大豆萌发过程的活性氧代谢

本文研究了大豆萌发过程中活性氧的产生与清除,并探讨了光因子在活性氧代谢中的作用。大豆呼吸强度、O产生速率及H2O2水平都在吸水后第四天达到高峰,然后下降,三者的变化趋势同步。SOD、POD及APX的活性随萌发过程而逐渐增强,最后趋于平稳。SOD同工酶谱中分别于萌发的第二、第三天各出现一条新的酶带。CAT在萌发的初期猛增50倍左右,之后趋于稳定。在三种清除H2O2的酶（CAT、POD、APX）中,CAT清除H2O2的能力远远高于POD与APX,CAT可能是大豆萌发过程中最主要的H2O2清除酶。光萌发时呼吸强度低于暗中萌发,但O产生速率与H2O2水平高于暗萌发,光萌发时O的产生占总耗氧量的1．1—2．7％,而暗中萌发为0．9—1．3％。光条件下SOD、APX活性明显高于暗中萌发,而POD与CAT则在光和暗条件下相差不大。     

Control of seed development in Arabidopsis thaliana by atmospheric oxygen

Seed development is known to be inhibited completely when plants are grown in oxygen concentrations below 5·1 kPa, but apart from reports of decreased seed weight little is known about embryogenesis at subambient oxygen concentrations above this critical level. Arabidopsis thaliana (L.) Heynh. plants were grown full term under continuous light in premixed atmospheres with oxygen partial pressures of 2·5, 5·1, 10·1, 16·2 and 21·3 kPa O₂, 0·035 kPa CO₂ and the balance nitrogen. Seeds were harvested for germination tests and microscopy when siliques had yellowed. Seed germination was depressed in O₂ treatments below 16·2 kPa, and seeds from plants grown in 2·5 kPa O₂ did not germinate at all. Fewer than 25% of the seeds from plants grown in 5·1 kPa oxygen germinated and most of the seedlings appeared abnormal. Light and scanning electron microscopic observation of non-germinated seeds showed that these embryos had stopped growing at different developmental stages depending upon the prevailing oxygen level. Embryos stopped growing at the heart-shaped to linear cotyledon stage in 5·1 kPa O₂, at around the curled cotyledon stage in 10·1 kPa O₂, and at the premature stage in 16·2 kPa O₂. Globular and heart-shaped embryos were observed in sectioned seeds from plants grown in 2·5 kPa O₂. Tissue degeneration caused by cell autolysis and changes in cell structure were observed in cotyledons and radicles. Transmission electron microscopy of mature seeds showed that storage substances, such as protein bodies, were reduced in subambient oxygen treatments. The results demonstrate control of embryo development by oxygen in Arabidopsis .     

PI3K调控水稻种子萌发的机理研究

PI3K在植物的正常生长和胁迫应答过程中发挥着很重要的功能.在本文中,我们证实了在种子萌发过程中,PI3K促进了种子的萌发.通过RT-PCR的分析,我们发现,PI3K在整个过程中,伴随着吸胀时间的延长,表达量逐渐上升.而PI3K抑制剂的处理,证实了萌发过程中,PI3K促萌发的效应.DCF检测ROS的产生发现,在萌发的过程中,PBK促进了ROS的生成.PI3K产物PI3P亚细胞定位的分析发现,PI3P主要定位于膜结构区域.总之,本文借助于光学分子成像技术发现PI3K在种子萌发过程中的重要作用,提出PI3K通过调控ROS生成促进种子萌发的重要机理.     

Seed coat structure and oxygen availability control lowtemperature germination of melon (Cucumis melo) seeds

The involvement of the seed coat in low-temperature germination of melon seeds was examined in two accessions differing in their ability to germinate at 14°C: Noy Yizre'el (a cold-sensitive cultivar) and Persia 202 (a cold-tolerant breeding line). Decoating resulted in full germination of Noy Yizre'el at 14°C, but splitting the coat increased germination only partially. Thus, the inhibition of Noy Yizre'el germination at 14°C is not due to physical constraint on radicle protrusion. At 25°C, seeds of both accessions submerged in water or agar germinated fully as long as the hilum aperture remained uncovered. Submerging the whole seed, or covering the hilum with lanolin, strongly depressed germination of Noy Yizre'el but not of Persia 202. Accessions differed in germination response to decreasing O₂ concentration, with Noy Yizre'el showing higher sensitivity to hypoxia. These differences were correlated with differences in seed coat structure as well as in embryo sensitivity to hypoxia. Intercellular spaces in the outer layer of the seed coat were evident in the more tolerant Persia 202, while in the sensitive Noy Yizre'el this layer was completely sealed. Sensitivity to hypoxia increased at 15°C as compared with 25°C, the increase being greater in Noy Yizre'el. It is proposed that the seed coat-imposed dormancy at low temperature in Noy Yizre'el is the combined result of more restricted oxygen diffusion through the seed coat and a greater embryo sensitivity to hypoxia, rather than to physical constraints of radicle break-through or impairment of imbibition.     

Cd胁迫对紫花苜蓿种子发芽及幼苗生理生化特性的影响

以‘甘农3号’紫花苜蓿(Medicago sativa L.cv.‘Gannong 3’)品种为试验材料,研究不同浓度Cd胁迫对紫花苜蓿种子萌发及幼苗生理生化特性的影响。结果显示:(1)Cd胁迫显著抑制紫花苜蓿种子萌发及幼苗生长,种子发芽势、发芽率及幼苗的胚芽长、胚根长和干重均随着Cd处理浓度提高显著降低,且对发芽势的抑制作用大于发芽率,对胚根生长的抑制作用大于胚芽。(2)Cd胁迫第4d时,萌发种子中蛋白水解酶的活性受到显著抑制,可溶性蛋白和可溶性糖含量显著降低。(3)Cd胁迫第10d时,随着Cd胁迫浓度的增加,苜蓿幼苗的超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)、愈创木酚过氧化物酶(GPX)活性均先升高后降低,过氧化氢酶(CAT)活性持续下降,超氧阴离子自由基产生速率、H2O2含量和丙二醛(MDA)含量均显著增加。研究表明,低浓度Cd胁迫下,苜蓿幼苗抗氧化系统清除活性氧的能力上升,高浓度Cd胁迫下,苜蓿幼苗抗氧化系统活性下降,膜脂过氧化程度加剧,活性氧的过量积累是Cd伤害苜蓿幼苗和其生物量下降的主要原因。     

种子萌发过程中胚乳的突破性研究

胚乳将许多种子的胚完全包裹,是这些种子萌发的物理屏障,其破裂与否是决定种子萌发与否的最后开关。胚乳破裂是胚生长产生由内向外“顶”的机械力量以及胚乳组织本身机械强度下降（胚乳弱化）的共同结果,而胚乳弱化则包括细胞壁的酶促和非酶促松弛机制。本文综述胚生长产生的机械力量、胚乳破裂的部位和方式、胚乳的组织结构及其细胞壁的化学组成、各种细胞壁降解酶及非酶的扩展蛋白（expansin）和活性氧在胚乳弱化中的作用等方面的研究进展。     

ROS production and protein oxidation as a novel mechanism for seed dormancy alleviation

At harvest, sunflower (Helianthus annuus L.) seeds are dormant and unable to germinate at temperatures below 15 degrees C. Seed storage in the dry state, known as after-ripening, is associated with an alleviation of embryonic dormancy allowing subsequent germination at suboptimal temperatures. To identify the process by which dormancy is broken during after-ripening, we focused on the role of reactive oxygen species (ROS) in this phenomenon. After-ripening entailed a progressive accumulation of ROS, namely superoxide anions and hydrogen peroxide, in cells of embryonic axes. This accumulation, which was investigated at the cellular level by electron microscopy, occurred concomitantly with lipid peroxidation and oxidation (carbonylation) of specific embryo proteins. Incubation of dormant seeds for 3 h in the presence of hydrogen cyanide (a compound that breaks dormancy) or methylviologen (a ROS-generating compound) also released dormancy and caused the oxidation of a specific set of embryo proteins. From these observations, we propose a novel mechanism for seed dormancy alleviation. This mechanism involves ROS production and targeted changes in protein carbonylation patterns.     

Spd浸种对盐胁迫下番茄（Solanum lycopersicum)幼苗的保护效应

通过水培试验,研究了100 mmol/L NaCl盐浓度下,0.25 mmol/L Spd浸种处理对两个番茄品种白果强丰(耐盐基因型)和江蔬14号(盐敏感基因型)植株干重、根冠比(R/T)、幼苗叶片和根系抗氧化酶活性及活性氧含量的影响.具体试验处理如下:(a) 对照(蒸馏水浸种+ 0 mmol/L NaCl),(b) NaCl (蒸馏水浸种+ 100 mmol/L NaCl),(c) Spd(0.25 mmol/L Spd浸种 +100 mmol/L NaCl).结果表明,在盐胁迫下,两个番茄品种幼苗叶片和根系内超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性升高,H2O2含量和O·-2产生速率增高,幼苗生长受到抑制,幼苗地上部、地下部干重均明显低于对照,R/T增大,且江蔬14号的变化幅度大于白果强丰.Spd浸种处理降低了盐胁迫下番茄幼苗叶片和根系内O·-2产生速率和H2O2含量,进一步提高了SOD、POD和CAT活性,促进幼苗干重增加,缓解了盐胁迫对植株的伤害.与耐盐基因型番茄品种白果强丰相比,Spd浸种处理对盐敏感基因型番茄品种江蔬14号的作用效果更为明显.总之,Spd浸种处理通过提高盐胁迫下植株体内抗氧化酶活性,降低ROS水平来缓解盐胁迫对番茄幼苗的伤害,提高幼苗耐盐能力.     

Effect of seed soaking with thiols on the antioxidant enzymes and photosystem activities in wheat subjected to water stress

Photosystem 1 and 2 and antioxidant enzyme activities were determined in wheat (Triticum aestivum L. cv. Sonalika) leaves. Seedlings from both control seeds and seeds soaked in solutions like dithiothreitol, thioglycollic acid and thiourea were subjected to water stress induced by polyethylene glycol. Photosystem 1 and 2 activities were less inhibited by water stress due to seed soaking with sulphydryl compounds. The changes in activities of antioxidant enzymes induced by water stress were higher in seedlings from thiol-pretreated seeds than from water-soaked seeds.     

Seed birth to death: dual functions of reactive oxygen species in seed physiology

Background Reactive oxygen species (ROS) are considered to be detrimental to seed viability. However, recent studies have demonstrated that ROS have key roles in seed germination particularly in the release of seed dormancy and embryogenesis, as well as in protection from pathogens.Scope This review considers the functions of ROS in seed physiology. ROS are present in all cells and at all phases of the seed life cycle. ROS accumulation is important in breaking seed dormancy, and stimulating seed germination and protection from pathogens. However, excessive ROS accumulation can be detrimental. Therefore, knowledge of the mechanisms by which ROS influence seed physiology will provide insights that may not only allow the development of seed quality markers but also help us understand how dormancy can be broken in several recalcitrant species.Conclusions Reactive oxygen species have a dual role in seed physiology. Understanding the relative importance of beneficial and detrimental effects of ROS provides great scope for the improvement and maintenance of seed vigour and quality, factors that may ultimately increase crop yields.     

分子探针定量和定位分析种子吸涨早期活性氧的生成

借助活性氧发光分子探针,利用荧光光谱和激光共聚焦扫描显微技术,在不同年份的玉米种子吸胀早期,对其胚、淀粉和糊粉层细胞活性氧生成进行了定量和亚细胞定位分析.结果表明:胚细胞产生的活性氧最多,糊粉层细胞次之,淀粉细胞几乎不产生活性氧;而且胚细胞产生的活性氧主要定位在细胞内,细胞膜上不产生:糊粉层细胞产生的活性氧主要定位在细胞膜.这一种子吸涨早期活性氧生成机制的揭示,为化学发光检测种子活力提供了生理依据.     

Negative correlation between altitudes and oxygen isotope ratios of seeds: exploring its applicability to assess vertical seed dispersal

Vertical seed dispersal, which plays a key role in plant escape and/or expansion under climate change, was recently evaluated for the first time using negative correlation between altitudes and oxygen isotope ratio of seeds. Although this method is innovative, its applicability to other plants is unknown. To explore the applicability of the method, we regressed altitudes on δ¹⁸O of seeds of five woody species constituting three families in temperate forests in central Japan. Because climatic factors, including temperature and precipitation that influence δ¹⁸O of plant materials, demonstrate intensive seasonal fluctuation in the temperate zone, we also evaluated the effect of fruiting season of each species on δ¹⁸O of seeds using generalized linear mixed models (GLMM). Negative correlation between altitudes and δ¹⁸O of seeds was found in four of five species tested. The slope of regression lines tended to be lower in late‐fruiting species. The GLMM analysis revealed that altitudes and date of fruiting peak negatively affected δ¹⁸O of seeds. These results indicate that the estimation of vertical seed dispersal using δ¹⁸O of seeds can be applicable for various species, not just confined to specific taxa, by identifying the altitudes of plants that produced seeds. The results also suggest that the regression line between altitudes and δ¹⁸O of seeds is rather species specific and that vertical seed dispersal in late‐fruiting species is estimated at a low resolution due to their small regression slopes. A future study on the identification of environmental factors and plant traits that cause a difference in δ¹⁸O of seeds, combined with an improvement of analysis, will lead to effective evaluation of vertical seed dispersal in various species and thereby promote our understanding about the mechanism and ecological functions of vertical seed dispersal.     

Development of seed coat-imposed dormancy during seed maturation in Cynoglossum officinale

The relationship between seed phenolics and appearance of seed coat–imposed dormancy during seed development in Cynoglossum officinale L. was studied. Up to 24 days after anthesis, seeds failed to germinate upon imbibition in Petri dishes at 25°C. At 44 days after anthesis, seeds were fully germinable; removal of seed coats did not improve their germination or O₂ uptake. At 72 days after anthesis, mature seeds at the base of the cyme did not germinate unless their coats were removed. Removal of seed coat also stimulated O₂ uptake at this harvest date. The methanol-soluble phenolic content of the seeds increased during the early stages of seed development, in both the seed coat and the embryo. As seed development continued, the methanol-soluble phenolic content of the embryo stabilized, but that of the seed coat declined. This decline was associated with an increase in the thioglycolic acid–soluble phenolics, presumably lignins, in the seed coat. These results suggest that polymerization of methanol–soluble phenolics into lignins in the seed coat during later stages of seed development renders the seed coat of C. officinale impermeable to 03, and thus keeps the seed dormant.     

低能氩离子注入对甜瓜种子发芽及幼苗某些生理生化指标的影响

以能量25 keV、不同剂量Ar 离子注入甜瓜种子,其发芽率均有所降低,且可不同程度提高O2-·产生速率和H2O2含量,同时过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性增加,膜脂过氧化产物丙二醛(MDA)含量下降;剂量过大时,CAT、SOD活性下降,MDA含量上升.     

Response of Chinese Wampee Axes and Maize Embryos to Dehydration at Different Rates

Survival of wampee （Clausena lansium Skeels） axes and maize （Zea mays L.） embryos decreased with rapid and slow dehydration. Damage of wampee axes by rapid dehydration was much less than by slow dehydration, and that was contrary to maize embryos. The malondialdehyde contents of wampee axes and maize embryos rapidly increased with dehydration, those of wampee axes were lower during rapid dehydration than during slow dehydration, and those of maize embryos were higher during rapid dehydration than during slow dehydration. Activities of superoxide dismutase （SOD）, ascorbate peroxidase （APX） and catalase （CAT） of wampee axes markedly increased during the early phase of dehydration, and then rapidly decreased, and those of rapidly dehydrated axes were higher than those of slow dehydrated axes when they were dehydrated to low water contents. Activities of SOD and APX of maize embryos notable decreased with dehydration. There were higher SOD activities and lower APX activities of slowly dehydrated maize embryos compared with rapidly dehydrated maize embryos. CAT activities of maize embryos markedly increased during the early phase of dehydration, and then decreased, and those of slowly dehydrated embryos were higher than those of rapidly dehydrated embryos during the late phase of dehydration.     

International principles and standards for native seeds in ecological restoration

The growing demand for native seeds in ecological restoration and rehabilitation, whether for mining, forest, or ecosystem restoration, has resulted in a major global industry in the sourcing, supply, and sale of native seeds. However, there are no international guidance documents for ensuring that native seeds have the same standards of quality assurance that are regular practice in the crop and horticultural industries. Using the International Principles and Standards for the Practice of Ecological Restoration as a foundation document, we provide for the first time a synthesis of general practices in the native seed supply chain to derive the Principles and Standards for Native Seeds in Ecological Restoration (“Standards”). These practices and the underpinning science provide the basis for developing quality measures and guidance statements that are adaptable at the local, biome, or national scale. Importantly, these Standards define what is considered native seed in ecological restoration and highlight the differences between native seeds versus seeds of improved genetics. Seed testing approaches are provided within a logical framework that outline the many different dormancy states in native seed that can confound restoration outcomes. A “pro‐forma” template for a production label is included as a practical tool that can be customized for local needs and to standardize reporting to end‐users on the level of seed quality and germinability to be expected in a native seed batch. These Standards are not intended to be mandatory; however, the guidance statements provide the foundation upon which regulatory approaches can be developed by constituencies and jurisdictions.     

不结球白菜种子活力及抗氧化特性在人工老化过程中的变化

以不结球白菜品种‘寒笑’种子为材料,研究高温(42℃)高湿(相对湿度100%)人工老化处理过程中种子活力及抗氧化相关特性的变化。结果显示:不结球白菜种子的发芽率、发芽势、发芽指数和活力指数随老化处理时间的延长而逐渐下降,不正常苗率逐渐增加;种子的超氧阴离子(O2.-)产生速率先增高后降低,过氧化氢(H2O2)含量逐渐增加,脂氧合酶(LOX)活性和丙二醛(MDA)含量下降,种子浸出液相对电导率增加;种子超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和谷胱甘肽还原酶(GR)活性随老化处理时间的延长逐渐下降,抗坏血酸过氧化物酶(APX)和谷胱甘肽过氧化物酶(GPX)活性在老化处理初期(老化3 d前)均增加,APX活性随后降低,GPX活性无显著变化;种子抗坏血酸(AsA)和还原型谷胱甘肽(GSH)含量在老化处理1 d后即显著降低并持续保持较低水平。研究表明,不结球白菜种子在人工加速老化过程中其抗氧化系统代谢紊乱并造成活性氧累积伤害,这可能是引起不结球白菜种子老化的重要原因。     

Response of Chinese Wampee Axes and Maize Embryos to Dehydration at Different Rates

Survival of wampee (Clausena lansium Sksels) axes and maize (Zea mays L.) embryos decreased with rapid and slow dehydration. Damage of wampee axes by rapid dehydration was much less than by slow dehydration, and that was contrary to maize embryos. The malondialdehyde contents of wampee axes and maize embryos rapidly increased with dehydration, those of wampee axes were lower during rapid dehydration than during slow dehydration, and those of maize embryos were higher during rapid dehydration than during slow dehydration. Activities of superoxide dismutsse (SOD), ascorbate peroxidase (APX) and catalase (CAT) of wampee axes markedly increased during the sady phase of dehydration, and then rapidly decreased, and those of rapidly dehydrated axes were higher than those of slow dehydrated axes when they were dehydrated to low water contents. Activities of SOD and APX of maize embryos notable decreased with dehydration. There were higher SOD activities and lower APX activities of slowly dehydrated maize embryos compared with rapidly dehydrated maize embryos. CAT activities of maize embryos markedly increased during the eady phase of dehydration, and then decreased, and those of slowly dehydrated embryos were higher than those of rapidly dehydrated embryos during the late phase of dehydration.     

含水量对种子贮藏寿命的影响

建立以收集种子为主体的基因库乃是当今保护植物种质资源最为普遍且可靠易行的方式,在世界库存约 61 0 0 0 0 0份种质资源中,近 90 %是以种子形式保存于约 1 30 0个基因库中。低温贮藏仍是目前基因库中种子种质保存的主要方法。种子含水量和贮藏温度是影响种子在贮藏期间生活力和活力保持的关键因素。传统的经验认为控制温度比控制水分来得安全有效,因而趋向于向低温或超低温的贮藏方向发展。国际植物遗传资源研究所（ＩＰＧＲＩ）曾推荐 5%～ 6%的含水量和 - 1 8～- 2 0℃低温作为各国长期保存种子的理想条件。目前,世界各国都把更多的…