[Show abstract][Hide abstract] ABSTRACT: Peas were grown in controlled environments (12h white fluorescent light. ∼47 μmol photons m-2 s 1/12 dark, 25 °C), using (1) 15-min far-red illumination at the end of each photoperiod (brief FR) to simulate the increase in the far-red/red ratio near the end of the day, and (2) high levels of supplementary far-red light (red:far-red ratio=0.04) during the entire photoperiod (long-term FR) to simulate extreme shade conditions under a plant canopy. Brief FR illumination led to marked morphological effects attributable to phytochrome regulation, namely, an increase in internodal length, but a decrease in leaflet area, chloroplast size and chlorophyll content per chloroplast compared with the control. Significantly, brief FR illumination had little or no effect on the amounts of the major chloroplast components (ribulose 1.5-biphosphate carboxylase, adenosine triphosphate synthase, cytochrome b/f complex and Photosystem II) relative to chlorophyll or Photosystem I, and the leaf photosynthetic capacities per unit chlorophyll were similar. In contrast, supplementing high levels of far-red light during the entire photoperiod not only led to the phytochrome effects above, but there was also a marked increase in leaf photosynthetic capacity per unit chlorophyll. due to increased amounts of the major chloroplast components relative to chlorophyll or Photosystem I. We hypothesize that supplementary far-red light, absorbed by Photosystem I, induced an increase in the major chloroplast components by a photosynthetic feedback mechanism. In fully greened leaves, we propose that the two photosystems themselves, rather than phytochrome, may be the predominent sensors of light quantity in triggering modulations of the stoichiometries of chloroplast components, which in turn lead to varying photosynthetic capacities.
[Show abstract][Hide abstract] ABSTRACT: Immunoblotting was used to probe the reactivity of rabbit polyclonal antibodies against PS1I and PSI light-harvesting chlorophyll a/b-proteins of spinach (Spinacea oleracea L.) with the light-harvesting complexes of a siphonaceous marine alga, Codium, that have more chlorophyll b, siphonaxanthin and siphonein instead of the lutein. The spinach LHCII antibodies cross-reacted only with the apoproteins of Cod-ium LHCII. Antisera against the spinach LHCI apoproteins showed strong affinity for the apoproteins of Codium LHCI, and also reacted with the polypeptides of spinach LHCII and Codium LHCII. Our results indicate some similarities in the amino acid sequences between the Codium siphonaxanthin-Chl a/fe-proteins of LHCII and LHCI and the corresponding spinach lutein-chlorophyll a/b-proteins.
Physiologia Plantarum 07/1987; 70(4):597 - 602. · 3.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To probe the location of the carboxyl-terminus of the 28 kDa apoprotein of the light-harvesting chlorophyll a/b-protein complex of PS II (LHCII), an antibody was generated against a synthetic octapeptide corresponding to the C-terminal region of LHCII. The high specificity of the octapeptide antiserum was deonstrated by immunoblots and immunogold labelling. The octapeptide antiserum agglutinated destacked thylakoid membranes, but no significant agglutination occurred with inside-out vesicles suggesting that the COOH-terminus is located at the outer, stroma-exposed surface where the NH2-terminus is also located [(1983) J. Biol. Chem. 258, 9941-9948]. Our results support a model for LHCII with four transmembrane-spanning domains.
[Show abstract][Hide abstract] ABSTRACT: Antibodies directed against purified cytochrome f, isolated from the cytochrome b/f complex of spinach chloroplasts, were used in on-grid immunogold labelling studies of spinach leaf tissue. Our results show unambiguously that cytochrome f, and hence the cytochrome b/f complex, is located in both appressed and non-appressed thylakoid membranes.
Cell Biology International Reports 09/1985; 9(8):715-21.
[Show abstract][Hide abstract] ABSTRACT: Antibodies directed against purified cytochrome f, isolated from the cytochrome complex of spinach chloroplasts, were used in on-grid immunogold labelling studies of spinach leaf tissue. Our results show unambiguously that cytochrome f, and hence the cytochrome complex, is located in both appressed and non-appressed thylakoid membranes.
[Show abstract][Hide abstract] ABSTRACT: The effect of light quality on the composition, function and structure of the thylakoid membranes, as well as on the photosynthetic rates of intact fronds from Asplenium australasicum, a shade plant, grown in blue, white, or red light of equal intensity (50 microeinsteins per square meter per second) was investigated. When compared with those isolated from plants grown in white and blue light, thylakoids from plants grown in red light have higher chlorophyll a/chlorophyll b ratios and lower amounts of light-harvesting chlorophyll a/b-protein complexes than those grown in blue light. On a chlorophyll basis, there were higher levels of PSII reaction centers, cytochrome f and coupling factor activity in thylakoids from red light-grown ferns, but lower levels of PSI reaction centers and plastoquinone. The red light-grown ferns had a higher PSII/PSI reaction center ratio of 4.1 compared to 2.1 in blue light-grown ferns, and a larger apparent PSI unit size and a lower PSII unit size. The CO(2) assimilation rates in fronds from red light-grown ferns were lower on a unit area or fresh weight basis, but higher on a chlorophyll basis, reflecting the higher levels of electron carriers and electron transport in the thylakoids.The structure of thylakoids isolated from plants grown under the three light treatments was similar, with no significant differences in the number of thylakoids per granal stack or the ratio of appressed membrane length/nonappressed membrane length. The large freeze-fracture particles had the same size in the red-, blue-, and white-grown ferns, but there were some differences in their density. Light quality is an important factor in the regulation of the composition and function of thylakoid membranes, but the effects depend upon the plant species.
[Show abstract][Hide abstract] ABSTRACT: The sensitivity of detection of proteins by immunolabelling embedded and sectioned material depends upon retention of antigenicity during tissue processing. Losses in pea seed storage protein antigenicity have been assessed using a solid phase radioimmunoassay. Storage proteins adsorbed to wells of microtiter plates were treated with the various "tissue preparation" steps and reacted with 125I-antibodies to the storage proteins. The glutaraldehyde or formaldehyde fixation steps caused approximately 60% and 30% loss in antigenicity, respectively. With each subsequent preparative step, losses accumulate and following treatment with Spurr's epoxy resin reached approximately 85% and 90%, respectively. However, if Lowicryl K4M, a methacrylate-acrylate embedding medium was used, losses were retained at approximately 70% and 60%, respectively. These observations have been verified on sections of embedded material using two labelling procedures, with protein A-gold and ferritin as the markers.
European Journal of Cell Biology 11/1982; 28(2):251-6. · 3.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The major intrinsic protein from spinach chloroplast membranes, the light-harvesting chlorophyll a/b-protein complex, contains two distinct polypeptides of Mr 23,500 and 26,000 and 31% lipid by weight, comprising five diacyl lipids and seven chlorophylls, together with some carotenoids, per 26,000-Mr polypeptide. The chlorophyll a/b ratio is 1.1. Low-temperature fluorescence emission spectra of the light-harvesting complex revealed a major peak at 681 nm with a shoulder of variable intensity at 695 nm. The 695-nm emission has been correlated with a progressive aggregation of the complex into two-dimensional, semi-crystalline sheets. To determine the role of the light-harvesting complex in cation-dependent thylakoid stacking, the purified complex has been quantitatively incorporated into liposomes containing the four major chloroplast diacyl lipids using a simple freeze-thaw technique. The proteoliposomes appeared largely as unilamellar vesicles, with diameters between 0.1 and 0.8 micron. Freeze-fracture analysis showed intramembrane particles of 8-10 nm corresponding to the incorporated complex. Both monovalent and divalent cations caused an immediate aggregation of the proteoliposomes, which was reversed at low cation concentrations and was largely inhibited by prior trypsin treatment. Since lipid vesicles themselves showed none of these effects, it is concluded that surface-exposed polypeptide regions of the light-harvesting complex are directly involved in thylakoid stacking in vivo.
European Journal of Biochemistry 07/1980; 107(2):345-54. · 3.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Improved immunofluorescent techniques have been developed for the high resolution light microscopic localization of intracellular antigens in plant tissue. Thin sections of pea cotyledon tissue which had been fixed in paraformaldehyde and embedded in glycol methacrylate were reacted with mono-specific antibodies to the storage proteins legumin and vicilin. These antibodies were raised in sheep, purified by affinity chromatography and tested by immunoelectrophoresis and immunodiffusion. Using the indirect technique, rhodamine-labeled antibodies permitted specific fluorescent localization of the legumin and vicilin to small (ca. 1 micrometer) cytoplasmic organelles in near mature tissue. Subsequent histochemical staining verified the proteinaceous nature of these organelles. Parameters affecting staining specificity and background fluorescence are discussed.
Journal of Histochemistry and Cytochemistry 11/1979; 27(10):1312-6. · 2.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Light, transmission electron and scanning electron microscopy have been used to investigate the
ultrastructural arrangement of leaf tissue in Triodia irritans, a C4 grass adapted to a hot, dry environment. Photosynthetic tissue was found to constitute 25% of the cross-sectional area of the leaf
and includes mesophyll and bundle sheath cell types. The mesophyll is restricted to discrete areas
and consists of long files of cells interconnected by a complex network of cytoplasm-filled cross
bridges. It is in contact with the vascular tissue via extensions from the bundle sheath, which make
intimate contact with it by way of plasmodesmata located in frequent pit fields. The mesophyll
cytoplasm is largely non-vacuolate, but in other respects is similar to that found in most other
species-viz., contains chloroplasts, mitochondria and occasional microbodies. Cells of the bundle
sheath extensions exhibit a uniform to slightly centripetal distribution of cytoplasm, consisting
mainly of grana-containing chloroplasts, mitochondria possessing elongate cristae, and microbodies.
Cells of the bundle sheath proper, which partially encircles the vascular tissue, do not make direct
contact with the mesophyll and contain fewer chloroplasts than the extension cells.
The arrangement of photosynthetic and of vascular tissues are discussed in terms of the classical
Kranz anatomy that is a feature of C4 plants, and the possible relationships between leaf structure,
photosynthetic activity and the translocation of photosynthate are considered.
Australian Journal of Botany - AUST J BOT. 01/1977; 25(3).
[Show abstract][Hide abstract] ABSTRACT: Chlorella fusca, strain 211-15, cells degreened in a nitrogen-deficient mineral growth medium in the light for 4-6 weeks were regreened for up to 24 hrs in a nitrogen rich medium that leads to synchronous cell division at 24-26 hrs. Structural changes in the plastid membranes during the regreening period were observed by thin section and freeze-fracture electron microscopy. Nitrogen-deficient plastids were found to have non-appressed lamellae, prolamellar body-like membrane aggregations, and only 2 types of freeze-fracture face. At this time no photosynthetic oxygen evolution could be demonstrated. After 6 hrs regreening the plastid lamellae had fused to form bands of appressed lamellae and the four types of freeze-fracture face, described previously, were visible. At this time photosynthetic oxygen evolution could be demonstrated. After 24 hrs regreening the plastids had an appearance typical of normally grown Chlorella and had commenced to divide. Supporting evidence for these developmental stages is presented from isolated chloroplast particle fractions. An unusual type of cell wall proliferation was observed in the nitrogen-deficient Chlorella cells that resulted in the laying down of several walls, each with a trilaminar component.
Archives of Microbiology 06/1975; 103(3):259-70. · 1.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Aggregations of approximately 11 nm spaced spherical particles are described in both freeze-fractured and chemically fixed bean and spinach leaf plastids. It is suggested that the aggregations were induced as a result of the dehydrating action of the cryoprotectants used. It is tentatively concluded, on the basis of previous reports, that the aggregations consist of Fraction I protein.
[Show abstract][Hide abstract] ABSTRACT: Chlorella fusca, strain 211-15, cells degreened in a nitrogen-deficient mineral growth medium in the light for 4–6 weeks were regreened for up to 24 hrs in a nitrogen rich medium that leads to synchronous cell division at 24–26 hrs. Structural changes in the plastid membranes during the regreening period were observed by thin section and freeze-fracture electron microscopy. Nitrogen-deficient plastids were found to have non-appressed lamellae, prolamellar body-like membrane aggregations, and only 2 types of freeze-fracture face. At this time no photosynthetic oxygen evolution could be demonstrated. After 6 hrs regreening the plastid lamellae had fused to form bands of appressed lamellae and the four types of freeze-fracture face, described previously, were visible. At this time photosynthetic oxygen evolution could be demonstrated. After 24 hrs regreening the plastids had an appearance typical of normally grown Chlorella and had commenced to divide. Supporting evidence for these developmental stages is presented from isolated chloroplast particle fractions.An unusual type of cell wall proliferation was observed in the nitrogen-deficient Chlorella cells that resulted in the laying down of several walls, each with a trilaminar component.
Archives of Microbiology 12/1974; 103(1):259-270. · 1.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Chloroplasts were isolated from leaves of three species of tropical rainforest plants, Alocasia macrorrhiza, Cordyline rubra and Lomandra longifolia; these species are representative of extreme “shade” plants. It was found that shade plant chloroplasts contained 4–5 times more chlorophyll than spinach chloroplasts. Their chlorophyll a/chlorophyll b ratio was 2.3 compared with 2.8 for spinach. Electron micrographs of leaf sections showed that the shade plant chloroplasts contained very large grana stacks. The total length of partitions relative to the total length of stroma lamellae was much higher in Alocasia than in spinach chloroplasts. Freeze-etching of isolated chloroplasts revealed both the small and large particles found in spinach chloroplasts.Despite their increased chlorophyll content, low chlorophyll a/chlorophyll b ratio, and large grana, the shade plant chloroplasts were fragmented with digitonin to yield small fragments (D-144) highly enriched in Photosystem I, and large fragments (D-10) enriched in Photosystem II. The degree of fragmentation of the shade plant chloroplasts was remarkably similar to that of spinach chloroplasts, except that the subchloroplast fragments from the shade plants had lower chlorophyll a/chlorophyll b ratios than the corresponding fragments from spinach. The D-10 fragments from the shade plants had chlorophyll a/chlorophyll b ratios of 1.78-2.00 and the D-144 fragments ratios of 3.54–4.07. We conclude that Photosystems I and II of the shade plants have lower proportions of chlorophyll a to chlorophyll b than the corresponding photosystems of spinach. The lower chlorophyll a/chlorophyll b ratio of shade plant chloroplasts is not due to a significant increase in the ratio of Photosystem II to Photosystem I in these chloroplasts.The extent of grana formation in higher plant chloroplasts appears to be related to the total chlorophyll content of the chloroplast. Grana formation may simply be an means of achieving a higher density of light-harvesting assemblies and hence a more efficient collection of light quanta.
Biochimica et Biophysica Acta (BBA) - Bioenergetics. 12/1973;
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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,P(i) 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 (14)CO(2) 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 C(4) 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 C(4)-dicarboxylic acid pathway. Possible routes for the transfer of carbon from C(4) dicarboxylic acids to sugars are discussed.
[Show abstract][Hide abstract] ABSTRACT: In the Zea mays L. mutant M11 grown in the dark at 15 degrees , the ultrastructure of the etioplast is abnormal. The pigment content of the etioplasts is reduced but the in vivo absorption characteristics suggest that the normal protochlorophyll (ide)-holochrome is present. The lowered synthetic ability of the etioplasts is not primarily due to a reduced complement of plastid ribosomes. The plastids of mutant M11 grown in the light at 15 degrees contain little pigment, are markedly deficient in ribosomes and their ultrastructure is abnormal. In mutant M11 grown at 15 degrees , an extreme sensitivity of the plastid membranes to light was observed.
[Show abstract][Hide abstract] ABSTRACT: Structural changes in pea cotyledons during development were studied using light and electron microscopy. Changes in the vacuolar system and cytoplasm of cotyledon parenchyma cells, during the period of storage protein deposition, are reported. Eight days after flowering, the parenchyma cells each contain one or two large vacuoles that are replaced by progressively smaller vacuoles during the next 10 days of development. Stainable material that can be histochemically identified as protein appears on the inner surface of the vacuole tonoplast 8 days after flowering. These vacuoles become smaller and more frequent during development and the amount of proteinaceous material within each vacuole increases until, at days 16-20 after flowering, they become densely packed with protein and are described as protein bodies. At day 8, the vacuole(s) have an average diameter of 39 µm, an average volume of 41 000 µm³ , representing 75 % of the cell volume, and a surface area of 5500 µm². By day 20, the average protein body diameter has fallen to 1 µm. There are, however, approx. 175 000 such protein bodies per cell, occupying 91 500 µm³ or approx. 20 % of the cell volume, and whose total surface area is 550 000 µm². The surface to volume ratlo of the vacuole/protein bodies Increases 55 times between days 8 and 20. Apart from this increase in surface area available for possible entry of protein, no mechanism for such entry can be suggested from our nlicrographs.