Laser-induced fluorescence (LIF) spectra of herbaceous and woody pre- and post-digested plant material

Filtrate from pre- and post-digested plant material was exposed to 355-nm pulsed laser light and the subsequent laser-induced fluorescence (LIF) was recorded. Similarities and differences among spectra from 20 materials are discussed. Each material was replicated once, dried, ground, and exposed to chloroform (CHCl₃) for 24 h. The material represented aged (1 to 18 years old) plants from different herbaceous (grasses and forbs) and woody plant life forms. Mean peak fluorescence recorded among materials differed (P<0.0001) in both wavelength and peak amplitude (counts) across the spectral range (387 to 788 nm). Peak fluorescence was evaluated within each of three arbitrary color categories, blue near 455 nm and red near 674 nm, while only 16 of the materials produced a green peak near 528 nm. In general, the blue and green fluorescence peaks were broad while the red peak was narrow. Mean peak counts were largest in the red range. Varying amounts of laser beam absorption occurred among the materials evaluated due to different concentrations of filtrate and different absorption efficiencies; therefore, amplitude data (counts) were not used to determine statistical differences among materials. To overcome difficulties attributed to the raw count data, red/blue, red/green and blue/green count ratios within replicates were calculated. Using all three count ratios in a multivariate analysis of variance, the 16 materials could be separated into nine different (P<0.05) material groupings. The LIF technique may provide a reliable means to separate ground pre- and post-digested plant materials following further research into determining what fluorophores are producing the spectral signatures and how sample preparation affect peak wavelengths.     

Characterization of the laser-induced blue, green and red fluorescence signatures of leaves of wheat and soybean grown under different irradiance

The blue, green and red fluorescence emission of green wheat ( Triticum aestivum L. var. Rector) and soybean leaves ( Glycine max L. var. Maple Arrow) as induced by UV light (nitrogen laser: 337 nm) was determined in a phytochamber and in plants grown in the field. The fluorescence emission spectra show a blue maximum near 450 nm, a green shoulder near 530 nm and the two red chlorophyll fluorescence maxima near 690 and 735 nm. The ratio of blue to red fluorescence, F450/F690, exhibited a clear correlation to the irradiance applied during the growth of the plants. In contrast, the chlorophyll fluorescence ratio, F690/F735, and the ratio of blue to green fluorescence, F450/F530, seem not to be or are only slightly influenced by the irradiance applied during plant growth. The blue fluorescence F450 only slightly decreased, whereas the red chlorophyll fluorescence decreased with increasing irradiance applied during growth of the plants. This, in turn, resulted in greatly increased values of the ratio, F450/F690, from 0.5 – 1.5 to 6.4 – 8.0. The decrease in the chlorophyll fluorescence with increasing irradiance seems to be caused by the accumulation of UV light absorbing substances in the epidermal layer which considerably reduces the UV laser light which passes through the epidermis and excites the chlorophyll fluorescence of the chloroplasts in the subepidermal mesophyll cells.     

Investigations of the Blue-green Fluorescence Emission of Plant Leaves

The UV light (337 nm) induced blue-green fluorescence emission of green leaves is characterized at room temperature (298 K) by a maximum near 450 nm (blue region) and a shoulder near 525 nm (green region) and was here also studied at 77 K. At liquid nitrogen temperature (77 K) the blue (F450) and green fluorescence (F525) are much enhanced as is the red chlorophyll fluorescence near 735 nm. During development of green tobacco leaves the blue fluorescence F450 (77 K) is shifted towards longer wavelengths from about 410 nm to 450 nm. The isolated leaf epidermis of tobacco showed only slight fluorescence emission with a maximum near 410 nm. The green fluorescence F525 was found to mainly originate from the mesophyll of the leaf, its intensity increased when the epidermis was removed. The red chlorophyll fluorescence emission was also enhanced when the epidermis was stripped off; this considerably changed the blue/red fluorescence ratios F450/F690 and F450/F735. The epidermis, with its cell wall and UV-light-absorbing substances in its vacuole, plays the role of a barrier for the exciting UV-light. In contrast to intact and homogenized leaves, isolated intact chloroplasts and thylakoid membranes did not exhibit a blue-green fluorescence emission.     

Studies on the Localization and Spectral Characteristics of the Fluorescence Emission of Differently Pigmented Wheat Leaves

Intensity, spectral characteristics and localization of the UV-laser (337 nm) induced blue-green and red fluorescence emission of green, etiolated and white primary leaves of wheat seedlings were studied in a combined fluorospectral and fluoromicroscopic investigation. The blue-green fluorescence of the green leaf was characterized by a maximum near 450 nm (blue region) and a shoulder near 530 nm (green region), whereas the red chlorophyll fluorescence exhibited maxima in the near-red (F690) and far-red (F735). The etiolated leaf with some carotenoids and traces of chlorophyll a, in turn, showed a higher intensity of the blue-green fluorescence with a shoulder in the green region and a strong red fluorescence peak near 684 to 690 nm, the far-red chlorophyll fluorescence maximum (F735) was, however, absent. The norfluorazone-treated white leaf, free of chlorophylls and carotenoids, only exhibited blue-green fluorescence of a very high intensity. In green and etiolated leaves the blue-green fluorescence primarily derived from the cell walls of the epidermis and the red fluorescence from the chlorophyll a of the mesophyll cells. In white leaves the blue-green fluorescence emanated from all cell walls of epidermis, mesophyll and leaf vein bundles. The shape and intensity of the blue-green and red fluorescence emission is determined by the reabsorption properties of chlorophylls and carotenoids in the mesophyll, thus giving rise to quite different values of the various fluorescence ratios F450/F690, F450/F530, F450/F735 and F690/F735 in green and etiolated leaves.     

Fluorescence emission spectra of plant leaves and plant constituents

Summary The UV-B radiation (e.g. 337 nm) induced blue fluorescence (BF) and red chlorophyll fluorescence spectra (RF) of green leaves from plants with different leaf structure were determined and the possible nature and candidates of the blue fluorescence emission investigated. The blue fluorescence BF is characterized by a main maximum in the 450 nm region and in most cases by a second maximum/shoulder in the 530 nm region. The latter has been termed green fluorescence GF. The red chlorophyll fluorescence RF, in turn, exhibits two maxima in the 690 and 730 nm region. In general, the intensity of BF, GF and RF emission is significantly higher in the lower than the upper leaf side. The ratio of BF to RF emission (F450/F690) seems to vary from plant species to plant species. BF and GF emission spectra appear to be a mixed signal composed of the fluorescence emission of several substances of the plant vacuole and cell wall, which may primarily arise in the epidermis. Leaves with removed epidermis and chlorophyll-free leaves, however, still exhibit a BF and GF emission. Candidates for the blue fluorescence emission ( max near 450 nm) are phenolic substances such as chlorogenic acid, caffeic acid, coumarins (aesculetin, scopoletin), stilbenes (t-stilbene, rhaponticin), the spectra of which are shown. GF emission ( max near 530 nm) seems to be caused by substances like the alkaloid berberine and quercetin. Riboflavine, NADPH and phyllohydroquinoneK ₁ seem to contribute little to the BF and GF emission as compared to the other plant compounds. Purified natural-carotene does not exhibit any blue fluorescence.     

Blue,Green and Red Fluorescence Signatures and Images of Tobacco Leaves*

Laser-induced fluorescence images of the leaf of an aurea mutant of Nicotiana tabacum were recorded for the blue and green fluorescence at 440 and 520 nm and the red chlorophyll fluorescence at 690 and 735 nm. The results obtained were compared with direct measurements of the fluorescence emission spectra of leaves using a conventional spectrofluorometer. The highest emission of blue (F440) and green fluorescence (F520) within the leaf was found in the leaf veins, particularly the main leaf vein. In contrast, the intercostal fields of leaves, which exhibited the highest chlorophyll content, showed only a very low blue and green fluorescence emission, which was much lower than the red and far-red chlorophyll fluorescence emission bands (F690 and F735). Correspondingly, the ratio of blue to red leaf fluorescence F440/F690 of upper and lower leaf side was much higher in the leaf veins (values 1.2 to 1.5) than in intercostal fields (values of 0.6 to 0.7). The results also demonstrated that in the intercostal fields the major part of the blue-green fluorescence was reabsorbed by chlorophylls and carotenoids. A partial reabsorption of the red fluorescence band near 690 nm by leaf chlorophyll took place, but did not affect the far-red fluorescence band near F735. As a consequence the chlorophyll fluorescence ratio F690/F735 exhibited significantly higher values in the chlorophyll-poor leaf vein regions (1.7 to 1.8) than in the chlorophyll-rich intercostal fields (0.8 to 1.3). Imaging spectroscopy of leaves was shown to be much more precise than the screening of fluorescence signatures by conventional fluorometers. It clearly demonstrated that the blue-green fluorescence and the red chlorophyll fluorescence of leaves exhibit an inverse contrast to each other. The advantage of the fluorescence imaging spectroscopy, which allows the simultaneous screening of the whole leaf surface and distinct parts of it, and its possible application in the detection of stress effects or local damage by insects and pathogens, is discussed.     

Borax Methylene Blue: A Spectroscopic And Staining Study

Borax methylene blue is quite stable at room temperatures of 22-25 C. At 30 C polychroming is slow; during 50 days in a water bath at this temperature the absorption peak moves from 665 to 656 nm. At 35 C, the absorption peak reaches 660 nm in 7 days, 654 nm in 14. At 60 C polychroming is rapid, the absorption peak reaching 640-620 nm in 3 days. When the pH of the borax methylene blue solutions, normally about 9.0, is adjusted to pH 6.5, the absorption peak remains at 665 nm even when incubated at 60 C for extended periods.

When used as a blood stain 0.4 ml borax methylene blue (1% methylene blue in 1% borax), 4 ml acetone, 2 ml borax-acid phosphate buffer to bring the solution to pH 6.5, and distilled water to make 40 ml, with 0.2 ml 1% eosin added just before using, an excellent Nocht-Giemsa type stain is achieved after 30 minutes staining. The material plasmodia P. falciparum, P. vivax, and P. berghei stain moderate blue with dark red chromatin and green to black pigment granules.

The study confirms Malacnowski's 1891 results and explains Gautier's 1896-98 failure to duplicate it.     

Uptake of the Herbicide Diuron as Visualised by the Fluorescence Imaging Technique

A new fluorescence imaging system for monitoring the uptake of the PSII-herbicide diuron (OCMU) was tested in tobacco leaves. UV-laser-induced (Λ_exc = 355 nm) fluorescence images were collected for blue fluorescence F440 (Λ_em = 440 nm), green fluorescence F520 (Λ_em = 520 nm), red chlorophyll fluorescence F690 (Λ_em = 690 nm) and for far-red chlorophyll fluorescence F740 (Λ_em = 740 nm). Diuron-treated leaf parts exhibited a higher red and far-red chlorophyll fluorescence emission (F690 and F740) than untreated leaf halves, whereas the blue and green fluorescence, F440 and F520, remained unaffected. As a consequence, the fluorescence ratios blue/red (F440/F690) and blue/far-red (F440/F740) significantly decreased in diuron-treated leaf parts. The time course of diuron uptake into the leaf could be followed by fluorescence images taken 10 and 30 min after diuron application. The novel high resolution fluorescence imaging method supplies information on the herbicide uptake of each point of the leaf area. Its great advantage as compared to the point data fluorescence measurements applied so far is discussed.     

Evaluating UV-B effects and EDU protection in cucumber leaves using fluorescence images and fluorescence emission spectra

A newly developed laboratory fluorescence imaging system was used to obtain fluorescence images (FImage) of freshly excised cucumber (Cucumis sativus L.) leaves in spectral bands centered in the blue (F450), green (F550), red (F680), and far-red (F730) spectral regions that resulted from a broad-band (300-400 nm) excitation source centered at 360 nm. Means of relative fluorescence intensities (RFI) from these spectral fluorescence images were compared with spectral fluorescence emission data obtained from excitation wavelengths at 280 nm (280EX, 300-550 nm) and 380 nm (380EX, 400-800 nm) of dimethyl sulfoxide (DMSO) extracts from these leaves. All three fluorescence data types (FImage, 280EX, 380EX) were used to assess ultraviolet-B (UV-B, 280-320 nm) induced physiological changes and the possible use of N-[2-(2-oxo-1-imidazolidinyl) ethyl]-N′-phenylurea (EDU or ethylenediurea) as a chemical protectant against UV-B damage. Plants exhibited well known foliar growth and pigment responses to UV-B exposure (e.g., increased UV-B absorbing compounds and decreased leaf area, chlorophyll a content; and and lower chlorophyll a/b and chlorophyll/carotenoid pigment ratios). Since EDU alone had no effect on foliar variables, there was no evidence that EDU afforded protection against UV-B. Instead, EDU augmented some UV-B effects when provided in conjunction with UV-B irradiation (e.g., reductions in the chlorophyll/carotenoid ratio, total photosynthetic pigments, and chlorophyll b content).Relative fluorescence intensities (RFI) in the longer visible wavelengths (green, red, and far-red) were uncorrelated for comparisons between the FImage and 380EX data sets. However, blue and green RFI were significantly correlated (0.8r0.6; P ≤0.002) for comparisons between FImage and 280EX data sets. UV-B treatment caused an increase in blue RFI (e.g., F450) in both images and 280EX measurements. One explanation is that the UV-B excitation of both 280EX and FImage stimulates processes that produce excess blue fluorescence. The molecules that produce the excess blue fluorescence in both the 280EX and the Fimage data are different electron transfer agents that operate in parallel. For FImage, the UV excitation penetrates leaf surface layers to stimulate fluorescence from compounds in mesophyll and epidermal tissues (as occurs for the extracts of leaf discs), whereas emissions captured at longer, less energetic wavelengths, were primarily from the epidermal layer. UV-B irradiated leaves showed much greater heteorgeneity of RFI in both the green (F550_FImag) and the red (F680_FImag) bands than unirradiated leaves; this was true irrespective of EDU treatment.Although qualitative responses in individual bands differed between FImage and 380EX data, similar results were obtained in the detection of UV-B induced effects when the red/green and blue/far-red fluorescence ratios of these data were compared. The red/green ratio (either F680/F550_FImage or F675/F525_380EX) was lower for UV-B exposed plants in both images and 380EX data. UV-B exposure also significantly enhanced the blue/far-red ratio of images (F450/F740_FImage) and the comparable 380EX ratio (F450/F730_380EX) for the combined UV-B/EDU group. The far-red/red ratios were not useful in separating treatment effects in images or 380EX. Although comparable ratios were not available in 280EX data, the UV/blue ratio (F315/F420_280EX) was substantially reduced by UV-B exposure and was inversely related to total photosynthetic pigment content. These findings suggest that the red/green ratio (FImage, 380EX) and the UV/blue ratio (280EX) may be as useful as the blue/far-red ratio (380EX) reported previously in detection of UV-B stress. Furthermore, the results support the validity of the imaging technique as a non-destructive diagnostic tool for assessing UV-B stress damage in plants.     

Influence of 2,4-D, IAA, and duration of callus induction in anther cultures of spring wheat

Culture media and environmental factors may significantly influence the yield of haploid plants from anther cultures. Our objectives were to identify a combination of 2,4-dichlorophenoxyacetic acid (2,4-D) and indoleacetic acid (IAA) concentrations which produce the maximum number of haploid plants, and to evaluate the effects of duration in induction medium on calli induction, plant regeneration, and green plant production from anther cultures in spring wheat. Significant (P ≤ 0.01) plant growth regulator concentration effects (2,4-D and IAA) were observed on the number of calli, green plants and albino plants produced, and on direct plant regeneration. Addition of 2,4-D to the induction medium resulted in significantly (P ≤ 0.01) higher means for all anther culture components compared to IAA> While addition of 2,4-D significantly (P ≤ 0.01) reduced plant regeneration, it substantially increased green plant percentage at a 0.3-mg l⁻¹ concentration of IAA. Use of response functions to estimate the maximum effective 2,4-D × IAA combination implied that higher 2,4-D levels in the induction medium should be investigated, and that the optimum hormone combination differs for plant regeneration and green plant percentage. Significant (P ≤ 0.01) effects of duration on callus induction medium were observed for plant regeneration and green plant percentage.     

Distribution of UV-shielding of the epidermis of sun and shade leaves of the beech (Fagus sylvatica L.) as monitored by multi-colour fluorescence imaging

Plants can protect against damaging ultraviolet (UV) radiation by accumulating UV-absorbing substances in the epidermis of the leaves. Sun and shade leaves of a free standing beech tree (Fagus sylvatica L.) were studied for the differences in UV-shielding of the epidermis by means of multi-colour fluorescence images taken with UV and blue excitation. The distribution of the fluorescence intensity was detected over intact leaves in the emission maxima in the blue at 440 nm (F440), in the green at 520 nm (F520), in the red at 690 nm (F690) and in the far red at 740 nm (F740). Images of the logarithmic ratio between F690 excited in the blue and the UV (log (^BF690/^UVF690)) were calculated representing the relative absorption of UV in the epidermis and thus the degree of UV-shielding. It was found that UV-shielding is stronger for sun leaves than for shade leaves and better for the upper (adaxial) leaf side than for the lower (abaxial) leaf side of both leaf types. Within one leaf the highest value for the ratio log (^BF690/^UVF690) and thus the highest UV-shielding was found at the leaf rim which in broad leaves contains young tissue.     

Imaging of the Blue,Green, and Red Fluorescence Emission of Plants: An Overview

An overview is given on the fluorescence imaging of plants. Emphasis is laid upon multispectral fluorescence imaging in the maxima of the fluorescence emission bands of leaves, i.e., in the blue (440 nm), green (520 nm), red (690 nm), and far-red (740 nm) spectral regions. Details on the origin of these four fluorescence bands are presented including emitting substances and emitting sites within a leaf tissue. Blue-green fluorescence derives from ferulic acids covalently bound to cell walls, and the red and far-red fluorescence comes from chlorophyll (Chl) a in the chloroplasts of green mesophyll cells. The fluorescence intensities are influenced (1) by changes in the concentration of the emitting substances, (2) by the internal optics of leaves determining the penetration of excitation radiation and partial re-absorption of the emitted fluorescence, and (3) by the energy distribution between photosynthesis, heat production, and emission of Chl fluorescence. The set-up of the Karlsruhe multispectral fluorescence imaging system (FIS) is described from excitation with UV-pulses to the detection with an intensified CCD-camera. The possibilities of image processing (e.g., formation of fluorescence ratio images) are presented, and the ways of extraction of physiological and stress information from the ratio images are outlined. Examples for the interpretation of fluorescence images are given by demonstrating the information available for the detection of different developmental stages of plant material, of strain and stress of plants, and of herbicide treatment. This novel technique can be applied for near-distance screening or remote sensing.     

Probing the interactions of alcohols with biological membranes with the fluorescent probe Prodan.

Prodan [6-propionyl-2-(dimethylamine)naphthalene] is a hydrophobic fluorescent probe which is extremely sensitive to both the polarity and the hydrogen-bond donating capacity of the solvent. In binary mixtures of solvents, the hydrogen-bond donating effect on Prodan fluorescence saturates at relatively low concentrations of protic solvent while the polarity effect is proportional to the mixture's dielectric constant. The fluorescence emission maximum is approximately a linear function of the dielectric constant in both protic and aprotic solvents, and this allows estimation of the dielectric constant in both environments. In phospholipid bilayers and biological membranes, Prodan exhibits two distinct emission peaks: blue (430-445 nm) and green (470-505 nm). Temperature determines the relative intensity of the two peaks, but their wavelengths depend on the type of membrane and appear to reflect a specific membrane environment. In phospholipid vesicles, alcohols reduce the fluorescence intensity of the blue peak and produce a red-shift in the emission maximum of the green peak. Taking the partition coefficients of the alcohols into account, short-chain alcohols are much more effective than longer-chain alcohols in red-shifting the emission maximum of the green peak. Alcohols have similar effects on Prodan fluorescence in liver microsomal and mitochondrial membranes, synaptosomal membranes, and red blood cell plasma membranes. However, in liver organelle membranes the red-shift of the green peak is the dominant effect while in plasma membranes the quenching of the fluorescence of the blue peak is dominant. These effects are observed at low (pharmacological) ethanol concentrations and provide a unique tool for probing the interactions of ethanol with biological membranes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Combined blood cell counting and classification with fluorochrome stains and flow instrumentation.

A multiparameter flow cytophotometer was used to count and classify fixed human blood cells fluorochromed with a mixture of ethidium bromide (EB), brilliant sulfaflavine and a blue fluorescent stilbene disulfonic acid derivative (LN). The system measures light scattered by the cells and absorption at 420 nm for all cells. In addition, nuclear EB fluorescence (540 leads to 610 nm) and cytoplasmic fluorescence from LN (366 leads to 470 nm), brilliant sulfaflavine (420 leads to 520 nm) and EB exicted by energy transfer from LN (366 leads to 610 nm) are measured for all nucleated cells. This information is sufficient to perform red and white blood cell counts and to classify leukocytes as lymphocytes, monocytes, basophils, eosinophils or neutrophils. Light scattering and/or nuclear and cytoplasmic fluorescence values may be further analyzed to obtain the ratio of immature to mature neutrophils. Counts produced by the system are in reasonable agreement with those obtained by electronic cells counting and examination of Wright's-stained blood smears; some discrepancies appear to be due to systematic errors in the manual counting method.     

Measurement of gradients of absorbed light in spinach leaves from chlorophyll fluorescence profiles

Profiles of chlorophyll fluorescence were measured in spinach leaves irradiated with monochromatic light. The characteristics of the profiles within the mesophyll were determined by the optical properties of the leaf tissue and the spectral quality of the actinic light. When leaves were infiltrated with 10^?4M DCMU [3‐(3,4‐dichlorophenyl)‐1, 1‐dimethyl‐urea] or water, treatments that minimized light scattering, irradiation with 2000 μmol m^?2 s^?1 green light produced broad Gaussian‐shaped fluorescence profiles that spanned most of the mesophyll. Profiles for chlorophyll fluorescence in the red (680 ± 16 nm) and far red (λ > 710 nm) were similar except that there was elevated red fluorescence near the adaxial leaf surface relative to far red fluorescence. Fluorescence profiles were narrower in non‐infiltrated leaf samples where light scattering increased the light gradient. The fluorescence profile was broader when the leaf was irradiated on its adaxial versus abaxial surface due to the contrasting optical properties of the palisade and spongy mesophyll. Irradiation with blue, red and green monochromatic light produced profiles that peaked 50, 100 and 150 μm, respectively, beneath the irradiated surface. These results are consistent with previous measurements of the light gradient in spinach and they agree qualitatively with measurements of carbon fixation under monochromatic blue, red and green light. These results suggest that chlorophyll fluorescence profiles may be used to estimate the distribution of quanta that are absorbed within the leaf for photosynthesis.     

Photoperiodic and light spectral conditions which inhibit circulating concentrations of thyroxine in the male hamster

Adult male Syrian hamsters were exposed daily for 12 weeks to 11 h/day of cool white fluorescent light (350 +/- 50 microW/cm2) followed by an additional 3 h of near ultraviolet (339-317 nm), blue (435-500 nm), green (515-550 nm), yellow (558-636 nm) or red (653-668 nm) light at an irradiance of 0.2 microW/cm2 or to total darkness. Animals exposed to the wavelengths between 558-668 nm (yellow or red half peak bandwidths) or those receiving a total of 13 h of darkness/day had suppressed circulating levels of thyroxine (T4), a depressed free T4 index (FT4I) and a higher T3/T4 ratio compared to animals receiving a total of 14 h of white light (350 +/- 50 microW/cm2). These results suggest that specific wavelengths of light can affect the neuroendocrine-thyroid axis.     

Multispectral fluorescence and reflectance imaging at the leaf level and its possible applications

Images taken at different spectral bands are increasingly used for characterizing plants and their health status. In contrast to conventional point measurements, imaging detects the distribution and quantity of signals and thus improves the interpretation of fluorescence and reflectance signatures. In multispectral fluorescence and reflectance set-ups, images are separately acquired for the fluorescence in the blue, green, red, and far red, as well as for the reflectance in the green and in the near infrared regions. In addition, 'reference' colour images are taken with an RGB (red, green, blue) camera. Examples of imaging for the detection of photosynthetic activity, UV screening caused by UV-absorbing substances, fruit quality, leaf tissue structure, and disease symptoms are introduced. Subsequently, the different instrumentations used for multispectral fluorescence and reflectance imaging of leaves and fruits are discussed. Various types of irradiation and excitation light sources, detectors, and components for image acquisition and image processing are outlined. The acquired images (or image sequences) can be analysed either directly for each spectral range (wherein they were captured) or after calculating ratios of the different spectral bands. This analysis can be carried out for different regions of interest selected manually or (semi)-automatically. Fluorescence and reflectance imaging in different spectral bands represents a promising tool for non-destructive plant monitoring and a 'road' to a broad range of identification tasks.     

Ultrastructure of the vegetative gametophytic cells of Porphyra leucosticta (Rhodophyta) grown in red, blue and green light

The ultrastructure of the vegetative gametophytic cells of Porphyra leucosticta Thuret grown in red, blue and green light was studied both in ultrathin sections and in replicas of rapidly frozen cells. High activity of dictyosornes and mucilage sacs results in a dramatic decrease of the protoplasmic area and in thicker cell walls in red light in comparison with blue light and the control. There are numerous well‐formed phycobili‐somes in blue light, whereas not well‐formed ones are present in red and especially in green light. There are also many phycobilisomes in the intrapyrenoidal thylakoids in blue light, fewer in green light, but they are absent in red light and in the control. It seems that in red and especially in green light, the phycobilisomes have fewer rods than in blue light. In green light, chloroplasts bear numerous genophores in contrast to blue and red light. The spacings of neighboring parallel thylakoids are as follows: control 64.3 nm, blue light 90.6 nm, red light 41.3 nm, green light 43.7 nm. Due to the relatively small spacing of the neighboring parallel thylakoids in red (41.3 nm) and in green light (43.7 nm) and of the given height of phycobilisomes (35 nm), the alternate phycobilisomes attached to neighboring lamellae are forced to interdigitate. The density of phycobilisomes per square micrometer of thylakoid surface dramatically increases in blue light (800 μm^?2) in relation to red (250 μm^?2) and green light (180 μm^?2). The protoplasmic fracture face of the thylakoids reveals numerous, tightly packed, but randomly distributed particles. The particle size distribution is uniform in the two types of fracture faces, with an average diameter of about 11.5 nm. In blue light, both the phycobilisomes and exoplasmic face particles are organized into rows with a spacing of 60–70 nm. The results (changes: in the protoplasmic area; in the spacing of the thylakoids; in phycobilisome arrangement; in structure, shape and size of phycobilisomes; and in the accumulation of plastoglobuli), have shown that the monochromatic light (blue, red and green) brings about marked changes in the package effect and consequently in the efficiency of light absorption. In addition, the blue light contributes to the intense production of chlorophyll a, phycoerythrin, phycocyanin and soluble proteins, while intense production of polysaccharidic material is attributed to red light.     

发光二极管光质对念珠藻葛仙米生长及生理生化特性的影响

利用发光二极管（LED）作为光源,以冷百荧光灯光作为对照,研究不同光质红光637 nm、绿光529 nm、蓝光453 nm、白光（400700） nm对念珠藻葛仙米生长和生理生化特性的影响。结果表明:在培养前期,红光促进藻蓝蛋白合成,而藻红蛋白合成受抑制;蓝光和绿光则促进藻蓝蛋白合成。在培养后期,红光处理有利于叶绿素a和类胡萝卜素积累,其含量分别达到干重的1.33%和0.24%;绿光、白光和冷白荧光培养物的相应色素的含量均约占1.0%和0.16%;蓝光培养物的相应色素含量分别仅为0.45%和0.11%。红光培养物的氨基酸含量达干重的23.1%,是对照的1.58倍。除蓝光外其他光质对还原糖的含量影响无显著差异。在培养过程中LED白光和冷白荧光培养物的平均相对生长速率分别约为其他色光培养物的1.3和1.5倍。       

Studies on the constancy of the blue and green fluorescence yield during the chlorophyll fluorescence induction kinetics (Kautsky effect)

Blue (F 450) and green (F 530) leaf fluorescence were studied together with the red chlorophyll fluorescence (emission maxima F 690 and F 735) during light-induced chlorophyll fluorescence induction kinetics (Kautsky effect) in predarkened leaves of wheat (Triticum aestivum L.) and soybean (Glycine max L.). The intensity of the red chlorophyll fluorescence decreased from maximum fluorescence Fm to steady-state fluorescence Fs, and the fluorescence ratio F 690/F 735 decreased by about 10% from Fm to Fs. However, blue and green fluorescence intensities remained constant throughout the measuring time. Consequently, the ratio of blue to red fluorescence (F 450/F 690) increased during chlorophyll fluorescence induction kinetics, whereas the ratio of blue to green fluorescence (F 450/F 530) remained unchanged within the same period. The knowledge of these ratios will be a prerequisite for the interpretation of remote sensing data from terrestrial vegetation.