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  • 1
    Electronic Resource
    Electronic Resource
    Growth Substances and Dormancy in Ceratophyllum demersum (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 45 (1979), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ceratophyllum demersum L. occurs in winter in the dormant form, in summer in the vegetative form. Factors that affect growth and dormancy in Ceratophyllum were studied. After several weeks of severe winter conditions the plants changed from dormant to quiescent state. Under natural conditions Ceratophyllum plants remain quiescent for several months, due to unfavourable growth conditions. Experimentally the dormant could also be broken by high and low temperature treatments (shocks), and most effectively by addition of GA, An attempt to induce dormancy in full grown plants by the addition of ABA under extreme summer or winter conditions proved unsuccessful.The IAA and ABA contents in the plants were measured during the year. In winter the concentration of ABA was high and that of IAA low, whereas in summer the IAA concentration increased and that of ABA was variable. IAA only slightly antagonized the inhibition of growth by ABA. Both the growth regulators were readily taken up from the culture medium, as was confirmed by a study with the radioactive labelled compounds. The uptake rate of IAA was significantly higher than that of ABA. being 762 μg and 3.26, μg per plant in 24 h, respectively. GA, was found to have a strong antagonistic effect on the ABA induced growth inhibition.The total GA activity in dormant and quiescent plants was similar, in full grown plants it was much lower. In the dormant state a large part of GA was in a bound form, whereas during quiescence relatively more GA occurred in a free state in the plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1979.tb02603.x
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  • 2
    Electronic Resource
    Electronic Resource
    Photosynthetic characteristics of the submerged macrophyte Ceratophyllum demersum (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 68 (1986), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The photosynthetic and growth characteristics of Ceratophyllum demersum L. were investigated under laboratory conditions which simulated those encountered in the plants' normal environment. The carbon fixation rate of C. demersum measured with 14C at light and carbon saturation at pH 8.0 was 4.48 mg C (g ash-free dry weight)−1 h−1. It was lower at pH 6.5 than at pH 8.0. The light use efficiencies in quiescent plants and actively growing plants were 6.3 and 8.7 × 10−9 kg CO2 J−1, respectively, with corresponding maximum photosynthetic rates of 2.67 and 4.36 mg C (g ash-free dry weight)−1 h−1. Photorespiration in actively growing plants consumed 24% of the carbon fixed. Incubation with DCMU demonstrated that about one-third was refixed. The optimum temperature for carbon fixation was 25°C. The C3-photosynthetic pathway was the main operational route as indicated by the early photosynthetic products (largely C3-acids) and the absence of Krantz anatomy and the chlorophyll a:b ratio (2.7). The maximum relative growth rates ranged from 0.025 to 0.041 g ash-free dry weight (g ash-free dry weight)−1 day−1 in the field (Lake Vechten, 1 to 3 m depth classes).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1986.tb03389.x
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  • 3
    Electronic Resource
    Electronic Resource
    Seasonal Effects in the Hormonal Control of Growth in the Submerged Aquatic Macrophyte Ceratophyllum demersum (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 38 (1976), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The season dependent changes in growth response to treatment with auxin or gibberellin were studied in the aquatic macrophyte Ceratophyllum demersum.Control plants show, under experimental conditions, a maximum growth in length in February. In the same period most of the lateral buds appear. Growth of the lateral buds occurs later.IAA causes a stimulation of growth in length from late November or December until February, in concentrations of 10−9M and 10−6M. There is almost no stimulation of lateral bud formation by IAA, only a slight increase from late November until December occurs by the lowest concentrations used. The highest concentration used, 10−4M, is in most cases supraoptimal for lateral bud formation; only when plants become dormant (August), this high dose may stimulate the process.GA3, in concentrations of 10−9, 10−6 or 10−4M, exhibits a dose dependent increase of the response with respect to growth in length and lateral bud formation. The response occurs earlier than that for IAA: already early in November, or December, until February.Growth of the lateral buds may show only a slight stimulation by IAA as well as GA in winter. From February until April all GA concentrations used could cause a small increase of the growth of sprouts. In the case of IAA, however, only the lowest concentration could cause a small increase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1976.tb03999.x
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  • 4
    Electronic Resource
    Electronic Resource
    Towards an integrated study of the ecosystem of Lake Vechten (1978)
    Springer
    Aquatic ecology 12 (1978), S. 107-118 
    Details
    ISSN: 1573-5125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02260711
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  • 5
    Electronic Resource
    Electronic Resource
    Photosynthesis inCeratophyllum demersum. Carbon fixation rates in relation to the plants' physiological stage, and the contents of chlorophylland non-structural carbohydrates (1979)
    Springer
    Aquatic ecology 13 (1979), S. 112-112 
    Details
    ISSN: 1573-5125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Since the role of the submerged aquatic macrophytes in the carbon cycle of lake Vechten (the Netherlands) is in study, attention is paid to several aspects of their productivity.Ceratophyllum demersum is a predominant macrophytic species in the littoral zone of this lake, occurring mainly from three to five metres depth. In situ measurements of its photosynthetic rate demonstrated a maximum in spring (May), followed by a distinct decrease early in summer and a second maximum in late summer. The spring maximum of the photosynthetic rate coincided with the maximum increase of plant biomass. Maximum biomass occurred in early autumn (August–September). Althoughinsitu measurements pointed to the upper plant portions (70 cm) as the most important with respect to photosynthetic activity, it was demonstrated under standard experimental conditions that lower portions might be equally active depending on the age of the plant. In the lake, light reduction with depth is one of the major causes in the commonly observed decrease in photosynthetic activity in lower plant parts. Comparison of the photosynthetic rates in plant tipsin situ and under standard experimental conditions indicated that in spring, both water temperature and the chlorophyll content of the plant limit photosynthesis. This was concluded since under experimental conditions (a) photosynthetic rate and chlorophyll content were strongly correlated during the first half of the growing season and (b) higher rates were measured thanin situ. In the subsequent stage, however, light and the distribution of non-structural carbohydrates (TNC) in the plant also play an important role. At the second half the growing season, the lower parts of plants growing in the lake lose gradually their buoyancy, caused by a deteriorating light climate resulting in a decreasing photosynthetic activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02284742
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  • 6
    Electronic Resource
    Electronic Resource
    The submerged aquatic macrophytes in Lake Maarsseveen I: Species composition, spatial distribution and productivity (1981)
    Springer
    Aquatic ecology 15 (1981), S. 72-81 
    Details
    ISSN: 1573-5125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02260260
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  • 7
    Electronic Resource
    Electronic Resource
    Growth and production ofPhragmites australis in Lake Vechten (the Netherlands) (1981)
    Springer
    Aquatic ecology 15 (1981), S. 165-173 
    Details
    ISSN: 1573-5125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A study was carried out on several production characteristics ofPhragmites australis stands in Lake Vechten, the Netherlands. The aim was to quantify the role of this plant species in the lake's primary production and nutrient cycles (C, N and P). Maximum biomass values of 1247 and 286 g org.wt.m−2 were measured in, respectively, shoots and underground organs in August. The shoot: root ratio was always〉1. Plant litter accumulated particularly in spring and autumn. The relative growth rates of early shoots differed from those determined for the whole vegetation, indicating shoots of different ages in the latter. This was confirmed by counting the number of plants. The chemical composition of the plants changed with season. A carbon peak as high as 50.94% org.wt. was found in spring, which coincided with a nitrogen peak of 2.88% org. wt. At the end of the season N dissapeared faster from the shoots than C, whereas P declined from spring onwards. The production ofPhragmites contributed in 1979 for 5.8% to the lake's total primary production expressed in C, whereas the share of the total macrophytic unit amounted to 8.7%. The potential role ofPhragmites in the lake's nutrient cycles was largely due to nutrient leakage and decomposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255175
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  • 8
    Electronic Resource
    Electronic Resource
    Research into the characteristics of C3 and C4 plants inCeratophyllum demersum L. (1981)
    Springer
    Aquatic ecology 15 (1981), S. 199-199 
    Details
    ISSN: 1573-5125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The leaf anatomy was investigated with respect to the arrangement of cells involved in photosynthesis. The full-grown leaf has one vascular bundle consisting mainly of phioem cells. In similarity to terrestrial C4 plants the vascular bundle is surrounded by mesophyll bundle sheath cells. However, in contrast to C4 plants, these cells do not contain chlorophyll or starch inCeratophyllum. The early products in photosynthesis (10 seconds14C labelling) were analyzed. Although no complete separation of all radioactivity in the plant extracts was reached, it was clear that malate was the major labelled component, indicating C4 activity in the plants. No light saturation could be proven inCeratophyllum in several stages of post-dormancy in a statistically significant way, although a tendency to light saturation was observed at intensities higher than 36 Wm−2. The photosynthetic activity was only slightly depressed by enhancement of the O2 concentration in the medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255183
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  • 9
    Electronic Resource
    Electronic Resource
    Studies on decomposition ofPhragmites australis leaves under laboratory conditions (1982)
    Springer
    Aquatic ecology 16 (1982), S. 21-33 
    Details
    ISSN: 1573-5125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The decomposition ofPhragmites leaves was studied under experimental conditions in vessels during 147 days. This process was compared in vessels filled with (a) lake water, (b) lake water and sediment, and (c) lake water, sediment and plant material. In the course of time the ash-free dry weight and the N and C concentration in the plant material decreased gradually to, respectively, 64, 54 and 66% of the initial values. The P concentration fluctuated due to accumulation of bacteria and their excretion products. Almost all C and N which had disappeared from the plant material during the first 100 days of incubation was recovered in the water. Subsequently, these nutrients accumulated in the sediment. Only 10% of the C and N in the water was soluble (〈0.33 μm). Ortho-P increased substantially from 60 to 100 days of incubation in the vessels (b) and (c), possibly given off by the sediment or originating from decaying algae and bacteria. Only a minor part of the plant-P was recovered as ortho-P in the water. The effect of the decomposing plant material on the diversity within the microscopical primary producers was studied using paper chromatography of the pigments. The changes in bacterial numbers were followed by epifluorescence microscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255410
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  • 10
    Electronic Resource
    Electronic Resource
    The submerged macrophytes in Lake Maarsseveen I: Changes in species composition and biomass over a six year period (1987)
    Springer
    Aquatic ecology 21 (1987), S. 55-60 
    Details
    ISSN: 1573-5125
    Keywords: submerged macrophytes ; species composition ; biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The submerged macrophytes of Lake Maarsseveen I were surveyed in 1983 using SCUBA diving techniques. Only 40% of the characeans and 75% of the angiosperms detected in 1977 remained. The area colonized by submerged macrophytes was 0.45% in 1983, compared with 25.10% in 1977. The observed decreases were largely attributable to a shift of the plantcolonized areas to shallower depths. By 1983, most of the earlier predominant vegetation types had disappeared and the biomass had decreased. The decline in submerged vegetation may be attributed to increasing eutrophication, fish populations and recreational activities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255455
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