Nitrate Assimilation in Rice Grown under Lowland Conditions

Pattern and extent to which the main shoot of rice (Oryza sativa L.) cv. Pusa 33 assimilates NO₃^- when grown under lowland conditions was determined in a field study. The in vivo NR (nitrate reductase) activity is low as compared to the value in other cereals grown under aerobic soil conditions. The leaf blades had higher NR activity (g fr. wt.)^-1 than the sheaths and stem. Calculation of total NO₃^- (mol) reduced in the main shoot, obtained by integrating the in vivo NR assay values per plant part and per day over the duration for which the various plant parts on the main shoot remained metabolically active, showed that out of the total reduced N at harvest, 16.6% was assimilated via the enzyme nitrate reductase. In the leaf sheaths and stem the NO₃^- was reduced to slightly over 50% of the total NO₃^- that was reduced in the main shoot. The rest of the amount was reduced in the leaf blades.     

Oxygen Diffusion from the Roots of Rice Grown under Non-waterlogged Conditions

Three rice varieties, cv. Norin 36, cv. Norin 37 and cv. Yubae, were grown in a loam with a 20 cm water-table which gave aerobic conditions to a depth of not less than 15 to 17 cm. Under these conditions Norin 36 grew more vigorously and tillered more frequently than the other two varieties. The rates of oxygen diffusion at 23°C from roots up to 11 cm in length were however appreciably lower for Norin 36 (4.3 × 10^?8g · cm^?2 of root surface · min^?1) than for Norin 37 or Yubae (c. 7.8 × 10^?8g). A considerable increase (up to 200 %) in the oxygen diffusion rate (ODR) from the roots occurred if they were cooled to 3°C, and at this temperature differences in ODR between the varieties were not significant. For a purely physical system, because of the decrease in the diffusion coefficient of oxygen in water, and, the increase in oxygen solubility, a drop of c. 20 % in ODR should accompany the above 20°C drop in temperature. A 16 % drop was recorded for artificial ‘roots’ under these conditions. It was concluded that respiratory activity at the higher temperature must have been responsible for the low readings and intervarietal differences observed at 23°C. By increasing the 3°C values by 25 % a mean value of 14.2 × 10^?8g · cm^?2 of root surface · min^?1 was recorded for the three varieties, being the probable ODR at 23°C in the absence of a respiratory factor. Calculations show that respiratory activity removed enough oxygen to reduce the ODR for Norin 36 by more than 9 × 10^?8g, and for Norin 37 and Yubae by c. 6.7 × 10^?8g · cm^?2 of root surface · min^?1. Anatomical investigations showed that cortical breakdown was always extensive at 4 to 4.5 cm from the apex of the roots. In some cases however breakdown had not occurred in the basal segment of the root. No opinion could be formed as to whether differences in the amount of cortical breakdown between the varieties might have occasioned the respiratory differences observed. An interesting feature of the root anatomy was the failure of breakdown in those regions of the roots through which lateral roots emerged.     

Light-controlled Leaf Expansion in Peas Grown under Different Light Conditions

Several photosystems control leaf expansion in Alaska peas (Pisum sativum). Phytochrome is known to control expansion in dark-grown peas. But plants exposed briefly to red light are insensitive to phytochrome, an insensitivity that is itself phytochrome-produced. Leaf expansion in these plants is promoted by 440 or 630 nm of light (probably mediated by protochlorophyll). Plants grown in white fluorescent light required simultaneous exposure to high intensity blue and yellow light for promotion of leaf expansion. Since these results parallel studies on light-controlled inhibition of stem elongation, shoot growth as a whole is coordinated by these photosystems. Such coordination might be a mechanism of plant competition for light.     

The Influence of Nitroxyl on Escherichia coli Cells Grown under Carbonyl Stress Conditions

Applied Biochemistry and Microbiology - Carbonyl stress is an increase in the amount of monosaccharides and active dicarbonyl compounds (glyoxal and methylglyoxal (MG)), which leads to raising the...     

Changes in Mineral Content of Eucalyptus marginata and E. calophylla Grown under Controlled Conditions and Inoculated with Phytophthora cinnamomi

Mineral concentrations in infected roots and shoots were compared with similar material, but pathogen free, for the susceptible Eucalyptus marginata and the field resistant E. calophylla. All plants were mycorrhiza-free, grown under controlled conditions and inoculated with an axenic suspension of zoospores of Phytophthora cinnamomi. Plant material was ashed 30 days after inoculation and analyzed in an external proton beam using PIXE and nuclear reaction analyis to detect differences in mineral concentrations. The mineral content of infected roots of E. marginata was below that of the uninfected roots for all elements detected except chlorine, chromium and rubidium. The reductions were significant for calcium and copper. No such reduction was found, in E. calophylla roots, but some changes were detected. Shoot: root ratios of E. marginata showed significant differences associated with infection in phosphorus, calcium, copper and zinc. Relatively large differences were also recorded for sulphur chlorine and potassium. Shoot: root ratios of infected E. calophylla showed fewer differences but contained only half the concentrations of sulphur and potassium present in the controls. The reduced mineral concentrations reflect the failure in conduction of water and minerals through the infected and susceptible root system.     

Light-controlled Stem Elongation in Pea Seedlings Grown under Varied Light Conditions

There appears to be an orderly transition from one photosensitive state to another in light-controlled stem elongation in the garden pea, Pisum sativum L. cv. Alaska. Stem elongation in dark-grown plants is known to be phytochrome-controlled. However, seedlings are insensitive to phytochrome after a red light pretreatment. An action spectrum for inhibition in these seedlings has peaks at 440 and 620 nm. Protochlorophyll is suggested as the photoreceptor. If these red pretreated seedlings are further exposed to white light, sensitivity to 440 to 620 nm light is lost. Promotion by blue-green light is the only photoresponse shown by these seedlings. Inhibition of completely white light-grown seedlings required simultaneous exposure to high intensity blue light and 600 nm light.     

Lectin in Vegetative Tissues of Adult Barley Plants Grown under Field Conditions

A study of the distribution of lectins over different vegetative tissues of barley (Hordeum vulgare L.) plants, which were grown under normal crop conditions, indicated that lectin occurs in roots, leaves, and developing ears. Isolation and characterization of both root and leaf lectins led to the conclusions (a) that they are indistinguishable from the embryo lectin and (b) that the total lectin content of these vegetative organs is many times higher than that of the embryo. Finally, in vivo labeling experiments demonstrated that the lectin is synthesized de novo in roots and leaves.     

Pyruvate Kinase Activity of Wheat Plants Grown under Potassium Deficient Conditions

The activity of pyruvate kinase was determined in the first leaves of wheat plants grown under K⁺-deficient conditions. An enhancement of the enzyme activity compared with the normal plants was found to start from eighth day of growth, and about 4-fold increase in the enzyme activity was observed in 14-day wheat leaves. The addition of K₂SO₄ to the nutrient solution given to the K⁺-deficient plants at tenth day resulted in the restoration of the enzyme activity to the normal level after 3 days. The levels of K⁺ as well as carbohydrates and chlorophyll were found to return normal over the same period. These findings are discussed in relation to the metabolic pattern of plants at the early stages of K⁺-deficiency.     

Carbon- and Nitrogen-to-Volume Ratios of Bacterioplankton Grown under Different Nutritional Conditions

Carbon- and nitrogen-to-volume (C/V and N/V) ratios were determined for freshwater bacterial assemblages grown in lake water filtrate or in water enriched with nutrients (aqueous extract of lake seston, glucose, arginine, phosphate, or ammonium). Biovolume was measured by epifluorescence microphotography, and carbon and nitrogen biomasses were measured with a CHN analyzer. Despite large variations of nutritional conditions (i.e., the composition and concentration of the dissolved organic carbon) and different mean cell sizes of the bacterial assemblage (0.17 to 1.8 μm³ per cell), the C/V, N/V, and carbon-to-nitrogen weight ratios varied little (C/V ratio, 0.14 pg of C per μm³ [standard deviation, 0.057; n = 15]; N/V ratio, 0.027 pg of N per μm³ [standard deviation; 0.011, n = 15]; carbon-to-nitrogen weight ratio, 5.6 [standard deviation, 2.2, n = 15]). An average C/V ratio of 0.12 pg of C per μm³ that was derived from natural and cultured bacterial assemblages is proposed as an appropriate conversion factor for estimation of the biomass of freshwater bacteria.     

The Activity of the Root Vacuolar H+-Pyrophosphatase in Rye Plants Grown under Conditions Deficient in Mineral Nutrients

Compared to rye plants grown under normal conditions of mineralnutrients, those grown under deficient conditions of mineralnutrients were shown to have a high potential activity of theroot vacuolar H⁺-pyrophos-phatase (H⁺-PPiase), with a low levelof PP₁ in roots. Im-munoblot analysis suggested a qualitativechange of the enzyme. (Received April 3, 1998; )     

猕猴桃(Actinidia Lindl.)叶片与果实维生素C含量的相关性研究

以猕猴桃属中华猕猴桃（Actinidia chinensis）32个品种和1个种间杂交后代群体为研究对象,对猕猴桃属植物叶片与果实维生素C含量的相关性进行了研究。结果表明,在中华猕猴桃种内水平上,幼果与成熟果实的果肉维生素C含量间存在极显著的正相关关系;在种间杂交后代群体中成熟叶片和成熟果实的维生素C含量存在极显著正相关关系,为利用早期相关性状开展猕猴桃育种的可行性提供了理论依据。此外,对15个常见中华猕猴桃品种的果实维生素C含量进行了多重比较,为人工杂交时的亲本选择提供了依据。     

脱落酸与镉处理对辣椒果实中辣椒素和维生素C含量的影响

本文以湘研15号辣椒为材料,研究了脱落酸（ABA）与镉（Cd^2＋）在辣椒米实不同发育时期对辣椒素和维生素C含量的影响,并分析了处理后辣椒素、维生素C含量变化与POD活性以及叶片光合特征之间的关系。结果表明：湘研15号辣椒植株经ABA与Cd^2＋处理后果实中辣椒素含量峰值分别比对照提高了80．4％与61．4％,POD活性均显著升高,二者处理后辣椒果实中的辣椒素、POD变化趋势基本一致,处理后叶片光合速率均有下降趋势。ABA处理后果实中维生素C含量在转色期比对照降低12．8％～21．7％,叶片中叶绿素相对值显著增加;Cd^2＋处理后果实中维生素C含量在转色期比对照减少18％～25％,红熟期减少13％-26％,叶片叶绿素相对值在红熟期之前比CK显著降低。     

The Level of Orally Ingested Vitamin C Affected the Expression of Vitamin C Transporters and Vitamin C Accumulation in the Livers of ODS Rats

We investigated the effects of vitamin C administration on vitamin C-specific transporters in ODS/ShiJcl-od/od rat livers. The vitamin C-specific transporter levels increased in the livers of the rats not administered vitamin C and decreased in the livers of those administered vitamin C at 100 mg/d, indicating that these transporter levels can be influenced by the amount of vitamin C administered.     

The Proteome and Lipidome of Synechocystis sp. PCC 6803 Cells Grown under Light-Activated Heterotrophic Conditions

Cyanobacteria are photoautotrophic prokaryotes with a plant-like photosynthetic machinery. Because of their short generation times, the ease of their genetic manipulation, and the limited size of their genome and proteome, cyanobacteria are popular model organisms for photosynthetic research. Although the principal mechanisms of photosynthesis are well-known, much less is known about the biogenesis of the thylakoid membrane, hosting the components of the photosynthetic, and respiratory electron transport chain in cyanobacteria. Here we present a detailed proteome analysis of the important model and host organism Synechocystis sp. PCC 6803 under light-activated heterotrophic growth conditions. Because of the mechanistic importance and severe changes in thylakoid membrane morphology under light-activated heterotrophic growth conditions, a focus was put on the analysis of the membrane proteome, which was supported by a targeted lipidome analysis. In total, 1528 proteins (24.5% membrane integral) were identified in our analysis. For 641 of these proteins quantitative information was obtained by spectral counting. Prominent changes were observed for proteins associated with oxidative stress response and protein folding. Because of the heterotrophic growth conditions, also proteins involved in carbon metabolism and C/N-balance were severely affected. Although intracellular thylakoid membranes were significantly reduced, only minor changes were observed in their protein composition. The increased proportion of the membrane-stabilizing sulfoqinovosyl diacyl lipids found in the lipidome analysis, as well as the increased content of lipids with more saturated acyl chains, are clear indications for a coordinated synthesis of proteins and lipids, resulting in stabilization of intracellular thylakoid membranes under stress conditions.Cyanobacteria are a widespread group of photoautotrophic organisms, which significantly contribute to global carbon fixation. Cyanobacteria and plant chloroplasts share a common ancestor, and thus cyanobacteria have a plant-like photosynthetic metabolism (1, 2). Consequently, they are established model organisms for studies, aiming to elucidate photosynthetic mechanisms. Both, chloroplasts and cyanobacteria, have two internal membrane systems, that is, the inner envelope and the cytoplasmic membrane (CM)¹ in chloroplasts or cyanobacteria, respectively, as well as the thylakoid membrane (TM) system, which harbors the complexes of the photosynthetic electron transfer chain (3, 4). The photosynthetic electron transfer chain typically consists of the three membrane integral protein complexes: photosystem I (PS I), photosystem II (PS II), and the cytochrome b₆f complex, as well as of the soluble electron carriers plastoquinone and plastocyanin (5, 6). In the end, reduction equivalents are produced, which are used for CO₂-fixation (7). However, besides the ability to grow photoautotrophically, some cyanobacteria are also capable to grow photoheterotrophically, where they use reduced organic compounds as carbon source, or even completely heterotrophically by using reduced organic compounds as carbon and energy source (8). The well-characterized cyanobacterium Synechocystis sp. PCC 6803 (9) (hereafter: Synechocystis) can grow in darkness under light-activated heterotrophic growth (LAHG) conditions by using glucose as carbon and energy source (10). Enhanced sugar catabolism in LAHG cultures is, for example, reflected by increased activities of enzymes involved in sugar catabolism, such as glucokinase and pyruvate kinase (11). The effects of LAHG conditions on the abundance of soluble Synechocystis proteins have been analyzed previously, although only 23 proteins with a significantly altered expression level (LAHG versus autotrophic growth) have been described. This study has e.g. indicated that under LAHG conditions glucose is mainly degraded by the oxidative pentose phosphate (OPP) pathway (12). The histidine kinase 8 (Hik8) as well as the sigma factor E (SigE), regulating the expression of sugar-degrading genes, were shown to be essential for LAHG (13, 14).Although readjustments of the cellular energy metabolism are important, the impact on the cellular membrane architecture is more striking. The ability of Synechocystis to grow under LAHG conditions has been used recently to analyze TM formation within cyanobacterial cells (15). Although dark-adapted Synechocystis cells have no active PS II complex, complete photosynthetic activity is regained within 24 h after transferring dark-adapted cells into the light. Furthermore, reappearance of photosynthetic electron transfer processes is coupled to the formation of internal TMs. However, it is essentially still completely enigmatic how the formation of internal TM is controlled, although some proteins have been suggested to be involved. These proteins include the vesicle inducing protein in plastids 1 (Vipp1), DnaK proteins, a prohibitin-like protein, as well as the YidC protein, a membrane protein integrase (16–19). Nevertheless, although some proteins have been suggested to be more directly involved in TM formation, the stability of the TM is also globally affected indirectly by pathways, which control the biogenesis of lipids and/or cofactors, and mutants defective in synthesis of chlorophyll or of the membrane lipid phosphatidylglycerol (PG) have severely reduced TM systems (20, 21).In the present work, we combined prefractioning of Synechocystis cellular membranes with a global proteome and lipidome analysis, to shift the analytical focus toward the rearrangement of the internal thylakoid membrane system observed in Synechocystis cells under LAHG conditions, with a significantly larger coverage of the proteome than in former studies. Furthermore, also the effect on Synechocystis lipids was analyzed in a targeted mass spectrometric approach, revealing significant adjustment of fatty acid saturation in response to the LAHG conditions.     

Gas Exchange Characteristics in Rice Leaves Grown under the Conditions of Physiologically Low Temperature and Irradiance

The photosynthetic rate measured at 20°C was higher in ricegrown under 20/18°C day/night temperature and 350 µmoIquanta m^–2s^–1 than in rice grown under 25/20°Cand 1,000 µmol quanta m^–2s^–1, whereas therewas no difference in the photosynthetic rate measured at 25°Cbetween rice grown in these two ways. This difference was suggestedto be caused by an enhanced ribulose-l,5-bis-phosphate-regenerationcapacity in the low-temperature/ir-radiance-grown rice. (Received July 14, 1998; Accepted September 25, 1998)     

Structural Complexity of Non-acid Glycosphingolipids in Human Embryonic Stem Cells Grown under Feeder-free Conditions

Due to their pluripotency and growth capability, there are great expectations for human embryonic stem cells, both as a resource for functional studies of early human development and as a renewable source of cells for use in regenerative medicine and transplantation. However, to bring human embryonic stem cells into clinical applications, their cell surface antigen expression and its chemical structural complexity have to be defined. In the present study, total non-acid glycosphingolipid fractions were isolated from two human embryonic stem cell lines (SA121 and SA181) originating from leftover in vitro fertilized human embryos, using large amounts of starting material (1 × 10⁹ cells/cell line). The total non-acid glycosphingolipid fractions were characterized by antibody and lectin binding, mass spectrometry, and proton NMR. In addition to the globo-series and type 1 core chain glycosphingolipids previously described in human embryonic stem cells, a number of type 2 core chain glycosphingolipids (neo-lactotetraosylceramide, the H type 2 pentaosylceramide, the Le^x pentaosylceramide, and the Le^y hexaosylceramide) were identified as well as the blood group A type 1 hexaosylceramide. Finally, the mono-, di-, and triglycosylceramides were characterized as galactosylceramide, glucosylceramide, lactosylceramide, galabiaosylceramide, globotriaosylceramide, and lactotriaosylceramide. Thus, the glycan diversity of human embryonic stem cells, including cell surface immune determinants, is more complex than previously appreciated.