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31.
概述了“大树进城”之风形成的背景,对“大树进城”的弊端与危害进行了归纳,分析了“大树进城”之风难以遏止的原因,提出了“控两头、掐中间”、多管齐下、综合治理的基本思路和具体措施。 相似文献
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对上海市杨浦区45条城市道路绿化状况进行调查,从道路行道树绿带、分车绿带和路侧绿带3个方面分别调查分析了植物的种类、配置方式、观赏特性以及植物应用的频度,并对道路植物的配置模式进行探讨,提出了措施和建议。 相似文献
35.
Recent advances in molecular genetics of forest trees 总被引:3,自引:0,他引:3
M.R. Ahuja 《Euphytica》2001,121(2):173-195
The use of molecular markers has greatly enhanced our understanding of the genome structure of forest trees. Conifers, in
particular, have a relatively large genome, containing a very high proportion of repeated DNA, consisting of tandemly repetitive
and dispersed repetitive DNA sequences. The nature of highly conserved tandemly repetitive rRNA genes has been investigated
in a number of tree species, and their sites mapped on specific chromosomes by fluorescent in situ hybridization (FISH). Different families of retrotransposons (IFG, and TPE1) have been isolated and characterized from the dispersed repetitive DNA of pines. Genome maps have been constructed in a
number of forest tree genera: Pinus, Picea, Pseudotsuga, Cryptomeria, Taxus, Populus, and Eucalyptus. EST databases have been established from cDNA clones of pines and poplars. The structure and maternal or paternal modes
of inheritance of organelle genomes have been investigated in forest trees. Comparative mapping in conifers has shown that
gene families are conserved across genera. Due to lack of polyploidy in conifers, the evolution of this group of trees may
have occurred primarily by duplication and dispersal of genes, probably by retrotranspositions, to form complex gene families.
The evolution of angiosperm tree species has presumably involved both gene duplication as well as genome duplication (polyploidy).
Application of genetic engineering has shown that genes from phylogenetically unrelated organisms can be introduced and expressed
in trees, thus offering prospects of genetic improvement of forest trees.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
36.
Progress in mapping agronomic genes in apple (The European Apple Genome Mapping Project) 总被引:4,自引:0,他引:4
Graham J. King 《Euphytica》1994,77(1-2):65-69
Summary The progress of the European Apple Genome Mapping Project is described. Populations segregating for a range of agronomic genes
have been established in six European countries. The need for robust methods of analysis has been identified, especially with
regard to the development of molecular markers. Isozyme systems, RAPDs, RFLPs and amplified genes are being used to construct
a reference genetic linkage map. Standardisation and precise definition of both genotypic and phenotypic measurements has
been recognised as being essential for future exploitation of genetic markers in apple breeding. Phenotypic measurements are
being replicated in different geographical locations over several years. Statistical and genetic analyses are aimed at defining
components of genetic variation which account for ‘genes’, as defined by apple breeders. A relational database is being constructed
which will combine disparate sources of data relating to the genetics of apple. Comparative mapping has been identified as
an efficient means of expanding genetic knowledge within and between Rosaceae genomes. 相似文献
37.
对矮砧苹果新植苗木和2~5年生幼树死亡的原因进行研究,表明苗木失水与轮纹病菌协同危害是主要原因;冻害、根部与主干病害、肥害及苗木质量差是重要原因。生产上及时发现问题,根据不同症状,进行准确的病因诊断,有针对性地采用不同的防控措施:培育不潜带轮纹病菌的苗木;苗木贮运、栽植和管理过程防止失水;栽植前用杀菌剂铲除部分病菌;防止冻害;2~5年生幼树合理肥水管理;防止贪绿徒长;有效地预防根部和枝干病虫害发生。 相似文献
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近年来有关果树组织培养的研究很多,其中对果树体细胞胚胎发生的研究越来越受到重视。现对近10a来国内外果树通过体细胞胚胎发生途径再生植株的研究现状进行了总结,分析了果树体细胞胚胎在发生途径上的特点,并从发生过程分析了体细胞胚胎发生的影响因素,同时对其生理生化代谢以及实际应用等方面进行综述。提出该领域今后应逐步开展对果树体细胞胚胎发生的生理生化和分子机理研究,促进体细胞胚胎发生研究成果在生产实践中的应用。 相似文献
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