Showing papers in "Planta in 1970"

Cell wall regeneration and cell division in isolated tobacco mesophyll protoplasts.

Abstract: Protoplasts were isolated from palisade tissue of tobacco leaves by treatment with pectinase and cellulase under aseptic conditions, and were cultured in a synthetic liquid medium. Calcofluor, a fluorescent brightener, was found to be an excellent stain for plant cell walls and was used to demonstrate regeneration of cell walls in these protoplasts. The cultured protoplasts regenerated cell walls by the 3rd day of culture, giving rise to spherical cells. The majority of the protoplasts regenerating cell walls underwent mitosis and cell division. The cycle of mitosis and cell division was repeated 2-3 times during 2 weeks of culture. Some of the nutritional conditions affecting division in the cultured protoplasts were studied.

Stimulation of rice coleoptile growth by ethylene.

Abstract: The growth rate of rice coleoptiles is increased by low concentrations of ethylene, especially in oxygen concentrations lower than air; carbon dioxide enhanced this response. C2H4 is produced by rice seedlings, and this production is also enhanced by carbon dioxide. Ethane and propane were produced in trace amounts but were inactive in growth stimulation as were also methane, propylene, and butane.

Callose in cell walls during megasporogenesis in angiosperms.

Abstract: Callose was detected by fluorescence microscopy in megasporogenesis in all investigated species with mono- and bisporic embryo-sac development. Callose occurs first in the meiotic prophase in the chalazal part of the megasporocyte wall and by the first meiotic metaphase the whole cell is enveloped in a callose-containing wall. Later, there is a marked decrease of callose fluorescence, usually at the chalazal end of the megasporocyte. In Oenothera, where the micropylar megaspore is active, decrease of fluorescence takes place at the micropylar pole of the megasporocyte. Callose appears centrifugally in the cell plates forming eventually the walls dividing the megaspores. It disappears from the walls of the megaspores during degeneration and differentiation.

Charakterisierung einer Synchronkultur von Scenedesmus obliquus, ihrer potentiellen Photosyntheseleistung und des Photosynthese-Quotienten während des Entwicklungscyclus

Abstract: Using synchronous cultures, the change in the potential photosynthetic capacity and the behavior of the photosynthetic quotient were investigated during the life cycle of Scenedesmus obliquus, strain D 3. Scenedesmus obliquus was synchronized under a light-dark regime of 14:10 hours. The quality of synchrony was demonstrated by complete synchronization, homogeneity, exponential growth, shortest possible life cycle and non-susceptibility of the life cycle to the synchronizing procedure. Furthermore, the synchronous culture was characterized by determination of cell number, dry weight, packed cell volume, chlorophylls a and b and the carotenoids during the life cycle. The potential photosynthetic capacity (as O2 evolution) was measured manometrically and polarographically in white light. This capacity increased from the beginning of the light period until the 8th hour and then declined until the 16th hour, that is until just before release of daughter cell. The percentage difference between the maximum and the minimum of the photosynthetic capacity was the same in the light saturating and light limiting region of photosynthesis. — The photosynthetic quotient was measured by means of Warburg's “indirect method”. It proved to be constant throughout the life cycle under light saturating and light limiting conditions. The ratio of O2 evolved to CO2 consumed was just below unity. The results were compared with those of other authors and their significance was discussed. It was concluded that the change in the photosynthetic capacity is inherent in the normal life cycle of green algae and is not a result of the synchronizing light-dark regime.

Growth and regeneration of waxes on the leaves of Eucalyptus.

Abstract: The relationships of wax morphology to wax chemistry and the effects of light intensity on wax development were investigated using rubbing techniques to produce nearly wax free cuticular surfaces. Wax regeneration took place rapidly on leaves which were in their exponential stage of expansion, but only slowly on those that had fully expanded. The pattern of wax development suggested that tube waxes originate as flat plates that fuse along one edge to form a hollow structure.

Phytochrome and hormonal control of expansion and greening of etiolated wheat leaves

Abstract: Unrolling of etiolated wheat leaf segments is stimulated by short periods of exposure to red light. Both gibberellic acid and kinetin will stimulate unrolling in the dark, whereas abscisic acid (ABA) inhibits the unrolling response to these two hormones and to red light. Exposure to 5 minutes of red light leads to a rapid increase in endogenous gibberellin levels in etiolated wheat leaves, and this increase is followed by a rapid decline. Pre-treatment with ABA inhibits the increase in gibberellin levels in response to red light, but the ihibitory effect of ABA on unrolling cannot be ascribed only to its effect on gibberellin levels. Pre-treatment with red light reduces the lag-phase in chlorophyll development when wheat leaf segments are subsequently exposed to white light; the effect of red light may be replaced by pre-treatment with kinetin, but gibberellic acid is relatively ineffective in this respect.

Gibberellic acid and the fine structure of barley aleurone cells : III. Vacuolation of the Aleurone cell during the phase of ribonuclease release.

Abstract: Summary. Ultrastructural changes in barley aleurone cells treated with gibberellic acid (GA3) for 24-36 hr are described. Many large vacuoles are seen in the ground cytoplasm; these coalasce to form one large central vacuole. Evidence is presented indicating that the vacuoles are formed from the aleurone grains. The dictyosomes of aleurone cells treated with GA3 for 24 hr or longer proliferate many vesicles. This proliferation of dictyosome vesicles is associated with the phase of rapid ribonuclease release from the aleurone cell. Estimates indicate that microbodies are considerably reduced in number with GA3 treatment from 24-36 hr while the number of mito chondria is not substantially affected relative to controls. P-Protein-like material is seen in the cytoplasm of these cells often in close proximity to endoplasmic reticulum and spiny vesicles.

Comparative photosynthesis, growth and transpiration of two species of Atriplex.

Abstract: Throughout a period of 23 days, during which the photosynthesis, growth and transpiration of two species of Atriplex were compared, A. spongiosa, a "C4" species (first products of photosynthesis = 4-C dicarboxylic acids), maintained net rates of leaf photosynthesis as high as, or higher than, those of A. hastata, a "C3" species (photosynthesis exhibiting the Calvin-type characteristics).However, as the experiment progressed, the proportion of photosynthate which was used to produce new leaf material declined progressively in A. spongiosa, so that total plant growth rate, initially more than twice as high as in A. hastata, declined to only 0.8 of the A. hastata value. This result demonstrated clearly that more efficient photosynthesis is only one factor, and in this case a relatively minor factor, in total growth rate.Transpiration rates were consistently lower in A. spongiosa than in A. hastata and the ratio declined slightly during the experiment. In consequence, water-use efficiency, both on a single-leaf and whole-plant basis, was much greater in the C4 species.Levels of mesophyll resistance (r m ) were consistently lower in A. spongiosa and increased from about 0.4-0.6 to 1.2-1.5 s cm(-1) during the experiment. In A. hastata there was more variability in r m levels but little overall trend towards a higher r m , initial and final values being of the order of 2.5-2.6 and 2.6-2.9 s cm(-1), respectively. Levels of stomatal resistance (r l ) were higher in A. spongiosa (about 1.0-1.2 s cm(-1)) than in A. hastata (about 0.7-0.8 s cm(-1)) at the beginning of the experiment and increased to 2.0-2.6 s cm(-1), whereas they remained relatively constant in A. hastata.The combination of relatively low r m levels and relatively high r l levels provide the explanation for the substantially greater water use efficiency in A. spongiosa. The progressive changes in these levels and in the pattern of leaf area development in A. spongiosa provide an elegant example of adaptation to arid conditions by this species.

A correlative ultrastructural and enzymatic study of cotyledonary microbodies following germination of fat-storing seeds.

Abstract: Sunflower, cucumber, and tomato cotyledons, which contain microbodies in both the early lipid-degrading and the later photosynthetic stages of post-germinative growth, were processed for electron microscopy according to conventional procedures and examined 1, 4 and 7 days after germination. Homogenates of sunflower cotyledons were assayed for enzymes characteristic of glyoxysomes and leaf peroxisomes (both of which are defined morphologically as microbodies) at stages corresponding to the fixations for electron microscopy. The particulate nature of these enzymes was demonstrated by differential and equilibrium density centrifugation, making it possible to relate them to the microbodies seen in situ.One day after germination, the microbodies are present as small organelles among large numbers of protein and lipid storage bodies; the cell homogenate contains catalase but no detectable isocitrate lyase (characteristic of glyoxysomes) or glycolic acid oxidase (characteristic of leaf peroxisomes). 4 days after germination, numerous microbodies (glyoxysomes) are in extensive and frequent contact with lipid bodies. The microbodies often have cytoplasmic invaginations. At this stage the cells are rapidly converting lipids to carbohydrates, and the homogenate has high isocitrate lyase activity. 7 days after germination, microbodies (peroxisomes) are appressed to chloroplasts and frequently squeezed between them in the green photosynthetic cells. The homogenate at this stage has substantial glycolic acid oxidase activity but a reduced level of isocitrate lyase. It is yet to be determined whether the peroxisomes present at day 7 are derived from preexisting glyoxysomes or arise as a separate population of organelles.

Protein filaments-structural components of the phloem exudate : I. Observations with Cucurbita and Nicotiana.

Abstract: Fine structure and chemical composition of the phloem exudate of Cucurbita maxima and Nicotaiana glauca x suaveolens are investigated. Filamentous structures, several microns in length, are identified as structural components of the exudate by means of negative staining and electron microscopy. Two types of filaments are described: one form measures nearly 40 A in diameter and shows a beaded appearance with regular spacings of about 50 A; it is termed "elementary filament". The second form has a diameter of about 90 A and presumably consists of two helically arranged 40 A subunits.The proteinaceous nature of the filaments is indicated by chemical analysis. The main macromolecular component of the exudate is demonstrated to be protein. Only traces of nucleic acids are detectable, lipids and polysaccharides cannot be found. The identity of the protein filaments with the filamentous structures ("slime", "P-protein"), as revealed in thin sections of mature sieve tubes, is discussed.

Preferential polar pathways in the cuticle and their relationship to ectodesmata

Abstract: Ectodesmata-like structures, referred to here as mercurous or mercury precipitates (MP) and considered to be identical to precipitates observed after treatment of leaf tissue with Gilson solution for demonstration of ectodesmata, were demonstrated with cuticle enzymatically isolated from Allium bulb scales and leaves mounted on ascorbic acid-enriched agar or gelatin. The MP distribution patterns obtained with isolated cuticle, in the absence of a cell wall, were identical to those observed with living tissue. Since the distribution in either the presence or absence of the cell wall was similar, the distribution pattern must be determined by the cuticle and not by the cell wall. Disruption of the physical arrangement of epicuticular wax by brushing or removal with chloroform altered the distribution pattern and increased the frequency of MP. This was interpreted to mean that epicuticular wax plays an important role and also that the necessary reductant was not localized in specific structures in the cell wall. Based on this evidence, it appears that ectodesmata, as demonstrated with Gilson solution, are not specific cell-wall structures, whether plasmic or not plasmic. More likely, the MP observed in the cell wall reflect areas in the cuticle permeable to mercuric chloride and undoubtedly to other polar compounds. The presence of such pathways in the cuticle, long established as the prime barrier to penetration of polar compounds, has marked implications in foliar uptake and excretion.

The fine structure of the cells that perceive gravity in the root tip of maize

Abstract: Within the root cap, in maize, the cells believed to be responsible for the perception all possess large well-developed amyloplasts. They also have normal mitochondria and Golgi bodies, normal rough-surfaced ER with a very striking pattern of distribution, few free ribosomes, walls with an abnormal reticulate encrusting material, irregularly distributed plasmodesmata and an as yet unidentified fine quadruple membranous system. All of these features are discussed in relation to the role of the cells in perception.

Comparison of endogenous gibberellins and response to applied gibberellin of some dwarf and tall wheat cultivars.

Abstract: A number of dwarf wheat cultivars of the Norin 10 type were compared with several tall forms. Applied gibberellic acid markedly stimulated the growth of seedlings of the tall cultivars but not the growth of dwarf seedlings. Several other gibberellins were also inactive when tested with one dwarf cultivar. De-embryonated grains of all cultivars formed α-amylase in response to gibberellic acid. Gibberellic acid caused an increase in soluble carbohydrates in the leaves of the tall cultivars but not in those of the dwarfs. Germinating grains, light-grown seedlings and developing stems of the dwarf cultivars contained more endogenous gibberellin-like activity than those of tall cultivars. It is suggested that the dwarf cultivars have a block to the utilisation of gibberellin in the shoot.

Untersuchungen über die lichtabhängige Carotinoidsynthese

Abstract: The purpose of these studies was to find which steps in the biosynthetic pathway of carotenoids in Fusarium are under photoregulation. After separation by column chromatography ζ-carotene, neurosporene, γ-carotene, torulene, neurosporaxanthin and lycopene were identified from their absorption spectra in visible light and by co-chromatography tests with carotenoids from other organisms. No other carotenoids were detected. These components were each present in trace amounts (0.5–2 μg/g dry weight) in stricly dark grown cultures. During incubation of the mycelium in buffered glucose solutions in darkness these carotenoids accumulated slowly but linearly with time.

The role of the mesophyll cell wall in leaf transpiration

Abstract: Evidence is presented which suggests that the mesophyll cell walls of cotton leaves may influence observed rates of transpiration.The net diffusive flux of water vapour, from the upper and lower surfaces of a leaf, was compared with the flux of nitrous oxide through a leaf and evidence obtained of an extra resistance in the water-vapour pathway associated with water transport in the mesophyll cell walls.This extra resistance appeared to be insignificant at low transpiration rates and in turgid leaves, but increased with transpiration rate and dehydration. The most likely explanation for its origin appeared to be a reduction in hydraulic conductivity across the internal cuticle which lines the outer surfaces of the mesophyll cell walls. In turn this served to reduce the relative vapour pressure at the sites of evaporation.The experiments were conducted under conditions where stomatal opening was induced by CO2-free air. Under normal conditions stomatal closure would tend to reduce the development of this extra resistance. Even so, the results throw doubt on the validity of the long-standing assumption that the water-vapour pressure at the evaporation sites is equal to the saturation vapour pressure under all conditions.

Gibberellic acid, β-1,3-glucanase and the cell walls of barley aleurone layers.

Abstract: A glucanase from barley aleurone layers can be assayed using the algal polysaccharide laminarin as substrate. Gibberellic acid (GA3) enhances the release of this enzyme from isolated aleurone layers but has no significant effect on its synthesis. Concentrations of GA3 effective in stimulating this release are in the range of 3×10(-11)-3×10(-7)M. The time course of glucanase release was found to be significantly different from that of α-amylase, glucanase release being completed before that of α-amylase. Evidence based on using various histochemical stains suggests that barley aleurone cell walls contain a β-1,3-linked polymer. Following treatment of aleurone layers with GA3, digestion of these walls is seen to occur. These observations strongly suggest that the β-1,3-glucanase produced by aleurone cells is resposible for the observed cell-wall digestion.

[Formation of maxima in the absorption spectrum of carotenoids in the region around 370 nm; consequences for the interpretation of certain action spectra].

Abstract: 1. Most carotenoids show a 3-peak-absorption curve in the visible spectral region in polar solutions. The addition of a definite quantity of H2O to such solutions (ethanol, methanol, aceton, isopropanol) changes the absorption curve of these pigments in a characteristic manner. A new peak appears in the uv region of the spectrum (e.g.in the case of lutein at 370 nm); simultaneously the 3-peak fine structure of the visible spectrum diminishes and completely disappears after further addition of H2O. Such changes are observed especially in the case of lutein and zeaxanthin, but also in the case of neoxanthin, violaxanthin and lycopene (of the carotenoids analyzed). During thermic excitation (45° C) the uv-peak in the carotenoid spectrum disappears and the normal 3-peak curve is restored; upon cooling the uv-peak appears again. The variation of the carotenoid spectrum and the formation of a maximum in the uv-region are possibly caused by an aggregation of the pigment molecules with participation of H2O molecules. This formation of polymers obviously leads to an alteration in the distribution of electrons in the chromophore system of the carotenoid molecule and thereby to a change of the light absorption. 2. Water-soluble carotenoid complexes isolated from spinach chloroplasts show a strong light absorption in the uv-region and a one-peak absorption curve in the visible blue. After transfer of the complex to polar solutions a characteristic 3-peak carotenoid curve appears in the blue region of the spectrum; concomitantly the maximum in the uv disappears. That means that carotenoids which are bound to membranes or particles in the intact cell may have a 4-peak absorption curve similar to that of pigments which are dissolved in the water-containing alcohols mentioned above. It is conceivable that those carotenoids which do not form uv peaks in the dissolved state are able to do so under conditions under which carotenoids are bound to membranes or particles. 3. The similarity of some action spectra to certain 4-peak, carotenoid spectra is striking. This is true particularly for the action spectrum of the first positive curvature of Avena coleoptile (Fig. 10).

Phytochrome action in Oryza sativa L. : V. Effects of decapitation and red and far-red light on cell wall extensibility.

Abstract: The mechanical properties of the cell wall were measured in coleoptiles of totally etiolated rice seedlings. Coleoptiles were either decapitated or briefly exposed to red (R) and/or far-red (FR) light. The elastic and plastic extensibilities of the cell wall changed with age (length) of the coleoptiles. Decapitation and exposure to R induced changes in these properties, and the time-courses were similar. Following decapitation or R irradiation, the plastic extensibility of the cell wall decreased more conspicuously than elastic extensibility. Exogenous application of auxin immediately following decapitation alleviated the effect of removal of the tip. FR irradiation reduced both kinds of extensibilities, but its effect was much less than that of R, and it reversed the R-induced effect to the level of tissue treated with FR only. In repeated R-FR treatments, the decrease of elastic extensibility by R and its reversal by FR could be repeated, but the effect of a second irradiation with R after FR on plastic extensibility was not as apparent as that of the first. Reduction of cell-wall extensibility of etiolated rice coleoptiles caused by R light appeared, at least partly, to be due to a reduced auxin supply in the elongating region from the tip, similar to that caused by decapitation.

Changes in endogenous growth regulators in nasturtium leaves during senescence.

Abstract: By use of lettuce-hypocotyl and wheat-coleoptile bioassay, the presence of both gibberellin (GA)-like and abscisic-acid(ABA)-like components in acidic ethyl-acetate extracts of fully expanded nasturtium (Tropaeolum majus) leaves has been shown. During senescence of detached leaves there was a progressive decline in GA-like components and an increase in ABA-like components. Pretreatment of detached leaves with GA3 or kinetin prevented changes in the levels of endogenous growth regulators and delayed senescence. The observations provide experimental verification for the concept that senescence is associated with changes in endogenous growth regulators.

Light-induced flavone biosynthesis and activity of phenylalanine ammonia-lyase and UDP-apiose synthetase in cell suspension cultures of Petroselinum hortense.

Abstract: The formation of flavone glycosides in cell suspension cultures from parsley leaf petiols after illumination with high intensities of white light was demonstrated. Changes in the activities of two of the enzymes involved in flavone glycoside biosynthesis (phenylalanine ammonia-lyase and UDP-apiose synthetase) were measured over a period of 14 days. The two enzymes reached maximum specific activities after significantly different periods of time.

Fertilization in fucus.

Abstract: Methods are described for the collection, treatment and uniform discharge of large quantities of gametes, and a measure of fertilization control in the monoecious brown alga, Fucus distichus. Fertilization was examined using the techniques of blister-formation, gamete separation experiments, and electron microscopy. Sperm enter the freshly-discharged egg packets through a mesochite pore and juxtaposition with the eggs early. However, experimental and thinsection data indicate that fertilization does not occur until the eggs dissociate from the mesochite and round up. Hence, the egg surface appears to undergo three functional changes following its release from the thallus: (1) a pre-dissociation state which inhibits fertilization within the mesochite; (2) a dissociation state when fusion of gametes is possible; and (3) a post-fertilization state characterized by the formation of extraneous coats. As the egg is activated by the sperm a nonmembranous layer appears to detach from the egg surface to form an activation layer. This is augmented by fibrous units to function as a fertilization barrier which ultimately thickens to form the cell wall. The area between the eggs within the egg packet is characterized by the presence of fibrous and particulate substances which are continuously given off through the egg surface. These apparently play a functional role in the sequential stages of fertilization in Fucus. These observations are discussed in terms of analogies with fertilization in the sea urchin.

Hydrogen evolution by several algae.

Abstract: Out of 33 strains of unicellular algae examined, H2 evolution was observed only in species of Chlamydomonas, Chlorella and Scenedesmus. While the photoevolution of H2 by these algae was generally stimulated both by an organic substrate and by the uncoupler CCCP1, response to DCMU varied. On the basis of the response to DCMU, it was concluded that the mechanism of photoevolution of H2 differed from one alga to another. The reaction in some algae appeared to be dependent on either the photooxidation of water or oxidative carbon metabolism for reductant; that in other algae was supported by reductant from both these sources.

Changes in phosphatase activity in phosphorus-deficient Spirodela.

Abstract: Onset of phosphorus deficiency in Spirodela oligorrhiza was accompanied by a 50-fold increase in phosphatase activity of cell extracts. The enzyme behaved like other plant acid phosphatase, and was both inhibited and repressed by inorganic phosphate. The phosphatase activity comprised at least three isozymes. Two, of low molecular weight, were present only in P-deficient Spirodela; one of high molecular weight was also present, though in smaller amounts, in normal Spirodela. Presence of 2-thiouracil during onset of P-deficiency partly inhibited the development of phosphatase activity. The nature and role of the increased phosphatase activity in P-deficient plants are discussed.

Influence of indole-3-acetic acid on adventitious root primordia of brittle willow.

Abstract: Removal of the stem apex and certain leaves and axillary buds of brittle willows (Salix fragilis) was employed to limit the supply of endogenous auxin to adventitious root primordia during their formation, which occurs at predetermined sites. Limiting endogenous auxin by this surgical treatment resulted in reduced primordium initiation and, to a lesser degree, primordium growth in cell number. Root primordium cells in surgically treated plants differentiated into mature parenchyma after losing their meristematic character. Application of indole-3-acetic acid (IAA) to surgically treated plants partially overcame the effects of the surgical tretament, increasing root primordium initiation and growth by cell division. When IAA-2-14C was applied to surgically treated plants, label was detected in root primordium cells by means of autoradiography. Root primordium cells took up more label during the earliest stage of initiation than during a later stage of growth. The data indicate that the initiation of these primordia is more dependent on a supply of auxin than is their subsequent development. Further, the auxin apparently acts directly in the cells which initiate primordia.

Phloem exudation from castor bean: Induction by massage.

Abstract: Exudation can be induced or greatly enhanced in Ricinus by massaging the stem periodically some time before tapping the sap by making an incision. Nevertheless temporary massage during exudation stops flow completely indicating that flow is prevented normally by a pressure sensitive sealing mechanism which becomes desensitised by regular massage.

Temperature dependence of CO2 assimilation and stomatal aperture in leaf sections of Zea mays

Abstract: CO2 exchange and air flow through the stomata were measured in leaf sections of Zea mays at temperatures between 7 and 52° and under optimal water supply. The results were summarized in polynomials fitted to the data. In leaf samples brought from 16° and darkness into different experimental temperatures and light, CO2 assimilation has a maximum near 30°. Above 37° (in other experiments above 41°), net CO2 uptake stops abruptly and is replaced by CO2 evolution in light. If a 1-hr treatment with 25° and light is inserted between darkness and the experimental temperatures, the threshold above which the assimilatory system collapses shifts 3 degrees upwards, to 40° (or 44°); the decline of CO2 assimilation with high temperatures is less steep than without pretreatment; and the upper compensation point moves upscale by as much as 5 degrees. Stomatal conductance for CO2 does not, in general, follow an optimum curve with temperature. Between 15 and 35° it is approximately proportional to net CO2 assimilation, indicating control by CO2; but above 35°, stomatal aperture increases further with temperature (and so does stomatal variability): the stomata escape the control by CO2 and above 40° may be wide open even if CO2 is being evolved. Stomatal conductance for CO2 below 15° may also be larger than would be proportional to CO2 assimilation. Net CO2 assimilation and stomatal conductance at 25° were reduced if the leaf samples were pretreated with temperatures below approximately 20° and above 30°. Stomata were more sensitive to past temperatures than was CO2 assimilation.

Isolierung und Charakterisierung schnell markierter, hochmolekularer RNS aus frei suspendierten Calluszellen der Petersilie (Petroselinum sativum)

Abstract: By culturing of callus tissue originating from root explants of Petroselinum sativum in a synthetic liquid medium under aeration, freely suspended single cells and small clusters consisting of mostly five cells were obtained. The rapidly dividing cells did not exhibit any morphogenesis. Their nucleic acid metabolism was investigated by pulse experiments with 32P-orthophosphate. Rapidly labelled RNA was prominently found associated with high molecular RNA. During the fractionation of the total nucleic acids on MAK columns it was eluted after the ribosomal RNA components. Its base ratio, however, differed from the latter in that the AMP content was higher than the GMP content. Sucrose gradient centrifugation and polyacrylamide gel electrophoresis resulted in the separation of the ribosomal RNA from the rapidly labelled RNA, thus proving the higher molecular weight of the latter. Based upon the migration in the gel a sedimentation coefficient of approximately 32S was calculated. The possible function of the heavy rapidly labelled RNA component as precursor of ribosomal RNA is discussed.

A cotyledon slice system for the electron autoradiographic study of the synthesis and intracellular transport of the seed storage protein of Vicia faba.

Abstract: Cultured slices of cotyledon tissue from 60-day broad bean have been shown to synthesise globulin protein extensively. About 80% of the 3H-leucine incorporated into protein was incorporated into globulin protein; 35S-sulphate was also incorporated by the slices.

On the formation of the pattern of crystal idioblasts - in Canavalia ensiformis DC : IV. The fine structure of the crystal cells.

Abstract: Light and electron-microscope observations were made of the crystal idioblasts in the leaves of Canavalia. The crystal-containing cells occur as pairs in which the crystals, nuclei, and the majority of the chloroplasts are symmetrically arranged with regard to the common wall. The chloroplasts are found in the cytoplasm along this wall.The crystals originate in a vacuole. The space in which the young crystal develops is delimited by a membrane. One to several additional membranes surround the crystal inside the vacuole. Numerous vesicles are distributed between these vacuolar membranes. Dense groups of tubules or fibrils are oriented toward a portion of the crystal surface, suggesting that the material forming the crystal might be transported to the surface by these structures.The cytoplasm of the young idioblasts contains many mitochondria and dictyosomes with associated vesicles. Concentrations of what is assumed to be protein are present in the cytoplasm. These protein accumulations are not seen in neighboring cells, suggesting that protein synthesis is especially high in the idioblasts.In older crystal cells, layers of wall material are deposited on the wall between the two crystals of the pair and towards the cell wall adjacent to the mesophyll. Not only does the original wall become thickened but a new wall develops at the border of the crystal vacuole. Eventually this wall material becomes continuous and the crystal becomes, on two sides, directly connected with the wall.

Carotenoid synthesis in mustard seedlings as controlled by phytochrome and inhibitors.

Abstract: Accumulation of carotenoids in the mustard seedling (Sinapis alba L.) is controlled by phytochrome (Pfr). Separation of the carotenoids shows that the control is quantitative rather than qualitative. Kinetic studies indicate that Pfr exerts a rapid and nearly reversible control over the rate of carotenoid accumulation. Whereas carotenoid accumulation between 36 and 60h after sowing is relatively insensitive towards Actinomycin D, the sensitivity towards cycloheximide and Puromycin is high. It is concluded that at least some of the enzymes required for carotenoid biosynthesis are made in the extraplastidal cytoplasm and it is suggested that Pfr acts at the level of carotenoid accumulation by providing a structural prerequisite for carotenoid accumulation in the plastid compartment. This latter suggestion is mainly based on the fact that carotenoid accumulation in light and dark is very sensitive towards chloramphenicol if the compound is applied at the time of sowing. If, however, the compound is applied 36 h after sowing, the effect of chloramphenicol is different in light and dark. In the dark there is no influence up to 200 μg·ml-1, whereas in the light there is a significant inhibition of carotenoid accumulation.