Influence des héméropériodes très courtes sur la croissance de Lolium multiflorum,sa composition pigmentaire et l'ultrastructure chloroplastique

Summary We have described some characteristics of Lolium multiflorum cultivated under very short photoperiods (2 hours and 1 hour). The estimations of leaf growth were based on dry weight, surface measurements, and chlorophyll content. The pigment analyses were carried out by column chromatography; chloroplast ultrastructure was observed after chemical fixation.These measurements have permitted us to note a sharp drop in the growth curve of plants grown under different day-lengths: the limiting photoperiod lies between 1 hour and 2 hours of daily illumination.Pigment analyses and chloroplast ultrastructure observations show that there is a greater difference between plants cultivated under 1 hour and 2 hours of daily illumination than between plants cultivated under 2 hours and 12 hours.A decrease in day-length causes a deficit in the chlorophyll b content as well as a poor development of the grana.We have attempted to correlate these structural anomalies with the abnormal chlorophyll a/chlorophyll b ratio.     

Importance quantitative de différentes classes de taille phytoplanctoniques en milieu lacustre eutrophe

The distribution of three phytoplanktonic size fractions was studied in an eutrophic lake. Size fractionation experiments were performed using cell enumeration by inverted microscopy and chlorophyll a estimation. The results were also compared with the ATP content in the analysed algal fractions.The (1–12 µm) fraction represented only on average 5 % of the total biomass, when estimated by the cell enumeration method, but made up 26 % of the total chlorophyll a and 33 % of the total ATP. This discrepancy confirms that cell enumeration with an inverted microscope seriously underestimates the nanoplankton biomass.The (12–45 µm) fraction made up to 50% of the total biomass regardless the method of analysis used. The chlorophyll a and biovolume estimation in this fraction were positively correlated.The contribution of algal species with large cell size (45–160 µm) to the total algal biomass was higher (39%) when based on their biovolume estimation than when on the chlorophyll a (27%). The low ATP contribution of this fraction (17%) may be attributable to high percentage of dead cells.

     

Effets de la fumitoxine A sur le tissu foliaire de Pisum sativum L.

Etiolated pea seedlings are treated with fumitoxin A, a mycotoxin produced by Aspergillus fumigatus Fres. The effects observed on the greening process relate to the production of chlorophyll and fatty acid biosynthesis. The effects vary in relation to the dose of toxin used. With high doses, fumitoxin A gives rise to a diminution of chlorophyll level and an inhibition of fatty acid biosynthesis. Lower doses cause a significant augmentation of chlorophyll level and at the same time, an acceleration of polyunsaturated fatty acid biosynthesis.     

Die Protochlorophyll(ID)-Umwandlung und Ihre Beziehungen zur Photooxydation der Ascorbinsäure bei Etiolierten Keimpflanzen

Zusammenfassung Bei etiolierten Keimpflanzen von Triticum vulgare wurden die vom protochlorophyll(id) zum Chlorophyll führenden Syntheseschritte untersucht.Dabei zeigte sich, daß die Chlorophyllsynthese, zumindest vor der Lag-Phase, nicht nur den Weg über das Chlorophyllid nimmt, sondern auch über Protochlorophyll erfolgen kann, wobei allerdings etwa 90% des gebildeten Chlorophylls durch Protochlorophyllid-Reduktionen entstehen.Von diesem Pigment werden 76–88% photoreduziert, vom Protochlorophyll hingegen nur etwa 40–70%.Was die Frage des Wasserstoffdonators für diese Photoreduktion anbetrifft, so haben die vorliegenden Untersuchungen ergeben, daß im Rotlicht stöchiometrische Beziehungen zwischen der Protochlorophyll(id)-Reduktion und der Photooxydation der AS bestehen. Dadurch wird der Gedanke nahegelegt, daß bei der in vivo stattfindenden Phototransformation des Protochlorophyll(id)-Holochroms die AS als Wasserstoffdonator eine Rolle spielt.Daraus ergibt sich für die Rolle der AS in den Chloroplasten eine neue Deutungsmöglichkeit.

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The protochlorophyll(ide) transformation and its relation to the photooxidation of ascorbic acid in etiolated seedlings

Summary The terminal steps in chlorophyll synthesis leading from protochlorophyll(ide) to chlorophyll have been investigated on etiolated seedlings of Triticum vulgare.It could be demonstrated that at least before the lag-phase the synthesis of chlorophyll proceeds not only via protochlorophyllide but also via protochlorophyll; however, about 90% of the synthesized chlorophyll originates from protochlorophyllide reduction.By a two-minute illumination with 7000 Lux 76–88% of the protochlorophyllide but only 30–60% of the protochlorophyll is transformed into chlorophyll(ide).As to the question of the hydrogen donor for this transformation, the present investigations have revealed that in red light the protochlorophyll(ide) reduction corresponds to the photooxidation of ascorbic acid. Hence it is suggested that in the photoreduction in vivo ascorbic acid could be involved as a reductant for the pigment. This supposition offers a new interpretation of the role of ascorbic acid in the chloroplasts.

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Im Text werden folgende Abkürzungen verwendet: AS=Ascorbinsäure, DAS=Dehydroascorbinsäure.     

Untersuchungen zur Synchronisierbarkeit einzelner Pigmentmangel-Mutanten von Chlorella

Zusammenfassung Verschiedene Chlorella-Mutanten, die Chlorophyll a und b (Mutanten 10 und 11), je nach Kulturbedingungen nur Chlorophyll a oder Chlorophyll a und b (Mutante 41) oder nur Spuren von Chlorophyllen (Mutante 31) enthielten, wurden auf ihr Verhalten unter synchronisierenden Kulturbedingungen untersucht.Eine optimale Synchronisation war in einem Licht-Dunkel-Wechsel von 10 Licht- zu 14-Dunkelstunden zu erzielen.Die Synchronisationsschärfe war relativ gering. Unter keiner der angewendeten Kulturbedingungen ließ sich eine Vollsynchronisation erzielen; der Synchronisationstyp war am besten mit einer Gruppen-synchronisation zu vergleichen, bei der laufend Zellen von der einen in die andere Gruppe überwechseln.Unabhängig vom Vorhandensein von Chlorophyll a oder b und vom Ausmaß organischer Zusätze zu den Nährlösungen zeigten alle untersuchten Chlorella-Mutanten den gleichen Synchronisationstyp.Da die untersuchten Mutanten trotz verschiedener Pigmentzusammensetzung bis hin zum praktischen Chlorophyllverlust in gleicher Weise synchronisierbar sind, ist eine Beteiligung der Chlorophylle am Zeitgeber-Mechanismus als sehr unwahrscheinlich anzusehen.

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Studies on synchronization of some pigment-deficient Chlorella mutants

Summary Four different mutant strains of Chlorella pyrenoidosa were studied under conditions giving rise to synchronized mass cultures. The mutants contained either both chlorophyll a and b, only chlorophyll a or only traces of green pigments.Optimal synchronization was found to occur under a light-dark-regiment of 10:14 hours. It was impossible to achieve a complete synchronization; most of the cells developed autospores only every second cycle. This behavior was independent from the pigmentation of the strain; this was taken as evidence for the assumption, that the chlorophylls are not engaged in the timing process.

     

Aspects toxiques du cuivre sur la biomasse et la productivité du phytoplancton de la rivière du Saguenay,Québec

In 1979 and 1980, batch culture experiments were conducted to observe the inhibitory effect of copper ion (concentrations of 10, 50, 100, 200 and 400 µg Cu · l^–1) on the standing crops and photosynthesis of phytoplankton of the Saguenay River (for 124 hours) and in Chlorella vulgaris (for 8 days). These algal assays were carried out using the surface water of the Saguenay River. In natural populatoins of phytoplankton, it was found that photosynthesis was more sensitive than growth: at the lowest concentrations, such as 10 µg Cu · 1^–1, copper seemed to increase the chlorophyll concentrations whereas the rates of primary production show a decrease of 60% with respect to the control. At higher concentrations of copper, the effect is weak in chlorophyll concentrations and more pronounced in the rates of primary production (decrease of 86 to 90%). The pennate diatoms are dominant (in all the samples) and these organisms are known as relatively resistant to copper. In Chlorella vulgaris, it was observed that with 100 µg Cu · 1^–1, chlorophyll concentrations and rates of photosynthesis respectively decrease by 63 and 99% with respect to the control. At higher concentrations of copper, a maximum decrease of 70% and 99% respectively for chlorophyll concentrations and rates of primaryproduction are observed.

     

Quelques nouvelles données sur le phytoplancton marin et la production primaire à Tuléar (Madagascar)

Summary A list of 152 Diatoms and 158 Dinoflagellates is given and its biogeographic composition is discussed. Some quantitative data are presented: cells counts after sedimentation, spectrophotometric determination of plant pigments, and in situ primary production measurement using 14-C method. A nycthemeral study, carried out during 30 hours, shows that chlorophyll a values are highest between 15.00 and 21.00, and that photosynthesis increases from morning to evening.

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Quelques nouvelles données sur le phytoplancton marin et la production primaire à Tuléar (Madagascar)

     

Hemmung der lichtabhängigen Chloroplastenentwicklung etiolierterEuglena gracilis durch Glucose

Summary In order to examine the inhibitory effect of heterotrophic nutrition on the regreening of etiolatedEuglena gracilis, strain Z, the organisms were cultivated in the light in the presence of glucose or carbon dioxide as carbon source. After about 120 hours of illumination the chlorophyll and carbohydrate contents per cell of the photoheterotrophically cultivatedEuglena differs significantly from that of autotrophically grown cells. Mainly in so far as the addition of glucose diminishes the number and size of the chloroplasts per cell and the amount of the chlorophyll-protein-complex CP II in the thylakoids, whereas the amount of the chlorophyll-protein-complex CP I is not influenced.

     

Beziehungen Zwischen Chlorophyllgehalt und Chloroplastenstruktur in Einer Chlorina-Mutante von Arabidopsis Thaliana (L.) Heynh

Zusammenfassung In einer chlorina-Mutante (ch ₃) von Arabidopsis thaliana war der Gesamtchlorophyllgehalt auf etwa 1/10 der Menge in der grünen Normalform vermindert und zugleich das Verhältnis der Chlorophylle a/b wesentlich erhöht. Die parallel dazu durchgeführte elektronenmikroskopische Analyse der Chloroplasten zeigte eine starke Reduktion des Membrankörpers und vor allem eine Hemmung der Granadifferenzierung, die in bestimmten Stadien zur Ausbildung völlig abnormer Schichtstapel führte. In Abhängigkeit von der Entwicklung sowie von Umweltbedingungen änderten sich Chlorophyllgehalt und Chloroplastenstruktur in der Mutante in verschiedener Richtung. Diese Änderungen durch endogene und exogene Faktoren wurden vergleichend untersucht, um Einblick in die Beziehungen zwischen Pigmentmangel und Strukturstörung der Chloroplasten zu gewinnen.Das charakteristisch abweichende a/b-Verhältnis (d.h. der relative Chlorophyll b-Mangel) in der Mutante normalisierte sich unter bestimmten Versuchsbedingungen auf zweierlei Weise: 1. Unter dem Einfluß einer Dauerbeleuchtung erhöhte sich mit der Gesamtchlorophyllmenge auch der relative Chlorophyll b-Gehalt, offenbar weil eine Schwellenkonzentration von Chlorophyll a überschritten und damit eine normale Synthese von Chlorophyll b (aus Chlorophyll a?) möglich wurde. 2. Bei Kultur von Keimlingen unter 8:16 Std Licht-Dunkelwechsel oder bei alten, ausbleichenden Rosettenblättern beruhte die Normalisierung des a/b-Verhältnisses auf einem relativ schnelleren Abbau von Chlorophyll a.Im elektronenmikroskopischen Querschnitt nahmen Anzahl, Differenzierung und Schichtung der Thylakoide mit steigender Gesamtchlorophyllmenge zu, während die Membranen bei abnehmendem Chlorophyllgehalt abgebaut wurden. Jedoch ließ sich keine Beziehung der Chloroplastenstruktur zum absoluten oder relativen Chlorophyll b-Gehalt erkennen. Daß Chlorophyll b für den Aufbau einer normalen Chloroplastenfeinstruktur tatsächlich nicht nötig ist, ergab die elektronenmikroskopische Analyse einer anderen, Chlorophyll b-freien Arabidopsis-Mutante (ch ¹), in deren Chloroplasten Membrankörper mit typischen Granastapeln nachgewiesen werden konnten.

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Relations between chlorophyll content and chloroplast fine structure in a Chlorina mutant of Arabidopsis thaliana (L.) Heynh

Summary In a chlorina mutant (ch ₃) of Arabidopsis thaliana the total chlorophyll content was reduced to about 1/10 the amount of the green wild-type. At the same time the ratio of chlorophyll a/b was markedly increased. The electron microscopic analysis of the chloroplasts showed a considerable reduction in the membrane formation. Especially an inhibition of the grana differentiation was apparent, leading in some stages to an entirely abnormal thylakoid stacking. Depending on developmental as well as environmental conditions, chlorophyll content and chloroplast structure varied in the mutant in a different manner. These changes induced by endogenous and exogenous factors were comparatively investigated in order to reveal the relations between pigment deficiency and structural disturbances in the chloroplasts.The characteristically deviating a/b-ratio (i.e. the relative chlorophyll b deficiency) in the mutant was normalized under particular experimental conditions in two different ways: 1. Under the influence of continous illumination the relative chlorophyll b content increased together with the total amount of chlorophyll, obviously because a threshold of concentration of chlorophyll a was exceeded and thus a normal synthesis of chlorophyll b (from chlorophyll a?) became possible. 2. In cultures of seedlings under an 8:16 hr light-dark-succession as well as in old bleaching rosette leaves the normalization of the a/b-ratio was due to a relatively more rapid destruction of chlorophyll a.In electron microscopic cross sections the number, differentiation, and stacking of the thylakoids increased with an increasing total amount of the chlorophylls, while with decreasing chlorophyll content the membranes evidently disintegrated. However, no relation between chloroplast differentiation and absolute or relative chlorophyll b content could be established. Indeed, the proof that chlorophyll b is actually not necessary for the formation of a normal chloroplast structure was furnished by the electron microscopic analysis of another, chlorophyll b-less mutant (ch ¹), in the chloroplasts of which a membrane differentiation with typical grana piles could be demonstrated.

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Für die Gewährung eines Stipendiums an den ersten Autor, das diese Arbeit ermöglichte, sei der Alexander von Humboldt-Stiftung, Bad Godesberg, verbindlichst gedankt.     

Über das Vorkommen eines cytokininartigen Faktors inCuscuta reflexa

Zusammenfassung InCuscuta reflexa-Extrakten konnte mit Hilfe verschiedener biologischer Teste ein cytokininartiger Faktor nachgewiesen werden. Die Bedeutung dieses Faktors für das Verhältnis zwischen derCuscuta und ihren Wirtspflanzen wird diskutiert.

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On the existence of a cytokinin-like factor in cuscuta reflexa

Summary In extracts ofCuscuta reflexa Roxb. a cytokinin like factor (CAF = Cuscuta active factor) was found. It was shown that activity of this factor is similar to that of kinetin in all essential points. In tobacco-stem-tissue tests a promotion of growth by CAF was observed. In chlorophyll-preservation tests CAF produced a strong inhibition of chlorophyll dissimilation. Moreover in tests with¹⁴C-labelled glycine a migration of the glycine and other amino acids due to CAF was found.The occurrence of the observed cytokinin-like factor inCuscuta reflexa is discussed with respect to the parasite-host relations ofCuscuta.

     

不同光照强度对假紫万年青生长和叶绿素荧光参数的影响

为了解光照对假紫万年青(Belosynapsis ciliata)生长的影响,研究了不同光照强度下假紫万年青形态特征和叶绿素荧光参数的变化。结果表明,随着遮阴强度的增加,假紫万年青的自然株高有所增加,节数、茎粗、分枝数和茎长度均减少;而不同光照强度对假紫万年青节间长的影响不明显;其叶绿素a、叶绿素b、叶绿素总含量和叶绿素a/b先增加后又减少,以15.2%NS时达到最大。叶绿素b含量与叶绿素荧光的Fv/Fm呈负相关,Fv/Fm为0.75~0.8。因此,在高光照条件下,假紫万年青匍匐近地生长,随着光照条件的逐渐减弱,趋向直立生长。在屋顶绿化种植的初期采用适度遮阴(35.2%NS)可使其更好的生长,加速成坪,降低管理成本。     

The interaction of light intensity and DDT concentration upon the marine diatom,Nitzschia delicatissima cleve

Summary The effects of p, p-DDT were determined on photosynthesis and chlorophyll a content in the marine diatom Nitzschia delicatissima Cleve at four light intensities. A consistent reduction in carbon fixation and chlorophyll a per cell over controls in a 24-hour period was observed with increasing DDT concentration between 9.4 ppb and 1000 ppb. The maximum reductions of carbon uptake, chlorophyll a and carbon/chlorophyll a uptake per cell occurred at the highest light intensities. Carbon fixation per cell was reduced by as much as 94% in water containing an initial DDT concentration of 100 ppb, and chlorophyll a per cell by as much as 86% in 220 ppb DDT. Above 100 ppb, further decreases of carbon fixation and chlorophyll a per cell were not observed. Distortion of the chloroplasts in the cells exposed to DDT was also observed at the lowest concentration of DDT used. At 1000 ppb, chloroplasts were totally destroyed within 24 hours.

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Zusammenfassung Die Wirkung von p, p-DDT auf Photosynthese und Chlorophyll a Gehalt der Meeresdiatomee Nitschia delicatissima Cleve wurde untersucht unter vier Lichtintensitäten. Bei DDT Konzentrationen, steigend von 9,4 ppb bis 1000 ppb, wurde eine fortschreitende Reduktion der Kohlenstoff bindung und des Chlorophyll a Gehaltes pro Zelle gefunden, wobei die höchtse Lichtintensität die stärkste Reduktion, sowie auch die niedrigste Kohlenstoff/Chlorophyll a Aufnahme pro Zelle zeigte. In Wasser mit anfänglichem DDT Gehalt von 100 ppb, wurde die Kohlenstoff bindung pro Zelle 94% reduziert und beim DDT Gehalt von 220 ppb, wurde der Chlorophyll a Gehalt mit 86% reduziert. Bei Konzentrationen über 100 ppb, fielen Kohlenstoff bindung und Chlorophyll a Gehalt pro Zelle nicht weiter ab.Schädigungen der Chloroplasten in der Zelle wurden schon bei den niedrigsten DDT Gehalten festgestelt. Bei 100 ppb wurden die Chloroplasten innerhalb 24 Stunden völlig zerstört.

     

Modifications pigmentaires et ultrastructurales chez la diatomée Detonula sp. cultivée en lumière rouge

Résumé La diatomée Detonula sp. lorsqu'elle est cultivée en lumière rouge (650 nm), est enrichie en holochrome chlorophyllien Ca 705 (pour la nomenclature des holochromes voir French et al., 1971). La composition pigmentaire est alors modifiée par rapport à celle de l'algue cultivée en lumière blanche. Si les mêmes composants, Chlorophylle a, Chlorophylle c, Carotène, Diadinoxanthine, Diatoxanthine, Fucoxanthine, Violaxanthine, sont tous présents, on note un abaissement du taux de Chlorophylle c (le rapport Chl c/Chl a passe de 30% à 5%) et un abaissement du taux de Fucoxanthine (le rapport Fucoxanthine/Chlorophylle a passe de 85% à 60%). Cette modification pigmentaire s'accompagne d'une modification ultrastructurale des plastes. Au lieu d'une vingtaine de thylakoïdes disposés par groupe de 4 au milieu d'un stroma abondant, on observe une disparition du stroma accompagnée d'une augmentation très importante du nombre de thylakoïdes, tous juxtaposés en un seul ensemble.La diminution importante du taux de Chlorophylle c et de la Fucoxanthine, pigments du photosystème II, liée à l'enrichissement en Chlorophylle a 705, indique une modification de l'équilibre entre les deux photosystèmes au profit du photosystème I. Cet enrichissement en photosystème I s'accompagne d'une modification ultrastructurale qui est rapprochée des modifications observées dans d'autres organismes lorsque l'équilibre des deux photosystèmes est perturbé.

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Pigments and ultrastructure modifications in diatom Detonula sp. cultivated in red light

Summary Cultivation of the diatom Detonula sp. with red light, which causes an enrichment of the chlorophyll holochrome Ca 705 (for nomenclature of chlorophyll holochromes see French et al., 1971), also modifies the gross pigment composition of the cells. Relative to chlorophyll a, the cellular contents of chlorophyll c and fucoxanthin are considerably lower than in cells grown with white light; and this is accompanied by a change in plastid ultrastructure. The plastids of cells grown in white light contain about 20 thylakoids disposed in groups of 4, within an abundant stroma; those of cells grown in red light contain a much greater number of thylakoids (about 40), evenly distributed throughout the plastid.The diminution of chlorophyll c and fucoxanthin, pigments associated with photosystem II, coupled with the enrichment in chlorophyll a 705, points to a shift in the ratio between photosystems I and II in favor of the former. The accompanying ultrastructural modification of the plastid resembles that observed in other organisms as a result of changes in the relative amounts of the two photosystems.

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Cet article recouvre en partie le travail d'une thèse de Doctorat d'Etat ès Sciences Naturelles qui sera soutenue à la Faculté des Sciences de Paris. VI.     

Lichtabhängigkeit der Phytolakkumulation

Summary Phytol is identified by gas chromatography and mass spectrometry and its concentration determined (range 0.005–3 g) in darkgrown and irradiated plants. Seeds of oats (Avena sativa L.), wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) contain bound phytol (2–5 g/g). The phytol content decreases during germination in the dark. Phytol synthesis in dark-grown seedlings starts in the light and stops in the dark again. The degradation of phytol in the dark is much slower than that of chlorophyll. The action spectra of phytol and chlorophyll accumulation are identical. The phytol/chlorophyll ratio increases at higher intensities of the monochromatic light, independent of the wavelength.     

Wachstum und photosyntheseleistung der halophyten Mesembryanthemum nodiflorum L. und Suaeda maritima (L.) Dum. bei variierter NaCl-Salinität des anzuchtmediums

Summary The effect of various concentrations of NaCl in the culture solution (up to 400 mM) on growth (fresh weight, dry weight, chlorophyll content) and net CO₂ gas exchange was studied in two halophytes, Mesembryanthemum nodiflorum L. and Suaeda maritima (L.) Dum. Mesembryanthemum nodiflorum reaches optimal growth at concentrations of 100 to 200 mM NaCl in the culture medium, whereas growth of Suaeda maritima is stimulated up to concentrations of 400 mM NaCl. Independent of this stimulated plant growth, net CO₂ uptake in the light appears to be decreased with increased salinity when net CO₂ assimilation is calculated on a fresh weight or dry weight basis. However, expressed per mg chlorophyll, net CO₂ uptake is clearly correlated with plant productivity at different levels of salinity.     

Der Chlorophyllgehalt von Tumoren an bleichem und grünem Blattgewebe von Kalanchoe fedtschenkoi

Summary Pale and green leaves of Kalanchoe fedtschenkoi var. variegata were inoculated with Agrobacterium tumefaciens. Six weeks later the chlorophyll contents of the leaves and their tumors were investigated. The tumor tissues possess very similar concentrations of chlorophylls and a low number of chloroplasts per cell. Thereby they differ from each of the initial tissues. The qualitative composition of pigments (chlorophylls and carotenoids) of the 4 tissues is the same.     

Effects of air temperature, photoperiod and leaf age on foliar senescence of western larch (Larix occidentalis Nutt.) in environmentally controlled chambers

We induced foliar senescence in western larch (Larix occidentalis Nutt.) needles (100 to 400 d old) in chambers set to combinations of photoperiod (8 or 16 h) and air temperature (8 or 15°C). We used regression analysis to estimate the effects of air temperature, photoperiod, provenance and leaf age on the date of decline in chlorophyll, photosynthesis, and chlorophyll a/b ratio. Increased air temperature delayed the decline in chlorophyll and photosynthesis without affecting chlorophyll a/b: seedlings with 200-d-old needles placed under 8h days and 8°C lost chlorophyll, photosynthesis and chlorophyll a/b in 22, 37 and 63d, respectively, while those senescing under 15°C lost them in 54, 61 and 63d. Extended photoperiod delayed the decline in chlorophyll but not photosynthesis or chlorophyll a/b ratio: the 200-d-old needles placed in 8°C and 16 h photoperiod lost chlorophyll, photosynthesis, and chlorophyll a/b in 34, 37 and 63 d, compared with 22, 37 and 63 d for seedlings in 8 h days. Our analysis shows that it is possible to quantify the extent to which the timing and process of senescence vary with environmental conditions.     

Photosynthetic and growth responses of three freshwater algae to phosphorus limitation and daylength

1. Three common species of freshwater phytoplankton, the diatom Nitzschia sp., green alga Sphaerocystis schroeteri and cyanobacterium Phormidium luridum, were grown under contrasting daylengths [18 : 6 h light : dark cycles (LD) versus 6 : 18 h LD] and phosphorus (P) regimes (P‐sufficient versus 1 μm P). The rates of growth and photosynthesis, as well as growth efficiencies and pigment concentrations, were compared among treatments. 2. The growth and photosynthetic parameters of the three species depended on both P status and daylength in a species‐specific way. The responses to P limitation depended on daylength and, conversely, the responses to daylength depended on P status. 3. Growth rates and the maximum rates of photosynthesis (P_max) of all species decreased under P limitation under both light regimes. However, the decrease of P_max because of P limitation was greater under long daylength. The P_max of the green alga S. schroeteri decreased the most (ca. sixfold) under P limitation compared with the other two species. The photosynthesis saturation parameter I_k also decreased under P limitation; the decline was significant in Nitzschia and Sphaerocystis. P‐limitation significantly increased photoinhibition (β) in Nitzschia and Sphaerocystis, but not in Phormidium. The excess photochemical capacity (the ratio of the maximum photosynthesis rate to the photosynthesis rate at the growth irradiance), characterising the ability to utilise fluctuating light, was significantly lower under P limitation. 4. The growth efficiency (growth rate normalised to daylength) declined with increasing daylength in all species. Under short daylength the cyanobacterium Phormidium had the lowest growth efficiency of the three species. 5. The cellular chlorophyll a concentration in both Nitzschia and Sphaerocystis was significantly higher under short daylength, but only under P‐sufficient conditions. In Nitzschia, under short daylength, P‐limitation significantly decreased cellular chlorophyll concentration. In contrast, P‐limitation increased cellular chlorophyll concentration in Sphaerocystis, but under long daylength only. The ratio of chlorophyll a to b in the green alga also declined under short daylength and under P‐limited conditions.     

Chlorophyllase activities and chlorophyll degradation during leaf senescence in non-yellowing mutant and wild type of Phaseolus vulgaris L

The activities of chlorophyllase, contents of pigments including chlorophyll a and b, chlorophyllide a and b, and phaeophorbide a during leaf senescence under low oxygen (0.5% O2) and control (air) were investigated in a non-yellowing mutant and wild-type leaves of snap beans (Phaseolus vulgaris L.). Chlorophyllase from leaf tissues had maximum activity when incubated at 40C in a mixture containing 50% acetone. In both mutant and wild type, chlorophyllase activity was the highest in freshly harvested non-senescent leaves and decreased sharply in the course of senescence, indicating that the loss of chlorophylls in senescing leaves is not directly related to the activity of chlorophyllase and that chlorophyllase activity is not altered in the mutant. The wild type had higher ratios of chlorophyll a to chlorophyll b than the mutant and chlorophyll a : b ratios increased during senescence in both types. In the senescent mutant leaves, accumulations of chlorophyllide a and chlorophyllide b were detected, but no phaeophorbide a was found. Chlorophyllide b had a greater accumulation than chlorophyllide a in the early stage of senescence. Low oxygen treatment not only delayed chlorophyll degradation but also enhanced the accumulations of chlorophyllide a and b and lowered the ratios of chlorophyll a to chlorophyll b.