阳春砂种子休眠与萌发过程中同工酶活性变化的研究

[目的]研究阳春砂种子休眠与萌发过程中同工酶的活性及酶谱变化规律,为阳春砂种子休眠与萌发过程生理调控机制的分析探讨奠定基础.[方法]以赤霉素浸种前、浸种后、培养10 d、种子露白、胚芽长至1 cm时各阶段的阳春砂种子为材料,测定其种子中过氧化物酶(POD)和超氧化物歧化酶(SOD)的活性,并采用聚丙烯酰胺凝胶电泳(PAGE)技术研究建立过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)及酯酶(EST)同工酶的电泳酶谱.[结果]阳春砂种子在休眠和萌发过程中,POD、SOD、CAT和EST同工酶的活性及酶谱带的数量均发生了一定的变化,其中POD和SOD同工酶活性均呈先减弱后增强的趋势;CAT同工酶在萌发前期变化不明显,后期酶的活性增强,且酶的种类也增加;EST同工酶的酶活性呈先减弱后增强再减弱的变化趋势,且在种子露白时活性达到最强.[结论]阳春砂种子休眠与萌发过程中同工酶谱的变化特点一定程度上可反应出种子休眠与萌发不同阶段的生理特性,这些同工酶基因的差异表达导致了阳春砂种子打破体眠和最终的萌发.     

特定磁波对作物某些生理生化特性的影响

报道特定电磁波变辐射器（TDP）辐照各种大田作物及蔬菜作物,包括小麦、水稻、玉米、高粱、番茄、萝卜、碗豆等的种子和萌发种子后对作物某些生理生化特性的影响。结果指出,TDP辐照能显著促进淀粉酶、过氧化物酶、SOD的活力,增加ATP含量、超弱发光强度、种子放热量,提高P/O值和蛋白质含成强度。     

滇龙胆草种子休眠机制与萌发特性初步研究

为探索滇龙胆草种子的休眠机制及解除种子休眠的措施,对滇龙胆草种子采取了休眠程度测定、种子萌发时吸水规律测定、种子休眠机制的生物学鉴定、室温贮藏下种子生活力变化测定及低温层积处理效果.结果表明:新采集的滇龙胆草种子较经低温(4℃)贮藏了1年的种子萌发时间长;由于种皮相对透水、透气差,在室温下种子需经39 h才能充分吸水膨胀;新采集的滇龙胆草种子中有可溶于水的萌发抑制物,其水浸提液对白菜籽萌发及胚根生长均有抑制作用;滇龙胆草种子在室温下贮藏时,随着贮藏时间的延长,其活力逐渐下降,在生产实践中,种子在室温下的贮藏时间不宜超过6个月;一定时间的低温层积处理有利于种子萌发,为缩短刚采收种子的萌发时间,50 ～80 d的低温层积处理效果相对较好.     

60Co-γ射线对芹菜种子的辐射效应

以3个芹菜品种的干种子为材料,用不同剂量的60Co-γ射线进行辐照处理,研究辐照对种子活力和M1代苗期生长及生理指标的影响。结果表明,辐射对3个品种的效应一致。当辐照剂量达到或高于200 Gy时,芹菜种子的萌发能力和种子活力显著下降,当辐照剂量为300 Gy时,种子没有发芽能力。60Co-γ射线辐照影响了芹菜M1代幼苗的生长和生理代谢,当辐照剂量达到或大于200 Gy时,幼苗的株高下降了50%~60%;50、100、150 Gy的辐照剂量刺激了幼苗的超氧化物歧化酶（SOD）、过氧化物酶（POD）、抗坏血酸过氧化物酶（APX）和谷光甘肽还原酶（GR）活性的增加,50、100、150 Gy的辐照剂量下超氧阴离子（O2ˉ?）产生速率和丙二醛（MDA）的含量和对照差异不显著,当辐照剂量达到或超过200 Gy时,幼苗SOD、POD和APX活性显著下降,且O2ˉ?产生速率和MDA含量显著上升,说明低于或等于150 Gy的辐照不会对芹菜幼苗的生长造成影响。综合分析所测定的指标,芹菜干种子的适宜诱变剂量为100~150 Gy。     

高压静电场对南瓜种子萌发及幼苗生长的生物学效应

南瓜种子经不同电场强度处理一定时间,研究其萌发状况并测定了12项生理生化指标.实验结果表明:经电场处理后,与对照相比,种子发芽率提高了3.2%～9.7%,电解质外渗率、呼吸强度均有不同程度的改善,可溶性蛋白的含量明显提高,静电处理还提高了种子中CAT、SOD等清除自由基的酶的活性,起到了提前打破种子休眠、提高种子活力、促进种子代谢水平的作用.各项指标显示:以H、I、J效果最为显著,可视为高压静电场处理南瓜种子的最佳剂量.     

水杨酸对盐胁迫下三角滨藜种子萌发及幼苗生长的影响

以盐生植物三角叶滨藜为材料。研究不同浓度水杨酸（SA）处理对三角滨藜在不同浓度盐胁迫（NaCl）下种子萌发和幼苗生长的影响。结果表明：随着盐胁迫浓度的增加．滨藜种子发芽率逐步降低．当NaCl浓度达200mmol／L时严重抑制滨藜种子的萌发。用SA浸种后，在没有盐胁迫的情况下，可以增加滨藜种子的萌发率．但在有盐胁迫的情况下，SA不能增加种子的萌发率，甚至加剧了盐胁迫的不利影响。滨藜幼苗在0～200mmol／L的盐浓度下均能正常生长，用SA处理幼苗，能够促进盐胁迫下幼苗的生长。测定SA处理后幼苗体内过氧化物酶（POD）、超氧化物歧化酶（SOD）的活性变化。结果表明：SA处理可以提高盐胁迪下幼苗体内的SOD和POD活性。     

广西绞股蓝种子休眠与萌发特性研究

对广西绞股蓝种子进行了生活力测定、发芽试验、吸水率测定及离体胚萌发试验,并对广西绞股蓝种子进行酸碱处理、低温层积和干藏处理、GA₃和6-BA溶液处理,探讨不同的处理对广西绞股蓝种子萌发的影响。结果表明新鲜广西绞股蓝种子的活力高达98%,但在6个恒温和1个变温条件下,其萌发率最高仅为11.7%,说明广西绞股蓝具有明显的休眠现象。种子吸水性测定结果表明,广西绞股蓝种皮限制种子吸水,离体胚萌发实验证实广西绞股蓝种子的胚在离体条件下没有休眠现象,说明种皮障碍是导致广西绞股蓝种子休眠的主要原因。低温层积不能解除广西绞股蓝种子的休眠,而干藏则会导致种子内部失水,从而导致种子生活力降低。浓硫酸和不同浓度的NaOH溶液处理均不能打破种子的休眠,仅6-BA溶液处理对4℃层积后的种子萌发起到一定的促进作用。     

不同萌发率胡杨种子萌发前后同工酶动态变化分析

对不同萌发率的胡杨种子萌发前后酯酶同工酶、过氧化物酶同工酶和超氧化物歧化酶同工酶电泳谱带的动态变化进行分析.研究表明:对于吸胀的种子,过氧化物酶同工酶没有表达;酯酶同工酶得到表达,且萌发率中等的种子表达最高;超氧化物歧化酶同工酶也得到表达,但萌发率高的种子几乎没有表达;对于干种子,酯酶同工酶没有表达,过氧化物酶同工酶得到表达,且萌发率中等的种子表达最高;超氧化物歧化酶同工酶得到充分的表达.     

迷人杜鹃种子萌发过程中的生理变化

通过对迷人杜鹃种子在萌发过程中可溶性蛋白质、抗氧化保护酶和代谢产物的测定,了解这些生理指标在种子萌发过程中的变化趋势.结果表明:可溶性蛋白质、超氧化物歧化酶SOD、过氧化物酶POD、过氧化氢酶CAT在种子萌发过程中变化趋势基本一致,随着培养时间的延长,含量或活性都呈上升趋势,丙二醛MDA的含量变化则相反,在萌发过程中逐渐减少.说明种子萌发过程中抗氧化酶协同作用,降低了脂膜氧化程度,促进发芽.     

黄秋葵种子快速萌发试验研究

在２５℃适宜温度条件下测定了黄秋葵种子的吸水曲线，在浸种１２小时内吸水迅速，１２－１６小时吸水速度开始减慢，至２０小时后种子内水分饱和，不再吸水，在春季干旱播种播前必须进行浸种处理。用过氧化氢和赤霉素处理黄秋葵种子可快速促进种子萌发，显著提高发芽率，两者的最适浓度为过氧化氢０．５％，赤霉素１ｇ／Ｌ；过氧化氢的作用在于软化种皮，促进呼吸作用，加速贮藏物质分解，而赤霉素的作用则是打破休眠，促进种子萌发     

A note on the origin of Kalanchoë x vadensis Boom & Zeilinga (Crassulaceae)

Summary K x vadensis is a hybrid of K. blossfeldiana and K. marmorata obtained after doubling the number of chromosomes.     

Mechanisms and diversity of resistance to sorghum shoot fly,Atherigona soccata

Sorghum shoot fly, Atherigona soccata, is one of the important pests of postrainy season sorghums. Of the 90 sorghum genotypes evaluated for resistance to this pest, RHRB 12, ICSV 713, 25026, 93046 and 25027, IS 33844‐5, Giddi Maldandi and RVRT 3 exhibited resistance in postrainy season, while ICSB 463, Phule Anuradha, RHRB 19, Parbhani Moti, ICSV 705, PS 35805, IS 5480, 5622, 17726, 18368 and 34722, RVRT 1, ICSR 93031 and Dagidi Solapur showed resistance in rainy season, suggesting season‐specific expression of resistance to A. soccata. ICSB 461, ICSB 463, Phule Yasodha, M 35‐1, ICSV 700, 711, 25010, 25019 and 93089, IS 18662, Phule Vasudha, IS 18551 and 33844‐5 and Barsizoot had fewer deadhearts than plants with eggs across seasons, suggesting antibiosis as one of the resistance mechanism. Five genotypes exhibited resistance with high grain yield across seasons. Correlation, path and stepwise regression analyses indicated that leaf glossiness, seedling vigour, trichome density, oviposition and leaf sheath pigmentation were associated with the expression of resistance/susceptibility to shoot fly, and these can be used as marker traits to select and develop shoot fly‐resistant sorghums.     

Reaction of tritordeum to Fusarium culmorum and Septoria nodorum

Summary Hordeum chilense is a wild barley extensively used in wide crosses in the Triticeae. It could be a valuable source of resistance to Fusarium culmorum and Septoria nodorum. Some H. chilense x Triticum spp. amphiploids, named tritordeums, were more resistant than the parental wheat line to these diseases, others were not. Average contents of ergosterol and deoxynivalenol (DON) suggested that resistance to colonization by Fusarium was the highest for Hordeum chilense, followed by tritordeum and wheat in decreasing order. In particular, the H. chilense genotypes H7 and H17 enhanced the wheat resistance to F. culmorum in its tritordeum offsprings. Resistance to S. nodorum in tritordeum was not associated with tall plant height. There is sufficient genetic variation for resistance to F. culmorum and S. nodorum among tritordeum to allow the breeding of lines combining short straw and resistance to both diseases.     

Disease resistance in protected crops and mushrooms

Summary Cultivars of tomatoes, cucumbers, lettuce and peppers have been bred for resistance to one or more pathogens. Some tomato and cucumber cultivars have resistance to a wide range of diseases. Resistance has been transient in many cases and a succession of cultivars with new genes or new combinations of resistance genes has been necessary to maintain control. There has been a number of notable exceptions and these have included durable resistance to such pathogens asFulvia fulva and tomato mosaic virus. With lettuce the resistance situation is complicated by the occurrence of fungicide resistant pathotypes. There are no strains ofAgaricus bisporus purposely bred for disease resistance.In protected flower crops only resistance to Fusarium wilt in carnations has been purposely bred but differences in disease resistance are apparent in cultivars of many ornamental crops. This is particularly so in chrysanthemums where there are cultivars with resistance to many of the major pathogens. Similar situations occur with other flower crops and pot plants. Cultivars of some species have not been systematically investigated for resistance.The need for genetic resistance will increase with the further reduction, in the limits on pesticide use and an increasing public awareness and importance of pesticide pollution.ADAS is an executive agency of the Ministry of Agiculture, Fisheries and Food and the Welsh Office.     

Avoidance of leaf rust fungi in wild relatives of cultivated cereals

Summary Avoidance of rust fungi that was based on poor appressorium induction was previously found in Hordeum chilense. In the present study 95 accessions of Triticeae were screened for avoidance of Puccinia hordei. The percentage of appressorium formation per germinated spore ranged from 6 to 90%. On none of the 41 accessions of Aegilops, Agropyron, Elymus, Secale, Thinopyrum or Triticum studied was the rate of appressorium formation lower than 25%. Lower rates of appressorium formation were, however, found on accessions of wild barley species Hordeum brachyantherum, H. marinum, H. parodii and H. secalinum. Its implications in cereal breeding are discussed.     

Genetic constitution and diversity in four narrow endemic redwoods from the family Cupressaceae

The genetic constitution and diversity of four relictual redwoods are discussed in this review. These include monotypic genera of the family Cupressaceae: coast redwood (Sequoia sempervirens), giant sequoia (Sequoiadendron giganteum), dawn redwood (Metasequoia glyptostroboides), and alerce (Fitzroya cupressoides). All four species are narrow endemics, share a number of common phenotypic traits, including red wood, and are threatened species. Fossil history suggests that the ancestors of redwoods probably originated during the Cretaceous and Tertiary periods and flourished thereafter for millions of years. Towards the end of the Tertiary period began their decline and struggle for existence that continued during the subsequent geologic upheavals and climate changes, until the survival of the present-day redwoods in the current restricted locations in the world (USA, China, and South America). Although two species, Sequoiadendron and Metasequoia, are diploids (2n = 22), and the other two are polyploids: Fitzroya a tetraploid (2n = 4x = 44), and Sequoia a hexaploid (2n = 6x = 66); they all share the same basic chromosome number x = 11. The genome size in the hexaploid Sequoia is one of the largest (31,500 MB) in the conifers, while the genome sizes of diploid Metasequoia and Sequoiadendron are about one-third (~10,000 MB) of Sequoia. Genetic diversity in the redwoods is lower than most other gymnosperms, except in Sequoia, which seems to rank near the upper quarter of the coniferous forest trees. Genomic research is sparse in the redwoods, and should be pursued for a better understanding of their genome structure, function, and adaptive genetic diversity.     

Distribution,ecology and reproductive biology of wild tomatoes and related nightshades from the Atacama Desert region of northern Chile

Over the past 20 years, several expeditions were made to northern Chile to collect populations of wild tomatoes (Solanum chilense, S. peruvianum) and allied nightshades (S. lycopersicoides, S. sitiens), and obtain information about their geographic distribution, ecology and reproductive biology. Restricted mainly to drainages of the Andean and the coastal cordillera, populations are geographically fragmented. The two nightshade species are rare and threatened by human activities. Adaptation to extreme aridity and soil salinity are evident in S. chilense and S. sitiens (the latter exhibits several xerophytic traits not seen in the tomatoes) and to low temperatures in S. lycopersicoides and S. chilense. All tested accessions are self-incompatible, with the exception of one S. peruvianum population collected at the southern limit of its distribution. Several distinguishing reproductive traits—anther color, attachment, and dehiscence, pollen size, and flower scent—suggest S. sitiens and S. lycopersicoides attract different pollinators than S. chilense and S. peruvianum. The four Solanum spp. native or endemic to Chile provide a variety of novel traits which, through hybridization and introgression with cultivated tomato, could facilitate development of improved varieties, as well as research on a variety of basic topics, including plant-pollinator interactions, abiotic stress responses, and evolution of reproductive barriers.     

The induction in vitro of adventitious shoots in Rosa

Summary Adventitious shoots were formed on excised leaves, roots and callus of Rosa persica x xanthina and on excised leaves of R. laevigata and R. wichuraiana on culture media that included BAP and NAA as growth regulators. Shoots formed freely on freshly cultured callus of R. persica x xanthina but their production declined in successive cultures and ceased after twelve weeks. Transplantation to soil was improved by rooting plantlets in cellulose plugs in vitro and transferring plantlets to soil while still in the plugs.     

The exploration of genetic resources of Portuguese cabbage and kale for resistance to several Brassica diseases

Summary Twenty three accessions of nine Portuguese cabbage and kale land races from different geographic origins were tested at the seedling stage for resistance to several important brassica diseases. Resistance to downy mildew (Peronospora parasitica), expressed as necrosis of the cotyledon mesophyll, was found in all the accessions. Type A resistance to cabbage yellows (Fusarium oxysporum f. sp. conglutinans race 1) was present in most of the landraces. Resistance to clubroot (Plasmodiophora brassicae race 6) was found in one accession of the Portuguese tree kale. High resistance to blackleg (Leptosphaeria maculans) and white rust (Albuco candida) was not detected, although several accessions showed 20 to 30% of plants with intermediate expression of resistance. All Portuguese cole accessions were susceptible to blackrot (Xanthomonas campestris pv. campestris).     

Production and characterization of intergeneric diploid cybrids derived from symmetric fusion between Microcitrus papuana Swingle and sour orange (Citrus aurantium)

Plants were regenerated from intergeneric somatic hybridization between embryogenic protoplasts of Microcitrus papuana Swingle and leaf-derived protoplasts of sour orange (Citrus aurantium L.) via electrofusion. The regenerated plants were morphologically similar to the leaf parent in growth vigor, leaf and branch structure. FCM analysis showed that they were diploids. Simple-sequence-repeat (SSR) and cleaved-amplified-polymorphic-sequence(CAPS) were employed for hybridity characterization. SSR banding patterns of the regenerated plants were identical to the leaf parent, sour orange, indicating that they possessed nuclear component derived from sour orange. DNA amplification with chloroplast and mitochondrial universal primers, followed by restriction endonuclease digestion, revealed polymorphism between the fusion parents. Therefore, this method was used to determine the cytoplasmic compositions of the regenerated plants. Banding patterns for all the polymorphic primer/enzyme combinations of the regenerated plants were similar to those of the embryogenic parent, M. papuana, suggesting that only the cytoplasmic components derived from the embryogenic parent were present in the regenerated plants. FCM, SSR and CAPS demonstrated that intergeneric diploid cybrids have been successfully obtained by symmetric fusion. Related results concerning nuclear and cytoplasmic composition of previous diploid somatic hybrids and potential mechanism for regeneration of such kind of plants are discussed herein. This revised version was published online in July 2006 with corrections to the Cover Date.