Discovery of signaling effect of UV-B/C light in the extended UV-A/blue-type action spectra for step-down and step-up photophobic responses in the unicellular flagellate algaEuglena gracilis

Summary Cultures of unicellular algal flagellateEuglena gracilis grown in different conditions were subjected to action spectroscopy for step-down and step-up photophobic responses, respectively. The spectral region was extended into the UV-B/C as well as in the UV-A and visible regions with the Okazaki Large Spectrograph as the monochromatic light source. The photophobic responses of the cells were measured with an individual-cell assay method with the aid of a computerized video motion analyzer. In the UV-A and visible regions, the shapes of the action spectra were the so-called UV-A/blue type. In the newly studied UV-B/C region, new action peaks were found at 270 nm for the step-down response and at 280 nm for the step-up one. The absorption spectrum of flavin adenine dinucleotide (FAD) appeared to fit the action spectrum for the step-up response, whereas the shape of the step-down action spectrum, which has a UV-A peak (at 370 nm) higher than the blue peak (at 450 nm), appeared to be mimicked by the absorption spectrum of a mixed solution of 6-biopterin and FAD. These observations might also account for the fact that the UV-B/C peak wavelength at 270 nm of the action spectrum for the step-down response is shorter by 10 nm than the action spectrum for the step-up response at 280 nm.Abbreviations FAD flavin adenine dinucleotide - FWHM spectral full width at half maximum - NIBB National Institute for Basic Biology - OLS Okazaki Large Spectrograph - PFB paraflagellar body - UV-A ultraviolet light of spectral region between 320 and 400 nm - UV-B/C ultraviolet light of spectral region between 190 and 320 nm     

Effect of SO(2) and O(3) on Production of Antioxidants in Conifers

Production of antioxidants was investigated in needles of fir (Abies alba Mill.) and spruce (Picea abies (L.) Karst) after exposure to low concentrations of SO₂, O₃, and a combination of both pollutants. Glutathione reacted most sensitively to pollutants followed by vitamin E and vitamin C. In spruce needles, the overall increase of antioxidants after exposure to air pollutants was lower than in needles of fir. SO₂ was more potent than O₃. Maximum increase of antioxidants was found in needles after exposure of trees to SO₂ + O₃.     

Photosynthetic action spectra of trees: I. Comparative photosynthetic action spectra of one deciduous and four coniferous tree species as related to photorespiration and pigment complements

Comparative isoenergetic action spectra of net photosynthesis for intact, current year foliage of five tree species were determined from 400 to 710 nm by CO₂ exchange analysis. The blue (400 to 500 nm) peak of net photosynthetic activity for the green broadleaves of red alder (Alnus rubra Bong.) was reduced to a plateau for the green needle-leaves of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) and Sitka spruce (Picea sitchensis [Bong.] Carr.), a shoulder for the blue-green needles of Colorado spruce (Picea pungens Engelm.), and a reduced shoulder for the blue-white needles of Blue spruce (Picea pungens var. hoospii). These differences were attributable neither to a differential blue light stimulation of photorespiration nor to a differential presence of a nonplastid screening pigment. The conifers all had similar carotenoid-chlorophyll ratios, with approximately 50% more carotenoid relative to chlorophyll as compared to red alder. Blue light absorption and low efficiency of energy transfer by the carotenoids probably accounts for the low net photosynthetic activity of the green conifers in blue light as compared to red alder. Leaf form per se (broad versus needle) had no distinguishable influence on these results.     

Elongation of Scots pine seedlings under blue light depletion is independent of etiolation

Two- and 3-year-old Scots pine (Pinus sylvestris L.) seedlings were grown in plexiglass chambers and control plots at two study sites in northern Finland. The chambers were made of either orange or transparent plexiglass. The former removed the blue wavelengths (400–500 nm) of incoming sunlight, while the latter was transparent to all visible wavelengths. The removal of blue reduces the total amount of incoming light. This may theoretically enhance etiolation responses (i.e. increased stem elongation and reduced leaf development) in the seedlings grown under blue light depletion. Artificial removal of blue light did increase elongation of the main stem, although only at the sub-arctic latitude (69°N) of the experiment, not at the mid-boreal (64°N) latitude. However, elongation of the lateral branches, needle area and the weight of the new stem and needles were also increased in the seedlings grown in orange chambers at the sub-arctic latitude. Therefore, the increased elongation of the main stem of the seedlings grown under blue light depletion cannot be attributed to etiolation alone.     

BLUE LIGHT AND UV-A RADIATION CONTROL THE SYNTHESIS OF MYCOSPORINE-LIKE AMINO ACIDS IN CHONDRUS CRISPUS (FLORIDEOPHYCEAE)

The induction of UV-absorbing compounds known as mycosporine-like amino acids (MAAs) by red, green, blue, and white light (43% ambient radiation greater than 390 nm) was examined in sublittoral Chondrus crispus Stackh. Fresh collections or long-term cultures of sublittoral thalli, collected from Helgoland, North Sea, Germany, and containing no measurable amounts of MAAs, were exposed to filtered natural radiation for up to 40 days. The MAA palythine (λ_max 320 nm) was synthesized in thalli in blue light to the same extent observed in control samples in white light. In contrast, thalli in green or red light contained only trace amounts of MAAs. After the growth and synthesis period, the photosynthetic performance of thalli in each treatment, measured as pulse amplitude modulated chlorophyll fluorescence, was assessed after a defined UV dose in the laboratory. Thalli with MAAs were more resistant to UV than those without, and exposure to UV-A+B was more damaging than UV-A in that optimal (F_v/F_m) and effective (φ_II) quantum yields were lower and a greater proportion of the primary electron acceptor of PSII, Q, became reduced at saturating irradiance. However, blue light-grown thalli were generally more sensitive than white light control samples to UV-A despite having similar amounts of MAAs. The most sensitive thalli were those grown in red light, which had significantly greater reductions in F_v/F_m and φ_II and greater Q reduction. Growth under UV radiation alone had been shown previously to lead to the synthesis of the MAA shinorine (λ_max 334 nm) rather than palythine. In further experiments, we found that preexposure to blue light followed by growth in natural UV-A led to a 7-fold increase in the synthesis of shinorine, compared with growth in UV-A or UV-A+B without blue light pretreatment. We hypothesize that there are two photoreceptors for MAA synthesis in C. crispus, one for blue light and one for UV-A, which can act synergistically. This system would predispose C. crispus to efficiently synthesize UV protective compounds when radiation levels are rising, for example, on a seasonal basis. However, because the UV-B increase associated with artificial ozone reduction will not be accompanied by an increase in blue light, this triggering mechanism will have little additional adaptive value in the face of global change unless a global UV-B increase positively affects water column clarity.     

Physical, immunological and kinetic properties of ribulose-1,5-bisphosphate carboxylase/oxygenase from fir (Abies alba) and spruce (Picea abies)

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) from fir ( Abies alba Mill.) and spruce ( Picea abies [L.] Karst.) needles was purified to homogeneity. The enzyme was isolated from crude extracts through quantitative precipitation in 40-55% and 40-60% (NH₄)₂SO₄ for fir and spruce. respectively, followed by linear sucrose gradient centrifugation. Using two dimensional gel electrophoresis, the isoelectric points were determined. For the large subunit (LSU) it was 6.7 for both species, and for the small subunit (SSU) it was 7.1 and 7.7 for fir and spruce, respectively. Very few differences in tryptic peptides and amino acid composition of Rubisco LSU were observed between fir and spruce. By contrast, marked differences characterized the same analyses for the Rubisco SSU of the two species. Moreover, substitution of residues was observed in the sequenced N-terminal region when comparing fir and spruce SSU. The Ouchterlony technique showed no immu-nochemical difference between Rubisco of fir and spruce when a rabbit antiserum to spinach Rubisco was used. The Eadie-Hofstee plots of carboxylase activity indicated that the apparent K_m(CO₂) were 31 and 36 μ M for the fir and spruce enzymes, respectively.     

Photosynthetic Electron Transport in Plants of Sitka Spruce Subjected to Differing Light Environments during Growth

Seedlings of Picea sitchensis (Bong.) Carr. (Sitka spruce) have been grown in four different light regimes in growth chambers. Chloroplast fragments have been isolated from the needles and Photosystem I and Photosystem II activities measured. Measurements were made at eight photon flux densities giving light response curves for photosystem activity in needles grown in the four different light regimes. Chlorophyll concentration was higher in needles from the low cultivation light environments than in those from the high light environments. Photosystem activity was higher in needles from the high cultivation light environments. Evidence that Photosystem I was limiting photosynthesis in needles grown in the high light environments was obtained.     

Foliar elemental composition of spruce-fir in the southern blue ridge province

Data are presented for what we believe to be the first assessment of the elemental foliar status of red spruce (Picea rubens Sarg.) and Fraser fir [Abies fraseri (Pursh.) Poir.] trees in the high elevation forests of the southern Appalachian mountans. Needle samples were collected from September–November 1984. Needles were separated according to flush year for the 1984, 1983 and 1982 growing seasons. Each sample was analyzed without washing for 28 macro- and micronutrients and trace elements. Significant differences in foliar concentrations were observed between flush year for N, P, Ca, Mg, K, Cl, Cu, Ce, Th, Cs, Pb, Fe, La and Rb for Fraser fir (n=41), and P, Ca, K, Cl, Cu, Pb and Rb for red spruce (n=30). Nitrogen concentrations ranged from 11.2–20.2 mg g^?1 for Fraser fir, and 8.7–15.9 mg g^?1 for red pruce. The mean concentration of Ca observed in red spruce needles (1.4 mg g^?1 1984 growing season) fell at the low extreme of reported values for non-necrotic red spruce foliage in the northeastern United States (1.2–11.6 mg g^?1). The mean concentration of Ca in Fraser fir foliage (3.4 mg g^?1, 1984 growing season) was also lower than reported values for eastern fir, but not to the extent demonstrated for red spruce. Fraser fir needles had higher concentrations of Al than red spruce (310vs 91 mg kg^?1, respectively, 1984 growing season), but both values are higher than those reported for spruce or fir from the northeastern United States. Calcium:aluminum ratios in current foliage are the lowest yet reported for the eastern spruce/fir forest type, suggesting that Al toxicity and/or Ca deficiency may be important stresses in these stands. Comparison of Pb concentrations with those of other rare-earth elements known to be associated with dust on needle surfaces (Ce, La, Sc, Sm, and Th) suggested that a substantial portion of the Pb found was due to particulates on the needle surfaces. The significance of these results to the observed forest decline syndrome in high elevation forests of the eastern United States is also discussed.     

Photoinactivation of catalase in needles of Norway spruce

Catalase IEC 1.11.1.6) activity in Norway spruce ( Picea abies [L.] Karst.) needles was examined under different environmental conditions. When shade-adapted spruce trees were exposed to full sunlight or to high light intensities in growth chambers, the catalase activity decreased. Under continuous light the activity was reduced in comparison to the control grown in light/dark cycles. The reduction of the activity was not temperature dependent. Under field conditions the activity was higher in hranches oriented north than in those oriented south. A diurnal rhythm with a maximum in the night was delected. The reduction in catalase activity also occurred in young white needles of Picea ahies vur. argenteospica . which are free of chlorophyll. It is concluded that in Norway spruce needles there is a ligh:-dependent photoinactivation of catalase. which is not temperature-dependent.     

Effects of red, far-red and blue light in maintaining growth in latitudinal populations of Norway spruce (Picea abies)

Seedlings of trees with a free growth pattern cease growth when night-lengths become shorter than a critical value, and this critical night-length (CNL) decreases with increasing latitude of origin. In northern populations, the light quality also appears to play an important role and a clinal variation in requirement for far-red (FR) light has been documented. In this study we dissected the light quality requirements for maintaining growth in different latitudinal populations of Norway spruce (Picea abies (L.) H. Karst.) using light emitting diodes for red (R), FR and blue (B) light, as 12 h day extension to provide 24 h photoperiod. At equal spectral photon flux, FR light was more effective than R light in maintaining growth, and the requirement of both R and FR increased with northern latitude of origin. One-to-one mixtures of R and FR light were more effective in maintaining growth than either FR or R light alone, indicating a possible interaction between R and FR light maintaining growth. Using the blue light as day extension could not prevent growth cessation in any of the populations, but delayed the bud set slightly in all populations. Our results suggest that phytochrome(s) are the primary photoreceptors in high irradiance responses maintaining growth in Norway spruce seedlings.     

Role of dissolved organic carbon in the attenuation of photosynthetically active and ultraviolet radiation in Adirondack lakes

1. We surveyed eighty-five lakes located in the Adirondack Mountain Region of New York State, U.S.A., to characterize the attenuation of photosynthetically active (PAR) and ultraviolet radiation (UVR) in relation to dissolved organic carbon (DOC) concentrations and pH. Attenuation of PAR was quantified in situ . Attenuation was also inferred by measuring the light absorption of filtered lake water samples at wavelengths (300, 340 and 440 nm) representing UV-B, UV-A and PAR.
2. Substantial variation in transparency was observed among lakes in this region. Attenuation depths ( z _1%) for PAR ranged from 0.5 to greater than 20 m, while inferred values for UV-B and UV-A ranged from a few centimetres to > 5 m. Median values of UV-A penetration (0.75 m) and UV-B penetration (0.45 m) corresponded to 11% (UV-A) and 6% (UV-B) of lake maximum depth.
3. Much of the variation in PAR and UVR attenuation was explained by differences in lake DOC. Univariate power models based solely on DOC accounted for 85% (PAR), 90% (UV-A) and 91% (UV-B) of the variation in absorption.
4. Attenuation and absorption coefficients were generally lower for recently acidified lakes compared to acidic and circumneutral lakes which have not undergone recent acidification. However, differences among these three groups of lakes were not statistically significant. Our results suggest that the effects of acidification on the optical properties of a regional population of lakes, even in an area experiencing widespread acidification, are relatively subtle in comparison with other factors contributing to inter-lake variability.
5. The presence of near-shore wetlands is probably a key factor influencing regional variability in DOC and light climate among Adirondack lakes. Temporal variability in climatic factors influencing wetland DOC production and export may mask more subtle influences on lake DOC associated with anthropogenic acidification.     

Conifer decline in the north-east of France: Characteristic changes in chloroplast protein pattern and absence of anti-oxidative defense capability point to an involvement of ozone

A method yielding intact and biologically active chloroplasts from needles of mature spruce ( Picea abies L. cv. Karsten) or fir ( Abies alba Mill.) growing in the field is presented. Using this method, chloroplasts were prepared from yellow and green needles of declining spruce and fir from two forest areas of the Vosges mountains (north-east of France). Both quantitative and qualitative changes could be shown in the two-dimensional chloroplast protein pattern of yellowing needles, as compared to that of apparently healthy needles. We observed that an accumulation of photosystem II D1-protein in the thylakoids was associated with needle decline. Furthermore, a lack of resistance capability against free radical attack was observed in yellow needles. We have attempted to correlate our observations with pollutant levels and we propose that, in the forest areas studied, O₃ is one of the main factors involved in conifer decline. It also appears from our results that decline and senescence are distinct phenomena.     

Influence of solar ultraviolet radiation on photosynthesis and motility of marine phytoplankton

Abstract: The effects of solar ultraviolet radiation (UV) on carbon uptake, oxygen evolution and motility of marine phytoplankton were investigated in coastal waters at Kristineberg Marine Research Station on the west coast of Sweden (58° 30'N, 11° 30'E). The mean irradiances at noon above the water surface during the investigation period were: photosynthetic active radiation (PAR, 400–700 nm) 1670 μmol m⁻² s⁻¹; ultraviolet-A radiation (UV-A, 320–400 nm) 35.9 W m⁻² and ultraviolet-B radiation (UV-B, 280–320 nm) 1.7 W m⁻². UV-B radiation was much more attenuated with depth in the water column than were PAR and UV-A radiation. UV-B radiation could not be detected at depths greater than 100–150 cm. Inhibition of carbon uptake by UV-A and UV-B in natural phytoplankton populations was greatest at 50 cm depth and the effects of UV-B were greater than those of UV-A. At depths greater than 50 cm there was almost no effect of ultraviolet radiation on carbon uptake. PAR, UV-A and UV-B decreased oxygen evolution by the dinoflagellate Prorocentrum minimum . Inhibition of oxygen evolution was greater after 4 h than 2 h but it was not possible to distinguish the negative effects of the different light regimes. The motility of P. minimum was not affected by PAR, UV-A and UV-B. The importance of exposure of phytoplankton to different light regimes before being exposed to natural solar radiation is discussed.     

Photosynthetic Action Spectra of Trees: II. The Relationship of Cuticle Structure to the Visible and Ultraviolet Spectral Properties of Needles from Four Coniferous Species

The relative reflectance spectra for control and treated (surface wiped) current-year foliage of Douglas fir, and Sitka, Colorado, and Blue spruce (Pseudotsuga menziesii [Mirb.] Franco, Picea sitchensis [Bong.] Carr., Picea pungens Engelm., and Picea pungens Engelm. var. hoopsii, respectively) were obtained from 220 to 700 nm. The green color of the control foliage of both Douglas fir and Sitka spruce was unaffected by the treatment whereas the blue-green and blue-white foliage of control Colorado and Blue spruce, respectively, became “green” as a result of the wiping. The relative reflectance curves for all green foliage, including the treated Colorado and Blue spruce, were all very similar with a peak in the green (540-560 nm), minima in the red (660-680 nm) and blue (450-500 nm), and very low reflectivities in the ultraviolet (λ < 400 nm). In contrast, the control foliage for Colorado and Blue spruce both showed a generally higher relative reflectance over most of the visible spectrum (400-700 nm) with a marked increase in the blue region (400-500 nm). At wavelengths below 420 nm, their relative reflectances increased sharply with decreasing wavelength, the reflectance at 220 nm for Blue spruce being over four times that at 540 nm.     

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.     

Spectral reflectance of Picea rubens (Pinaceae) and Abies balsamea (Pinaceae) needles along an elevational gradient, Mt. Moosilauke, New Hampshire, USA

Relationships among elevation, foliar morphology, spectral reflectance, and chlorophyll fluorescence of two co-occurring montane conifers, red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea [L.] Mill.), were investigated along two transects from 460 to 1460 m on Mt. Moosilauke in the White Mountains of New Hampshire, USA. Spectral reflectance (300-1100 nm wavelengths) and the chlorophyll fluorescence F(v)/F(m) ratio were measured on dark-adapted needles. Foliar morphology (needle size, shape, and mass) and nitrogen concentrations were measured in the laboratory. Reflectance spectra varied between species and with elevation. Two chlorophyll measures, red edge position and a chlorophyll-based difference index (Chl NDI = R750 - R705/R750 + R705), indicated more chlorophyll in fir than in spruce and decreasing chlorophyll with increasing elevation in both species. The structure-independent pigment index (SIPI = R800 - R445/R800 - R680) increased with elevation, indicating an increasing carotenoid?:?chlorophyll ratio. The photochemical reflectance index (PRI = R531 - R570/R531 + R570), a measure of photosynthetic radiation use efficiency, decreased with increasing elevation up to 1370 m. In the highest elevation site, within the stunted alpine krummholz at 1460 m, PRI was higher than at 1370 m, but still lower than at 1070 m. This same pattern was evident in the chlorophyll fluorescence F(v)/F(m) measurements. These independent indices indicate higher stress in spruce than fir, which may be related to the "spruce decline" reported in the northeastern USA. Results also indicate progressively increasing stress with increasing elevation up to 1370 m. Stress appears to be lower at 1460 m than at 1370 m, despite the harsher conditions at the very summit of Mt. Moosilauke. This may be a consequence of stress-tolerant physiology and/or prostrate architecture.     

Characteristics of morphogenesis and growth processes of conifers in the Chernobyl nuclear accident zone

In the article we present data on the study of morphogenesis and of growth processes of Scotch pine (Pinus sylvestris L.) and of Norwey spruce (Picea abies (L.) Karst.) vegetative organs after radiation exposure in the Chernobyl nuclear accident zone. The anomalies in morphogenesis processes at different absorbed doses are described in detail. It is established that the death of pine forest began under absorbed dose 80-100 Gy and more, mass yellowing of needles at 50-60 Gy, and maximal morphosis at 8-12 Gy. Inhibition phenomenon of growth processes under acute irradiation and giantism under durable chronic irradiation were also put under investigation. Features of radiation exposure on pine and fir growth processes at different ontogeny phases were characterized. High radio-sensitivity of Norwey spruce is established.