括可见光对植物气孔器运动、叶片生长、叶绿体结构、光合色素、D1蛋白及其编码基因和光合碳同化等的调节,以及紫外光对植物光系统Ⅱ的影响.蓝光和红光能促进气孔的开张,而绿光能够逆转这种作用.蓝光有利于叶绿体的发育,红、蓝、绿复合光有利于叶面积的扩展,而红光更有利于光合产物的积累;不同光质对不同植物、不同组织器官叶绿素积累的影响不同.蓝光和远红光可以促进psbA基因转录物质的积累.大多数高等植物和绿藻在橙、红光下光合速率最高,蓝紫光其次,绿光最低.紫外光可以导致光系统Ⅱ的电子传递活性下降.此外,针对光质与光合作用研究领域中存在的问题,对今后的研究方向进行了讨论.     

Phytochrome Modifies Blue-light-induced Electrical Changes in Corn Coleoptiles

Unilateral blue light administered to corn coleoptile segments produces no alteration of transmembrane potential on the light side, and only a small and slow hyperpolarization on the dark side. Red light causes a 5-15 millivolt depolarization in cells on the light side causes and somewhat smaller effects on the dark side. Blue given after red causes a rapid hyperpolarization on both sides of the coleoptile. The effect of the potentiating red preirradiation is probably due to phytochrome, being largely abolished by far-red given after red, but before the blue light. The effect of prior red irradiation decays in the dark, showing a half-time of about 45 minutes at room temperature. This rapid cooperativity between phytochrome and the phototropic pigment may indicate a common locale, possibly in a membrane.     

Photosynthetic metabolism and cell-wall polysaccharide accumulation inGelidium sesquipedale (Clem.) Born. et Thur. under different light qualities

The influence of different light qualities on the photosynthetic rate, dark respiration, intracellular carbon and nitrogen content, and accumulation of photosynthetic pigments and cell-wall polysaccharides during short-term incubation (5 h) of the red algaGelidium sesquipedale was investigated. The same photon irradiance of 50mol m^–2 s^–2 below the light saturation point of photosynthesis was applied in each case. Blue light stimulated photosynthesis, dark respiration and the accumulation of chlorophyll and biliproteins, phycoerythrin in particular. The accumulation of internal carbon and nitrogen was greater under blue light than under the other light qualities. In contrast, the percentage of cell-wall polysaccharides was higher in red light. The content of cell-wall polysaccharides decreased during the time of incubation in all light treatments except in red light. The action of a non-photosynthetic photoreceptor in the control of cell-wall polysaccharide synthesis is suggested because the accumulation of cell-wall polysaccharides was not correlated with net photosynthesis in contrast to what occurred with carbon, chlorophyll and phycoerythrin accumulation.     

Einfluss verschiedener Lichtwellenlängen auf die Zusammensetzung von Chlorella in Glucosekultur bei gehemmter Photosynthese

Summary Increasing blue light intensity inhibits the growth of Chlorella pyrenoidosa in glucose culture in which photosynthesis is blocked by DCMU, whereas red light supports growth which is the same as or better than that in dark controls.The action spectrum of light induced protein synthesis from exogenous glucose (photosynthesis inhibited, blue light addition resulting in growth >90% of the dark control) shows only one broad maximum at 450–490 nm which resembles the absorption spectrum of carotenoids.     

Adaptations in Pigment Composition and Photosynthesis by Far Red Radiation in Chlorella pyrenoidosa

Chlorella pyrenoidosa has been cultivated in radiation of wavelengths between 690–975 nm for several months. Absorption spectra and action spectra of photo-synthesis have been determined for far red and “white” light brown cultures, In vivo spectrophotometric analyses and action spectra showed that fur red growth Chlorella adapted to the extreme light conditions by an increase both in absorption and photosynthesis above 700 nm. It is proposed that som of the in vivo normal chlorophyll a forms were converted to a far red absorbing chlorophyll a form, giving the far red exposed suspension an increased photosynthetic activity between 700–740 nm. The analyses of far red grown Chlorella have also shown an increased photosynthesis in the blue part of the spectrum, presumably due to a decrease in photosynthetically inactive carotenoid content. By culturing Chlorella in a “white” light gradient between 0.5 × 10⁴ and 3.7 × 10⁴ erg cm^?2 s^?1, it has been demonstrated that light intensity did not influence pigment ratios between 500–750 nm. In the blue part, however, high light levels caused increased absorption because of increased carotenoid content. Some ecological aspects of this far red effect have also been discussed.     

Effect of Light Quality on the Circadian Expression of Nitrate Reductase in the Red Macroalga Gracilaria tenuistipitata

A circadian rhythm in the activity of nitrate reductase (NR: EC 1.6.6.1) isolated from the marine red algae Gracilaria tenuistipitata is shown to be attributable to the daily oscillation of protein levels. The experiments reported here indicate that light quality has differential effects over NR expression. In extracts of algae grown under white light : dark, red light : dark and blue light : dark cycle, the activity of NR peaks during photophase, as does photosynthesis. Staining with a monoclonal antibody (NR10), raised against NR purified from Porphyra yezoensis, shows that the amount of protein changes by a factor of about 20, with a maximum occurring during photophase when algae are submitted to white and blue light. Red light changes the circadian rhythm of NR protein levels and also inhibits its night degradation. Illumination with blue light is able to restore the NR activity as well as its protein levels only when the light irradiance was the same of the white light. Surprisingly, the red light promoted 40% induction on NR activity under the same conditions.     

Amaranthin accumulation in continuous red and blue light by seedlings ofAmaranthus caudatus L.

Four days oldAmaranthus seedlings responded to light treatment with an increase of amaranthin accumulation. With increasing irradiation time, red light caused a saturation effect. Blue light induced a high irradiation response. The blue light effect was reversible to a certain extent by far-red irradiation given at the end of the treatment with blue light. Intermittent red light (3 h red light, 3 h dark, …) caused a higher amaranthin accumulation than 24 h continuous red light. Results obtained with red and blue light are discussed on the basis of the phytochrome system.