Selection for mutants with low nitrate uptake ability in rice (Oryza sativa)

Screening for mutants deficient in the high affinity system of nitrate uptake was performed using mutagenized M₂ population of rice ( Oryza sativa , cv. Nipponbare or Kinmaze). For selecting mutants, M₂ seedlings were transferred individually to 10 ml solution containing 250 μ M potassium nitrate and 500 μ M calcium sulphate at 20 or 28°C. After 6 or 24 h, nitrate concentration of the solution was determined with a nitrate selective electrode and the seedlings showing impaired nitrate uptake were selected as nitrate uptake deficient variants. Of 74 variants, three were confirmed to be mutants with low nitrate uptake ability in the M₃ generation. Potassium uptake ability also decreased in the mutants. Three mutants were divided into two groups based on the analysis of nitrate reductase (NR, EC 1.6.6.1) activity and chlorate resistance. Two, NUE13 and NUE36 , had a lower level of NR activity than the original cultivar and were not resistant to chlorate, while the seedlings of NUE50 had the same level of NR activity as the original cultivar and were more resistant to chlorate than the original cultivar. All mutants were resistant to cesium, a toxic ion analogue for potassium, suggesting that the decreased levels of both nitrate and potassium uptake were coupled to the change of plasma membrane H⁺-ATPase activity.     

Three-year measurement of methane emission from an Indonesian paddy field

Yearly and seasonal (rainy and dry seasons) variations of CH₄ emission from a Sumatra paddy field were measured for 3 years. The mean CH₄ emission rates during the growth period were in the range of 16.0–26.1 mg CH₄ m^-2 h^-1 for the chemical fertilizer plots and 23.3–34.9 mg CH₄ m^-2 h^-1 for the plots with rice straw application, respectively. The increase in the amounts of CH₄ emission by rice straw application were from 1.3 to 1.6 times. There was no significant difference in the mean CH₄ emission rates between rainy and dry seasons.Total amounts of CH₄ emitted during the period of rice growth were in the ranges of 29.5–48.2 and 43.0–64.6 g CH₄ m^-2 for the plots applied with chemical fertilizer and those with rice straw application, respectively. Nearly the same amounts of CH₄ were emitted in the first and second half of the growth period, irrespective of rice straw application.     

Intracellular magnetophoresis of amyloplasts and induction of root curvature

High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, (H²/2), was about 10⁹ Oe² · cm^–1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 ± 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 ± 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.Abbreviations HGMF high-gradient magnetic field - emu electromagnetic units - Oe Oersted We thank Dr. John Kiss, Miami University, Ohio for providing the Arabidopsis seeds. This work was supported by NASA grant NAGW-3656     

Use of low temperature sem to locate free water in frozen,hydrated seed tissues of Glycine max (Leguminosae)

Low temperature field emission electron microscopy was used to determine the location of free water in soybean seeds. Frozen, hydrated soybean seeds were fractured, the water etched from the fractured surface, and then part of the etched surface was refractured. The resulting surface, which contained a freeze-fractured face as well as a freeze-etched face was coated with platinum and viewed on the cryostage of a low temperature field emission electron microscope. Two surfaces could be viewed simultaneously to determine the location of water in the seed tissue. Viewing the fractured surface gave an indication of the extent of hydration of the tissue. Viewing the etched surface detailed the macro- and microanatomy of the tissue. Viewing the intersection between the fractured and etched surfaces allowed observation of the environment of partially etched cells and organelles. The technique avoids artifacts associated with chemical fixation, dehydration, and critical-point drying, procedures that affect the water content of the seed. The technique does not affect the degree of hydration of the seed and can be used to localize water in the inter- and intracellular environment of the seed. This technique could find wide application in studies of water relationships of seeds during development, maturation, and imbibition.     

水稻高脯氨酸愈伤组织变异体盐胁迫下氨基酸和蛋白质组分的变化

游离氨基酸组分分析表明,水稻培养细胞中谷氨酸和丙氨酸含量很高,占氨基酸总量的４０％。高脯氨酸愈伤组织变异体总游离氨基酸含量比原型高４５．５％,其中脯氨酸增加最多,其次是雨氨酸和谷氨酸。当ＮａＣｌ１００ｍｍｏｌ／Ｌ处理时变异体和原型的总氨基酸都增加,而变异体的增量约为原型增量的３倍。蛋白水解氨基酸组分中变异体和原型各氨基酸的相对含量无大差异。蛋白质双向电泳表明,高脯氨酸变异体的蛋白组分发生变化,明显比原型多４个蛋白点。在ＮａＣｌ１００ｍｍｏｌ／Ｌ处理下原型亦产生５３．３ｋＤ蛋白,变异体中该蛋白的含量变得更多。盐胁迫下变异体和原型的蛋白质组分变化的差异十分显著,主要表现在蛋白质等电点的变化不同。     

Regressive development in neuronal structure during song learning in birds

We investigated the development of spiny neurons in the lateral magnocellular nucleus of the anterior neostriatum before, during, and after song learning in male zebra finches (Taeniopygia guttata). The frequency of dendritic spines, dendritic field size, and branching characteristics were quantified at different ages in Golgi-stained tissue using a three-dimensional computerized tracing system. During development, overall spine frequencies increase between 3 and 5 weeks and decrease thereafter. In particular, spine frequencies of middle segments decrease significantly by 14% between 5 and 7 weeks posthatching (p = 0.017). A further reduction of 48% occurs between 7 weeks and adulthood (p < 0.001), resulting in a spine reduction of 56% on middle segments between 35 days of age and adulthood. In addition to the reduction of spine frequencies, we find regressive events also on some of the neuronal parameters that we have quantified. In general, dendrites of adult animals terminate closer to the cell body than those of 7-, 5-, or 3-week-old birds. Whereas no changes in segment length of first- and second-order dendrites have been identified, third-order dendrites end 19% closer to the cell body in adults than in younger birds (p < 0.024). Second-order dendrites in adult animals branch less frequently than in 3-week-old animals (35%, p = 0.017). There is also a trend of a smaller number of tertiary branches in adulthood compared with 3-week-old birds (41%, p = 0.060). The morphological changes may be related to the function of this nucleus and the sensitive phase for song acquisition. © 1995 John Wiley & Sons, Inc.     

锰对作业工人血液流变学的影响及清栓酶的疗效观察

本文对１０３例锰作业工人测定了血液流变学中的七项指标,结果表明：全血粘度（高切、低切）、血浆粘度、红细胞压积、纤维蛋白原、红细胞电泳、血小板粘附、血沉等项指标,均明显高于正常对照组（Ｐ＜０．０１）,证实锰作业工人普遍存在高粘滞血症,为临床治疗锰中毒开辟新的途径提供了依据。对其中的５２例锰中毒（包括症状较重的观察对象）,用清栓酶治疗后,复查其七项指标与治疗前比较,均有明显下降（Ｐ＜０．０１）,其症状与体征得以改善,进一步说明清栓酶是治疗锰中毒的理想药物之一。     

Impact of grazing on vegetation dynamics in former ricefields

Abstract. In the Rhône delta, Juncus gerardi and Scirpus maritimus are often the dominant species in abandoned rice fields which are artificially flooded in early spring to improve forage production. Under these conditions they occur either in mixed communities, or form monospecific stands. Monitoring the vegetation dynamics in quadrats located in six abandoned rice fields artificially flooded from November to April confirmed the important role of grazing. In ungrazed plots, communities dominated by Scirpus maritimus mixed with Juncus gerardi developed fast. After 42 months of management Scirpus maritimus had established in nearly all quadrats and continued to expand, whereas Juncus gerardi had started to decline. In grazed plots Juncus gerardi alone dominated and continued to increase in cover up to the 42nd month. Scirpus maritimus established at low densities mainly in quadrats where Juncus gerardi was initially absent. Introduction of seeds of Scirpus maritimus in communities of Juncus gerardi under controlled conditions demonstrated the existence of the phenomenon of preemption. The increase in cover of Juncus gerardi suggests that the preemption of Juncus gerardi over Scirpus maritimus plays a more pronounced role in the field in the presence of grazing.     

Magnetic-field flux density and spectral characteristics of motor-driven personal appliances

Flux density and spectral measurements were carried out on magnetic fields generated by several types of motor-driven personal appliances used near the body. Among the units tested were several for which the average flux densities, as determined at the surfaces of the appliance, exceeded 0.4 mT. Time-rates-of-change (dB/dt) for several units exceeded 1000 T/s, and several units exhibited high-frequency components in the low-MHz range. Use of such appliances, although normally of short duration, can represent exposure to magnetic fields of relatively high flux density, which may also have high-frequency components. Compared to other household and commercial sources of magnetic fields, those generated by certain motor-driven personal appliances may represent a significant contribution to time-weighted average exposure and may represent an important source of local induced currents in the body. Furthermore, high-frequency transients that represent only a minor contribution to time-weighted average exposure may generate significant instantaneous induced currents. © 1994 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.