Effects of solar UV radiation on birch and pine seedlings in the sub-Arctic

Polar Record ◽  
2002 ◽  
Vol 38 (206) ◽  
pp. 233-240 ◽  
Author(s):  
M. Turunen ◽  
M.-L. Sutinen ◽  
K. Derome ◽  
Y. Norokorpi ◽  
K. Lakkala
Keyword(s):  
Uv Radiation ◽  
Dry Weight ◽  
Growing Season ◽  
Control Treatment ◽  
Daily Maximum ◽  
Solar Uv Radiation ◽  
Growing Seasons ◽  
Acrylic Plate ◽  
Solar Uv ◽  
Uv Exclusion

AbstractThe responses of Betula pubescens Ehr. (European white birch), B. pendula Roth (silver birch) and two provenances of Pinus sylvestris L. (Scots pine) to solar ultraviolet (UV < 400 nm) radiation were investigated in a UV-exclusion field experiment during the 1997–99 growing seasons in Finnish Lapland (68°N). The seedlings were grown from seed under UV-B exclusion (a clear polyester filter) and UV-B/UV-A exclusion (a clear acrylic plate) as compared to control treatment (a polyethene filter) and ambient plants (no plastic filter). The mean daily maximum solar biologically effective UV-B irradiance (UV-BE) was 88 mW m-2, 68 mW m-2, and 91 mW m-2 for 1997, 1998, and 1999. A number of growth and biomass variables, PSII (Photosystem II) efficiency, and total concentration of nitrogen were recorded during and/or at the end of the experiment. Exposure (191 d) to solar UV radiation over three growing seasons did not cause many statistically significant UV effects in the growth or biomass of the seedlings. The only significant impacts of UV exclusion were found in P. sylvestris provenance Enontekiö. During the first growing season, the UVB/ UV-A exclusion treatment significantly accelerated the height increment (18–20%) off. sylvestris, and in the same seedlings, the UV-B exclusion treatment resulted in significantly increased dry weight of one-year-old needles (45–57%) after the second growing season. These UV impacts could not be seen at the end of the experiment or in any other species. The low concentration of N in current foliage was related to increased dry weight, but not to solar UV radiation (control vs UV exclusion). The present study indicated that solar UV radiation had limited, but sometimes transient, impacts on the growth of tree seedlings in the sub-Arctic. Longer-term field studies are needed, however, in order to detect the cumulative characteristics of the UV responses.

scholarly journals Role of Dipicolinic Acid in Survival ofBacillus subtilis Spores Exposed to Artificial and Solar UV Radiation

2001 ◽  
Vol 67 (3) ◽  
pp. 1274-1279 ◽  
Author(s):  
Tony A. Slieman ◽  
Wayne L. Nicholson
Keyword(s):  
Uv Radiation ◽  
Dipicolinic Acid ◽  
Aqueous Suspension ◽  
Dry Weight ◽  
Full Spectrum ◽  
Solar Uv Radiation ◽  
Wet Heat ◽  
Solar Uv ◽  
Uv C

ABSTRACT Pyridine-2,6-dicarboxylic acid (dipicolinic acid [DPA]) constitutes approximately 10% of Bacillus subtilis spore dry weight and has been shown to play a significant role in the survival of B. subtilis spores exposed to wet heat and to 254-nm UV radiation in the laboratory. However, to date, no work has addressed the importance of DPA in the survival of spores exposed to environmentally relevant solar UV radiation. Air-dried films of spores containing DPA or lacking DPA due to a null mutation in the DPA synthetase operon dpaAB were assayed for their resistance to UV-C (254 nm), UV-B (290 to 320 nm), full-spectrum sunlight (290 to 400 nm), and sunlight from which the UV-B portion was filtered (325 to 400 nm). In all cases, air-dried DPA-less spores were significantly more UV sensitive than their isogenic DPA-containing counterparts. However, the degree of difference in UV resistance between the two strains was wavelength dependent, being greatest in response to radiation in the UV-B portion of the spectrum. In addition, the inactivation responses of DPA-containing and DPA-less spores also depended strongly upon whether spores were exposed to UV as air-dried films or in aqueous suspension. Spores lacking the gerA, gerB, and gerK nutrient germination pathways, and which therefore rely on chemical triggering of germination by the calcium chelate of DPA (Ca-DPA), were also more UV sensitive than wild-type spores to all wavelengths tested, suggesting that the Ca-DPA-mediated spore germination pathway may consist of a UV-sensitive component or components.

scholarly journals Biologically effective doses of ambient solar-UV radiation in Indonesia and Japan

2000 ◽  
pp. 123 ◽  
Author(s):  
Nobuo Munakata ◽  
Santoso Cornain ◽  
Ketut Mulyadi ◽  
Masamitsu Ichihashi ◽  
Joedo Prihartono ◽  
...  
Keyword(s):  
Uv Radiation ◽  
Solar Uv Radiation ◽  
Solar Uv ◽  
Effective Doses

Solar UV radiation variations and their stratospheric and climatic effects

1985 ◽  
Vol 5 (6) ◽  
pp. 145-148 ◽  
Author(s):  
Richard F. Donnelly ◽  
Donald F. Heath
Keyword(s):  
Uv Radiation ◽  
Climatic Effects ◽  
Solar Uv Radiation ◽  
Solar Uv

scholarly journals Interaction between variable solar UV radiation and tropospheric circulations as a possible cause of five year oscillation in Earth rotation

2000 ◽  
pp. 51-56
Author(s):  
P. Jovanovic ◽  
D. Djurovic
Keyword(s):  
Uv Radiation ◽  
Earth Rotation ◽  
Solar Uv Radiation ◽  
Solar Uv ◽  
Possible Cause

It is shown that Five Year Oscillation in Earth rotation is possibly caused by variable solar UV radiation and a corresponding perturbation mechanism is suggested.

scholarly journals The Effect of Irradiance, Defoliation, and Bulb Size on Flowering of Nerine bowdenii W. Watson (Amaryllidaceae)

1996 ◽  
Vol 121 (1) ◽  
pp. 115-122 ◽  
Author(s):  
K.I. Theron ◽  
G. Jacobs
Keyword(s):  
Developmental Stage ◽  
Dry Weight ◽  
Growing Season ◽  
Growth Unit ◽  
Growing Seasons ◽  
Number Of Leaves

Large Nerine bowdenii bulbs (>14 cm in circumference) were exposed to low ligbt intensities for different periods during two successive growing seasons. The flowering percentage and number of florets in the current season's inflorescence were recorded at anthesis. Small and large bulbs were subjected to continual defoliation starting at different times during the growing season. Bulbs were dissected at planting (26 Sept. 1992) and on 12 Jan. 1993 (nondefoliated control bulbs) to determine growth and developmental stage. At anthesis, inflorescences were harvested and the florets per inflorescence were counted. After anthesis in the fall, all bulbs were dissected and the following variables recorded: 1) percentage flowering, quiescence, or abortion of the current season's inflorescence; 2) developmental stage of quiescent inflorescences; 3) number of florets in the outermost inflorescence; 4) developmental stage of the innermost inflorescence; 5) number of leaves or leaf bases in each growth unit; 6) number of daughter bulbs; and 7) dry weight of new leaf bases. There were three reasons for nonflowering of the bulbs, viz., failure to initiate an inflorescence, inflorescences remaining quiescent, and inflorescence abortion. Individual florets that had not reached stage “Late G” (gynoecium elongated, carpels fused) at the start of rapid inflorescence elongation aborted. The more florets that aborted, the greater the probability that the entire inflorescence aborted. The inflorescence was more vulnerable to stress during the first half of the growing season due to its relatively weak position in the hierarchy of sinks within the bulb.

scholarly journals Effects of Solar UV Radiation on Morphology and Photosynthesis of Filamentous Cyanobacterium Arthrospira platensis

2005 ◽  
Vol 71 (9) ◽  
pp. 5004-5013 ◽  
Author(s):  
Hongyan Wu ◽  
Kunshan Gao ◽  
Virginia E. Villafañe ◽  
Teruo Watanabe ◽  
E. Walter Helbling
Keyword(s):  
Solar Radiation ◽  
Cell Density ◽  
Uv Radiation ◽  
Time Scales ◽  
Morphological Development ◽  
Filamentous Cyanobacterium ◽  
Solar Uv Radiation ◽  
Solar Uv ◽  
Adaptive Time ◽  
The Impact

ABSTRACT To study the impact of solar UV radiation (UVR) (280 to 400 nm) on the filamentous cyanobacterium Arthrospira (Spirulina) platensis, we examined the morphological changes and photosynthetic performance using an indoor-grown strain (which had not been exposed to sunlight for decades) and an outdoor-grown strain (which had been grown under sunlight for decades) while they were cultured with three solar radiation treatments: PAB (photosynthetically active radiation [PAR] plus UVR; 280 to 700 nm), PA (PAR plus UV-A; 320 to 700 nm), and P (PAR only; 400 to 700 nm). Solar UVR broke the spiral filaments of A. platensis exposed to full solar radiation in short-term low-cell-density cultures. This breakage was observed after 2 h for the indoor strain but after 4 to 6 h for the outdoor strain. Filament breakage also occurred in the cultures exposed to PAR alone; however, the extent of breakage was less than that observed for filaments exposed to full solar radiation. The spiral filaments broke and compressed when high-cell-density cultures were exposed to full solar radiation during long-term experiments. When UV-B was screened off, the filaments initially broke, but they elongated and became loosely arranged later (i.e., there were fewer spirals per unit of filament length). When UVR was filtered out, the spiral structure hardly broke or became looser. Photosynthetic O2 evolution in the presence of UVR was significantly suppressed in the indoor strain compared to the outdoor strain. UVR-induced inhibition increased with exposure time, and it was significantly lower in the outdoor strain. The concentration of UV-absorbing compounds was low in both strains, and there was no significant change in the amount regardless of the radiation treatment, suggesting that these compounds were not effectively used as protection against solar UVR. Self-shading, on the other hand, produced by compression of the spirals over adaptive time scales, seems to play an important role in protecting this species against deleterious UVR. Our findings suggest that the increase in UV-B irradiance due to ozone depletion not only might affect photosynthesis but also might alter the morphological development of filamentous cyanobacteria during acclimation or over adaptive time scales.

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