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  • 1
    Electronic Resource
    Electronic Resource
    Occurrence and significance of nitrogen transport in the brown alga Laminaria digitata (1983)
    Springer
    Marine biology 77 (1983), S. 107-112 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen transport in a Laminaria digitata (Huds.) Lamour population growing at Arbroath, Scotland has been investigated (during the period 3 June 1981 to 3 July 1981), using 15N as tracer. NO 3 - was assimilated both by the blade meristem and by the mature blade. NO 3 - uptake by the blade meristem alone was insufficient to supply the nitrogen demand for growth. This additional demand was met by nitrogen transport from the mature blade to the meristem. It was estimated that 70% of the nitrogen demand of the meristematic region was supplied by nitrogen transport from the mature blade. Although transport occurred, the size of the endogenous pool of stored nitrogen in the mature blade did not change, the quantity of nitrogen transported being equivalent to the amount of NO 3 - assimilated during the experimental period. The possible co-transport of nitrogen and carbon is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396307
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  • 2
    Electronic Resource
    Electronic Resource
    Freezing rate and duration determine the physiological response of intertidal fucoids to freezing (1993)
    Springer
    Marine biology 115 (1993), S. 353-362 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Differential thermal analysis (DTA) was used to measure the freezing temperature of nine species of red brown intertidal macroalgae from the coast of Maine, USA in 1991. Using slow and rapid cooling rates approximating those found in the field for Ascophyllum nodosum (L.) Le Jol. we found that, for a given rate, the freezing points of all species were similar: -7.06 to -8.02°C for slow cooling (ca. 0.25°C min-1) and -3.42 to -4.56°C for rapid cooling (ca. 5.0°C min-1). In the low shore species, Fucus evanescens C. Ag., photosynthesis was inhibited to a greater extent when plants were frozen or thawed rapidly than after slow freezing or thawing. However, in the upper shore species, F. spiralis (L.), photosynthesis recovered rapidly and completely regardless of freezing rate. Rapidly frozen F. evanescens also experienced greater loss of plasmalemmal integrity, evidenced by a greater loss of cellular contents on re-immersion, than those frozen slowly. Light-limited photosynthesis following freezing was more severely inhibited than light-saturated photosynthesis. Respiration was generally enhanced immediately after freezing, but then declined to rates below those of unfrozen controls within 2 h following re-immersion, with control rates of respiration being achieved after a 24 h recovery period. Our data suggest that the physiological consequences of winter emersion at sub-zero temperatures may vary widely between individual plants of freezing-susceptible species, due to the wide variations in freezing rate associated with microhabitat effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349832
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of freezing on photosynthesis of intertidal macroalgae: relative tolerance of Chondrus crispus and Mastocarpus stellatus (Rhodophyta) (1989)
    Springer
    Marine biology 101 (1989), S. 107-114 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of freezing on photosynthetic metabolism was studied in the red algae, Chondrus crispus and Mastocarpus stellatus. Plants of both species were collected from the intertidal at Chamberlain or Kresge Point, Maine, USA (43°56′N, 69°54′W) between February and March 1987. Photosynthetic rates were measured immediately after freezing at-20°C and following recovery periods in seawater. Photosynthesis in C. crispus declined rapidly following freezing, falling to 70% of control values within 1 h and 30% after 3 h exposure. Minimum photosynthetic rates (7 to 9% of controls) occurred following freezing exposures of 12 h or more. Full photosynthetic recovery in C. crispus after 3 h at-20°C required 48 h. Photosynthesis in C. crispus did not fully recover in plants frozen for 6 h or more. In contrast, photosynthesis in M. stellatus was relatively unaffected by freezing exposures of 〈12 h. Twelve hours or more at-20°C reduced photosynthesis to 55% of controls. Photosynthesis in M. stellatus fully recovered from 24 h at-20°C within 24 h. In both species the reduction of photosynthesis by freezing was associated with damage to the plasma membrane and reduced efficiency of energy transfer from phycobilisomes to chlorophyll a, but did not appear to involve ribulose-1,5-bisphosphate carboxylase oxygenase activity. The freezing tolerance of C. crispus and M. stellatus positively correlates with their respective intertidal distributions, suggesting that freezing may be involved in controlling the distributions of these species on the shore.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393483
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature acclimation of respiration and photosynthesis in the brown algaLaminaria saccharina (1991)
    Springer
    Marine biology 110 (1991), S. 449-454 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sporophytes of the brown algaLaminaria saccharina (L.) Lamour grown at 15°C contained significantly more chlorophylla (chla) than did similar plants grown at 5°C. The increase in chla in 15°C plants was due to increased numbers of photosystem II reaction centes, and possibly to increased photosynthetic unit size, compared with 5°C plants. These changes were associated with increasedα values (photosynthetic efficiencies) in 15°C-grownL. saccharina relative to 5°C-grown plants. The changes inα together with reduced respiration rates allowed 15°C-grownL. saccharina to achieve net photosynthesis and light-saturated photosynthesis at a lower photon fluence rate (PFR) than 5°C plants when both groups were assayed at the same temperature (15°C). The photon fluence rates necessary to reach the compensation point and achieve light-saturated photosynthesis (I c andI k , respectively) increased with increasing incubation temperature inL. saccharina grown at both 5 and 15°C. However, acclimation responses to growth temperature compensated for the short-term effect of temperature onI c andI k . Consequently, plants grown at 5 and 15°C were able to achieve similar rates of light-limited photosynthesis, and similarI c andI k values at their respective growth temperatures. These responses are undoubtedly important for perennial seaweeds such asL. saccharina, which frequently grow in light-limited habitats and experience pronounced seasonal changes in water temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01344363
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  • 5
    Electronic Resource
    Electronic Resource
    Freezing tolerance in the intertidal red algaeChondrus crispus andMastocarpus stellatus: Relative importance of acclimation and adaptation (1990)
    Springer
    Marine biology 106 (1990), S. 427-436 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of repeated daily freezing on photosynthesis, growth and phenotypic acclimation to freezing was studied in the red algaeChondrus crispus Stackhouse andMastocarpus stellatus (Stackhouse in With.) Guiry. Algae used for experiments were collected from Chamberlain, Maine, between March and August 1987, and field observations and experiments were carried out at Chamberlain and Kresge Point, Maine between March 1987 and March 1989. After ca 30 d of daily freezing for 3 h at −5°C photosynthesis ofC. crispus was reduced to 55% of control values. Growth rates ofC. crispus were also reduced in fronds frozen daily compared to unfrozen controls, and eventually fronds became bleached and fragmented resulting in biomass losses. Fronds ofC. crispus, frozen daily, had higher photosynthetic rates following freezing events than unfrozen controls indicating that this species can acclimate to freezing conditions. Acclimation to freezing involves the light-harvesting reactions of photosynthesis. In contrast, photosynthesis and growth inM. stellatus were unaffected by repeated daily freezing for 3 h at −5°C for 36 d. No differences in photosynthesis following freezing were observed between frozen and control fronds suggesting thatM. stellatus does not phenotypically acclimate to freezing. The greater freezing tolerance ofM. stellatus relative toC. crispus results, in part, from genetic adaptations associated with plasma membranes and the light-harvesting reactions of photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01344323
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  • 6
    Electronic Resource
    Electronic Resource
    Stress tolerance and reactive oxygen metabolism in the intertidal red seaweeds Mastocarpus stellatus and Chondrus crispus (1999)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Mastocarpus stellatus and Chondrus crispus are morphologically similar red seaweeds that co-occur on rocky intertidal seashores in the Northern Atlantic. Mastocarpus stellatus grows higher on the shore and is more tolerant of environmental stress, caused by factors such as freezing and desiccation, than C. crispus. Here we report a correlation between reactive oxygen metabolism and stress tolerance, which suggests that reactive oxygen metabolism may play a role in stress tolerance of intertidal red seaweeds. Mastocarpus stellatus scavenged added H2O2 slightly faster, and was more resistant to oxidative stress induced by addition of H2O2 and Rose Bengal, than C. crispus. These data were consistent with higher levels of ascorbate and β-carotene and higher activities of catalase and glutathione reductase, in M. stellatus. Tocopherol content and activities of superoxide dismutase and ascorbate peroxidase were similar in both species. Activities of reactive oxygen scavenging enzymes generally increased with tidal height in M. stellatus; this was, however, not a consistent trend in C. crispus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00477.x
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal acclimation and photoacclimation of photosynthesis in the brown alga Laminaria saccharina (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Thermal acclimation and photoacclimation of photosynthesis were compared in Laminaria saccharina sporophytes grown at temperatures of 5 and 17 °C and irradiances of 15 and 150μmol photons m−2 s−1. When measured at a standard temperature (17°C), rates of light-saturated photosynthesis (Pmax) were higher in 5 °C-grown algae (c. 3.0 μmol O2 m−2 s−1) than in 17 °C-grown algae (c. 0.9 μmol O2 m-2 s-1). Concentrations of Rubisco were also 3-fold higher (per unit protein) in 5 °C-grown algae than in algae grown at 17 °C. Light-limited photosynthesis responded similarly to high temperature and low light Photon yields (α) were higher in algae grown at high temperature (regardless of light), and at 5 °C in low light, than in algae grown at 5 °C in high light Differences in a were correlated with light absorption; both groups of 17 °C algae and 5 °C low-light algae absorbed c. 75% of incident light, whereas 5 °C high-light algae absorbed c. 55%. Increased absorption was correlated with increases in pigment content PSII reaction centre densities and the fucoxanthin-Chl ale protein complex (FCP). Changes in a were also attributed, in part, to changes in the maximum photon yield of photosynthesis (0max). PSI reaction centre densities were unaffected by growth temperature, but the areal concentration of PSI in low-light-grown algae was twice that of high-light-grown algae (c. 160.0 versus 80.0 nmol m−2). We suggest that complex metabolic regulation allows L, saccharina to optimize photosynthesis over the wide range of temperatures and light levels encountered in nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00207.x
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  • 8
    Electronic Resource
    Electronic Resource
    Regulation of growth in Laminaria digitata: use of in-vivo nitrate reductase activities as an indicator of nitrogen limitation in field populations of Laminaria spp. (1984)
    Springer
    Marine biology 84 (1984), S. 207-217 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The seasonal variation in growth rate of a population of Laminaria digitata (Huds.) Lamour growing at Arbroath, Scotland was studied between August 1981 and September 1982, and was found to follow the biphasic annual cycle typical of this genus. Growth rates were maximum (0.3 cm cm-1 mo-1) in early June and minimum (0.05 cm cm-1 mo-1) between September and January. An analysis of the relationship between the seasonal changes in environmental factors (inorganic nitrogen concentrations, irradiance and temperature) with those of growth rate and the accumulation or mobilisation of cellular reserves of carbohydrates and nitrate, indicated that growth was nitrogen-limited between June and October and light-limited (with a possible co-involvement of temperature) for the remainder of the year. These conclusions were supported by the seasonal changes in the ratio of actual: potential in-vivo nitrate reductase activities in L. digitata, thus confirming the suitability of this technique for monitoring the occurrence of nitrogen limitation in Laminaria spp. The seasonal changes in blade nitrate reductase activities closely followed those of growth rate, with maximum activities [0.3 μmol NO 3 - reduced g-1 (wet wt) h-1] being present in late May and minimum levels [0.01 μmol NO 3 - reduced g-1 (wet wt) h-1] occurring between November and March. The correlation observed between nitrate reductase activities and growth rate is consistent with the ability of Laminaria spp. to store excess inorganic nitrogen, available during winter and early spring, as NO 3 - , and with the requirement to conserve enzyme protein during the summer period of nitrogen limitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393006
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