Terms Of Chlorophyll Research Articles

Variability of feeding processes in the cockle Cerastoderma edule (L.) in response to changes in seston concentration and composition

Physiological processes controlling food acquisition by the filter feeding bivalve Cerastoderma edule (L.) were quantified under a broad range of seston concentrations and compositions. Experimental diets consisted of suspensions elaborated by adding variable amounts of microalgal cells of different species (or sediment particles in one case) to natural sea-water. Clearance rates exponentially decreased with seston concentration, but the rate of reduction was higher with suspensions of high organic content. Pseudofaeces production appeared as a positive function of the rate of particle filtration; however, for a given filtration rate, more pseudofaeces were rejected when filtered matter had a low organic content. As a consequence, after an initial elevation, ingestion rate remained almost constant across particle concentrations. Pre-ingestive food selection enhanced the rate of particulate organic matter ingestion and this organic enrichment of ingested matter became more pronounced for diets of low food value, where most filtered matter was being rejected as pseudofaeces. Selection of particles at the pre-ingestive level was more efficient in terms of chlorophyll, revealing preferential ingestion of algal particles compared with the whole organic matter. Stronger selection for algae, however, was not evident in terms of preferential nitrogen ingestion, as compared with carbon, which was probably due to similar low values of the C N ratios in all experimental conditions. Absorption efficiency depended on the organic content of ingested matter according to an exponential, saturating function. In general, feeding processes of cockles appear well adapted to cope with elevations in particle concentration and simultaneous reductions in the food value of available seston that occur when resuspended bottom sediments constitute a significant fraction of particulate materials of the water column. Under these conditions, high rates of seston filtration and pseudofaeces production, together with preferential organic ingestion act to compensate for the dilution of organic matter in suspension and its detrimental effect on the rate of food absorption. However, this compensatory behaviour is not so efficient as to make absorption rate independent of the organic value of available particles. The organic content of resuspensible sediments may thus become the main determinant of food acquisition in cockles.

Influence of dissolved silicate on vertical flux of particulate biogenic matter

The influence of dissolved silicate (DSi) addition on primary production, phytoplankton development and subsequent vertical export of particulate matter was studied in enclosures. Blooms of different phytoplankton communities were initiated in the upper part of 10 m deep enclosures supplied with nitrate and phosphate (NP) and nitrate, phosphate and silicate (NPS). Primary production was 31% higher in the NPS enclosure as compared to the NP enclosure over the experimental period of 27 days. Increased phytoplankton growth was mainly caused by mass development of diatoms in the NPS enclosure. Enhanced growth was accompanied by an increased vertical flux of organic matter (86, 15.9 and 16.9% in terms of chlorophyll, particulate nitrogen and particulate carbon, respectively) and was dominated by diatoms. The present study indicates that for each gram of DSi added, vertical flux was enhanced by 3.6 g C, implying that the ratio of DSi added/carbon exported was close to the Redfield ratio. Thus DSi presence appears to decrease the nutrient turn-over time in the euphotic zone by increasing vertical export. This may improve water quality of the surface layer of eutrophicated environments, but can lead to oxygen depletion of bottom waters.

瀬戸内海西部域，太平洋における植物プランクトン群集のサイズ構造とその制限栄養塩に関する研究

Horizontal variations of limiting nutrient and size structure of phytoplankton community at estuarine and oceanic stations from Hiroshima Bay to the Pacific Ocean were studied. The following results were obtained :1) Concentrations of DIN, DIP and chlorophyll a were very high in Hiroshima Bay estuary and decreased toward the south sea area.2) Limiting nutrient of phytoplankton in the Hiroshima Bay estuary was estimated to be phosphorus, whereas that in other stations was estimated to be nitrogen.3) Nanophytoplankton dominated total biomass of phytoplankton population in terms of chlorophyll a in Hiroshima Bay. On the contrary, picophytoplankton showed the greatest fraction of total biomass of phytoplankton population in terms of chlorophyll a from the Sea of Iyo to the Pacific Ocean.4) Cell density of picocyanobacteria was maximum in the Hiroshima Bay estuary, but the lowest was observed in southernmost station of the Pacific Ocean.

The development of phytoplankton blooms in upwelled waters of the southern Benguela up welling system as determined by microcosm experiments

Phytoplankton bloom development was examined in newly upwelled waters collected off the Cape Peninsula during active upwelling and incubated in the laboratory under conditions approximating those in the ocean. Of interest was the variability of the phytoplankton developmental processes following upwelling. Results were compared to those of drogue studies which shared the same objectives but utilized drogues to tag and follow parcels of upwelled water in order to monitor bloom development. Differences in the time required for bloom development and in the peak population size were attributed to differences in the duration of the lag period, in the size of the seed population, in grazing pressures and in the total amount of nutrient available in the source water. Bloom development was measured in terms of chlorophyll a, particle volume, phytoplankton species and phytoplankton carbon changes. Specific growth rates were initially low prior to the initiation of exponential growth during which maximum growth rates were recorded. Microflagellates were found to be capable of higher growth rates than diatoms. In terms of carbon the microflagellate fraction varied within narrow limits. The variation and peaks in the phytoplankton biomass were caused by the diatom fraction of the total carbon. Following the bloom peak, negative growth rates were attributed to cell death with the rapid autolysis of cell pigments. Changes in the nitrate, silicate and phytoplankton carbon concentration s relative to phosphate were similar to the ratios of Redfield et al. (1963). Growth of the bloom was terminated by either nitrate, silicate or phosphate limitation. Phytoplankton productivity was assessed in terms of changes in phytoplankton carbon, nitrate concentration and C 14 uptake. Based on the results of the microcosm studies simple equations were formulated for the prediction of phytoplankton growth in terms of chlorophyll a following upwelling. Predicted maximum chlorophyll a yield and duration of growth are compared to observed chlorophyll a concentrations during the drogue studies.

Effects of O2and CO2partial pressure on senescence of oat leaves and broccoli miniflorets

Abstract Effects of decreased O2 partial pressure P(O2) and increased CO2 partial pressure p(CO2) on senescence of 7-day-old oat plants or excised leaves (Avena sativa L. cv. Victory) and broccoli miniflorets (Brassica oleracea L. var. italica) were studied in terms of chlorophyll and protein loss, proteolytic activity, and stomatal behaviour. Senescence in darkness was delayed by decreasing p(O2), an effect which in oat leaves was unaffected by the CO2 partial pressure, p(O2). However, increased P(CO2) at low O2 levels gave the best colour and flavour retension in broccoli miniflorets. Chlorophyll level increased c. 25% during the first 2–3 days after plants or excised leaves were placed in darkness at a P(O2) of 0.5 kPa. Protein and chlorophyll breakdown were inhibited when p(O2) was 2 kPa or less. Excision of leaves accelerated breakdown when compared to whole plants regardless of p(O2). Modification of ubiquitin conjugates was observed in broccoli miniflorets stored at reduced p(O2). The data indicates ubiquit-independent proteolysis contributed to senescence of broccoli miniflorets.

Characterisation of nuclear gene controlled yellow stripe mutant of Pennisetum glaucum (L.) R.Br.

The plastid mutant of pearl millet exhibiting a pattern dependent material inheritance was characterised in terms of chlorophyll a/ b ratios, the levels of ribulose1,5-bisphosphate carboxylase (RuBPCase) and phosphoenolpyruvate carboxylase (PEPCase). The chlorophyll content varied from leaf to leaf in variegated plants while no consistent differences in chlorophyll a/ b ratios were evident. RuBPCase activity was lacking in yellow seedlings and yellow tissue from variegated plants and the enzyme levels were lower in variegated plants compared to that of green sibs and the RuBPCase activity in variegated leaves was dependent on the extent of green tissue in the material irrespective of their genotype. The PEPCase levels in the yellow and green seedlings were similar while yellow tissue had lower levels compared to green tissue within the variegated plants. Sedimentation analysis of the soluble protein fraction from the green and yellow tissues revealed lack of RuBPCase protein (19.45S) in the yellow tissue. Furthermore, the SDS-polyacrylamide gel electrophoresis revealed absence of the larger subunit (55 kDa) of RuBPCase. These observations are consistent with the information on ultrastructural and molecular changes associated with the altered plastids and their genetic basis in the same mutant.

Comparison of the Dl/D2/cytochrome b559 reaction centre complex of photosystem two isolated by two different methods

Photosystem 2 reaction centre complexes prepared either by solubilisation with Triton X-100 and subsequent exchange into dodecyl maltoside or by a procedure involving a combination of dodecyl maltoside and LiC10 4, were characterised in terms of chlorophyll a, pheophytin a, β-carotene and cytochrome b559 content. Time-resolved chlorophyll fluorescence decay kinetics were measured using both types of complexes. Our data show that the isolated photosystem two reaction centre complex contain, for two pheophytin a molecules, close to six chlorophyll a, two β-carotene and one cytochrome b559. No major differences were observed in the composition or the kinetic characteristics measured in the samples prepared by the different procedures. Time-resolved fluorescence measurements indicate that more than 94% of the chlorophyll a in both preparations is coupled to the reaction centre complex.

Remote sensing of water parameters in Madura Bay

During the Madura Bay Remote Sensing Experiment, which was conducted as part of the Snellius-II Expedition in August, 1984, space-borne, air-borne and ship-borne radiometric data were collected. They have been analysed in terms of chlorophyll, suspended matter, yellow substance and sea-surface temperature to map the distribution patterns and temporal variability of different water masses. A general correlation analysis between ship-borne radiance measurements and biochemical data (sea truth) indicates that the dominant factors which determine the reflectance spectra are the total amount of scattering and absorbing substances in the water, sun and sky glitter, and the chlorophyll and phaeophytin concentration. For a coastal area strongly influenced by river run-off, the chlorophyll concentration is comparatively low. As a result, the chlorophyll fluorescence is weak, but can still be detected. The blue/green colour ration and the fluorescence line height along the flight tracks derived from the Ocean Color Radiometer (OCR) over three consecutive days indicate at least three different types of water, viz. clear ocean water in the eastern part of the Bay, mixed water with moderate contents of chlorophyll and suspended matter in the middle and western parts of the Bay and finally estuarine and river water containing large amounts of inorganic and dissolved organic matter near the mouths of Solo and Brantas rivers and in the Strait itself. Distribution patterns change from one day to the next, possibly as a result of tidal effects. Vertical radiation profiles derived from aircraft flights at different altitudes and from modelling the radiative transfer through the atmosphere give an indication of how well ocean colour/chlorophyll fluorescence can be monitored through a typical tropical atmosphere from satellite altitude. Model calculations and comparative measurements show that even the small fluorescence signals (corresponding to a low pigment concentration) can still be detected above the atmosphere, while colour ratios, especially in the blue part of the spectrum, are heavily masked by aerosol and Raleigh scattering and have to be corrected carefully prior to any interpretation. At all wavelengths, upwelling spectra contain a considerable amount of light specularly reflected at the sea surface.

Feeding by the planktonic calanoid copepod Acartia clausi Giesbrecht on natural suspended particulate matter of varying quantity and quality

The defaecation rate of females of the calanoid copepod Acartia clausi Giesbrecht as a measure of the ingestion rate was measured in relation to quantity and quality of natural suspended particulate matter. In the April–September experiments, phytoplankton was the dominant component of suspended particulate matter and the ambient chlorophyll a concentration was high, ranging from l.11 to 23.91 μg·l −1. The defaecation rate became saturated below the ambient particle concentration and the weight-specific defaecation rate was rectilinearly fitted against particle concentration. In terms of chlorophyll a, the critical concentration for saturation of the weight-specific defaecation rate ranged from 0.616 to 1.710 μg·l −1. In the October–November experiments, the ambient chlorophyll a concentration ranged from 0.27 to 0.53 μg·l −1 and non-living particles became the dominant component. No critical concentration was observed and the slope of the line describing the relationship between particle concentration and weight-specific defaecation rate was greatly reduced in comparison with that obtained in the April–September experiments. The reduction of the slope may be due to the dominance of non-living particles.

Monocarpic senescence in wheat: Influence of sterile glumes and ear

The senescence of sterile glumes, flag leaf and the other two leaves below the ear of wheat (Triticum aestivum L. cv. Sonalika) was studied in relation to grain development and surgical manipulation. The senescence of sterile glumes was faster than that of the leaves in terms of chlorophyll and protein degradation. The flag leaf senesced later than the other two leaves below it. Removal of sterile glumes markedly reduced the harvest index (crop: straw ratio) and average dry weight per grain as compared to removal of the flag leaf. Maximum grain weight was achieved after the glumes had senesced completely. Removal of the ear delayed senescence of all the three leaves. It is concluded that sterile glumes are important suppliers of assimilate for grain filling and that nutrient drainage is the primary cause of the monocarpic senescence in wheat.

In situ culturing of larvae of the crown-of-thorns starfish Acanthaster planci

In situ culturing of larvae of the crown-of-thorns starfish Acanthaster planci

The effect of nutrient enrichment on the natural phytoplankton community of Lake Biwa maintained in glass bottles.

Near- and offshore waters of the south basin of Lake Biwa were bottled, enriched with nitrogen and phosphorus, alone and in combination, and incubated for a long period in the surface layer of the lake. Experiments were carried out during four seasons in the nearshore water and for one season in the offshore water. The phytoplankton response to wastewater was also investigated. Results of the experiments showed that nitrogen and phosphorus in combination have the most stimulatory effect on phytoplankton growth, whereas there was some evidence that nitrogen rather than phosphorus stimulated phytoplankton growth more in terms of chlorophyll a and total cell number. Nitrogen plus phosphorus and nitrogen treatments remarkably changed the phytoplankton composition leading to an increase in green algae. Polluted river water without nutrient addition also promoted algal growth.

Seasonal variations of dominant phytoplankton, chlorophyll a and nutrient levels in the pelagic regions of Lake Biwa.

In order to clarify the present trophic status of Lake Biwa, the largest, monomictic lake in Japan, seasonal variations of dominant phytoplankton, chlorophyll a and nutrient levels were surveyed for offshore waters of its north (main) and south (subsidiary) basins from February to December 1981. Annual means of Secchi disc transparency in the north and south basins were 4.8 and 1.7 m, respectively. In both basins, diatoms were most predominant in winter and early spring, and green algae in other seasons. Besides these algae, Uroglena americana and Anabaena macrospora formed dense blooms for short periods. Two peaks of chlorophyll a concentration in the surface water were observed in both basins, one in May and the other in October. Annual mean concentrations of chlorophyll a in the surface waters of the north and south basins were 9.1 and 10.1 g El-1, respectively, while those of total phosphorus were 9.2 and 16.7 g El-1, respectively. High concentrations of nitrate plus nitrite nitrogen were detected in both basins except for three months from August to October. It was concluded that phosphorus was the most limiting nutrient for phytoplankton growth for the most part of the year, but nitrogen seemed to be also limiting during August to October. Trophic degrees of both basins were intermediate between mesotrophic and eutrophic in terms of chlorophyll a and total phosphorus concentrations.

An optical classification of coastal and oceanic waters based on the specific spectral absorption curves of phytoplankton pigments, dissolved organic matter, and other particulate materials1

The variations of the spectral absorption coefficient of seawater can be attributed to three principal factors—phytoplankton, nonchlorophyllous particles, and yellow substances— whose concentrations are represented in this study in terms of chlorophyll a and pheophytin a content (C), the total scattering coefficient (b), and the absorption by filtered seawater at a given wavelength (Y). By assuming an exponential absorption by yellow substances, we developed a new iterative method for identifying the in situ apparent specific spectral absorption curves of the other two factors. The weighting coefficients for each of the three components are calculated for over 80 spectral absorption measurements from different representative marine regions. The reconstruction of spectral absorption curves from the three coefficients and the three specific absorption curves fits the original data with an overall average error of 3%. Relationships between these coefficients and C, b, and Y are examined. Results show that, though the spectral form of absorption by pigments can be considered as more or less invariant, the absorption “efficiency” per unit C depends on the nature of the water, and hence on the type of phytoplankton population considered. An optical classification based on the three optical coefficients related to three absorbing agents is proposed.

Seasonal and diurnal changes of chlorophyll in a tropical fresh water impoundment

The phytoplankton biomass was estimated in terms of chlorophyll in Sathiar reservoir. The chlorophyll values were high during the low water phase in the reservoir which was also the period of summer. Following the rains and increase in water depth phytoplankton biomass decreases on account of (a) dilution, (b) loss from the reservoir through the outlets and (c) settling to the bottom along with silt. The diel variations of chlorophyll showed that the peak value was reached mostly at 12 noon due to the migration of phytoplankton to the surface.

Pigment content and photosynthetic rate of the fronds of Macrocystis pyrifera

The Macrocystis pyrifera (L.) C. Ag. frond is here described in terms of chlorophyll a, fucoxanthin, chlorophyll c and photosynthetic rate. Pigment concentrations increased back from the apical meristem reaching a maximum after 2 to 3 m. Pigment concentrations were then generally constant throughout most of the length of the frond, finally decreasing again in the oldest parts of the frond with the exception of the sporophylls. Pigment ratios remained relatively constant throughout. Maximum net photosynthetic rates on a given frond showed a decrease with tissue age on both an area basis (1040 down to 463 nmol O2 cm-2 h-1) and on a chlorophyll a basis, which was shown as half-saturation constants (quantum irradiance) which dropped on an area basis from 85 μmol m-2 sec-1 at 4.5 m above the holdfast to 26 μmol m-2 sec-1 at 15.5 m. Young sporophytes transplanted from the sea floor to the surface (12 m) tended to decrease pigment content, while those transplanted to the bottom tended to increase all pigments, but especially fucoxanthin. Photosynthetic rates, however, changed little on a unit area basis. The results of these data are considered in the light of recent work on photosynthetic units, tissue age effects and general adaptations of the M. pyrifera frond to its light environment.

Seasonal dynamics of epiphytic algal growth in a marsh pond: composition, metabolism, and nutrient availability

Seasonal growth and succession of epiphytic algae on artificial substrates in a marsh pond were related to nutrient levels (N, P, and Si) and to various physiological indicators of nutrient availability, including chlorophyll content, protein to carbohydrate and lipid ratio, Si debt, storage phosphate levels, alkaline phosphatase activity, and nitrogenase activity. Low standing crops in June and early July coincided with indications of deficiency in terms of chlorophyll a content and protein to carbohydrate and lipid ratios at chosen Scirpus and Potamogeton sites. Low available N may have been limiting growth. In July and August, when available N, P, and Si were low, there was evidence of Si limitation of diatom growth at both sites. Growth of heterocystous, N2-fixing. blue-green algae and high alkaline phosphatase activity occurred in July at the Potanwgeton site. Increased standing crop of epiphytic algae in September and October at the Scirpus site coincided with higher nutrient levels and an absence of deficiency symptoms. A delay in the standing crop increase at the Potamogeton site correlated with low nutrient levels and various physiological deficiency symptoms.

Mutations induced in presoaked barley seeds by diethyl sulfate and 5-bromodeoxyuridine

Aftersoaking of barley seeds at 25°C, a 30 min-treatment with diethyl sulfate (dES) and a 1 hr-treatment with 5-bromodeoxyuridine (BUdR) were given at various G 1 and S phases of the first division cycle of their shoot apical cells. Genetic effects of these treatments were assessed in terms of chlorophyll and viable mutations, the latter mainly for heading time and short culm. With both mutagens, the frequency of viable mutations was higher when the mutagen was applied at S than at other stages. The effect of the mutagens on active genes, the number of which vary during a cell cycle, could account for such differential induction of mutations.

Physiological effects of 2, 4-dichloro-6-(orthochloroanilino)-1, 3, 5-s-triazine (Triazine, Dyrene) on the chlorophyll in the leaf of rice plant-1

In this paper the mechanism of increment of chlorophyll content in leaves of rice plants was discussed, when sprayed with 2, 4-dichloro-6-(orthochloroanilino)-1, 3, 5-s-triazine (Triazine, Dyrene). Rice plants were cultivated in nutrient solutions deficient in N, Mg and both of them respectively. After 5 days they were transferred to the complete nutrient solution, and then sprayed with Triazine. The chlorophyll content was measured 2 days after spraying. The chlorophyll content in the leaves sprayed with Triazine increased several folds irrelevant to the prior nutritional treatment.After spraying of Triazine, rice plants were continued to cultivate 2 days in the respective nutrient deficient solution and then transferred to the complete nutrient solution. After 2 days the chlorophlyl content of these leaves were measured. No effect of Triazine spraying was recognized in these cases.As the effect of Triazine spraying on the chlorophyll content seemed to diminish in a few days, and as Triazine might be decomposed and utilized as a nitrogen source, the effects of spraying urea and ammonium sulfate on the chlorophyll content were compared to that of Triazine. The result indicated that the effect of Triazine was nearly equal to that of urea and larger than that of ammonium sulfate in terms of chlorophyll content.The rate of chlorophyll decomposition was compared between the Triazine-sprayed and non-sprayed plants raised in complete nutrient solution.When the plants were transferred to deionized water after the spraying, the chlorophyll content increased about 8% in the Triazine-sprayed leaves 2 days after the spraying. The rate of decomposition of chlorophyll, however, seemed to be the same between Triazine sprayed and control leaves, at least for 8 days.

Physiological effects of 2, 4-dichloro-6-(orthochloroanilino)-1, 3, 5-s-triazine (Triazine, Dyrene) on the chlorophylls in the leaf of rice plant-2

In this paper the mechanism of increment of chlorophyll content in leaves of rice plants was discussed, when sprayed with 2, 4-dichloro-6-(orthochloroanilino)-1, 3, 5-s-triazine (Triazine, Dyrene). Rice plants were cultivated in nutrient solutions deficient in N, Mg and both of them respectively. After 5 days they were transferred to the complete nutrient solution, and then sprayed with Triazine. The chlorophyll content was measured 2 days after spraying. The chlorophyll content in the leaves sprayed with Triazine increased several folds irrelevant to the prior nutritional treatment.After spraying of Triazine, rice plants were continued to cultivate 2 days in the respective nutrient deficient solution and then transferred to the complete nutrient solution. After 2 days the chlorophlyl content of these leaves were measured. No effect of Triazine spraying was recognized in these cases.As the effect of Triazine spraying on the chlorophyll content seemed to diminish in a few days, and as Triazine might be decomposed and utilized as a nitrogen source, the effects of spraying urea and ammonium sulfate on the chlorophyll content were compared to that of Triazine. The result indicated that the effect of Triazine was nearly equal to that of urea and larger than that of ammonium sulfate in terms of chlorophyll content.The rate of chlorophyll decomposition was compared between the Triazine-sprayed and non-sprayed plants raised in complete nutrient solution.When the plants were transferred to deionized water after the spraying, the chlorophyll content increased about 8% in the Triazine-sprayed leaves 2 days after the spraying. The rate of decomposition of chlorophyll, however, seemed to be the same between Triazine sprayed and control leaves, at least for 8 days.