NaCl对库拉索芦荟的胁迫效应研究

温室盆栽条件下，研究了100～400mmol／L NaCl胁迫对2年生库拉索芦荟的生长及体内离子分布的影响。结果表明，100mmoL／L NaCl处理下芦荟植株干重和叶片叶绿素含量与对照差异不显著，200和400mmol／L NaCl处理下干重和叶绿素含量显著下降；芦荟根系活力在200mmol／L NaCl处理下达到最大值，增加盐浓度，根系活力下降；盐胁迫处理的叶片电解质渗漏率显著高于对照，随着胁迫强度的增加而增加。盐胁迫下，芦荟体内Na^＋和Cl^-含量随着盐浓度的增加而增加，K^＋和Ca^2＋表现出相反的变化趋势。Na^＋主要积累在茎部，叶片和根系含量较小；Cl^-主要积累在叶片，茎部含量相对高于根系。盐胁迫下芦荟体内K^＋和Ca^2＋含量明显低于对照，随着盐浓度增加，叶片K^＋含量明显增加，Ca^2＋则相反。芦荟叶片保持相对较低的Na^＋／K^＋比率和较强的K^＋和Ca^2＋向上选择性运输能力，是芦荟具有一定耐盐性的重要原因。     

不同盐碱区白榆、白蜡、紫穗槐、柽柳体内离子分布特征

以沧州地区不同盐碱区域内（非盐、轻盐、中盐、重盐）白榆、白蜡、紫穗槐、柽柳4种植物为实验材料,分析了不同盐碱区域内4种植物体内Na^＋、K^＋、Ca^2＋含量,及在4种植物体不同器官中的运输和分配特点。结果表明,不同盐碱区4种植物体内Na^＋、K^＋、Ca^2＋含量不同,并存在明显差异;其变化规律表现为：各植物体内Na^＋含量随盐碱区盐分含量的增加而迅速提高,但不同器官提高幅度不同,总体表现为根〉叶〉茎;K^＋、Ca^2＋含量在重盐区各树种均有所下降,其中,Ca^2＋含量下降的幅度较大;各植物体内Na^＋/K^＋、Na^＋/Ca^2＋的值随区域盐分含量的增加而提高,但不同器官升高幅度不同,其根部明显高于其他两种器官,且存在显著性差异。柽柳、白榆对K＋、Ca2＋向茎叶部的选择运输性比白蜡、紫穗槐的高,而对Na＋的选择运输性则低于白蜡、紫穗槐。综合分析,4种植物中柽柳的耐盐能力最强,白榆次之,白蜡、紫穗槐较差。     

植物逆境生理研究

一、小花碱茅抗盐性机理分析 小花碱茅（Puccinellia tenui flora）是禾本科盐生植物，抗盐能力很强，与禾本科作物有较近的亲缘关系。为了研究小花碱茅的抗盐机理，彭彦辉等以中等抗盐植物小麦（Triticum aestivum L．）为对照材料，应用离子分析和X-射线微分析技术检测了盐胁迫下小花碱茅根茎K^＋、Na^＋的含量和分布情况。研究表明，小花碱茅对K^＋／Na^＋具有很高的选择性吸收能力，无论在正常条件还是在盐胁迫下，小花碱茅吸收和累积钾的能力都很强。在盐胁迫下，小花碱茅根钾含量迅速增加2至3倍，钾元素主要分布在共质体和木质部，而盐分主要分布在内皮层以外的质外体；即使在低钾处理下，木质部中K^＋含量仍然较高。基于平面脂双层膜（PLBs）技术的电生理分析表明小花碱茅根细胞质膜的K^＋透性与K^＋／Na^＋选择性均远高于小麦。经内整流钾通道抑制剂Cs^＋和TEA处理后，小花碱茅吸收K^＋的能力明显下降，钾元素主要分布在小花碱茅根部的皮层细胞内；木质部中钾元素含量明显下降，K^＋／Na^＋显著下降。内皮层细胞有可能是钾通道抑制剂作用的主要部位，控制了K^＋、Na^＋进入木质部的过程。所有结果表明，钾通道的K^＋／Na^＋选择性和凯氏带造成的质外体阻障很可能是小花碱茅在根系与地上部间维持相当大的钠浓度梯度以及正常的植株钾浓度的关键因素。     

等渗PEG和NaCl溶液对西葫芦种子萌发及幼苗生长的影响

以2个耐盐性不同的西葫芦品种白美西葫芦（盐敏感）和黑皮西葫芦（耐盐）为材料,研究了PEG-6000、NaCl、Na^＋ -盐、Cl^- -盐对西葫芦相对发芽势、相对发芽率、电解质渗透率、MDA含量、叶绿素含量等指标的影响。结果表明,PEG-6000处理对西葫芦相对发芽势存在显著影响;NaCl、Na^＋ -盐、Cl^- -盐处理对西葫芦的各项生理指标的影响较PEG-6000更为显著;Na^＋和Cl^-相比,西葫芦对Cl^-更为敏感。     

硅对盐胁迫下黄瓜幼苗根系质膜、液泡膜酶活性的影响

研究硅对盐胁迫下黄瓜幼苗生长及根细胞质膜H^＋-ATPase、液泡膜H^＋-ATPase、H^＋-PPase和Ca^2＋-ATPase活性的影响。结果表明：盐胁迫严重抑制黄瓜幼苗生长,根细胞质膜H^＋-ATPase、液泡膜H^＋-ATPase、H^＋-PPase和Ca^2＋-ATPase活性明显降低。硅处理明显提高盐胁迫黄瓜根液泡膜H^＋-ATPase、H^＋-PPase、Ca^2＋-ATPase活性,一定程度上维持了液泡膜质子泵活性,有效地防御了细胞质酸化,这可能是硅提高黄瓜耐盐性的一个重要因素。     

水稻孕穗期剑叶形态和蒸腾特性与耐盐性的关系

以6个水稻品种为试验材料,在田间生长状态下灌溉NaCl配制的水溶液进行盐胁迫,于孕穗期取样分析Na+、K+、Ca2+的吸收规律和剑叶的形态及蒸腾特性,并分析与品种耐盐性的关系。结果表明,6个品种的耐盐性按耐盐系数高低依次为:龙稻5>长白10>松粳12>东农425>牡丹江26>牡丹江30。盐胁迫后水稻植株Na+含量增加,K+含量减少,耐盐品种地上部Na+积累量较少,根中较多,耐盐品种地上部K+积累多,根中差异不明显;Ca2+大多集中在根部,胁迫后耐盐品种在根部变化不明显,敏感品种下降较多。盐胁迫下,供试品种的剑叶长、剑叶宽和剑叶面积处理与对照的差异均达显著或极显著水平,耐盐品种剑叶受损较轻;部分品种的剑叶在胁迫后发生卷曲,部分品种由卷曲变为平展,耐盐品种的卷曲度要小于盐敏感品种。叶绿素含量相对值随品种耐盐性的降低逐渐降低,差异达显著或极显著水平。盐胁迫后,耐盐品种较盐敏感品种的蒸腾速率和气孔导度高,而冠层温度则随品种耐盐性的降低而升高。孕穗期地上部K+含量相对值、剑叶宽相对值、冠层温度相对值、根Na+含量相对值、根Ca2+含量相对值、剑叶面积相对值和蒸腾速率相对值可作为水稻耐盐性筛选鉴定的指标。     

种子盐引发对转基因抗虫棉耐盐性的影响

以2个转基因抗虫陆地棉品种为材料,以其遗传背景品种为对照,研究种子引发对转基因抗虫棉在NaCl胁迫条件下的种子萌发和田间出苗的影响。结果表明,0.5%的NaCl处理显著地降低陆地棉种子发芽势和发芽率,其中转基因抗虫棉品种(中棉所41和浙905)的种子萌发和田间出苗率差于遗传背景亲本(中棉所23)。种子盐引发处理可以有效地缓解NaCl的胁迫作用,显著地提高种子的发芽势、发芽率和田间出苗率,显著地提高棉花种子的耐盐性。种子盐引发处理对转基因抗虫棉品种的效果优于非转基因抗虫棉的背景品种。引发剂种类对于其耐盐性的影响有一定的差异,以K2SO4的效果更好,且引发剂的浓度与引发时间之间存在着一定的互作效应,高浓度引发剂的处理时间宜短,而低浓度引发剂的处理时间应适当延长。     

外源AsA对盐胁迫下水稻叶绿体活性氧清除系统的影响

研究了外源AsA对盐胁迫下不同耐盐性水稻品种Pokkali（耐盐）和Peta（盐敏感）叶绿体中活性氧清除系统的影响。结果表明：盐胁迫下,外源AsA能提高不同耐盐性水稻品种叶绿体中SOD、APX、GR活性,增加叶绿体内AsA和GSH含量,减少H2O2和MDA含量,提高叶绿体中活性氧的清除能力。在盐胁迫或同时加入AsA条件下耐盐品种Pokkali叶绿     

盐胁迫下转甜菜碱醛脱氢酶基因水稻幼苗耐盐生理的研究

在NaCl浓度0，3．0，5．0，7．0g／L下，对转甜菜碱醛脱氢酶(BADH)基因水稻的两个品系51—22，52—7及其受体亲本中花8号进行幼苗耐盐性试验。结果表明：转BADH基因水稻比其受体亲本耐盐性强，在高NaCl浓度(5．0，7．0g／L)胁迫下，甜菜碱醛脱氢酶基因可以提高盐胁迫下水稻幼苗过氧化氢酶(CAT)活性，提高根系活力和叶绿素含量，稳定细胞膜的透性，降低植株体内Na^ 的积累，从而减轻幼苗受盐害的程度。盐胁迫下水稻幼苗的CAT活性、SNa^ ／K^ 、叶Na^ ／K^ 、叶绿素含量是影响幼苗生长的主要生理指标。     

高温胁迫对早稻根系质膜ATPase活性及NH+4吸收的影响

选用高温耐性品种农大228、082和高温敏感品种茉莉占、协青早B，比较研究了高温胁迫对根系质膜ATPase活性和NH4^＋吸收速率的影响。结果表明，高温胁迫下，农大228和082根系质膜H^＋-ATPase和Ca^2＋-ATPase活性均比对照提高，而茉莉占和协青早B分别比对照大幅度下降，品种间差异显著（Duncan’s法检验）。根系质膜蛋白含量在高温胁迫后均表现下降。082的NH4^＋吸收速率不受高温影响，热敏感型品种NH4^＋吸收速率受高温胁迫明显下降。     

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.     

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.     

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.     

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.