Subsequent to inversion, horizontally pre-gravistimulated coleoptiles exhibit an increased gravicurvature capacity as compared to vertically pre-gravistimulated and subsequently horizontally gravistimulated coleoptiles. This indicates that gravistimulated inhibition of growth of the upper organ flank during gravicurvature is mediated via the retention of wall loosening potential. After inversion, this potential contributes to enhanced cell extension on the then physiologically lower side.
: Changes in chlorophyll, non-protein thiol and glutathione (GSH) levels, and the activity of glutathione S-transferase (GST) were investigated in cadmium(ll) and mercury(ll) cchloride treated leaf discs of mature pedunculate oak trees (Quercus robur). Both heavy metals caused decreases in chlorophyll content, but mercury was more toxic than cadmium. Cadmium treatments (30–250μiM) resulted in increasing non-protein thiol levels after 3d, but GSH contents decreased. Mercury (1–20μM) led to a concentration-dependent decline in both non-protein thiol and GSH levels. GST activities were not modified significantly by cadmium, but mercury treatments caused a dose- and time-dependent enzyme induction. Both the phytotoxic- and GST-inducing effect of mercury could be prevented by the cysteine precursor L-2-oxo-4-thiazolidinecarboxylic acid.
Although physiological control of nodule O-2 permeability is an active area of research, the gas diffusion pathway between the atmosphere and the infected zone has not been firmly established. Previous studies have used infiltration of ink or dyes to identify points of entry, but such water-soluble tracers could give a misleading picture of gas diffusion pathways. We therefore used iodine Vapor (and its reaction with starch) to trace gas-phase pathways into the infected zone of determinate birdsfoot trefoil (Lotus corniculatus) and indeterminate alfalfa (Medicago sativa) nodules. We also used histochemical methods to identify suberized or lignified layers that could act as barriers to gas diffusion. Birdsfoot trefoil nodules were surrounded by a suberized periderm, but nonsuberized cells and intercellular spaces were observed in the periderm between lenticels and their associated vascular bundles, iodine entered birdsfoot trefoil nodules only through lenticels. The periderm appears to provide a significant barrier to gas diffusion. Although airspaces were rare in the nodule parenchyma (also referred to as the "inner cortex"), we found some evidence that a few air-filled pathways cross this secondary barrier, also in the vicinity of vascular bundles. Alfalfa nodules were cylindrically surrounded by a suberized endodermis which ended near the meristematic tip; iodine entered principally at the end of the endodermis near the meristem. Future research on physiological control of nodule O-2 permeability should concentrate on strategic "choke points", associated with lenticels in determinate nodules, or in the zone proximal to the meristem in indeterminate nodules.
Botanica ActaVolume 111, Issue 3 p. 191-192 Decreased Oxygen Permeability: a Universal Stress Response in Legume Root Nodules R. F. Denison, Corresponding Author R. F. Denison Agronomy and Range Science, University of California, Davis, USAAgronomy and Range Science University of California One Shields Avenue Davis CA 95616–8515 USASearch for more papers by this author R. F. Denison, Corresponding Author R. F. Denison Agronomy and Range Science, University of California, Davis, USAAgronomy and Range Science University of California One Shields Avenue Davis CA 95616–8515 USASearch for more papers by this author First published: 27 February 2014 https://doi.org/10.1111/j.1438-8677.1998.tb00694.xCitations: 26AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume111, Issue3June 1998Pages 191-192 RelatedInformation
: Seed coats and fibers of aborted structures (termed “motes”) and mature seeds from an interspecific hybrid (ISH) of cotton (Gossypium hirsutum x G. barbadense) were studied by microscopy to determine (a) the developmental stages at which motes of various sizes stop growing and (b) the origin of lint-contaminating fragments. Small motes (1–2 mm wide, up to 3 mm long) were identified as ovules whose growth had been arrested before anthesis or soon afterwards, medium-size motes (1–3 mm wide, 3–5 mm long) as those whose growth had been arrested up to 10 days post-anthesis, and large motes (3–5 mm wide, 5–8 mm long) as those which had stopped growing about 20 days post-anthesis. Microscopic examination of lint-contaminating fragments showed that they derive mainly from medium-size motes and partly from mature seed coats. Reducing the number of medium-size motes by breeding can, therefore, improve the lint quality of ISHs of cotton.
Phytohormones are important intracellular components in controlling plant growth and development. By employing the differential display method, we have identified several genes which are upregulated by cytokinins and downregulated by abscisic acid in detached lupin cytoledons. One of the genes encodes the ribosomal protein S14 (rps14). The plant gene is highly homologous to rps14 genes from mammalian organisms, rps14 exhibits additional novel features: its mRNA level is developmentally expressed, and only detectable in young tissue. In addition, the steady-state mRNA level is high in dark-adapted lupin cotyledons and strongly down-regulated by light. These data suggest that rps14 might play a role in coupling translational processes to endogenous (developmental and hormonal) and exogenous (light) regulatory processes during early stages of plant development.
Abstract: Genome size was determined in thirty Austrian species of Sphagnum, using Feulgen absorbance photometry conducted on a video-based image analysis system (CIRES), and for comparison on a scanning cytophotometer (Leitz MPV II) with strongly correlated results. Pisum sativum (1C = 4.42pg DNA) was used for internal standardization. Between species, two levels of ploidy, haploid and diploid, could be unambiguously identified (although this identification remains, strictly speaking, hypothetical, as long as exact parallel chromosome counts are not available). Twenty-six haploid species yielded values from 0.392 pg to 0.506 pg DNA (1C), and four diploid species (including two varieties of S. palustre) from 0.814 pg to 0.952 pg. The average ratio between levels was 1:2.049. Variation between species within sections was lower than between sections. In some cases significant differences between accessions of one species were found. The genome size of Sphagnum palustre presented here strongly deviates from one estimate of this species in the literature.
Cyanobacteria are oxygenic phototrophic prokaryotes and are considered to be the ancestors of chloroplasts. Their photosynthetic machinery is functionally equivalent in terms of primary photochemistry and photosynthetic electron transport. Fluorescence measurements and other techniques indicate that cyanobacteria, like plants, are capable of redirecting pathways of excitation energy transfer from light harvesting antennae to both photosystems. Cyanobacterial cells can reach two energetically different states, which are defined as "State 1" (obtained after preferential excitation of photosystem I) and "State 2" (preferential excitation of photosystem II). These states can be distinguished by static and time resolved fluorescence techniques. One of the most important conclusions reached so far is that the presence of both photosystems, as well as certain antenna components, are necessary for State transitions to occur. Spectroscopic evidence suggests that changes in the coupling state of the light harvesting antenna complexes (the phycobilisomes) to both photosystems occur during state transitions. The finding that the phycobilisome complexes are highly mobile on the surface of the thylakoid membrane (the mode of interaction with the thylakoid membrane is essentially unknown), has led to the proposal that they are in dynamic equilibrium with both photosystems and regulation of energy transfer is mediated by changes in affinity for either photosystem.
A portable Chl fluorescence imaging system was used to characterise nonuniform Chl fluorescence quenching in Abutilon strictum leaves infected with phloem-localised abutilon mosaic virus. The instrument was used to observe fluorescence emission at intervals during induction transients, and to map nonphotochemical quenching during saturating pulses applied in the course of these transients. Two symptom types were distinguished: yellow vein-associated motifs that showed lower maximum Chl fluorescence than nearby green tissues, but virtually zero nonphotochemical quenching, and vein-defined mosaics (pale green) that initially showed normal maximum Chl fluorescence but strongly impaired nonphotochemical quenching. Mature vein-defined mosaics (yellow to white areas) resembled vein-associated symptoms with zero nonphotochemical quenching. Islands of apparently healthy green tissue enclosed by mosaic symptoms showed slower nonphotochemical quenching than controls. Possible effects of localised carbohydrate accumulation, thought to follow from infection by the phloem-limited virus, on photosynthetic processes as well as the synthesis and stability of chloroplast protein complexes, are discussed in the context of symptom development.
The first descriptions of sex chromosomes in plants, of the continuity of chromosomes during the mitotic cycle and of non-Mendelian inheritance as well as the introduction of UV-mutagenesis to genetic research are landmarks in biological sciences first achieved by scientists working on bryophytes. Haploidy of the tissue facilitates mutant isolation and many developmental moss mutants have been isolated. Early moss development is triggered by auxin, by cytokinin and by light, mainly acting via phytochrome and a blue-light receptor. Due to the simplicity of the plants, development can be pinpointed to the differentiation of a single cell and be analysed in living tissue, making mosses ideal candidates for the analysis of development in an integrated approach of cell and molecular biology. Molecular genetic techniques have been applied mainly to Physcomitrella patens (Hedw.) B.S.G., where efficient protocols for transformation of nuclear DNA have been established and several nuclear, chloroplast and mitochondrial genes have been analysed. These studies reveal that Physcomitrella may be an appropriate model to study plant development in molecular terms. Recently, it has been shown that, in this species, nuclear genes can be targeted very efficiently by homologous recombination, now opening the door to reverse genetics for plant biologists.
Norway spruce (Picea abies Karst.) seeds were frozen and stored for 15 months at + 3, - 25, - 75 or - 196 degrees C. After storage, seeds were germinated for 9-14 days to determine viability and plasma membrane protein composition, H+-ATPase activity and fluidity. The results indicate no significant differences in viability of seed 14 days after germination. Biochemical analyses revealed increased plasma membrane fluidity in 9-day-old Norway spruce seedlings raised from seeds pretreated at - 75 degrees C, and changes in the temperature profile of membrane fluidity in seedlings after pre-treatment of seeds at - 25 degrees C. On the other hand, the same treatments did not result in changes in plasma membrane protein content, protein composition or ATPase activity. There was also no difference in plasma membrane H+-ATPase activity assayed in the presence of different ATP hydrolysis inhibitors. Based on the presented results, and other experimental data, we suggest that during early seedling growth, adaptation of seeds to - 25 and - 75 degrees C freezing and/or storage temperature results in stability of the plasma membrane protein function and composition and increased fluidity or changes in the temperature-dependent fluidity profile of these membranes.
Microsomal membranes of Chlamydomonas reinhardtii possess PPase and V-ATPase activities. By immunogold labelling we have shown that H+-pyrophosphatase (PPase) is localized to membranes of lytic and contractile vacuoles of Chlamydomonas, in which the density of antigen in the latter is much higher. In addition, PPase is conspicuously present in trans cisternae and transpole elements of the Golgi apparatus. Such a distribution for PPase has hitherto not been reported. A positive in situ identification for PPase at the plasma membrane, including the flagellar membrane, was also made, and has also been confirmed by Western blotting and activity measurements on isolated plasma membranes. V-ATPase antisera which cross react with polypeptides of this transport complex from maize roots failed to recognize anything in Western blots of Chlamydomonas microsomal membranes. Thus immunogold labelling for V-ATPase was not possible with Chlamydomonas. On the other hand, surfaces of contractile vacuole membranes as revealed by deep-etching were covered by conspicuous 9-11.5 nm diameter smooth particles which had a central hole. These were very similar to those previously identified by Heuser et al., (1993) as the V-1-head of V-ATPase in Dictyostelium contractile vacuoles. Another type of membrane image, designated "intermediate-sized vesicle", was found associated with the contractile vacuole. It was characterized by densely-packed 6-7.5 nm diameter polygonal particles, which upon rotation analysis showed both 5- and 6-fold symmetries, also with a central hole. These particles are interpreted as representing either PPase complexes or the V-0 body of the V-ATPase in etched fractured membrane surfaces. We have incorporated these findings into a model of contractile vacuole function.
Pyrophosphate serves as an alternative energy donor to ATP for sucrose mobilisation via sucrose synthase, for glycolysis via pyrophosphate: fructose-6-phosphate phosphotransferase, and for tonoplast energisation via the tonoplast proton-pumping pyrophosphatase. This review considers the possible roles of these pyrophosphate-driven reactions. Correlative evidence based on expression patterns, the distribution of proteins and activities in various tissues, and comparisons of the in vitro properties of the enzymes with the in vivo metabolite levels indicates an important role in young growing tissues and in stress conditions including anaerobiosis, but interpretation is complicated by the reversibility of the pyrophosphate-driven reactions and by their duplication by ATP-dependent reactions. The review then considers the evidence emerging from experiments using reversed genetics to alter expression of sucrose synthase, the pyrophosphate: fructose-6-phosphate phosphotransferase, and the tonoplast proton-pumping pyrophosphatase. This approach has revealed that sucrose synthase plays an essential role in sucrose breakdown in potato tubers, and that pyrophosphate: fructose-6-phosphate phosphotransferase catalyses a near-equilibrium reaction with a net flux in the direction of glycolysis. However, it does not support a special role of the latter enzymes in stress responses. Interpretation is complicated by compensation, which can include expression of other members of a gene family, use of alternative pathways, and relaxation of the feed back regulation in response to decreased expression of the enzyme. In an alternative approach, ectopic overexpression of soluble pyrophosphatase from E. coli has been used as a tool to decrease the levels of pyrophosphate in the cytosol. Constitutive overexpression leads to dramatic changes in sucrose and starch synthesis, sink-source relations and plant growth, phloem-specific overexpression of soluble pyrophosphatase leads to an inhibition of phloem transport, leaf mesophyll-specific overexpression leads to a small stimulation of sucrose synthesis, and potato tuber-specific overexpression leads to an inhibition of starch accumulation.
The essential oil content and composition of Salvia fruticosa (Greek sage) plants growing wild in 20 localities scattered on the island of Crete are studied. The results of our analyses have shown a noticeable variation in the essential oil content (ranging from 1.1 up to 5.1 %) and the amount of the four main oil components: 1,8-cineole (22.7-64.2% of total oil), alpha-thujone (1.0-19.2%) beta-thujone (0.9-25.6%) and camphor (0.8-30.3%). Discriminant analysis revealed that the variation pattern of the essential oil content and the amount of the four main oil components is geographically related, following a W --> E direction. Plants grown in Western Crete show a lower essential oil content and their oils are characterised by the predominance of 1,8-cineole. On the other hand, those collected from Eastern Crete exhibit higher values in essential oil content and their oils, besides 1,8-cineole, are rich in alpha- and beta-thujone or camphor. Our findings are further discussed in relation to literature data.
The mechanical properties of isolated cuticles of leaves (Yucca aloifolia, Clusia fluminensis, Nerium oleander, Hedera helix) and one fruit (Lycopersicon esculentum) were investigated by means of a tensile test. Samples of the leaves and the fruit were cut to identical size (12.5 x 50 mm) and the cuticles were enzymatically isolated, cleaned, and air dried. The morphology of the isolated cuticular membranes (CM) was investigated by scanning electron microscopy (SEM) and showed considerable differences. The thickness of the CM was determined by a digital image analysis system and ranged between 2.4 and 13.4 mu m. The CM were subjected to a tensile test and the results are presented as stress-strain diagrams. From the latter, Young's moduli were calculated, a measure for the stiffness which allows the direct comparison of different materials. The obtained values ranged between 0.1 and 1.3 GPa. Hydration of CM caused a decrease of Young's moduli of about 35-50%. A possible role of the cuticle as a factor for the stabilization of plant organs is discussed.
Little is known about the mode of transmission of chloroplasts in ferns, despite the importance of such knowledge for molecular phylogenetic and biosystematic studies. Andersson-Kotto (1930, 1931) inferred from crossing experiments that chloroplasts are inherited biparentally in Asplenium scolopendrium L. Here we present evidence from artificial hybridisation that demonstrates maternal inheritance of chloroplast DNA in the genus Asplenium (Aspleniaceae, Pteridophyta) using length variation in a non-coding spacer (trnL(UAA)-trnF(GAA)) in the chloroplast DNA.
Abstract: Recent evidence suggests that the production and translocation of polyols will influence the phloem mobility of B in higher plants. The patterns of B distribution in plants, the procedures used to determine plant B status and the approaches used to manage B fertilization are all fundamentally affected by phloem B mobility. Detailed information on the occurrence of polyols in various species is unavailable and hence the extent of B mobility cannot be adequately predicted. Here, the phloem mobility of B has been tested in a number of plants producing polyols. Two approaches have been used, the B concentration gradient along a shoot and foliar 10B labelling. Results indicate that B exhibits significant phloem mobility in the species that produce polyols, but the extent of B retranslocation varies between species even within genera.
The involvement of kinases in heat stress signaling in tomato cells was studied by in gel kinase assays using myelin basic protein as substrate, and by in vitro phosphorylation assays in Mono Q fractions of tomato cell lysates.A kinase with an apparent molecular mass of approximately 50 kDa is rapidly deactivated upon heat stress as judged from in gel kinase assays. Cycloheximide treatment increases kinase activity, but concomitant heat treatment abolishes cycloheximide-induced activation. Kinase activity from untreated cells was recovered at about 130 and 250 mM NaCl from Mono Q columns.
