首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 127 毫秒
1.
The effects of benzyladenine (BAP), kinetin (KIN), zeatin (ZEA), isopentenyladenine (2iP), and thidiazuron (TDZ) were studied on in vitro growth of rudimentary embryos of Ilex paraguariensis St. Hil. Heart stage zygotic embryos were removed from seeds of immature, light green fruits and cultured aseptically on quarter-strength Murashige and Skoog medium containing 3% sucrose, 0.65% agar, and supplemented with or without three concentrations of BAP, KIN, ZEA, 2iP, or TDZ. Cultures were incubated in darkness at 27 ± 2°C. Media containing 4.4 × 10−6 m BAP, 4.6 × 10−6 m KIN, or 4.9 × 10−6 m 2iP were totally ineffective in inducing embryo growth after culture for 28 days. However, lower concentrations of these compounds (4.4 × 10−8 m BAP, 4.6 × 10−8 m KIN, 4.5 × 10−8 m ZEA, or 4.9 × 10−8 m 2iP) promoted embryo growth. TDZ at 9.9 × 10−9 m, 9.9 × 10−8 m, or 9.9 × 10−7 m induced embryo growth at similar rates. The maximum percentage of embryos converted to seedlings was achieved when the medium was supplemented with 4.5 × 10−7 m ZEA. Received August 1, 1997; accepted February 19, 1998  相似文献   

2.
Brush border membrane vesicles, BBMV, from eel intestinal cells or kidney proximal tubule cells were prepared in a low osmolarity cellobiose buffer. The osmotic water permeability coefficient P f for eel vesicles was not affected by pCMBS and was measured at 1.6 × 10−3 cm sec−1 at 23°C, a value lower than 3.6 × 10−3 cm sec−1 exhibited by the kidney vesicles and similar to published values for lipid bilayers. An activation energy E a of 14.7 Kcal mol−1 for water transport was obtained for eel intestine, contrasting with 4.8 Kcal mol−1 determined for rabbit kidney proximal tubule vesicles using the same method of analysis. The high value of E a , as well as the low P f for the eel intestine is compatible with the absence of water channels in these membrane vesicles and is consistent with the view that water permeates by dissolution and diffusion in the membrane. Further, the initial transient observed in the osmotic response of kidney vesicles, which is presumed to reflect the inhibition of water channels by membrane stress, could not be observed in the eel intestinal vesicles. The P f dependence on the tonicity of the osmotic shock, described for kidney vesicles and related to the dissipation of pressure and stress at low tonicity shocks, was not seen with eel vesicles. These results indicate that the membranes from two volume transporter epithelia have different mechanisms of water permeation. Presumably the functional water channels observed in kidney vesicles are not present in eel intestine vesicles. The elastic modulus of the membrane was estimated by analysis of swelling kinetics of eel vesicles following hypotonic shock. The value obtained, 0.79 × 10−3 N cm−1, compares favorably with the corresponding value, 0.87 × 10−3 N cm−1, estimated from measurements at osmotic equilibrium. Received: 28 January 1999/Revised: 15 June 1999  相似文献   

3.
Pre-matured florets of Benibana, a cultivar of saffron thistle (Carthamus tinctorius L.) was irradiated with UV-B (280–320 nm) or UV-C (254 nm) light for 48 h at 23±1 °C and the influence of UV-light on carthamin accumulation and floret elongation was investigated. UV-C light enhances carthamin accumulation most prominently, showing a specific value of 52.3 nmol carthamin·dm−3·h−1·25μm−2 (13.9 times of control), while it restricts floret elongation by a light-suppression manner (net elongation: 0.058 mm·h−1, one ninth of control). UV-B light is also promotive for the red colour appearance (25.0 nmol carthamin·dm−3·h−1·25 μm−2, 6.7 times of control) with suppressing floret elongation (net elongation: 0.17 mm·h−1, one third of control). Heterogeneous productivity of carthamin was seen in floret tissues after continuous treating under UV-C light. Carthamin accumulation, heterogeneous carthamin productivity and decrease of floret elongation restraint under UV-lights are discussed.  相似文献   

4.
The mechanical properties of brush border membrane vesicles, BBMV, from rabbit kidney proximal tubule cells, were studied by measuring the initial and final equilibrium volumes of vesicles subjected to different osmotic shocks, using cellobiose as the impermeant solute in the preparation buffer. An elevated intracellular hydrostatic pressure was inferred from osmotic balance requirements in dilute solutions. For vesicles prepared in 18 and 85 mosm solutions, these pressures are close to 17 mosm (290 mm Hg). The corresponding membrane surface tension is 6.0 × 10−5 N cm−1 while the membrane surface area is expanded by at least 2.2%. When these vesicles are exposed to very dilute solutions the internal hydrostatic pressure rises to an estimated 84 mosm (1444 mm Hg) just prior to lysis. The corresponding maximal surface tension (pre-lysis) is 18.7 × 10−5 N cm−1, and the maximal expansion of membrane area is 6.8%. The calculated area compressibility elastic modulus was 2.8 × 10−3 N cm−1. Received: 8 August 1996/Revised: 4 March 1997  相似文献   

5.
Indole-3-Acetic Acid Control on Acidic Oat Cell Wall Peroxidases   总被引:2,自引:0,他引:2  
Incubation of oat coleoptile segments with 40 μm indoleacetic acid (IAA) induced a decrease of 35–60% in peroxidase activity at the cell wall compartment. Treatment with IAA also produced a similar decrease in the oxidation of NADH and IAA at the cell wall. Isoelectric focusing of ionic, covalent, and intercellular wall peroxidase fractions showed that acidic isoforms (pI 4.0–5.5) were reduced preferentially by IAA treatment. Marked differences were found between acidic and basic wall isoperoxidases in relation to their efficacy in the oxidation of IAA. A peroxidase fraction containing acidic isoforms oxidized IAA with a V max/s0.5 value of 2.4 × 10−2 min−1· g fw−1, 4.0 times higher than that obtained for basic peroxidase isoforms (0.6 × 10−2 min−1· g fw−1). In contrast, basic isoforms were more efficient than acidic isoperoxidases in the oxidation of coniferyl alcohol or ferulic acid with H2O2 (5.6 and 2.1 times, respectively). The levels of diferulate and lignin in the walls of oat coleoptile segments were not altered by treatment with IAA. The decrease in cell wall peroxidase activity by IAA was related more to reduced oxidative degradation of the hormone than to covalent cell wall cross-linking. Received November 1, 1998; accepted December 14, 1998  相似文献   

6.
Hyperthermia induces transient changes in [Na+] i and [K+] i in mammalian cells. Since Cl flux is coupled with Na+ and K+ in several processes, including cell volume control, we have measured the effects of heat on [Cl] i using the chloride indicator, MQAE, with flow cytometry. The mean basal level of [Cl] i in Chinese hamster ovary cells was 12 mm. Cells heated at 42.0° or 45.0°C for 30 min had about a 2.5-fold increase in [Cl] i above unheated control values when measured immediately after heating. There was about a 3-fold decrease in [Na+] i under the same conditions, as measured by Sodium Green. The magnitude of the increase in [Cl] i depended upon time and temperature. The [Cl] i recovered in a time-dependent fashion to control values by 30 min after heating. When cells were heated at 45.0°C for 30 min in the presence of 1.5 mm furosemide, the heat-induced [Cl] i increase was completely blocked. Since furosemide inhibits the Na+/K+/2Cl cotransporter, Cl channels, and even ClHCO3 exchange, these ion transporters may be involved in the heat-induced increase in [Cl] i . Received: 15 June 1995/Revised: 9 April 1996  相似文献   

7.
Developing high-yielding rice genotypes is decisive to ensure global food security with current population growth and the threat of environmental pressures. Cytoplasmic male sterility (CMS) system provides a valuable approach for commercial exploitation of heterosis and producing high-yielding and quality hybrid rice. Three CMS lines and ten diverse restorers were crossed using line × tester mating design. The obtained thirty F1 hybrids and their thirteen parents were evaluated. Yield traits as well as certain floral traits characters that influence the efficiency of crossing and hybrid seed production as the duration of floret opening (min), stigma exsertion (mm), stigma length (mm), opening floret angle, and anther length (mm) were assessed. Highly significant variations were detected among parents, crosses, and parents vs. crosses for all the studied traits. The CMS line L2 and the restorer T5 were determined as good combiners for stigma exsertion, stigma length, opining floret angle, and duration of floret opening. Besides, the hybrids L1 × T1, L1 × T3, L2 × T2, L2 × T5, L3 × T4, L3 × T5, and L3 × T9 exhibited positive SCA effects for most floral traits. Moreover, the CMS lines L1 and L3 as well as the restorers T1, T2, T3, T6, and T9 were identified as good general combiners for grain yield and certain related traits. The hybrids L1 × T1, L1 × T5, L1 × T7, L2 × T3, L2 × T4, L2 × T5, L2 × T10, L3 × T1, L3 × T2, and L3 × T6 displayed positive SCA effects for grain yield and one or more of its attributes. Both additive and non-additive gene effects were involved in the governing inheritance of all evaluated traits. The biochemical variations among the certain evaluated genotypes were further studied. The esterase and peroxidase isozymes were applied for verifying the genetic diversity at the protein level among the used CMS lines, restorers, and their crosses. All the applied isozymes displayed polymorphism for the parents and their crosses. The banding pattern and intensity differences provided accurate results on the reliable variability among the tested genotypes.  相似文献   

8.
Qin Y  Yang J  Zhao J 《Protoplasma》2005,225(1-2):103-112
Summary. Potassium pyroantimonate precipitation was used to locate loosely bound calcium in rice (Oryza sativa L.) lodicules before and after anthesis, and flowering of panicles was accelerated by treatment with methyl jasmonate. From 1 day to 4 h before anthesis, the number of calcium precipitates in the cell walls and vacuole membranes decreased gradually, whereas they increased remarkably in the cytoplasm and nucleolus. At the beginning of anthesis, the number of calcium granules in lodicules reduced sharply, but there was a large accumulation of flocculent precipitates in the vacuoles. After anthesis, the flocculent precipitates decreased in number until they disappeared, whereas the granular precipitates started to accumulate once again. The rice florets treated with 2 mM methyl jasmonate were induced to open within 10–30 min and they then closed 0.5–1 h later. The nucleolus, cytoplasm, and vacuole membrane of the lodicule cells contained many calcium granules during flowering, although the cell walls lacked calcium. At 1 h after treatment, the number of calcium granules had decreased, while flocculent precipitates were regularly observed in the nondegenerated cells. At 6 h after treatment, calcium grains started to reappear in the cell walls. These changes in calcium precipitates before and after anthesis indicate that the opening and closing of florets correlates with the calcium level in lodicule cells. In addition, excised panicles, with florets judged to be nearing anthesis, were soaked in 2–200 mM EGTA solution for 2 min after treatment with 2 mM methyl jasmonate. The results indicate that EGTA had an antagonistic effect on the methyl jasmonate-induced floret opening in rice. Correspondence and reprints: Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, People’s Republic of China.  相似文献   

9.
The gating cycle of CFTR (Cystic Fibrosis Transmembrane conductance Regulator) chloride channels requires ATP hydrolysis and can be interrupted by exposure to the nonhydrolyzable nucleotide AMP-PNP. To further characterize nucleotide interactions and channel gating, we have studied the effects of AMP-PNP, protein kinase C (PKC) phosphorylation, and temperature on gating kinetics. The rate of channel locking increased from 1.05 × 10−3 sec−1 to 58.7 × 10−3 sec−1 when AMP-PNP concentration was raised from 0.5 to 5 mm in the presence of 1 mm MgATP and 180 nm protein kinase A catalytic subunit (PKA). Although rapid locking precluded estimation of P o or opening rate immediately after the addition of AMP-PNP to wild-type channels, analysis of locking rates in the presence of high AMP-PNP concentrations revealed two components. The appearance of a distinct, slow component at high [AMP-PNP] is evidence for AMP-PNP interactions at a second site, where competition with ATP would reduce P o and thereby delay locking. All channels exhibited locking when they were strongly phosphorylated by PKA, but not when exposed to PKC alone. AMP-PNP increased P o at temperatures above 30°C but did not cause locking, evidence that the stabilizing interactions between domains, which have been proposed to maintain CFTR in the open burst state, are relatively weak. The temperature dependence of normal CFTR gating by ATP was strongly asymmetric, with the opening rate being much more temperature sensitive (Q 10= 9.6) than the closing rate (Q 10= 3.6). These results are consistent with a cyclic model for gating of phosphorylated CFTR. Received: 28 August 1997/Revised: 4 February 1998  相似文献   

10.
Changes in volume of intestinal brush border membrane vesicles of the European eel Anguilla anguilla were measured as vesicles were exposed to media with different osmotic pressures. Preparing the vesicles in media of low osmotic pressure allowed the effects of a small hydrostatic pressure to become a significant factor in the osmotic equilibration. By applying LaPlace's law to relate pressure and volume and assuming a linear relation between membrane tension and area expansion, we estimate an initial membrane tension at 4.02 × 10−5 N cm−1 and an area compressibility elastic modulus at 0.87 × 10−3 N cm−1. The elastic modulus estimate falls in the low range of values reported for membranes from other tissues in other species. This lower modulus quantitatively accounts for why eel intestinal vesicles show measurable changes in volume in hypotonic media while rabbit kidney vesicles do not. Received: 28 January 1999/Revised: 15 June 1999  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号