Primary Wall Material Research Articles

Proximate analysis of the high phytochemical activity of encapsulated Mandai cempedak (Artocarpus champeden) vinegar prepared with maltodextrin and chitosan as wall materials

Background: Mandai cempedak vinegar (MCV) is a fermented vinegar produced from the inner skin of cempedak (Artocarpus champeden), which contains antioxidants classified as flavonoids, phenols, and tannins. These bioactive compounds are sensitive to heat and prone to oxidative damage. Therefore, an encapsulation process is proposed to protect the bioactive compounds. This study aimed to design a potential scaling-up formulation of spray-dried encapsulated MCV based on Total Soluble Solid (TSS) with the addition of maltodextrin and chitosan, followed by determining the nutrition and phytochemical values of the formulation. Methods: The formulation employed maltodextrin to achieve TSS of 15, 20, and 25 ºBrix as the primary wall material treatment factor. The second factor was chitosan as auxiliary wall material at 1, 2, and 3% (w/w of maltodextrin). Products were spray-dried at 100 ºC inlet temperature and 80 ºC outlet temperature. Analyses of nutrition, flavonoid, phenol, and tannin were conducted in triplicate for each encapsulated product. Results: The 15 ºBrix of TSS from maltodextrin with 1% chitosan emerged as the best-encapsulating material, giving 7.54% moisture, 0.75% ash, 0.42% protein, 0.35% fat, and 90.94% carbohydrate content, resulting in a phytochemical activity equivalent to 9.13 mg Catechin Equivalent kg-1, 69.61 mg Gallic Acid Equivalent kg-1, and 25.04 mg Tannic Acid Equivalent kg-1. Compared to maltodextrin, the chitosan generally contributed less to the proximate, flavonoid, phenol, and tannin content of the encapsulated MCV. Conclusions: The best formulation contained maltodextrin at 15 ºBrix of TSS and 1% chitosan. Maintaining optimum TSS was a key to producing consistent encapsulated MCV with high phytochemical activity.

Application of argun fruit polysaccharide in microencapsulation of Citrus aurantium L. essential oil: preparation, characterization, and evaluating the storage stability and antioxidant activity

The aim of this study was to evaluate the influences of the partial replacement of the maltodextrin (MD) as primary wall material by argun fruit polysaccharide (AFPS) as a new promising wall material in microencapsulation of Citrus aurantium L. essential oil (CAEO). The emulsions properties, yield, microencapsulation efficiency (MEE), structural and physicochemical characteristics, thermo-gravimetric analysis (TGA), glass transition temperatures by differential scanning calorimetry (DSC), crystallinity, oxidative and antioxidant stability of the freeze-dried CAEO microcapsules were investigated. The highest values of viscosity and droplet size were achieved by CAEO emulsion stabilized with GMA100 formulation. The yield and MEE of CAEO microcapsules were significantly enhanced with increasing of AFPS in the formulations. The partial replacement treatments by AFPS increased solubility, bulk density, tapped density, particle density, and porosity of the obtained microcapsules. FTIR, X-ray, DSC, and TGA techniques were confirmed that the encapsulation of CAEO was perfectly successful. The partial replacement of MD with AFPS improved the oxidative stability and antioxidant activity of microencapsulated CAEO during the storage. Depending on physicochemical properties, thermal stability, and antioxidant activity, it could be considered these microcapsules have promising applications in the functional food and medicine industry.

Thermal Degradation Kinetics of Encapsulated Palm Carotenes Using Different Combination of Wall Materials

Palm oil is known as one of the richest sources of carotenes. Carotenes concentrate could be prepared from crude palm oil and possessing potency to be used as nutraceutical materials. Due to the susceptibility of carotenes against heat, the encapsulation procedure might be applied to provide protections. The present study was aimed to learn the influence of using different combination of wall materials toward the thermal degradation kinetics of palm carotenes. Maltodextrin was used as primary wall material, being combined with various surface-active agents, i.e. Tween-80 (A), Tween-20 (B), and Arabic gum (C). The carotenes concentrate was encapsulated through emulsification steps, and the vivid yellow powder was obtained after freeze drying process. Then, encapsulated palm carotenes were stored in 200C, 350C, and 500C for several days, and the color, carotenes spectrum, as well as water content were monitored periodically. The kinetics of thermal degradation of carotenes were estimated using Arrhenius equation. The results showed that the use of different combination of wall materials exhibited distinct degradation rate. The combination of maltodextrin and Tween-80 gave preferable protection compared to the others, being half-degraded after 51 days in 200C.

Dynamics of structural polysaccharides deposition on the plasma-membrane surface of plant protoplasts during cell wall regeneration

In this study, dynamic changes in structural polysaccharide deposition on the plasma membrane and cortical microtubules (CMTs) behavior were monitored in protoplasts isolated from white birch callus using confocal laser scanning microscopy and atomic force microscopy. We focused on the influence of an environmental stimulus on cell wall regeneration in protoplasts by employing an acidic culture medium containing a high concentration of Ca2+ (the stress condition). Under the non-stress condition, cellulose microfibrils and callose were initially synthesized, and thereafter deposited on the plasma membrane as “primary cell wall material”. Under the stress condition, callose micro-sized fibers were secreted without cell wall regeneration. Behavior of CMTs labeled with mammalian microtubule-associated protein 4 with green fluorescent protein in transgenic protoplasts was monitored by time-lapse video analysis. Under the non-stress condition, CMTs behavior showed a linear arrangement at a fixed position, whereas unfixed manner of CMTs behavior was observed under the stress condition. These findings indicate that excessive Ca2+ affects cellulose synthesis and CMTs dynamics in plant protoplasts. Current study first demonstrated dynamics of cell wall regeneration and CMTs in woody protoplast, which provides novel insight to aid in understanding early stages of primary cell wall formation in plants.

Spray-dried novel structured lipids enriched with medium-and long-chain triacylglycerols encapsulated with different wall materials: Characterization and stability

Novel structured lipids (SLs) enriched with medium-and long-chain triacylglycerols (MLCTs) were synthesized to combine the benefits of both arachidonic acid and medium-chain fatty acids; however, they are susceptible to oxidative degradation. In this work, the influences of the partial replacement of whey protein isolate (WPI) as the primary wall material by prebiotic carbohydrates, such as maltodextrin (MD) and inulin (IN) as the secondary wall materials on the physicochemical characteristics and oxidative stability of the spray-dried MLCTs-rich SLs microcapsules were investigated. The highest values of viscosity and zeta-potential were achieved by the WPI/IN (1:1) emulsions. Size distributions of all the emulsions were mono modal and became bimodal after microencapsulation process. The microcapsules prepared with WPI/IN (1:1) had the lowest lightness and the highest yellowness values. The partial replacement treatments increased the solubility and reduced the moisture content of the produced microcapsules. The partial replacement of WPI by IN significantly enhanced the encapsulation efficiency (89.10 ± 1.03%), wettability properties (205 ± 10.61 S), and decreased the incidence of surface oil on the microcapsules. The free oil content was noted as 5.73 ± 0.05, 3.83 ± 0.01, and 2.40 ± 0.03% for the microcapsules produced using WPI, WPI/MD (1:1), and WPI/IN (1:1), respectively. Larger microcapsules and fairer flowing properties were achieved in the powders produced with only WPI. The partial replacement of WPI by IN provided the best oxidative stability of the microencapsulated MLCTs-rich SLs. The results revealed that MD and IN with WPI together, particularly IN proved to be a good substitute secondary wall material for spray-dried MLCTs-rich SLs, therefore suggesting its usefulness in functional food applications.

Optimizing microencapsulation of α-tocopherol with pectin and sodium alginate.

α-Tocopherol is a well-known fat-soluble antioxidant and is widely used in the food industry for stabilizing free radicals. Incorporation and stability of it into food is another challenge as directly added α-tocopherol is prone to inactivation by food constituents. This study was aimed at optimizing conditions for encapsulation of α-tocopherol using combination of sodium alginate (0.5, 1.0, 1.5 and 2.0%) as primary wall material and pectin (2.0%) as filler. The optimum conditions were selected on the basis of encapsulation efficiency, shape, size, bulk density, yield and swelling index with syringe method. The encapsulation efficiency of α-tocopherol in microencapsules produced under optimal conditions was 52.91% using sodium alginate 1.5% w/v and pectin 2.0% w/v. α-Tocopherol was encapsulated with encapsulator using standard conditions and was compared with syringe method. The encapsulation efficiency was found more (55.97%) in microencapsules prepared with encapsulator and 52.11% in microencapsules prepared with syringe.

Contribution of lignin to the strength properties in wood fibres studied by dynamic FTIR spectroscopy and dynamic mechanical analysis (DMA)

Abstract A deeper insight into the molecular interactions in the highly intermixed structure of the wood cell wall, from the point of view of both basic and applied science, is necessary. In particular, the role of the different matrix materials within the cell wall needs to be better understood, especially concerning how lignin contributes to the mechanical properties. In the present paper, the mechanical properties of spruce wood have been studied on a molecular scale by means of dynamic Fourier transform infrared (FTIR) spectroscopy. To this purpose, native spruce wood was subjected to chemical changes by impregnation and a mild pre-cooking with white liquor with a composition usual for kraft pulping. For comparison, lignin-rich primary cell wall material was also isolated by means of thermomechanical pulp (TMP) refining. Dynamic FTIR spectroscopy revealed that lignin took part in the stress transfer in all investigated samples. This finding is in contrast to literature data. A strong indirect coupling between lignin and cellulose was seen in the primary cell wall (P) material. In case of native wood, the lignin signal was much weaker and also indicated an indirect coupling to cellulose. In the case of pre-cooked wood samples (submitted to mild pulping), the interactions were modified so that the molecular straining of lignin was stronger and more directly related to that of cellulose. In other words, in these samples, lignin played a more active role in the stress transfer as compared to native wood. These findings were supported by a narrower lignin-softening region as measured by dynamic mechanical analysis (DMA). The interpretation is plausible in terms of the superior stiffness seen for high-yield pulps of a similar yield as the studied pre-cooked wood samples.

Impact of Milk Protein Type on the Viability and Storage Stability of Microencapsulated Lactobacillus acidophilus NCIMB 701748 Using Spray Drying

Three different milk proteins — skim milk powder (SMP), sodium caseinate (SC) and whey protein concentrate (WPC) — were tested for their ability to stabilize microencapsulated L. acidophilus produced using spray drying. Maltodextrin (MD) was used as the primary wall material in all samples, milk protein as the secondary wall material (7:3 MD/milk protein ratio) and the simple sugars, d-glucose and trehalose were used as tertiary wall materials (8:2:2 MD/protein/sugar ratio) combinations of all wall materials were tested for their ability to enhance the microbial and techno-functional stability of microencapsulated powders. Of the optional secondary wall materials, WPC improved L. acidophilus viability, up to 70 % during drying; SMP enhanced stability by up to 59 % and SC up to 6 %. Lactose and whey protein content enhanced thermoprotection; this is possibly due to their ability to depress the glass transition and melting temperatures and to release antioxidants. The resultant L. acidophilus powders were stored for 90 days at 4 °C, 25 °C and 35 °C and the loss of viability calculated. The highest survival rates were obtained at 4 °C, inactivation rates for storage were dependent on the carrier wall material and the SMP/d-glucose powders had the lowest inactivation rates (0.013 day−1) whilst the highest was observed for the control containing only MD (0.041 day−1) and the SC-based system (0.030 day−1). Further increase in storage temperature (25 °C and 35 °C) was accompanied by increase of the inactivation rates of L. acidophilus that followed Arrhenius kinetics. In general, SMP-based formulations exhibited the highest temperature dependency whilst WPC the lowest. d-Glucose addition improved the storage stability of the probiotic powders although it was accompanied by an increase of the residual moisture, water activity and hygroscopicity, and a reduction of the glass transition temperature in the tested systems.

Optimizing microencapsulation of nisin with sodium alginate and guar gum.

Nisin is a widely used bacteriocin active against gram positive bacteria and is also reported to be active against some gram negative bacteria. Incorporation of nisin into food systems is another challenge as directly added nisin is prone to inactivation by food constituents. Encapsulation of nisin has been done so far in liposomes which is rather an expensive technology involving multiple processes. Other cost effective alternatives with good encapsulation efficiency and better control release properties are sought. Alginate is useful as a matrix for entrapment of bioactive compounds. Present study was aimed at optimizing conditions for microencapsulation of nisin using calcium alginate as primary wall material and guar gum as filler at different air pressures using response surface methodology. The optimum conditions were: sodium alginate concentration (2% w/v), guar gum concentration (0.4% w/v), and air pressure (0.5bar gauge). The encapsulation efficiency of nisin in microcapsules produced under optimal conditions was 36.65%.

Physiochemical properties and prolonged release behaviours of chitosan-denatured β-lactoglobulin microcapsules for potential food applications

Chitosan (CS) and β-lactoglobulin (βlg) double-wall coating was designed as a shell structure to achieve prolonged release of core material in the gastrointestinal tract (GI) for potential food applications. A model core material, brilliant blue (BB) dye, was incorporated into CS as the primary wall material, and subsequently, denatured βlg, a secondary wall material, was used to coat the outer layer. The strongest interaction occurred between 0.5% (w/v) βlg and 0.5% (w/v) CS at pH 5.5 ± 0.1, where the opposite charges of CS and βlg formed a complex, which is especially favourable in acidic beverage systems. Under simulated stomach conditions, a denatured-βlg coat resisted acid conditions and pepsin hydrolysis for 2h. While mimicking small intestine conditions, βlg was degraded by pancreatin, causing the release of BB-loaded CS to the intestinal fluid at a constant rate. The sustained release of core material later in the GI tract provided an optimal absorption rate in the small intestine.

Characterizing wood polymers in the primary cell wall of Norway spruce (Picea abies (L.) Karst.) using dynamic FT-IR spectroscopy

Dynamic Fourier Transform Infra-Red (FT-IR) spectroscopy was used to examine the interactions among cellulose, xyloglucan, pectin, protein and lignin in the outer fibre wall layers of spruce wood tracheids. Knowledge regarding these interactions is fundamental for understanding the fibre separation in a mechanical pulping process. Sheets made from an enriched primary cell wall material were used for studying the viscoelastic response of the polymers. The results indicated that strong interactions exist among lignin, protein, pectin, xyloglucan and cellulose in the primary cell wall. This signified a closely linked network structure of the components on the fibre surface. This ultrastructural arrangement in the primary cell wall and the relatively high content of lignin, pectin and protein in it, means that the primary cell wall is more submissive to selective chemical attacks, when compared to the secondary cell wall. A low ratio of cellulose Iα to cellulose Iβ in the primary cell wall was also found.

Worm tube fossils from the Hollard Mound hydrocarbon-seep deposit, Middle Devonian, Morocco: Palaeozoic seep-related vestimentiferans?

The core facies of the Hollard Mound (southeastern Morocco) contains a dense cluster of worm tubes and a high-abundance but low-diversity assemblage of bivalve molluscs. The tube worms and bivalves lived at an Eifelian hydrocarbon-seep. They are enclosed in microbial carbonates, which are similar to those that form modern seep limestones. These carbonates show δ13C values as low as −21‰. Likely carbon sources include thermogenic methane or petroleum. Hydrothermalism was possibly a factor in the generation of hydrocarbons in the Early Devonian sedimentary succession of the Hamar Laghdad with its submarine volcanics, but it is considered unlikely that the Eifelian seep fluids were hydrothermal. The Hollard Mound worm tube fossils share some characteristics with living seep vestimentiferan worms, but differ in having calcitic tube walls. Deformed Hollard Mound tubes indicate that the primary tube wall material may originally have been flexible. Comparative analyses of tubes of modern vestimentiferan worms from Gulf of Mexico and Congo Fan seeps reveal that early taphonomic processes lead to the calcification of primary organic and flexible tube walls. A very specific fabric found in both modern taphonomically altered vestimentiferan tubes and the Hollard Mound tubes is created by the delamination of individual layers of the tube wall induced by cement growth. A particular carbonate phase of the Hollard Mound microbialites is the so-called ‘carbonate with spheres’. The thin rims of the sub-mm-sized spheres are made of apatite, which is thought to have precipitated by the action of microbes that were degrading fluid droplets (e.g., petroleum at the Eifelian seep site).

Pit membrane remnants in perforation plates of Hydrangeales with comments on pit membrane remnant occurrence, physiological significance and phylogenetic distribution in dicotyledons

Perforation plates from ten species of seven genera of Hydrangeales sensu Thorne were studied using scanning elec tron microscopy (SEM). The presence of pit membranes in perforations ranges from abundant, as in Carpenteria and Ilydrangea, to minimal, as in Deutzia, Escallonia and Fhiladelphus. Abnormally great pit membrane presence may result from the presence of secondary compounds that inhibit lysis, as in Quintinia serrata; such interference with the natural lysis process may or may not be evident from coarseness and irregularity of pit membrane surface and of threads composing the pit membrane remnants. The presence of pit membrane remnants in perforation plates is hypothesized to be a symplesiomorphy, found in a fraction of dicotyledons with scalarifonn perforation plates (but still in an appreciable number of species). Pit membrane remnant presence may represent incomplete lysis of pri mary wall material (cellulose microfibrils) in species that occupy highly mesic habitats, where such impedance in the conductive stream does not have an appreciable negative s&ective value. This physiological interpretation of pit membrane remnants in perforations is enhanced by the phylogenetic distribution as well as the strongly mesic eco logical preferences of species that exempli’ this phenomenon in dicotyledons at large. Families with pit membrane presence in perforations are scattered throughout phylogenetic trees, but they occur most often in basal branches of major clades (superorders) or as basal branches of orders within the major clades. Further study will doubtless reveal other families and genera in which this phenomenon occurs, although it is readily detected only with SEM. Phylo genetic stages in the disappearance of pit membrane remnants from perforation plates are described, ranging from intact pit membranes except for presence of pores of various sizes, to presence of membrane remnants only at lateral ends of perforations and in one or two perforations (arguably pits) at the transition between a perforation plate and subadj scent lateral wall pitting. Developmental study of the mechanism and timing of lysis of pit membranes in per forations, and assessment of the role of the conductive stream in their removal, are needed to enhance present under standing of vessel evolution. © 2004 The Linnean Society of London, Botanical Jottrnal of the Linnean Society, 2004, 146, 41—51. ADDITIONAL KEYWORDS: Cornales — ecological wood anatomy — Escalloniaceae — Ixerbaceae — Saxifragaceae — vessel evolution — wood evolution.

Structure and Function of Tracheary Elements inAmborella trichopoda

Recent phylogenetic analyses have placed the root of flowering plants near Amborella trichopoda, a woody plant restricted to cloud forest habitats in New Caledonia. A distinctive feature of A. trichopoda is its reported lack of xylem vessels. Here we present observations of pit membrane structure and end wall morphology for primary and secondary tracheary cells of A. trichopoda as well as field measurements of stem hydraulic properties of A. trichopoda compared with five cloud fforest species from New Caledonia. Observations of stem radial sections revealed that the primary wall material in the protoxylem and metaxylem elements was intact. No large porosities (such as those that have been observed in the pit membranes of Nymphaeales) were observed. However, a few elliptical pits of tracheary cells in the secondary xylem appeared to lack pit membranes. These observations are consistent with our measurements of functional conduit length, which indicate that the longest open conduits are equal to the length of two secondary xylem elements joined end to end. Thus, the xylem of A. trichopoda appears to be functionally vesselless, with the caveat that connections between individual vascular elements may occasionally be open (i.e., lacking in at least one pit membrane). Sapwood area and leaf area–specific hydraulic conductivities of A. trichopoda are similar to those of conifers and angiosperms, with and without xylem vessels, growing in understory cloud forest environments. These findings bear on discussions of the morphology and ecology of the first flowering plants as well as on the possible causes of their diversification.

Ultrastructural localization of polysaccharides and N-acetyl-D-galactosamine in the secretory pathway of green algae (Desmidiaceae)

In order to characterize the secretory pathway leading to multipolar tip growth in green algae of the family Desmidiaceae, different general polysaccharide stainings, such as the periodic acid-silver hexamine method and the periodic acid-silver proteinate method as well as different lectins specific to defined sugar residues have been employed. General polysaccharide stainings label different kinds of secretory vesicles starting from the onset of vesicle production up to their delivery into the primary cell wall, however, the discrimination of Golgi products is possible using lectins. Both gold-labelled lectins from Helix pomatia and from Glycine max with affinity to N-acetyl-D-galactosamine only produce labelling of primary wall material containing 'dark vesicles' on ultrathin sections of high-pressure frozen and freeze-substituted Micrasterias cells, whereas other vesicle types remain unstained. 'Dark vesicles' are labelled when still attached to trans-Golgi compartments, when distributed throughout the cytoplasm or when fusing with the plasma membrane with the same staining intensity which indicates that the sugars detected by the methods used are present from the onset of visible vesicle production. Gold-labelling of N-acetyl-D-galactosamine is also observed in the primary cell wall. In control experiments the staining vanishes when ultrathin sections are pre-incubated with N-acetyl-D-galactosamine. Various other lectins with affinity to different sugar residues than N-acetyl-D-galactosamine do not produce any staining of the cell wall nor of any kind of secretory vesicles. As N-acetyl-D-galactosamine is usually not present in N-linked polysaccharides the results point towards the presence of O-linked-glycoproteins in the primary cell wall of desmids.

Vessels in Nelumbo (Nelumbonaceae)

Vessels have been previously reported in the roots (but not rhizomes) of Nelumbo on the basis of light microscopy. We have reinvestigated vessel occurrence in Nelumbo by means of scanning electron microscopy (SEM). On the basis of these studies, vessels are characteristic of root metaxylem. Pores in primary walls of pits of end walls of these vessels are various in size, but feature incomplete lysis of pit membranes, often with residual webs or threads of primary wall material, much as in vessels of primitive woody dicotyledons. In addition, we newly report occurrence of vessels in metaxylem of rhizomes; pores in these vessels are smaller and more confined than in those of roots. The present study offers not only data of possible use in determining the phylogenetic position of Nelumbonaceae, but also contributes evidence that vessel origin in Nelumbonaceae relates to habit and ecology. We conclude that organographic distribution of vessels in Nelumbo follows the patterns seen in monocotyledons, which, like Nymphaeaceae and other aquatics, have sympodial architecture.

Vessels in Nelumbo (Nelumbonaceae)

Vessels have been previously reported in the roots (but not rhizomes) of Nelumbo on the basis of light microscopy. We have reinvestigated vessel occurrence in Nelumbo by means of scanning electron microscopy (SEM). On the basis of these studies, vessels are characteristic of root metaxylem. Pores in primary walls of pits of end walls of these vessels are various in size, but feature incomplete lysis of pit membranes, often with residual webs or threads of primary wall material, much as in vessels of primitive woody dicotyledons. In addition, we newly report occurrence of vessels in metaxylem of rhizomes; pores in these vessels are smaller and more confined than in those of roots. The present study offers not only data of possible use in determining the phylogenetic position of Nelumbonaceae, but also contributes evidence that vessel origin in Nelumbonaceae relates to habit and ecology. We conclude that organographic distribution of vessels in Nelumbo follows the patterns seen in monocotyledons, which, like Nymphaeaceae and other aquatics, have sympodial architecture.

Formation of the Pollen-aggregating Threads in Strelitzia reginae

Morphogenesis of the specialized thread-forming (TF) cells in the Strelitzia reginaeanther was investigated; particular attention was given to the cell walls and the degree of vacuolation. The mass of both cell wall and cytoplasm increased until just before dehiscence. However, cell growth and degradation were largely synchronous processes in the TF cells: before any wall thickening could be observed, degradation of primary cell wall material was already initiated. This degradation continued, with the result that the mature thread cells were eventually fully separated from their surrounding cells. Four stages of development, mainly relating to the degree of cell separation, were established. At stage 1, TF cells began to separate from the subepidermis, while at stage 2 some initial cell wall thickening was taking place. The walls of the TF cell were, at stage 3, thickened considerably (about 1 μm), especially along the radial axes. The texture of these walls was loose due to the presence of large intermicrofibrillar regions, and the previously vacuolated cells were filled with cytoplasm. Longitudinal sections revealed conical gaps in the thick cell wall over the plasmodesmata. Just before dehiscence (late stage 3), the TF cells separated from each other and the subepidermis to such an extent that only plasmodesmata and fibrillar wall remnants kept the files of TF cells in place. The released uniseriate threads were classified as stage 4. (Occasionally the threads were multicellular but only where the transverse walls had not separated from each other.) The threads had thinner cell walls than the TF cells at stage 3 and were vacuolated.

A Putative Oligosaccharin Growth Promoter from Vitis vinifera L. Primary Cell Walls

A growth-promotory agent which is consistent with being a carbohydrate was prepared by acid hydrolysis of primary cell wall material derived from callus cultures of Vitis vinifera L. cv. Cabernet Sauvignon. Bioactivities of crude and partially-purified hydrolysate preparations were determined using the Lemna minor L. bioassay. Growth stimulation caused by addition of the crude preparation to the assay was greatest at flask concentrations of about 360 ng ml -1. Partial purification of the crude hydrolysate fraction using gel permeation chromatography showed that approximately one half of the preparation consisted of carbohydrates which were trisaccharides or smaller, with the other half consisting of oligosaccharides. Bioactivity was retained only in the fraction which coeluted with oligosaccharides. Flask concentrations of 143 or 214 ng ml -1 of the partially-purified fraction elicited similar growth promotion to that caused by 360 ng ml -1 doses of the crude hydrolysate preparation. This work constitutes the first description of a putative oligosaccharin growth promoter isolated from the cell walls of grapevines.

Micrasterias cells as a model system for research on morphogenesis.

Micrasterias species have been the subject of numerous experimental studies on cell shape formation in the last 40 years. Chemical and physical treatment during different developmental stages, as well as investigations of ultrastructure by means of various different preparation methods, have yielded information about some principles of morphogenesis in the symmetric, highly ornamented Micrasterias cell. The basic symmetry of a Micrasterias cell is determined prior to mitosis and is established without nuclear control thereafter. Normal cell development, however, may occur only under the conditions of continuous protein synthesis throughout the cell cycle. A prepattern for the later cell shape seems to be present at the plasma membrane at the early stages of septum formation. It is realized by a local, patterned distributed incorporation of cell wall material that is delivered by Golgi-produced vesicles. The areas where fusions take place between the primary wall material containing vesicles and the plasma membrane are defined by inward ionic currents that are carried at least in part by calcium. These areas develop into lobes during the following course of cell growth. Cell shaping in Micrasterias cells is thus mediated by both an enhanced extension of the cell wall and an additional incorporation of wall material in the areas of the lobes. Numerous studies have indicated that actin plays an important role in morphogenesis, whereas microtubules do not participate in this process but are involved mainly in nuclear migration. The present review shows that although a wealth of details concerning Micrasterias morphogenesis has already been elucidated, two main questions, i.e., the method of septum formation and the splitting of the lobes, remain to be answered.