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Insights into the physiology of nitrogen (N) uptake help us to understand the adaption of boreal coniferous forests to their environment. We compared fluxes of nitrate and ammonium in white spruce [ Picea glauca (Moench) Voss] roots, measured using a non-invasive microelectrode ion flux measurement system (MIFE), and transcript abundance of ammonium and nitrate transporter genes in roots, determined by real time PCR. Seedlings were pretreated with water, or 50 μM or 1,500 μM NHNO + 200 μM CaSO + 25 μM KHPO. Measurements were made on seedling roots 0-5, 5-10, 10-20 and 20-30 mm from the root tip. As ammonium and nitrate transporter family members in spruce are still uncharacterized, primers for real time PCR were designed to cover one family with each set of primers (AMT1, AMT2, NRT1, NRT2). The expression patterns obtained by real time PCR differed significantly among transporter family, treatments and root segments. Expression of AMT1 did not show a relationship with distance from the root tip, but the expression of AMT2 was generally greater 0-5 mm from the root tip than in segments farther from the tip. Expression of NRT1 was greatest 10-30 mm from the root tip, while expression of NRT2 was greatest 5-10 mm from the tip in all treatments, except the 1,500 μM NHNO treatment. MIFE measurements showed the highest N uptake and proton efflux near the root tip and declining fluxes with increased distance from the root tip in the 50 μM N treatment. Significant net ammonium efflux was observed from some root segments in the 1,500 μM N treatment. Transporter gene expression and ion fluxes were not correlated. Though the measured net fluxes of ammonium were greater than the measured net fluxes of nitrate, the nitrate transporters were, in general, more highly expressed than the ammonium transporters. [ABSTRACT FROM AUTHOR]

The presented data set comprises a series of field experiments conducted in the period from 1993 to 1999 at the International Rice Research Institute, Philippines. Methane emissions from different rice cultivars were compared during nine seasons using an automated measuring system. The list of cultivars in this experiment consists of high yielding semi-dwarf cultivars (IR72, IR52, PSBRc20, PSBRc14), traditional tall cultivars (Dular, Intan), hybrid (Magat) as well as plant types with high yield potential that are currently under development (IR65597, IR65600). Seasonal averages in emission rates ranged from 20 to 89 mg CH4 m−2 d−1 under inorganic fertilization and from 129 to 413 mg CH4 m−2 d−1 following organic amendments. However, differences were generally small within a given season and stayed below significance level for the bulk of the inter-cultivar comparisons. Each experiment included IR72 to allow computation of cultivar-specific emission indices in relation to this reference. These indices ranged from 0.57 (PSBRc14) to 1.8 (Magat), but did not reveal consistent ranking for rice genotypes. The similarity in methane emissions was corroborated in a field screening of 19 cultivars using dissolved CH4 in soil solution as a proxy for relative emission rates. Irrespective of cultivars, higher plant density (10*20 cm spacing vs. 20*20 cm spacing of plant hills) stimulated methane production in the soil, but did not result in higher emission rates. This finding was attributed to higher oxygen influx into the soil and subsequent stimulation of methane oxidation when plants hills were more abundant. Over multi-seasonal periods, differences observed between cultivars were inconsistent indicating complex interactions with the environment. These results stress the need for more mechanistic understanding on cultivar effects to exploit the mitigation potential of cultivar selection in rice systems. [ABSTRACT FROM AUTHOR]

Analyzes the sulphate uptake and xylem loading in young pea seedlings. Interruption of the phloem transport by steam girding of the stem or root; Addition of sucrose to the nutrient solution; Significance of cotyledons for seedling development.

Summarizes emission results of biogenic volatile organic compounds (BVOC) achieved within the frame of the national German Tropospheric Research Programme (TFS) between 1997 and 2000. Use of measured BVOC emission rates in the determination of daily and seasonal variation of BVOC emission; BVOC dependence on important meteorological and plant physiological parameters; BVOC emission inventory of Germany.

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Of the total methane (CH4) emitted from a rice field during the growing season 60–90% is emitted through the rice plants. We determined the methane transport capacity (MTC) of rice plants at different physiological growth stages using an automatic measuring system under greenhouse conditions. A total of 12 cultivars (10 inbred varieties and 2 hybrids) were studied in sets of two experiments and was distinguished into three groups according to the patterns of MTC development. MTC is generally increasing from seedling stage to panicle initiation (PI), but differs in the development from PI to maturity. While the hybrid showed a gradual increase in MTC, the inbred cultivars showed either minor changes in MTC or a drastic decrease from flowering to maturity. Among tall cultivars, Dular showed the highest MTC, followed by B40; the lowest MTC was found in Intan. High-yielding dwarf cultivars showed MTC in the descending order of IR72 > IR52 > IR64 > PSBRc 20. New plant type cultivars showed very low MTC with IR65600 exhibiting the smallest MTC at PI, flowering, and maturity. Hybrids (Magat and APHR 2) showed the largest MTC that continued to increased with plant growth. The MTC patterns were attributed to growth parameters and the development of morphological characteristics of the aerenchyma. These results suggest that in tall, dwarf, and NPT cultivars, increase in root or aboveground biomass during initial growth determines a corresponding increase in MTC. Once aerenchyma has fully developed, further increase in plant biomass would not influence MTC. However, in the case of hybrids, a positive relationship of MTC with root + shoot biomass (r = 0.672, p ≥ 0.05) and a total plant biomass including grain (r = 0.849, p ≥ 0.01) indicate continuous development of aerenchyma with plant growth, resulting in enhanced MTC. In all cultivars, tiller number, but not height, was linearly related to MTC, indicating that the number of outlets/channels rather than plant size/biomass determines the transport of CH4. These results clearly demonstrate that rice cultivars differ significantly in MTC. Therefore, the use of high-yielding cultivars with low MTC (for example, PSBRc 20, IR65598, and IR65600) could be an economically feasible, environmentally sound, and promising approach to mitigate CH4 emissions from rice fields. [ABSTRACT FROM AUTHOR]

A major portion (60–90%) of the methane (CH4) emitted from rice fields to the atmosphere is transported through the aerenchyma of the rice plants. However, a rapid and accurate method to study the CH4 transport capacity (MTC) of rice plants is not available. We developed a gas sampling and analytical device based on a closed two-compartment chamber technique and analyzed the enrichment of the CH4 mixing ratio inside the shoot compartment of cylindrical cuvettes enclosing individual rice plants under ambient conditions. The computer-controlled analytical system consists of a gas chromatograph (GC) and a pressure-controlled autosampler for eight cuvettes (seven for plants and one for CH4-calibration gas). The system automates closure and opening of plant cuvettes using pneumatic pressure, air sample collection and injection into the GC, and CH4 analysis. It minimizes sources of error during air sampling by continuously mixing headspace air of each cuvette, maintaining pressure and composition of the headspace inside the cuvettes, purging the dead volumes between the sampler induction tube and GC, and running a reference CH4-calibration gas sample in each cycle. Tests showed that the automated system is a useful tool for accurate sampling of headspace air of cylindrical cuvettes enclosing individual rice plants and enables rapid and accurate fully automated analysis of CH4 in the headspace air samples. A linear relationship was obtained between CH4 transported by rice plants of two cultivars (IR72, a high-yielding dwarf, and Dular, a traditional tall cultivar) and concentration of CH4 up to 7,500 ppm used for purging the nutrient culture solution surrounding the roots in the root compartment of the chamber. Further increase in CH4 emission by shoots was not observed at 10,000 ppm CH4 concentration in the root compartment of the chamber. The MTC of IR72 was measured at six development stages; it was lowest at seedling stage, increasing gradually until panicle initiation. There was no further change at flowering, but a marked decrease at maturity was noted. These results suggest that the plants have 45–246% greater potential to transport CH4 than the highest CH4 emission rates reported under field conditions, and plants would not emit CH4 at early growth and at a reduced rate close to ripening. [ABSTRACT FROM AUTHOR]

Methane (CH4) emission rates were recorded automatically using the closed chamber technique in major rice-growing areas of Southeast Asia. The three experimental sites covered different ecosystems of wetland rice--irrigated, rainfed, and deepwater rice--using only mineral fertilizers (for this comparison). In Jakenan (Indonesia), the local water regime in rainfed rice encompassed a gradual increase (wet season) and a gradual decrease (dry season) in floodwater levels. Emission rates accumulated to 52 and 91 kg CH4 ha−1 season−1 corresponding to approximately 40% of emissions from irrigated rice in each season. Distinct drainage periods within the season can drastically reduce CH4 emissions to less than 30 kg CH4 ha−1 season−1 as shown in Los Baños (Philippines). The reduction effect of this water regime as compared with irrigated rice varied from 20% to 80% from season to season. Methane fluxes from deepwater rice in Prachinburi (Thailand) were lower than from irrigated rice but accumulated to equally high seasonal values, i.e., about 99 kg CH4 ha−1 season−1, due to longer seasons and assured periods of flooding. Rice ecosystems with continuous flooding were characterized by anaerobic conditions in the soil. These conditions commonly found in irrigated and deepwater rice favored CH4 emissions. Temporary aeration of flooded rice soils, which is generic in rainfed rice, reduced emission rates due to low CH4 production and high CH4 oxidation. Based on these findings and the global distribution of rice area, irrigated rice accounts globally for 70–80% of CH4 from the global rice area. Rainfed rice (about 15%) and deepwater rice (about 10%) have much lower shares. In turn, irrigated rice represents the most promising target for mitigation strategies. Proper water management could reduce CH4 emission without affecting yields. [ABSTRACT FROM AUTHOR]

The Interregional Research Program on Methane Emissions from Rice Fields established a network of eight measuring stations in five Asian countries. These stations covered different environments and encompassed varying practices in crop management. All stations were equipped with a closed chamber system designed for frequent sampling and long-term measurements of emission rates. Even under identical treatment--e.g., continuous flooding and no organic fertilizers--average emission rates varied from 15 to 200 kg CH4 ha−1 season−1. Low temperatures limited CH4 emissions in temperate and subtropical stations such as northern China and northern India. Differences observed under given climates, (e.g., within the tropics) indicated the importance of soil properties in regulating the CH4 emission potential. However, local variations in crop management superseded the impact of soil- and climate-related factors. This resulted in uniformly high emission rates of about 300 kg CH4 ha−1 season−1 for the irrigated rice stations in the Philippines (Maligaya) and China (Beijing and Hangzhou). The station in northern India (Delhi) was characterized by exceptionally low emission rates of less than 20 kg CH4 ha−1 season−1 under local practice. These findings also suggest opportunities for reducing CH4 emission through a deliberate modification of cultural practice for most irrigated rice fields. [ABSTRACT FROM AUTHOR]

Copyright of Bundesgesundheitsblatt - Gesundheitsforschung - Gesundheitsschutz is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effect of fertilizers on methane emission rates was investigated using an automated closed chamber system in Chinese rice fields (Human Province). Each of three experiments compared two fields treated with a first uniform fertilizer dose and a second fertilizer dose which was different for each of the two fields. The uniform fertilizer doses for both fields in each experiment comprised mineral (experiment 1), organic (experiment 2) and combined mineral plus organic components (experiment 3). In all three experiments the second fertilizer dose comprised organic amendments for field 1 and no organic amendments for field 2. The rate of increase in methane emission with a given amount of organic manure was found to depend on the total amount of organic manure applied. A single dose of organic manure increased the emission rates by factors of 2.7 to 4.1 as compared to fields without organic manure (experiment 1). In rice fields that had already been treated with organic manure, the application of a second dose of organic manure only slightly enhanced the emission rates in experiment 2 by factors of 1.1 to 1.5 and showed no detectable increase in experiment 3. The net reduction achieved by separation of organic and mineral fertilizers was maximized by concentrating the organic amendments in the season with low emission rates, i.e. early rice, and using exclusively mineral fertilizers on late rice when emission rates were generally higher. This distribution pattern, which was not associated with significant yield losses, resulted in an annual methane emission corresponding to only 56% of the methane emitted from fields treated with blended fertilizers. [ABSTRACT FROM AUTHOR]

Determines the methane production capacities of different rice soils derived from inherent and exogenous substrates. Temperature effects on methane production capacities; Enhancement of the methane rates by the acetate amendment; Correlation analyses of methane production.

Cites a study to determine fluxes of methane and nitrous oxide in a three year old seedling. Emission sources of methane and nitrous oxide in the atmosphere; Effect of flooding of soil on the emission of methane and nitrous oxide; Factors responsible for the decline in afflux of gases.

Mature leaves of Ricinus communis fed with SOin the light export labeled sulfate and reduced sulfur compounds by phloem transport. Only 1-2% of the absorbed radiosulfur is exported to the stem within 2-3 h, roughly 12% of S recovered was in reduced form. The composition of phloem translocate moving down the stem toward the root was determined from phloem exudate: 20-40% of the S moved in the form of organic sulfur compounds, however, the bulk of sulfur was transported as inorganic sulfate. The most important organic sulfur compound translocated was glutathione, carrying about 70% of the label present in the organic fraction. In addition, methionine and cysteine were involved in phloem sulfur transport and accounted for roughly 10%. Primarily, the reduced forms of both, glutathione and cysteine are prsent in the siever tubes. [ABSTRACT FROM AUTHOR]

Sulfur reduction in tobacco plants is a light-enhanced process that predominantly takes place in the leaves rather than the roots. The amount of sulfate reduced in mature leaves can exceed their own requirement and enables an export of reduced sulfur, both basipetal toward the roots as well as acropetal toward the growing parts of the stem. Evidence is presented that translocation of reduced sulfur toward the roots occurs in the phloem. TLC and paper chromatography reveal that glutathione is the main transport form of reduced sulfur in tobacco plants; 67-70% of reduced S was confined to glutathione, 27-30% to methionine, and 2-8% to cysteine. [ABSTRACT FROM AUTHOR]

The contribution of influx and efflux of NO3- on NO3- net uptake has been studied in excised mycorrhizae of 18-20 week old beech (Fagus sylvatica L.) trees. Net uptake rates of NO3- followed uniphasic Michaelis-Menten kinetics in the concentration range between 10 MuM and 1.0 mM external NO3-, with an apparent Kmof 88+/-7 MuM, and a Vmax of 110+/-7 nmol g-1 root f.wt. h-1. The relative xylem loading of N, i.e. the portion of NO3- taken up that was loaded into the xylem vessels as NO3- plus reduced N, was constant over the concentration range tested (4.6-7.7%). NO3- influx proceeded linearly with increasing external NO3- supply. When the assumed regulators of net NO3- uptake, i.e. NH4+ or L-glutamate, were applied together with NO3-, net uptake rates of NO3- decreased. This inhibitoryeffect was caused by a reduction of NO3- influx rather than an enhanced efflux. The comparison of the present data with a recent study with non-mycorrhizal beech roots (Kreuzwieser et al., 1997; J. Exp. Bot. 48, 1431-1438) revealed that mycorrhization leads to reduced rates of NO3- net uptake. This effect is caused by reduced influx plus enhanced efflux of NO3- as compared with non-mycorrhizal beech roots. [ABSTRACT FROM AUTHOR]

Sulfur nutrition of plants is largely determined by sulfate uptake of the roots, the allocation of sulfate to the sites of sulfate reduction and assimilation, the reduction of sulfate to sulfide and its assimilation into reduced sulfur-containing amino acids and peptides, and the allocation of reduced sulfur to growing tissues that are unableto fulfill their own demand for reduced sulfur in growth and development. Association of the roots of pedunculate oak (Quercus robur L.) and beech (Fagus sylvatica L.) trees with ectomycorrhizal fungi seemsto interact with these processes of sulfur nutrition in different ways, but the result of these interactions is dependent on both the plant and the fungal partners. Mycorrhizal colonisation of the roots canalter the response of sulfate uptake to sulfate availability in the soil and enhances xylem loading and, hence, xylem transport of sulfate to the leaves. As a consequence, sulfate reduction in the leaves may increase. Simultaneously, sulfate reduction in the roots seems to be stimulated by ectomycorrhizal association. Increased sulfate reduction in the leaves of mycorrhizal trees can result in enhanced phloem transport of reduced sulfur from the leaves to the roots. Different from herbaceous plants, enhanced phloem allocation of reduced sulfur does not negatively affect sulfate uptake by the roots of trees. Theseinteractions between mycorrhizal association and the processes involved in sulfur nutrition are required to provide sufficient amounts ofreduced sulfur for increased protein synthesis that is used for the enhanced growth of trees frequently observed in response to ectomycorrhizal association. [ABSTRACT FROM AUTHOR]