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1.
BACKGROUND: Although chromosome missegregation during oocyte maturation (OM) is a significant contributor to human morbidity and mortality, very little is known about the causes and mechanisms of aneuploidy. Several investigators have proposed that temporal perturbations during OM predispose oocytes to aberrant chromosome segregation. One approach for testing this proposal is to temporarily inhibit the activity of protein proteolysis during OM. We used the reversible proteasome inhibitor MG-132 to transiently perturb the temporal sequence of events during OM and subsequently analyzed mouse metaphase II (MII) for cytogenetic abnormalities. The transient inhibition of proteasome activity by MG-132 resulted in elevated levels of oocytes containing extra chromatids and chromosomes. RESULTS: The transient inhibition of proteasome-mediated proteolysis during OM by MG-132 resulted in dose-response delays during OM and elevated levels of aneuploid MII oocytes. Oocytes exposed in vitro to MG-132 exhibited greater delays during metaphase I (MI) as demonstrated by significantly (p < 0.01) higher levels of MI arrested oocytes and lower frequencies of premature sister chromatid separation in MII oocytes. Furthermore, the proportions of MII oocytes containing single chromatids and extra chromosomes significantly (p < 0.01) increased with MG-132 dosage. CONCLUSIONS: These data suggest that the MG-132-induced transient delay of proteasomal activity during mouse OM in vitro predisposed oocytes to abnormal chromosome segregation. Although these findings support a relationship between disturbed proteasomal activity and chromosome segregation, considerable additional data are needed to further investigate the roles of proteasome-mediated proteolysis and other potential molecular mechanisms on chromosome segregation during OM. 相似文献
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籼型光敏核不育水稻营养生长期光温条件对育性转换条件的影响 总被引：6，自引：0，他引：6
光敏核不育水稻（ＰＧＭＲ）营养生长期所遇光温条件，对后期育性转换的条件有一定影响。前期高温或短日条件，有使育性转换下限临界温度增高的作用；前期低温或长日条件，有使育性转换下限临界温度降低的影响。就此，作者讨论了各地所测的下限临界温度的相互参考价值。 相似文献
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研究出云南省宾川县亚麻种植的适宜播期为9月25日至10月25日，最适播期为10月5日至15日，在最适播期播种的亚麻经济性状好，原茎产量高。 相似文献
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The effect of in situ thermal stretching during oxidative stabilization on the orientation of cyclized ladder structure was investigated. Based on the structure evolution of PAN fibers with the increasing stabilization temperatures, the stabilization process was classified into three different stages, namely before the onset of cyclization, during cyclization in amorphous region, and during cyclization in crystalline region. The polyacrylonitrile (PAN) precursor fibers were stretched at the three stages with stretching ratios from 0 % to 8 % during continuous stabilization process. The results show that the orientation degree of cyclized ladder structure increases with the increase of stretching ratio at the three stages and the maximum orientation efficiency of cyclized ladder structure is obtained when PAN fibers are stretched at the stage of during cyclization in crystalline region. The orientation of resulting carbon fibers strongly depends on the orientation degree of cyclized ladder structure. The orientation efficiency of turbostratic graphite crystallite also agrees well with that of cyclized ladder structure. Meanwhile, the orientation efficiency of turbostratic graphite crystallite is higher than that of cyclized ladder structure and the difference values between orientation efficiency of the two structures decrease firstly then increase with the increase of degree of cyclization. 相似文献
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对名优茶杀青叶进行冷冻存贮,研究其贮藏中主要生化成份、香气等的变化。结果表明:杀青叶在冻贮期间,其氨基酸总量、茶多酚含量的变化均达显著、极显著水平,与存贮的成品茶生化成份的变化基本一致,但其主要生化成份特别是茶多酚含量的变化滞后于成品茶,这说明杀青叶冻贮期间,其内部生化反应速度低于成品茶存贮。杀青叶冻贮6个月后,其香气成份的保留量高于成品茶26.86%,特别有利于香气成份的保存,这可能与杀青叶存贮中保存了大量的香气前体物有关。冷冻杀青叶的解冻等后加工过程对茶叶生化成份、香气等有较大影响,以微波方式快速解冻对茶叶品质最有利。 相似文献
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Takemasa Koumoto Naoko Saito Naohiro Aoki Toshiki Iwasaki Shigenao Kawai Shuji Yokoi 《Plant Production Science》2016,19(4):497-507
We tested whether exposing rice plants to abiotic stress (salt or shade) during vegetative growth affects the chilling tolerance of reproductive organs, which is one of the most important traits for rice growing in a cool climate; we used two rice cultivars with different tolerance in two growing seasons. We divided the vegetative growth into three phases to clarify the most sensitive period: 7–22 days after transplanting (DAT), 23–38 DAT and 39–54 DAT. Chilling tolerance of the pre-stressed plants was based on the male sterility induced by low temperatures. Shade and salt stress during all three vegetative growth phases significantly reduced stomatal conductance. Shade decreased the specific leaf weight and the leaf sugar and starch contents, but salt had no significant effect, despite causing leaf damage. Low temperatures during the reproductive stage induced spikelet sterility in all plants, but the magnitude was greater in the salt- and shade-stressed plants of both cultivars, especially those stressed late during vegetative growth. The increased spikelet sterility caused by chilling was closely related to the reduction of the total spikelet number per panicle. This is the first study to show that salt and low light stress during vegetative growth increased the susceptibility of rice plants to chilling damage during panicle development. 相似文献
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Prabhjyot-Kaur Sandhu S. S. Dhillon Buta Singh Singh Harpreet 《Paddy and Water Environment》2021,19(4):673-681
Rice is a major kharif cereal crop cultivated in Punjab. Over the past five decades the rice yield has increased from as low as 1800 kg/ha during 1970–4815 kg/ha during 2017, i.e., an overall increase of 167.5% or increase @ 3.5% per year. One of the major reasons for this increase has been the introduction of improved and high-yielding varieties (PR 106, PR 111, PR 116, PR 118, PR 121, PR 122, PR 126, PR 127, etc.). Other important factors are the improved crop production and protection practices coupled with mechanization of farm operations. However, weather factors have always been a major bottleneck shattering the steady plateau of high rice yield (3443 kg/ha during 1979, 3231 kg/ha during 1995, 3273 kg/ha during 1998, 4257 kg/ha during 2011 and recent low yield of 4387 kg/ha during 2018). The actual weather data of the recent two decades at Ludhiana (2000–2018) were correlated with the historical rice yield. The results revealed a combination of high temperature coupled with clear sunny (total seasonal sunshine?~?900–1000 h) and dry (low relative humidity) days is conducive for proper growth, development and yield of rice in Punjab. The rainfall and rainy days were found to be negatively correlated with yield since heavy rainfall events and more number of rainy days create a humid weather which is conducive for insect-pest and disease incidence in rice and also reduces sunshine duration. Hence, a combination of ample sunshine hours and well-distributed rainfall during the vegetative stage of rice leads to high productivity of cultivars grown under optimized crop management techniques.
相似文献10.
Agronomic and horticultural crop species experience reductions in growth and harvestable yield after exposure to physical agitation (also known as mechanical stress), as by wind or rain. A greenhouse study was conducted to test the influence of mechanical stress on soybean yield and to determine if exposure to mechanical stress during discrete growth periods has differential effects on seed yield. A modified rotatory shaker was used to apply seismic (i.e., shaking) stress. Brief, periodic episodes of seismic stress reduced stem length, total seed dry weight, and seed number of soybean [Glycine max (L.) Merr.]. Lodging resistance was greater for plants stressed during vegetative growth or throughout vegetative and reproductive growth than during reproductive growth only. Seed dry weight yield was reduced regardless of the timing or duration of stress application, but was lowest when applied during reproductive development. Seismic stress applied during reproductive growth stages R1 to R2 (Days 3 to 4) was as detrimental to seed dry weight accumulation as was stress applied during growth stages R1 to R6 (Days 39 to 42). Seed dry weight per plant was highly correlated with seed number per plant, and seed number was correlated with the seed number of two- and three-seeded pods. Dry weight per 100 seeds was unaffected by seismic-stress treatment. Growth and yield reductions resulting from treatments applied only during the vegetative stage imply that long-term mechanical effects were induced, from which the plants did not fully recover. It is unclear which yield-controlling physiological processes were affected by mechanical stress. Both transient and long-term effects on yield-controlling processes remain to be elucidated. 相似文献
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秋季低温对水稻空瘪率的影响和有关指标值的研究 总被引：3，自引：0，他引：3
本试验旨在探索秋季低温对水稻开花结实影响的若干不够明确的问题。结果表明:低温指标中,日平均温度是主要指标;日最低温度是减数分裂期的辅助指标;日最高温度是开花期的辅助指标。如在不同低温敏感期均受害较重,则低温危害表现为累加效应。计算低温临界温度时,籼粳稻均以连续三天的温度平均为好。提出了开花期籼稻、籼型杂交稻、中粳、晚粳四类型的低温临界值。开花期的日温差过大或过小均导致空瘪率上升。气象因子中,温度对空瘪率的影响最大;适温条件下,空瘪率与日照呈负相关:雨量与空瘪率关系不显著。 相似文献
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1961～2004海南岛干旱演变特征分析 总被引：1，自引：0，他引：1
根据1961￣2004年海南岛18个观测站的逐月降水资料,采用Z指数作为旱涝等级划分标准,计算了海南岛干旱强度与干旱覆盖范围,诊断了海南干旱强度与干旱范围的趋势和变化,并重点分析了2004年的干旱情况。研究发现在过去44年中最严重的干旱年份是1977年,其次是1969,1987和2004年。从长期趋势来看,全岛逐年干旱强度呈减弱趋势,干旱范围趋于减小。海南岛干旱覆盖百分率还存在明显年际和年代际振荡:在1987年之前以6～8年长周期的低频变化为主,并且周期逐渐加长,但1987年之后4￣5年短周期振荡明显。在2003年秋冬季持续干旱的基础上,2004年各季节干旱继续发展,2004年秋季干旱成为过去44年中干旱最严重的季节。 相似文献
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[目的]茶树叶绿素a合成酶基因(CsG4)克隆及其在白茶萎凋过程中关于叶色变化的作用机制探究。[方法]利用聚合酶链式反应(RT-PCR)技术克隆CsG4的CDS全长序列并对其编码蛋白进行生物信息学分析;测定白茶萎凋48 h过程中的叶绿素a、叶绿素b和总叶绿素含量变化,并记录叶相变化;采用实时荧光定量PCR(qRT-PCR)技术检测CsG4在白茶萎凋过程中表达量变化趋势。[结果]CsG4的CDS全长为1125 bp,编码374个氨基酸。生物信息学分析表明,CsG4蛋白分子量为40.49 kD,理论等电点为8.74。CsG4属于跨膜蛋白,含有34个磷酸化位点,亚细胞定位预测其定位于叶绿体。进化树分析表明,CsG4的氨基酸序列与其他物种具有较高的同源性,CsG4蛋白与杜鹃花(Rhododendron dauricum)和咖啡(Coffea arabica)的G4蛋白序列同源性高。qRT-PCR分析表明,在白茶萎凋过程中,CsG4的相对表达量显著降低,且与萎凋过程中叶绿素含量的总体变化趋势呈正相关。[结论]该研究克隆了CsG4的全长CDS序列,推测其对白茶萎凋过程中叶绿素含量的变化具有重要的调控作用。 相似文献
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《Journal of Cereal Science》2004,39(3):341-349
In the gluten-starch separation process gluten is formed first as a result of breakdown of the gliadin-glutelin structures during mixing followed by their re-agglomeration. To date the effect of pentosans and enzymes have not been studied separately. A simple modification of TNO Glutomatic system enables pentosans, enzymes, and other materials to be added after the mixing step allowing the effect of these additives to be studied separately. Using this technique, we observed that re-aggregation of gluten proteins starts immediately after the first mixing step during the dough dilution phase. Xylanase addition prior to dough mixing can lead to ‘overdose effects’ but these were not observed when xylanase was added later during the re-agglomeration phase. We were able to distinguish between physical and chemical effects of pentosans on gluten formation. The effect of water-extractable pentosans is only partly related to its viscosity, a ferulic acid (FA) related reaction is more important. Pentosans affect the affect the agglomeration by increasing the size of the glutenin macropolymer particles. When the water-extractable pentosan effect is prevented by xylanase or FA addition, aggregation during dilution is more extensive and the glutenin macropolymer has a lower average particle size with a resulting difference in gluten rheology. 相似文献
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The effects of irrigation, water and nitrogen management on yield and quality of the Russet Burbank cultivar are discussed relevant to developmental stages of growth. Recent research on the interactions of irrigation and nitrogen management on total and U.S. No. 1 yields and specific gravity are presented. Total and U.S. No. 1 yields decline with increasing soil moisture stress. Yield of U.S. No. 1 potatoes is particularly sensitive to short periods of irrigation deficit during tuber initiation. Total yield appears most sensitive to short periods of irrigation deficit during tuber bulking. Allocation of longer term irrigation deficits during years of limited water supply should be either a) avoided during mid-season tuber bulking, or b) uniformly distributed over the entire tuber bulking growth period. Yield increases with higher total available soil nitrogen under deficit irrigation, but the yield response diminishes as the amount of total seasonal water decreases. The influence of irrigation and nitrogen availability is also discussed for specific gravity and tuber maturity. Seasonal (split) nitrogen management is proposed as a method to improve yield, quality and nitrogen fertilizer use efficiency of indeterminant cultivars. 相似文献
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红茶制造中多酚氧化酶同工酶谱与活性的变化 总被引：5，自引：1，他引：4
本文运用聚丙烯酰胺凝胶垂直板状电泳技术和酶活性测定相结合的方法,初步探明了红茶萎凋、揉捻、发酵和干燥工序中多酚氧化酶(PPO)活性及同工酶谱的变化动态,以及酶试液制备方法对PPO活性及同工酶的影响,发现造成萎凋期间PPO活性变化两种研究结果的原因,在于酶制液的制备方法不同。同时,在鲜叶和萎凋叶中发现了第7条小分子PPO组分。本试验还证明了红茶中残余酶活性的存在,并探讨了残余酶在贮藏中可能发生的作用。文中还探讨了PPO各组分在红茶制造中作用的大小,从酶学角度论证了萎凋工序的重要性。 相似文献
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Summary Management of soil moisture deficit during tuber initiation and early development was important for the optimisation of net
and marketable tuber yields of cv. Russet Burbank on the typical red ferrosol cropping soils of Northern Tasmania, Australia.
An effect of reduced water input during the tuber initiation period on increasing incidence of common scab disease was noted
in one trial. In subsequent trials disease inoculum levels were not sufficient to show differences between treatments despite
a history of disease at the site. For optimisation of marketable yield and probable assistance in the management of common
scab disease it is recommended that irrigation scheduling to known soil moisture deficits be adopted during this period of
growth on this soil type. 相似文献
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Andreja Rudolf Jelka Geršak Anna Ujhelyiova Majda Sfiligoj Smole 《Fibers and Polymers》2007,8(2):212-217
The properties of 100 % PES core-spun threads were studied before and after the sewing process at different stitching speeds,
by determination of the threads tensile force during the sewing process and by changes of the mechanical and thermo-mechanical
properties after the sewing process. This analytical method is especially advantageous when monitoring contemporary thermal
and mechanical effects, as is the case when loading the sewing thread. Loadings during the sewing process cause structural
changes in the thread-twisted fibres. This is confirmed by changes in the thermo-mechanical properties after the sewing process.
Simultaneously, changes in the threads mechanical properties after sewing were also observed. 相似文献
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超级杂交稻协优9308生理模型的研究 总被引：28，自引：3，他引：25
观察比较了超级杂交稻协优9308和高产杂交稻协优63的生理特性。与高产杂交稻协优63相比,超级杂交稻协优9308表现出两个明显的顶端优势,即营养生长期间的“茎蘖顶端优势”和灌浆成熟期间的“粒间顶端优势”。认为这两优势是协优9308超高产的生理特性和基础,据此提出以单茎（蘖）物质生产优势为基础,以“两个顶端优势”为中心的超级杂交稻协优9308的“生理模型”,即(1) 协优9308 干物质生产能力高,全生育期单株干物质生产量达120 g;抽穗后仍具有较高生产力,此间生物产量占总生物产量的40%。(2) 营养生长期“茎蘖顶端优势”显著,有效分蘖终止期较早,出现在移栽后2周左右,幼穗发育整齐,成穗率>65 %。(3) 灌浆成熟期“粒间顶端优势”显著,优势粒灌浆势高,齐穗后第2周便达到灌浆势的峰值,此后仍保持一定的灌浆能力;劣势粒灌浆进程比优势粒滞后,在临近成熟时,仍未出现灌浆势峰值;支撑劣势粒灌浆势不减的生理机制是：根系衰老迟缓,花后物质运转势较高,功能叶衰老迟缓。这一超级杂交稻“生理模型”的经济产量指标是11~12 t/hm2。 相似文献