scholarly journals Effects of Low Concentrations of O3 on Net Photosynthesis, Dark Respiration, and Chlorophyll Contents in Aging Hybrid Poplar Leaves

1983 ◽  
Vol 73 (2) ◽  
pp. 291-296 ◽  
Author(s):  
Peter B. Reich
Keyword(s):  
Dark Respiration ◽  
Hybrid Poplar ◽  
Net Photosynthesis ◽  
Chlorophyll Contents ◽  
Low Concentrations ◽  
Poplar Leaves

The ecology of Ramalina menziesii. VI. Laboratory responses of net CO2 exchange to moisture, temperature, and light

1987 ◽  
Vol 65 (1) ◽  
pp. 182-191 ◽  
Author(s):  
U. Matthes-Sears ◽  
T. H. Nash III ◽  
D. W. Larson
Keyword(s):  
Dark Respiration ◽  
Net Photosynthesis ◽  
Co2 Exchange ◽  
Response Curves ◽  
Central California ◽  
Photosynthetic Rates ◽  
Chlorophyll Contents ◽  
The Mean ◽  
The Difference ◽  
Thallus Water Content

The response of net CO2 exchange to thallus water content, thallus temperature, and photosynthetically active radiation was measured in the laboratory for two morphologically different forms of Ramalina menziesii collected from a coastal and an inland habitat in central California. Equations describing the response curves are fitted to the data and compared statistically for the two sites during two seasons. Significant differences were present for all responses both in summer and winter but were more pronounced for net photosynthesis than for dark respiration. The main differences between the two forms were in the absolute rates of net photosynthesis; a maximum of 6.2 was measured for the inland form but only 3.6 mg∙g−1∙h−1 for the coastal form. Chlorophyll contents were also different between the two forms, indicating that chlorophyll is the likely cause for the difference in net photosynthetic rates. Net photosynthetic rates were higher at low temperatures during winter than during summer, but otherwise seasonal variations in the gas exchange responses were relatively minor. Both forms of the lichen are light saturated at quantum fluxes greater than 200 μE∙m−2∙s−1. Both show an optimum temperature for maximum CO2 exchange at 25 °C, well above the mean operating temperature of R. menziesii in the field.

Early Responses of Periphyton to Experimental Lake Acidification

1987 ◽  
Vol 44 (S1) ◽  
pp. s135-s149 ◽  
Author(s):  
Michael A. Turner ◽  
Michael B. Jackson ◽  
David L. Findlay ◽  
Roger W. Graham ◽  
Edwin R. DeBruyn ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Littoral Zone ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Dark Respiration ◽  
Net Photosynthesis ◽  
Taxonomic Composition ◽  
Filamentous Algae ◽  
Low Concentrations ◽  
Selection Of

We studied the periphyton in two small lakes acidified experimentally with either sulfuric or nitric acid. For comparison, we monitored periphyton in one previously acidified (sulfuric) lake and in two neutral lakes. Net photosynthesis declined in epilithic periphyton in the middle littoral zone (1–2 m) of both recently acidified basins in response to reduced concentrations of dissolved inorganic carbon. Dark respiration and taxonomic composition remained largely unchanged in this zone. Attached filamentous algae proliferated early [Formula: see text] in the upper littoral zone (< 1 m) of the sulfuric acid basin confirming earlier observations made in the previously acidified lake. These Zygnematales-dominated filamentous algae (largely Mougeotia sp.) developed conspicuously on submerged rock and log surfaces. In contrast, growth on macrophytes was variable in both the neutral and nitric acid systems. We hypothesize that during the early stages of acidification proliferation of filamentous Chlorophyceae is due to selection of algae tolerant of increased H+and better adapted to obtain inorganic carbon at low concentrations, in combination with reduced grazing.

Ozone effects on the ultrastructure of the chloroplasts from hybrid poplar leaves

Micron (1969) ◽  
1980 ◽  
Vol 11 (1) ◽  
pp. 13-14 ◽  
Author(s):  
Reginald Noble ◽  
David Pechak ◽  
Keith Jensen
Keyword(s):  
Hybrid Poplar ◽  
Poplar Leaves

scholarly journals ALLELOPATHIC INFLUENCE OF TRIANTHIMA PORTULACASTRUM L. ON GROWTH AND DEVELOPMENTAL RESPONSES OF SESAME (SESAMUM INDICUM L.)

2017 ◽  
Vol 4 (2) ◽  
pp. 183-186
Author(s):  
Prabhakaran J ◽  
Kavitha D
Keyword(s):  
Block Design ◽  
Dry Weight ◽  
Germination Percentage ◽  
Sesamum Indicum ◽  
Negative Effects ◽  
Chlorophyll Contents ◽  
Whole Plant ◽  
Low Concentrations ◽  
Seedling Length ◽  
Developmental Responses

An experiment was conducted in order to determine the allelopathic effects of the aqueous extract of Trianthima portulacastrum L.on the seed germination, seedling growth and chlorophyll content ofsesame (Sesamum indicum L.). Greenhouse experiment was carried out as RCBD (Randomized complete block design)with four replications. Treatments included 0, 1, 2, 3 and 4% (W/W) residues of whole plant of T.portulacastrum with normal field soil. Results showed that the low concentrations of T.portulacastrum had no significant effect on the germination percentage, seedling length, dry weight, total chlorophyll contents at lower concentration(1%) of weed residues. However, treatments with higher concentrations had negative effects on germination, growth and seedling dry weight of sesame.

scholarly journals Impact of Ag Nanoparticles on Seed Germination and Seedling Growth of Green Beans in Normal and Chill Temperatures

Agriculture ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 312 ◽  
Author(s):  
Roman Prażak ◽  
Agata Święciło ◽  
Anna Krzepiłko ◽  
Sławomir Michałek ◽  
Marta Arczewska
Keyword(s):  
Seed Germination ◽  
Rhizobium Leguminosarum ◽  
Net Photosynthesis ◽  
Antimicrobial Effect ◽  
Dry Weight ◽  
Short Term ◽  
Green Beans ◽  
Low Concentrations ◽  
Microbial Preparation ◽  
Positive Effect

The study analysed the effect of silver nanoparticles (AgNPs) on seed germination, field emergence and the physiological parameters of seedlings of two bean cultivars, ‘Bali’ and ‘Delfina’, under normal and chill temperatures. AgNPs solutions (0.25, 1.25 and 2.5 mg dm−3) were applied together with the microbial preparation Nitragina (containing Rhizobium leguminosarum bv. phaseoli) on seeds as a short-term pre-sowing treatment. Low concentrations of AgNPs (0.25, 1.25 mg dm−3) had an immediate beneficial effect, resulting in fast and uniform germination in laboratory and field conditions, as well as a positive effect in the later stages of seedling development, manifested as an increase in the average seedling height, fresh and dry weight and net photosynthesis. Particularly, favourable effects were noted in suboptimal temperature conditions, suggesting that AgNPs activate plant mechanisms of tolerance to environmental stress. The highest concentration tested of AgNPs was not particularly effective for the plants but had a strong antimicrobial effect, which was beneficial in period of seed germination, but at the later stage of plant development was unfavourable probably due to disruption of symbiosis between the bean seedlings and rhizobia.

Two physiological races of Tsuga canadensis in Wisconsin

1975 ◽  
Vol 53 (9) ◽  
pp. 940-951 ◽  
Author(s):  
William Eickmeier ◽  
Michael Adams ◽  
Donald Lester
Keyword(s):  
Dark Respiration ◽  
Net Photosynthesis ◽  
Tsuga Canadensis ◽  
Seedling Morphology ◽  
Seed Sources ◽  
Temperature Regimes ◽  
Disjunct Populations ◽  
Use Efficiency ◽  
Osmotic Potentials ◽  
Carbon Dioxide Balance

Population differentiation in Tsuga canadensis (L.) Carr. from Wisconsin was tested by comparing seedlings grown from seed collected within the present range in the northeast and from seed collected in disjunct populations southwest of the present range. The seedlings, established in hydroponic culture, were subjected to two preconditioning temperature regimes and two water stress simulations. Net photosynthesis, dark respiration, and transpiration capacities were measured and internal leaf resistances were calculated.The southwestern Wisconsin population had a more favorable carbon dioxide balance at warmer tissue temperatures, particularly at low irradiance levels, and at higher osmotic potentials, than did the northeastern population, which was better adapted to lower tissue temperatures and lower osmotic potentials. Additional differences between seed sources in seedling morphology, transpiration rate, and water-use efficiency were found. These differences in morphology and physiological responses corresponded to the macroclimates in which these populations were found, southwestern Wisconsin being warmer and drier than the northeastern part of the state.

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