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  • 1
    Electronic Resource
    Electronic Resource
    Photoacclimation and photoinhibition in Ulva rotundata as influenced by nitrogen availability (1991)
    Springer
    Planta 184 (1991), S. 235-243 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Growth rate ; Nitrogen and photosynthesis ; Photoacclimation ; Photoinhibition of photosynthesis ; Photosynthesis and N supply ; Quantum yield ; Ulva
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Clonal tissue of the marine chlorophyte macroalga, Ulva rotundata Blid., was transferred from 100 to 1700 μmol photons · m−2 · s−1 under limiting (1.5 μM NH 4 + maximum, N/P=2) and sufficient (15 μM NH 4 + maximum, N/P=20) nitrogen supply at 18° C and 11 h light-13 h darkness daily. Photoinhibition was assayed by light-response curves (photosynthetic O2 exchange), and chlorophyll fluorescence at 77 K and room temperature. Daily surface-area growth rate (μSA) in N-sufficient plants increased sixfold over 3 d and was sustained at that level. During this period, respiration (R d) doubled and light-saturated net photosynthesis capacity (P m) increased by nearly 50%, indicating acclimation to high light. Quantum yield (ϕ) decreased by 25% on the first day, but recovered completely within one week. The ratio of variable to maximum fluorescence (F v/F m) also decreased markedly on the first day, because of an increase in initial fluorescence (F o) and a decrease in F m, and partially recovered over several days. Under the added stress of N deficiency, μSA accelerated fivefold over 4 d, despite chronic photoinhibition, then declined along with tissue-N. Respiration doubled, but P m decreased by 50% over one week, indicating inability to acclimate to high light. Both ϕ and F v/F m decreased markedly on the first day and did not significantly recover. Changes in F o, F m and xanthophyll-cycle components indicate concurrent photodamage to photosystem II (PSII) and photoprotection by thermal deexcitation in the antenna pigments. Increasing μSA coincided with photoinhibition of PSII. Insufficient diel-carbon balance because of elevated R d and declining P m and tissue-N, rather than photochemical damage per se, was the apparent proximate cause of decelerating growth rate and subsequent tissue degeneration under N deficiency in U. rotundata.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197952
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Two components of onset and recovery during photoinhibition of Ulva rotundata (1992)
    Springer
    Planta 186 (1992), S. 399-408 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Chloroplast protein (32 kDa) ; Photoinhibition of photosynthesis ; Photosynthesis (photoinhibition) ; Ulva ; Xanthophyll cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Short-term (up to 5 h) transfers of shade-adapted (100 μmol · m−2 · s−1) clonal tissue of the marine macroalga Ulva rotundata Blid. (Chlorophyta) to higher irradiances (1700, 850, and 350 μmol · m−2 · s−1) led to photoinhibition of room-temperature chlorophyll fluorescence and O2 evolution. The ratio of variable to maximum (Fv/Fm) and variable (Fv) fluorescence, and quantum yield (ϕ) declined with increasing irradiance and duration of exposure. This decline could be resolved into two components, consistent with the separation of photoinhibition into energy-dissipative processes (photoprotection) and damage to photosystem II (PSII) by excess excitation. The first component, a rapid decrease in Fv/Fm and in Fv, corresponds to an increase in initial (Fo) fluorescence and is highly sensitive to 1 mM chloramphenicol. This component is rapidly reversible under dim (40 μmol · m−2 · s−1) light, but is less reversible with increasing duration of exposure, and may reflect damage to PSII. The second (after 1 h exposure) component, a slower decline in Fv/Fm and Fv with declining Fo, appears to be associated with the photoprotective interconversion of violaxanthin to zeaxanthin and is sensitive to dithiothreitol. The accumulation of zeaxanthin in U. rotundata is very slow, and may account for the predominance of increases in Fo at high irradiances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195321
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Photoacclimation and photoinhibition inUlva rotundata as influenced by nitrogen availability (1991)
    Springer
    Planta 184 (1991), S. 235-243 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Growth rate ; Nitrogen and photosynthesis ; Photoacclimation ; Photoinhibition of photosynthesis ; Photosynthesis and N supply ; Quantum yield ; Ulva
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Clonal tissue of the marine chlorophyte macroalga,Ulva rotundata Blid., was transferred from 100 to 1700 μmol photons · m−2 · s−1 under limiting (1.5 μM NH 4 + maximum, N/P=2) and sufficient (15 μM NH 4 + maximum, N/P=20) nitrogen supply at 18° C and 11 h light-13 h darkness daily. Photoinhibition was assayed by light-response curves (photosynthetic O2 exchange), and chlorophyll fluorescence at 77 K and room temperature. Daily surface-area growth rate (μSA) in N-sufficient plants increased sixfold over 3 d and was sustained at that level. During this period, respiration (R d) doubled and light-saturated net photosynthesis capacity (P m) increased by nearly 50%, indicating acclimation to high light. Quantum yield (ϕ) decreased by 25% on the first day, but recovered completely within one week. The ratio of variable to maximum fluorescence (F v/F m) also decreased markedly on the first day, because of an increase in initial fluorescence (F o) and a decrease inF m, and partially recovered over several days. Under the added stress ofN deficiency, μSA accelerated fivefold over 4 d, despite chronic photoinhibition, then declined along with tissue-N. Respiration doubled, butP m decreased by 50% over one week, indicating inability to acclimate to high light. Bothϕ andF v/F m decreased markedly on the first day and did not significantly recover. Changes inF o,F m and xanthophyll-cycle components indicate concurrent photodamage to photosystem II (PSII) and photoprotection by thermal deexcitation in the antenna pigments. Increasing μSA coincided with photoinhibition of PSII. Insufficient diel-carbon balance because of elevatedR d and decliningP m and tissue-N, rather than photochemical damage per se, was the apparent proximate cause of decelerating growth rate and subsequent tissue degeneration under N deficiency inU. rotundata.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01102423
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The effects of temperature acclimation on the photoinhibitory responses of Ulva rotundata Blid. (1994)
    Springer
    Planta 192 (1994), S. 324-331 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Photoinhibition ; Photoprotection ; Temperature ; Ulva ; Xanthophyll cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of acclimation to 25, 18, or 10° C on the relationship between photoprotection and photodamage was tested in low-light-grown (80 μmol · m−2 · s−1) Ulva rotundata Blid. exposed to several higher irradiances at the acclimation temperature. Changes in chlorophyll fluorescence parameters (minimum fluorescence, F0, and the ratio of variable to maximum fluorescence, Fv/Fm, measured after 5 min darkness) were monitored during 5 h transfers to 350, 850, and 1700 μmol · m−2 · s−1, and during recovery after 1- or 5-h treatments. At all temperatures, rate of onset and final extent of photoinhibition, measured by a decrease in Fv/Fm, increased with increasing irradiance. At a given photoinhibitory irradiance, rate of onset was most rapid at 10 ° C, but the extent was temperature-independent. Recovery rates from mild light stress were similar at all temperatures, but recovery from the most extreme photoinhibitory treatment lagged 2 h at 10° C. De-epoxidation of xanthophyll-cycle components proceeded faster and to a lower epoxidation status at 25° C, but there was little difference in the pool size among the three growth conditions. Using chloramphenicol to inhibit chloroplast protein synthesis and dithiothreitol to inhibit violaxanthin de-epoxidation, it was shown that at the lowest light treatment given, the extent of photoinhibition could be attributed both to greater amounts of photodamage and to greater zeaxanthin-related photoprotection at 25 than at 10° C. While these two mechanisms for high-light-induced loss of photosynthetic efficiency were operating at 10° C, there was evidence for a relatively greater proportion of zeaxanthin-unrelated photoprotection at the low temperature. This photoprotective mechanism is related to a rapidly reversible increase in F0 and is insentivite to both chloramphenicol and dithiothreitol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198567
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Natural ultraviolet radiation and photosynthetically active radiation induce formation of mycosporine-like amino acids in the marine macroalga Chondrus crispus (Rhodophyta) (1998)
    Springer
    Planta 205 (1998), S. 257-262 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Chondrus ; Palythene ; Palythine ; Palythinol ; Shinorine ; UV-sunscreens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The UV-absorbing mycosporine-like amino acids (MAAs) are hypothesized to protect organisms against harmful UV radiation (UVR). Since the physiology and metabolism of these compounds are unknown, the induction and kinetics of MAA biosynthesis by various natural radiation conditions were investigated in the marine red alga Chondrus crispus collected from Helgoland, Germany. Three photosynthetically active radiation (PAR, 400–700 nm) treatments without UVR and three UV-A/B (290–400 nm) treatments without PAR were given. Chondrus crispus collected from 4–6 m depth contained only traces of the MAA palythine. After 24 h exposure to 100% ambient PAR, traces of three additional MAAs, shinorine, palythinol and palythene, were detected, and their concentrations increased strongly during a one-week exposure to all PAR treatments. The concentration of all MAAs varied directly with PAR dose, with palythine and shinorine being four- to sevenfold higher than palythinol and palythene. Likewise, naturally high doses of both UV-A and UV-B resulted in a strong accumulation of all MAAs, in particular shinorine. While shinorine accumulation was much more stimulated by UVR, the content of all other MAAs was more affected by high PAR, indicating an MAA-specific induction triggered by UVR or PAR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050319
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Multiple strategies for a high light existence in a tropical marine macroalga (1997)
    Springer
    Photosynthesis research 53 (1997), S. 149-159 
    Details
    ISSN: 1573-5079
    Keywords: Chlorodesmis fastigiata ; D1 protein ; fluorescence ; macroalgae ; photoinhibition ; photosynthesis ; Photosystem II heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acclimation to high light conditions on the top of coral reefs was examined in the coenocytic, filamentous green macroalga Chlorodesmis fastigiata (C. Ag.) Ducker. Despite having a pool of violaxanthin, high light does not induce formation of zeaxanthin in this macroalga. Exposure to 11 and 33% of surface irradiance resulted in parallel, reversible declines in Fv/Fmand in the number of functional PSII centers. The quantum requirement for PSII inactivation was calculated to be approx. 2×107photons. Recovery of PSII activity after low photon exposures did not depend on protein synthesis, unlike at higher photon exposures, where recovery was inhibited by 50% in the presence of lincomycin. Accumulation of inactive, quenching PSII centers is proposed as a mechanism of energy dissipation; only some of these centers require protein synthesis for reactivation. In natural-sized populations, midday photoinhibition was greater in filament tips than in bases, but the number of inactive PSII centers within entire filaments did not significantly change over the course of the day. It is proposed that the higher chlorophyll concentration in the tips provides protective shading to chloroplasts in lower regions, and that cytoplasmic streaming of chloroplasts within this siphonous alga limits the cumulative exposure to high light, thereby providing another level of protection from high light stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005820203585
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    Paper (German National Licenses)
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