Duration of rapid light curves for determining the photosynthetic activity of microphytobenthos biofilm in situ

we examined the photosynthetic responses of submerged marestail in three lakes using pulse amplitude modulated (PAM) fluorometry. Three lakes were studied across a gradient of water temperature, with low water temperature conditions in Grass Lake and Arrow Bamboo Lake, and higher water temperature in Five Colored Lake. In the field, electron transport rates (ETRmax) were measured as rapid light curves (RLCs) by in situ yield measurements. Submerged marestail showed higher photosynthetic activity in Five Colored Lake compared to the other lakes, a response consistent with the adaptation of marestail in Five Colored Lake to high water temperature. The optimal temperature for photosynthesis of submerged marestail in Jiuzhaigou is about 12 °C. These results indicate that in different lakes the function of these aquatic plants is associated with a diversity of place-dependent environmental conditions, especially water temperature that leads to pronounced differences in the plant’s ecophysiological reactions.

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The use of rapid light curves to evaluate photosynthetic changes in turfgrasses exposed to low‐light conditions

itsrj ◽

10.1002/its2.64 ◽

2021 ◽

Author(s):

David Jespersen ◽

Bo Xiao

Keyword(s):

Light Curves ◽

Light Conditions ◽

Low Light ◽

Rapid Light Curves

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Daily Variations of Photosynthetic Efficiency of Greenhouse Tomato Plants during Winter and Spring

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.125.2.235 ◽

2000 ◽

Vol 125 (2) ◽

pp. 235-241 ◽

Cited By ~ 16

Author(s):

O. Ayari ◽

M. Dorais ◽

A. Gosselin

Keyword(s):

Photosynthetic Efficiency ◽

Photosynthetic Activity ◽

Photon Flux ◽

Tomato Plants ◽

Greenhouse Tomato ◽

Northern Latitudes ◽

Protective Strategy ◽

Growing Conditions ◽

Source Limitation

Daily and seasonal variations of photosynthetic activity, chlorophyll a (Chl-a) fluorescence and foliar carbohydrate content were studied in situ on greenhouse tomato (Lycopersicon esculentum Mill. `Trust') plants grown under CO2 enrichment and supplemental lighting. The objective of this study was to assess the effect of seasonal variation of the photosynthetic photon flux (PPF) on photosynthetic efficiency of tomato plants and to determine the presence or absence of photosynthetic down-regulation under greenhouse growing conditions prevailing in northern latitudes. During winter, the fifth and the tenth leaves of tomato plants showed low, constant daily photosynthetic activity suggesting a source limitation under low PPF. In winter, the ratio of variable to maximum Chl-a fluorescence in dark adapted state (Fv/Fm) remained constant during the day indicating no photoinhibition occurred. In February, an increase in photosynthetic activity was followed by a decline during March, April, and May accompanied by an increase in sucrose and daily starch concentrations and constant but high hexose level. This accumulation was a long-term response to high PPF and CO2 enrichment which would be caused by a sink limitation. Thus, in spring we observed an in situ downregulation of photosynthesis. The ratio Fv/Fm decreased in spring compared to winter in response to increasing PPF. The daily decline of Fv/Fm was observed particularly as a midday depression followed by a recovery towards the end of the day. This indicated that tomato leaves were subject to a reversible inhibition in spring. Fv/Fm was lower in March than in April and May even though PPF was higher in April and May than in March. These results suggest that tomato plants develop an adaptive and protective strategy as PPF increases in spring.

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Diurnal gross photosynthetic patterns and potential seasonal CO2 assimilation in Cladonia stellaris and Cladonia rangiferina

Canadian Journal of Botany ◽

10.1139/b83-073 ◽

1983 ◽

Vol 61 (3) ◽

pp. 642-655 ◽

Cited By ~ 14

Author(s):

Thomas J. Moser ◽

Thomas H. Nash III ◽

Steven O. Link

Keyword(s):

Photosynthetic Activity ◽

Growing Season ◽

Early Morning ◽

Co2 Assimilation ◽

Atmospheric Moisture ◽

Growing Seasons ◽

Late Evening ◽

Summer Rain ◽

Cladonia Rangiferina

The daily, in situ gross photosynthetic patterns of Cladonia stellaris (Opiz.) Pouz. & Vězda. and Cladonia rangiferina (L.) Wigg. were monitored during portions of the 1977, 1978, and 1979 growing seasons at Anaktuvuk Pass, Alaska. Photosynthetic activity in both species closely paralleled atmospheric moisture status, where peak photosynthetic rates were attained during or following sporadic summer rain. In addition, thallus absorption of moisture during extended periods of high atmospheric water vapor content gave rise to short periods of minimal photosynthetic activity. During late evening and early morning hours moistened thalli exhibited minimal or no photosynthetic activity, coinciding with consistent attenuation in solar radiation during these periods. Photosynthetic activity was not homogeneous throughout the thallus. The greatest activity occurred in the apical regions and decreased progressively into the basal regions. The apical 10-mm regions of C. stellaris and C. rangiferina thalli accounted for approximately 50% of their photosynthetic capabilities. The potential gross CO2 assimilation of the apical 10-mm regions over 72 days of the 1978 growing season was estimated at approximately 35 g CO2∙m−2 and 16 g CO2∙m−2 for C. stellaris and C. rangiferina, respectively.

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Whole-Cell Immunolocalization of Nitrogenase in Marine Diazotrophic Cyanobacteria, Trichodesmiumspp.

Applied and Environmental Microbiology ◽

10.1128/aem.64.8.3052-3058.1998 ◽

1998 ◽

Vol 64 (8) ◽

pp. 3052-3058 ◽

Cited By ~ 67

Author(s):

Senjie Lin ◽

Sheri Henze ◽

Pernilla Lundgren ◽

Birgitta Bergman ◽

Edward J. Carpenter

Keyword(s):

Photosynthetic Activity ◽

Protein Localization ◽

Distribution Patterns ◽

Dark Cycle ◽

Fixation Rate ◽

Low Concentrations ◽

If Technique ◽

Dimethyl Urea ◽

Diazotrophic Cyanobacteria

ABSTRACT The mechanism by which planktonic marine cyanobacteria of the genusTrichodesmium fix N2 aerobically during photosynthesis without heterocysts is unknown. As an aid in understanding how these species protect nitrogenase, we have developed an immunofluorescence technique coupled to light microscopy (IF-LM) with which intact cyanobacteria can be immunolabeled and the distribution patterns of nitrogenase and other proteins can be described and semiquantified. Chilled ethanol was used to fix the cells, which were subsequently made permeable to antibodies by using dimethyl sulfoxide. Use of this technique demonstrated that about 3 to 20 cells (mean ± standard deviation, 9 ± 4) consecutively arranged in a Trichodesmium trichome were labeled with the nitrogenase antibody. The nitrogenase-containing cells were distributed more frequently around the center of the trichome and were rarely found at the ends. On average 15% of over 300 randomly encountered cells examined contained nitrogenase. The percentage of nitrogenase-containing cells (nitrogenase index [NI]) in an exponential culture was higher early in the light period than during the rest of the light-dark cycle, while that for a stationary culture was somewhat constant at a lower level throughout the light-dark cycle. The NI was not affected by treatment of the cultures with the photosynthetic inhibitor dichloro 1,3′-dimethyl urea or with low concentrations of ammonium (NH4Cl). However, incubation of cultures with 0.5 μM NH4Cl over 2 days reduced the NI. The IF technique combined with 14C autoradiography showed that the CO2 fixation rate was lower in nitrogenase-containing cells. The results of the present study suggest that (i) the IF-LM technique may be a useful tool for in situ protein localization in cyanobacteria, (ii) cell differentiation occurs inTrichodesmium and only a small fraction of cells in a colony have the potential to fix nitrogen, (iii) the photosynthetic activity (CO2 uptake) is reduced if not absent in N2-fixing cells, and (iv) variation in the NI may be a modulator of nitrogen-fixing activity.

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Field Studies of DCMU-Enhanced Fluorescence as an Index of in situ Phytoplankton Photosynthetic Activity

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f80-131 ◽

1980 ◽

Vol 37 (6) ◽

pp. 1028-1031 ◽

Cited By ~ 7

Author(s):

Suzanne Roy ◽

Louis Legendre

Keyword(s):

Photosynthetic Activity ◽

Field Work ◽

Field Studies ◽

Gulf Of Guinea ◽

Lawrence Estuary ◽

Technical Problems ◽

Lower Light ◽

St Lawrence Estuary ◽

Composition Changes

Comparison between the increase in fluorescence caused by DCMU (FD/FN: ratio of DCMU-enhanced to normal fluorescence) and the specific photosynthetic rate (P/B: photosynthetic activity per unit chlorophyll a) in the St. Lawrence Estuary showed that no overall correlation could be established between P/B and FD/FN, although there were significant correlations between these two variables on short transects. This reflected perhaps environmental and species composition changes. FD/FN vertical profiles in the Gulf of St. Lawrence and the Gulf of Guinea showed a characteristic increase with depth, as seen in laboratory cultures with a decrease in light intensity. This could be related to photosynthetic efficiency which is known to increase at lower light intensities. Technical problems involving the use of FD/FN as an estimator of P/B are also discussed. Further investigations are required before this fluorescence technique can be used regularly in field work to estimate photosynthetic activity.Key words: DCMU, fluorescence, photosynthesis, phytoplankton, St. Lawrence Estuary, Gulf of Guinea

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Plasticity of marine sponge habitat preferences with regard to light and water motion: the example of Batzella inops (Topsent, 1891) in submerged caves

Marine and Freshwater Research ◽

10.1071/mf18001 ◽

2018 ◽

Vol 69 (11) ◽

pp. 1784

Author(s):

P. Nemoy ◽

E. Spanier ◽

N. Kashtan ◽

A. Israel ◽

D. L. Angel

Keyword(s):

Marine Sponge ◽

Environmental Conditions ◽

Photosynthetic Activity ◽

Habitat Preferences ◽

Marine Sponges ◽

Reciprocal Transplantation ◽

Preferred Habitat ◽

Contrasting Habitats ◽

Transplantation Experiments

This study examined the effects of environmental conditions on the distribution of marine sponges. We measured the abundance of the sponge Batzella inops (Topsent, 1891) in two contrasting habitats: inside submerged caves and on the surfaces of submerged boulders. We hypothesised that caves are a preferred habitat for B. inops over the boulder surfaces, and tested this by descriptive (quadrate sampling) and manipulative (reciprocal transplantation) experiments. In addition, we tested B. inops in situ for the presence of photosynthetic activity. We found that B. inops is more abundant inside the caves (mean ± s.e.m., 1.2 ± 0.6individualsm–2) than on the outside boulder surfaces (0.15 ± 0.19individualsm–2). We also detected photosynthetic activity in B. inops in both habitats. The results of transplantation experiments suggested that the sponge prefers the transfer from inside to outside the cave rather than vice versa. Therefore, we conclude that although B. inops is more abundant in sheltered habitats, such as submerged caves, adult individuals of this sponge can survive transfer to exposed conditions. Altogether, our findings point to the plasticity of B. inops habitat preferences and may aid further research into conservation or mariculture of this and possibly other sponge species.

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