Showing papers on "Photosynthesis published in 1969"

Photosynthesis and Fish Production in the Sea

Abstract: Numerous attempts have been made to estimate the production in the sea of fish and other organisms of existing or potential food value to man (1-4). These exercises, for the most part, are based on estimates of primary (photosynthetic) organic production rates in the ocean (5) and various assumed trophic-dynamic relationships between the photosynthetic producers and the organisms of interest to man. Included in the latter are the number of steps or links in the food chains and the efficiency of conversion of organic matter from each trophic level or link in the food chain to the next. Different estimates result from different choices in the number of trophic levels and in the efficiencies, as illustrated in Table 1 (2). Implicit in the above approach is the concept of the ocean as a single ecosystem in which the same food chains involving the same number of links and efficiencies apply throughout. However, the rate of primary production is known to be highly variable, differing by at least two full orders of magnitude from the richest to the most impoverished regions. This in itself would be expected to result in a highly irregular pattern of food production. In addition, the ecological conditions which determine the trophic dynamics of marine food chains also vary widely and in direct relationship to the absolute level of primary organic production. As is shown below, the two sets of variables primary production and the associated food chain dynamics may act additively to produce differences in fish production which are far more pronounced and dramatic than the observed variability of the individual causative factors.

CARBOHYDRATE MOVEMENT FROM AUTOTROPHS TO HETEROTROPHS IN PARASITIC and MUTUALISTIC SYMBIOSIS

Abstract: Summary 1. The bulk of the fixed carbon which moves from autotroph to heterotroph in most symbiotic associations is in a single compound, a carbohydrate. Techniques employing 14C have been most valuable for investigating this movement. 2. Most ‘zoochlorellae’ belong to the Chlorococcales, and they release carbohydrate to the animal tissue as either glucose or maltose. In some molluscs, the ‘zoochlorellae’ are actually chloroplasts, possibly derived from siphonaceous algae. Although it is known that these chloroplasts supply photosynthetically fixed carbon to the animal tissue, the form of the carbon compounds which move is not known. In Convoluta roscoffensis the ‘zoochlorellae’ belong to the Pyramimonadales, but carbohydrate movement has not yet been directly studied in this association. 3. Most ‘zooxanthellae’ belong to the Dinophyceae. In associations involving co-elenterates and molluscs, glycerol is the main carbohydrate moving to the animal. Homogenates of the host animal tissue stimulate excretion by isolated zooxanthellae. 4. In lichens, symbiotic blue-green algae release glucose to the fungus, but the various genera of green algae that have been studied all release polyols (either ery-thritol, ribitol or sorbitol). Lichen fungi rapidly synthesize mannitol from all these compounds. When lichen algae are isolated into pure culture, they soon lose the ability to excrete carbohydrate, and intracellular production of the carbohydrate that is excreted either becomes much reduced, or ceases altogether. 5. Mostly indirect evidence indicates that sucrose is the main carbohydrate moving from flowering plants to their associated symbiotic fungi. Diversion of the translocation stream towards the site of the association occurs. The fungi convert host sugars to their own carbohydrates, principally trehalose and polyols. 6. ‘Saprophytic’ higher plants are all obligately mycotrophic and receive carbohydrate from their associated fungi. In at least some associations, the fungus is simultaneously associated with an autotrophic higher plant, which is the ultimate source of carbohydrate for the association. 7. Some parasitic higher plants possess chlorophyll, but the extent to which they depend on their host for carbohydrate varies with different species. Green mistletoes evidently derive negligible carbon from their hosts, but other green parasites derive at least some. There is no evidence that any of the chlorophyll-containing parasites export carbohydrate back to their hosts. Parasitic higher plants which lack chlorophyll presumably derive all their carbohydrates from their hosts, but experimental investigations of this are scarce. 8. Comparison between different types of symbiotic association show that a number of common features emerge. 9. The algal symbionts of both invertebrates and lichens have, in comparison to free-living forms, reduced growth rates and greater incorporation of fixed carbon into soluble carbohydrates. They excrete a much greater proportion of their fixed carbon than free-living forms, and most of it is usually as a single carbohydrate. Particularly striking is the fact that the excreted carbohydrate is one which is either not the major intracellular carbohydrate, or one which ceases or nearly ceases to be produced in culture. 10. The translocation stream of autotrophic higher plants is diverted towards the site of association with either fungi or parasitic higher plants, but it is not known how this is achieved. 11. In all associations, the cell walls of the autotroph become reduced or modified at the site of contact with the heterotroph, but it seems likely that this is not directly connected with the mechanism of carbohydrate transfer between the symbionts. 12. In many associations, the heterotroph rapidly converts host sugars into other compounds (frequently into its own carbohydrates which are usually different from those of the host). This may serve to maintain a concentration gradient and so ensure a continued flow from the host. 13. Polyols feature prominently in symbiotic and parasitic associations, not only as the carbohydrates of many plant heterotrophs, but also as the form of carbohydrate released by both zooxanthellae and the green algae of lichens to their heterotrophic partners.

Distribution of enzymes in mesophyll and parenchyma-sheath chloroplasts of maize leaves in relation to the C4-dicarboxylic acid pathway of photosynthesis

Abstract: 1. Mesophyll and parenchyma-sheath chloroplasts of maize leaves were separated by density fractionation in non-aqueous media. 2. An investigation of the distribution of photosynthetic enzymes indicated that the mesophyll chloroplasts probably contain the entire leaf complement of pyruvate,Pi dikinase, NADP-specific malate dehydrogenase, glycerate kinase and nitrite reductase and most of the adenylate kinase and pyrophosphatase. The fractionation pattern of phosphopyruvate carboxylase suggested that this enzyme may be associated with the bounding membrane of mesophyll chloroplasts. 3. Ribulose diphosphate carboxylase, ribose phosphate isomerase, phosphoribulokinase, fructose diphosphate aldolase, alkaline fructose diphosphatase and NADP-specific `malic' enzyme appear to be wholly localized in the parenchyma-sheath chloroplasts. Phosphoglycerate kinase and NADP-specific glyceraldehyde phosphate dehydrogenase, on the other hand, are distributed approximately equally between the two types of chloroplast. 4. After exposure of illuminated leaves to 14CO2 for 25sec., labelled malate, aspartate and 3-phosphoglycerate had similar fractionation patterns, and a large proportion of each was isolated with mesophyll chloroplasts. Labelled fructose phosphates and ribulose phosphates were mainly isolated in fractions containing parenchyma-sheath chloroplasts, and dihydroxyacetone phosphate had a fractionation pattern intermediate between those of C4 dicarboxylic acids and sugar phosphates. 6. These results indicate that the mesophyll and parenchyma-sheath chloroplasts have a co-operative function in the operation of the C4-dicarboxylic acid pathway. Possible routes for the transfer of carbon from C4 dicarboxylic acids to sugars are discussed.

Cation effects on the fluorescence of isolated chloroplasts.

Abstract: At room temperature, the fluorescence of chloroplasts in vivo and in vitro originates nearly exclusively from the chlorophyll of the oxygen evolving system II of the photosynthetic apparatus. The yield and the kinetics of this light emission are closely coupled to the primary photochemical events of photosystem II. Fluorescence studies, therefore, have contributed much to our knowledge about the water oxidizing photoact. According to Duysens and Sweers i(3) the fluorescence yield is determined by the oxidation state of the primary electron acceptor Q: when Q is oxidized, the fluorescence is quenched and, consequently, a low yield is observed; since reduced Q1(Q-) does not quench, a maximal fluorescence yield indicates a complete reduction of the electron acceptor pools containing Q. Several anomalies in the fluorescence kinetics of intact algae have led to the assumption of an non-homogeneous pool Q containing, even after the primary activation step (8), active and inactive oxidants Qa and Qi' (1,2, 4,12). Both forms of Q are thought to quench the fluorescence in their oxidized states, albeit with slightly different effectiveness. A photoreduction of the total pool Q requires an activation of any Qi' to Qa, which according to some authors (1,4,12) is sensitized by photosystem I. In this communication, we wish to report on an overriding influence of the ionic environment on the fluorescence yield of isolated chloroplasts. It will be shown that the fluorescence yield can be changed at will simply by varying the composition of the suspension medium. Accordingly, the fluorescence yield may possibly be governed not only by the oxidation state olf the Q-pool, but also by ion induced structural changes.

Iron-sulphur proteins.

Abstract: These electron transfer agents often have unusually low redox potentials. Eighteen are known from higher plants and bacteria, and are involved in nitrogen fixation as well as photosynthesis.

The Analysis of Photosynthesis Using Mutant Strains of Algae and Higher Plants

Abstract: INTRODUCTION Major contributions to the understanding of biological processes have been made with the aid of mutant organisms in which the processes have been disrupted; the use of auxotrophic mutant strains of microorganisms to elucidate metabolic pathways is a classic example of this approach. Muta­ tions that affect chloroplast structure, chlorophyll and carotenoid synthesis, synthesis of components of the photosynthetic electron transport chain, and synthesis of enzymes of the reductive pentose phosphate cycle are known to occur in higher plants and green algae, and it is the purpose of this review to describe how certain mutant strains have been 'used to study the mecha­ nism of photosynthesis. This review will be particularly concerned with the nature and function of components of the photosynthetic electron transport chain as deduced from studies of mutant strains of green algae and higher plants having normal pigment content, and only secondarily will it consider mutant strains having gross abnormalities in either their chloroplast struc­ ture or amounts of pigment. Several excellent general reviews of photosyn­ thesis have appeared recently (1, 2), and the material presented here should be considered as a special supplement to them rather than as an overall view of the subject. In organisms in which genetic analysis is possible, it has been shown that mutations affecting photosynthesis are of both nuclear and extranu­ clear genes. Nuclear gene mutations show a classical Mendelian inheritance, whereas mutations of extranuclear genes usually show maternal inheri­ tance. The plastom mutations of higher plants are examples that show ma­ ternal inheritance, and characteristically these mutations lead to marked changes in chloroplast structure and in the amount of chlorophyll. The principal mutant strains to be considered in this review (Table I) have been obtained from the algae Chlamydomonas reinhardi, Euglena gra­ cilis, and Scenedesmus obliquus and from the higher plants Hordeum vul­ gare, Nicotiana tabacum, and Vida faba. The mutations in C. reinhardi, H.

Effects of temperature on the gas exchange of leaves in the light and dark.

Abstract: Evolution of CO2 into CO2-free air was measured in the light and in the dark over a range of temperatures from 15 to 50°. Photosynthetic rates were measured in air and O2-free air over the same range of temperatures. Respiration in the light had a different sensitivity to temperature compared with respiration in the dark. At the lower temperatures the rate of respiration in the light was higher than respiration in the dark, whereas at temperatures above 40° the reverse was observed. For any one species the maximum rates of photosynthesis and photorespiration occur at about the same temperature. The maximum rate for dark respiration generally is found at a temperature about 10° higher. Zea mays and Atriplex nummularia showed no enhancement of photosynthesis in O2-free air nor any evolution of CO2 in CO2-free air at any of the temperatures.

Chloroplasts as functional organelles in animal tissues

Abstract: The marine gastropod molluscs Tridachia crispata, Tridachiella diomedea, and Placobranchus ianthobapsus (Sacoglossa, Opisthobranchia) possess free functional chloroplasts within the cells of the digestive diverticula, as determined by observations on ultrastructure, pigment analyses, and experiments on photosynthetic capacity. In the light, the chloroplasts incorporate H(14)CO(3) (-)in situ. Reduced radiocarbon is translocated to various chloroplast-free tissues in the animals. The slugs feed on siphonaceous algae from which the chloroplasts are derived. Pigments from the slugs and from known siphonaceous algae, when separated chromatographically and compared, showed similar components. Absorption spectra of extracts of slugs and algae were very similar. The larvae of the slugs are pigment-free up to the post-veliger stage, suggesting that chloroplasts are acquired de novo. with each new generation.

Leaf peroxisomes and their relation to photorespiration and photosynthesis

Abstract: Electron micrographs have revealed the presence of microbodies (also called cytosomes or crystal-containing bodies) in l e a v e ~ . 1 5 . ~ ~ ~ During the past year leaf peroxisomes have been separated from other organelles by sucrose density gradient centrifugation and partially characterized b i o c h e m i ~ a l I y . ~ ~ , ~ ~ . ~ ~ * ~ ~ The isolated leaf peroxisomes, as examined with the electron m i c r o ~ c o p e , ~ ~ are similar in appearance to the microbodies seen in ~ i t u . 1 ~ Isolation procedures for the leaf peroxisomes have been greatly facilitated by the pioneering work of de Duve's group on mammalian peroxisomes.11 Further, a great wealth of physiological and biochemical information collected over the past 20 years on photosynthetic C 0 2 fixation5 and subsequent carbon metabolism by the glycolate pathwaP9 can today be reinterpreted and evaluated as related to peroxisomal respiration. As a result, in a relatively short period of time, this subject has encompassed a diffuse research area involving numerous investigators in photosynthesis, plant respiration, and plant growth. Leaf peroxisomes are respiratory microbodies and have been found in the leaves of all plants that have been examined to datee52 A known function of these particles is glycolate metabolism and photorespiration. Leaf peroxisomes are characterized by a single membrane and a granular matrix without lamellae. Frederick and Newcomb15 have seen crystalline or dense cores in some of the particles in v i v a We also have observed the dense cores in isolated particles (unpublished). The isolated particles are characterized by specific enzymes, i.e., c a t a l a ~ e , ~ ' . ~ ~ glycolate oxidase,51*52 a major isozyme of malate d e h y d r o g e n a ~ e , ~ ~ , ~ ~ an isozyme of NADP-isocitrate dehydrogenase,56 and specific transaminases for glyoxylate-glutamate,2R hydroxypyruvate-serine,56 and oxalacetate-gl~tamate.~~ Leaf peroxisomes are estimated to vary in size between 0.5 to 1.5 p and in number from a few per cell to about one-third as many as there are mit~chondria. '~ In spinach and sunflower leaves they represent 1 to 1.5% of the total leaf prot e i r ~ . ~ ~ For these parameters there is, as yet, only a limited amount of data. In appearance, size, and enzymic components, leaf peroxisomes are similar, but not identical to, peroxisomes from liver and kidney," glyoxysomes from germinating seed endosperm,9 or peroxisomes from Tetrahyrnena.35 To date, the only electron carriers identified in leaf peroxisomes are FMN, NAD, NADP and the heme of catalase. Also, reactions catalyzed by leaf peroxisomes utilized only organic acids and amino acids; involvement of phosphate or phosphate esters as substrates has not been reported. Whereas mitochondrial respiration is linked to the energy-conserving process of ATP synthesis, peroxisomal respiration is characterized by H202 generation with flavin oxidases, and complete loss of this energy, as heat, during rapid destruction of the peroxide by catalase. Thus leaf peroxisomes, like mammalian peroxisomes, seem to represent a wasteful respiratory process of unproven function. The glycolate pathway of metabolism, which is partially located in leaf peroxisomes, is gluconeogenic, but the reason for glycolate formation is unknown. We shall discuss how a gly-

The Effect of Water Stress on Translocation in Relation to Photosynthesis and Growth

Abstract: Photosynthetic rate, leaf and root extension, dry weight changes, and the translocation of labelled photosynthates were followed in L. temulentum plants subjected to water shortage at a time when the eighth leaf was expanding.

The Adaptation of Plankton Algae IV. Light Adaptation in Different Algal Species

Abstract: Two types with regard to adaptation to different light intensities are described: tbe Chlorella type and the Cyclotella type. The Chlorella type is mostly found among the green algae, the Cyclotella type among the diatoms. The Chlorella type adapts to a new light intensity mainly by changing the pigment content. Therefore the cells adapted to a high light intensity have a lower chlorophyll a content per cell than cells adapted to a low light intensity. Light saturation is mostly rather low for cells adapted to low light intensities. The light-saturated rate of photosynthesisist mostly lower for cells adapted to a high light intensity than for cells adapted to a low light intensity. The actual photosynthesis is not much higher at a high light intensity than at a low one. The actual photosynthesis is the photosynthesis at the light intensity where the cells are grown. - The Cyclotella type adapts only by changing the light-saturated rate. The chlorophyll content is the same in cells grown at low and high light intensities. Light saturation for cells grown at a low light intensity is rather high. The light-saturated rate is much higher in the case examined at the high light intensity than at the low one. The actual photosynthesis is considerably higher for cells grown at the high light intensities than for cells grown at low light intensities.- The two adaptation types are not sharply separated since transition types occur.

Enzyme activities of the carbon reduction cycle in some photosynthetic organisms.

Abstract: Profile analyses of the enzymes comprising the photosynthetic carbon reduction cycle have been performed in extracts of dark grown and greening Euglena gracilis var. bacillaris. Chlorella pyrenoidosa grown photoautotrophically, in the light with glucose or in the dark with glucose, Tolypothrix tenuis, Chromatium and leaves of spinach. Amounts of activity are compared with the level of photosynthetic CO(2) fixation. Only in Chromatium were all enzyme activities sufficient to support the in vivo rate of CO(2) fixation. In organisms other than Chromatium, some enzymes and particularly fructose 1,6-phosphatase and ribulose 1.5-diphosphate carboxylase appeared to be present in insufficient amounts to support the photosynthetic rate of the intact cell. Developmental studies with Euglena and growth studies with Chlorella led to the conclusion that these enzymes were associated with the cycle. Suppression of CO(2) fixation in heterotrophically grown Chlorella was accompanied by a striking decrease in the same enzymes whose activities increased in greening Euglena.

LIGHT-INDUCED OXIDATION OF A CHLOROPLAST B-TYPE CYTOCHROME AT -189 degrees C.

Abstract: The b-type cytochromes of chloroplasts have heretofore been viewed as photosynthetic electron carriers that probably occupy an intermediate position in a light-induced electron flow. The oxidation-reduction of such intermediate electron carriers, being removed from the primary photochemical reaction linked to photon capture by chlorophyll, would be expected to show a temperature dependence. Evidence has now been obtained that cytochrome b559 is photooxidized at -189°C and that this photooxidation can be induced only by “short-wavelength” monochromatic light which activates the oxygen-evolving system in chloroplasts (photosystem II). In appears, therefore, that photooxidation of cytochrome b559 is closely linked with photon capture by the chlorophyll pigments characteristic of photosystem II.

Plant Water Status, Leaf Temperature, and the Calculated Mesophyll Resistance to Carbon Dioxide of Cotton Leaves

Abstract: The influence of plant water status and leaf temperature on the mesophyll resistance to C02 transfer for Deltapine cotton leaves was determined under condi-tions when the C02 supply was limiting photosynthesis. The mesophyll resistance was calculated from C02 response curves in normal air and oxygen-free air, under conditions when air was forced from the abaxial to adaxial side of the leaf to obtain a direct estimate of the CO2 concentration at the mesophyll cell wall.

The influence of growing temperature on photosynthesis and respiration of Pinus radiata seedlings

Abstract: Summary Rates of photosynthesis at five light intensities and rates of respiration at four temperatures, 9°, 16°, 24° and 30°C were measured in three P. radiata seedlings from each of the growing conditions 15°/10°, 24°/19°, and 33°/28°C day/night temperatures. Net photosynthesis at 30° and 9°C was reduced in seedlings grown under the cold and the two warmer preconditioning treatments respectively. Sixteen degrees appeared to be the optimum temperature for net photosynthesis in seedlings grown at 15°/10° and 24°/19°C, with 24°C being the optimum for the plants raised at 33°/28°C. Photosynthesis per seedling increased by almost 35% and rates of respiration were approximately halved within two days of the seedlings being transferred from 15°/10° to 33°/28°C. In that transfer (and also the reverse of it, i.e. 33°/28° to 15°/10°C in which photosynthesis dropped by some 25%) most of the adaptation of each seedling occurred within two days, and within a few days more the seedlings were similar in behaviour to s...

Photosynthetic Studies on a Pea-mutant Deficient in Chlorophyll.

Abstract: A chlorophyll-deficient mutant of pea (Pisum sativum) was found as a spontaneous mutation of the variety Greenfeast. Total chlorophyll of the mutant leaves was about one-half that of normal pea leaves per mg dry weight, and the ratio of chl a:chl b ranged from 10 to 18, compared with 3 for normal pea. In each generation the mutant plants gave rise to normal and mutant plants and lethal plants with yellow leaves.For a normal pea plant, CO(2) uptake was saturated at about 60,000 lux, whereas with mutant leaves, the rate of CO(2) uptake was still increasing at 113,000 lux. At 113,000 lux the mutant and normal leaves showed similar rates of CO(2) fixation per unit area of leaf surface, but on a chlorophyll basis the mutant leaves were twice as active. Hill reaction measurements on isolated chloroplasts also showed that the mutant chloroplasts were saturated at higher intensities than the normal, and that the activity of the mutant was at least double that of the normal on a chlorophyll basis.It is suggested that the photosynthetic units of the mutant chloroplasts contain about half the number of chlorophyll molecules as compared to the normal photosynthetic units.Electron microscopy of leaf sections of normal and mutant leaves showed that the mutant chloroplasts contain fewer lamellae per chloroplast and fewer lamellae per granum. The lethal chloroplasts, which were virtually devoid of chlorophyll, were characterized by an absence of grana.

Special aspects of nitrogen fixation by blue-green algae.

Abstract: When carbon dioxide fixation was over 90% inhibited by CMU, nitrogen fixation remained unaffected in nitrogen-starved cells of Anabaena cylindrica. In normal cells under the same conditions nitrogen fixation was about 50% inhibited by CMU. These data suggest, first, that nitrogen fixation in this organism is independent of reducing potential generated by non-cyclic photo-electron transport and, secondly, that nitrogen fixation is stimulated by photosynthetically produced carbon skeletons to assimilate the fixed nitrogen. Although nitrogen fixation occurred to a limited extent in the dark, increasing light intensity stimulated nitrogen fixation both in the presence and absence of CMU. This suggests that light-generated ATP is required for nitrogen fixation in this alga. A ratio of pyruvate decarboxylation to nitrogen fixation of 3:1 has been established for A. cylindrica. This accords with the hypothesis that pyruvate acts as a hydrogen donor for nitrogen reduction and that provision of the required reductant is independent of photosynthesis in blue-green algae.

The activities of the photosynthetic carbon cycle enzymes of greening bean leaves

Abstract: Summary After the transfer of 14-day old dark-grown bean seedlings into continuous illumination the etioplasts of the primary leaves develop into chloroplasts in a synchronous manner. Levels of activity in the leaves of most of the enzymes which have been implicated in the photosynthetic carbon cycle have been determined during the first 45 hours of chloroplast development. All of the enzymes investigated were present in etiolated leaves and the activities of most of them increased in response to illumination. One of the early effects of illumination was a rise in the protein content of the leaves, the level of which continued to rise throughout the 45 hours of illumination. Increases in the activity of some of the enzymes, notably phosphoglycerate kinase, fructosediphosphate aldolase, transketolase, NAD-linked triosephosphate dehydrogenase and triosephosphate isomerase, appeared to begin soon after the commencement of illumination. The onset of light-induced increases in the activities of ribosephosphate isomerase, phosphori-bulokinase and ribulosediphosphate carboxylase, showed lag periods of similar duration to the ‘positive’ photoresponse described by Mohr (1966). The longer lag period before an increase of NADP-Iinked triosephosphate dehydrogenase occurred is consistent with the suggestion of Ziegler and Ziegler (1965) that photosynthetically formed ATP and NADPH may be essential prerequisites for the synthesis of this enzyme. Possible mechanisms of control of the enzyme levels are discussed. The data do not provide any evidence in support of the participation of phosphopyruvate carboxylase, hexosediphosphatase and transaldolase in an important role in connection with the photosynthetic carbon cycle of bean leaves.