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31.
现代水产种业硅谷建设的几点思考 总被引：3，自引：1，他引：2
"国以农为本,农以种为先",种业位于农业产业链的最前端,是国家战略性、基础性产业,也是决定现代农业发展的核心要素。我国是世界上12个生物多样性特别丰富的国家之一,水产种质资源分布极为广泛。近年来,我国水产种业发展迅速,但水产增养殖业的良种覆盖率仍然较低。因此,加快发展水产种业尤显迫切。该文论述了国内外水产种业发展现状,分析了我国水产种业存在的问题和发展趋势,提出了建设水产种业硅谷的设想,并对建设目标、建设内容、建设原则及其保障措施提出了几点建议,以期为我国水产种业健康发展起到积极的促进作用。 相似文献
32.
Discretizing a domain of interest into a set of particles for discrete element simulation is the first step to generate a specimen. An improved algorithm, the Seed Expansion Method (SEM), is proposed in this work. A seed is first generated inside a given domain. Then, the domain is filled by the seed expansion based on a local Delaunay tessellation and a distance function. An optional operation, refilling, is suggested to further improve the packing density after the completion of SEM. Polydisperse dense packing can be generated by the proposed method for an arbitrarily shaped domain in both 2D and 3D. A specimen can be obtained that approximately conforms to a specified size distribution and packing density. Multiple subdomains of a domain can be filled by packings with different densities and size distributions. A specimen with higher density can be obtained by comparing it with the existing methods. Mathematically, the features of the method include both simplicity and high efficiency. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
33.
We studied current recruitment failure of Dobera glabra, an important famine-food throughout the dryland parts of the Horn of Africa. The species has previously been found to have recalcitrant seeds, a strategy not common for plants in dryland areas. We experimentally tested (1) how germination capacity of D. glabra is affected by seed form, storage period and moisture under nursery conditions, and (2) how seed predation by vertebrate herbivore and seed exposure at germination site affect germination under field conditions in northern Afar rangelands, Ethiopia. D. glabra seeds that received either mulching or supplementary watering (3 days/week) had a higher germination success than controls. The seeds are probably desiccation sensitive since stored seeds had poor germination performance compared to fresh seeds. Seeds in the rangeland plots protected from herbivores had significantly higher germination success compared to open plots. Our findings demonstrate that seed predation and moisture limitation highly reduced the germinability of the recalcitrant D. glabra seeds, indicating that the species might have persisted due to past wetter periods and low herbivore density in dry environments. 相似文献
34.
Oscar Vicente Monica Boscaiu Miguel ngel Naranjo Elena Estrelles Jos María Bells Pilar Soriano 《Journal of Arid Environments》2004,58(4):705
General responses to salt stress have been investigated in the halophyte Plantago crassifolia. Seed germination was strongly inhibited by NaCl, although seed viability and germination capacity were not affected by salt pre-treatments. A concentration-dependent inhibition of plant growth was observed in the presence of NaCl, which was accompanied by the accumulation of Na+ ions in the leaves, as determined by cation exchange HPLC. A 20-fold increase of proline content in leaves was observed when plants were treated with 500 m
NaCl, suggesting a protective role against high salinity stress for this amino acid, whose possible mechanism of action is discussed. 相似文献
35.
盐胁迫对西葫芦和黄瓜种子萌发影响的对比研究 总被引：35，自引：0，他引：35
用不同浓度的地下盐水胁迫西葫芦和黄瓜种子萌发，观察其发芽率和萌发后幼苗生长情况，计算其发芽指数和活力指数，进行了对比分析。结果表明：西葫芦种子萌发对盐水生境的适应性比黄瓜强，西葫芦种子萌发的盐胁迫适宜值为０．６１ｇ／１００ｃｍ３，而黄瓜为０．３６ｇ／１００ｃｍ３。 相似文献
36.
云南种子植物区系地理成分分布格局及其意义 总被引：5，自引：1，他引：4
以覆盖云南全境的31个地区植物区系研究报告为基础, 使用Arcview软件制作了14个种子植物属的地理成分多度分布图。 对这些种子植物属的多度分布格局进行分析,获得以下结果:①热带成分合计占所统计的地区植物区系属的29.6%~94.1%, 其最小值是在云南西北部, 最大值出现在云南南部; 温带成分合计占所统计的地区植物区系属的6%~70.4%, 其多度分布恰与热带成分相反。②在热带成分中, 全热带分布属占13.64%~46%, 居热带成分之首, 其最大值出现在云南怒江和元江的干热河谷; 热带亚洲分布属占3.33%~42.26%, 最大值出现在云南南部。③在温带成分中, 北温带分布属占所统计的地区植物区系的2%~30.39%, 居温带成分之首, 最大值出现在云南西北部山地, 其次是东亚分布属, 占2%~14.57%, 最大值出现在滇西北横断山区。④在与云南植被的关系上,热带亚洲分布属、旧世界热带分布属和热带亚洲至热带大洋洲分布属是云南热带森林的主要成分; 全热带分布属和热带亚洲至热带非洲分布属是干热河谷植被的主要成分,北温带分布属主要出现在冷湿山地森林植被中,而东亚分布属、东亚和北美洲间断分布属及旧世界温带分布属与温凉气候地区的森林植被联系相对密切。⑤生物地理上,云南种子植物属的多度分格局暗示了所谓的“田中线”在印度—马来西亚热带植物区系与东亚亚热带—温带植物区系的地理界限上有意义;热带亚洲至热带非洲分布属主要存在于云南的干热河谷,暗示了干热河谷植被具有一定非洲亲缘;云南西部的热带性很强,暗示了在印度板块同亚洲板块相撞、推挤北移及喜马拉雅隆升过程中, 云南西部至东南部的地块可能发生了顺时针转动。⑥在云南, 不论其纬度, 只要是海拔低的区域都是热带区域, 支持云南应是一个基带为热带的大的山原观点。 相似文献
37.
Seedling recruitment in a semi-arid steppe: The role of microsite and post-dispersal seed predation 总被引：2，自引：0，他引：2
Grasslands dominated by Stipa tenacissima are important ecosystems in the arid and semiarid climates of western Mediterranean, where they have originated by degradation of open dry forests and shrublands. At present, although the level of exploitation in these ecosystems is very low, succession processes seem to have stopped. In this study, we explore the role of microsite and post-dispersal seed predation on the seedling emergence of two species from advanced successional stages (Rhamnus lycioides, Quercus coccifera), three species from degraded stages (Cistus clusii, Helianthemum violaceum, Anthyllis terniflora), and of the dominant species (Stipa tenacissima). Seeds of these species were sown in plots divided into two microsites: (i) under tussocks of S. tenacissima and (ii) in the bare soil between tussocks. Soil moisture was significantly higher in the tussock microsites. The interaction observed between microsite and time, reflected the slower drying process under tussocks. Seed predation was in general high and differed significantly between species but not between microsites. Q. coccifera was especially affected by predation. The only germination detected in gap areas was that of H. violaceum. The results pointed to a direct facilitative effect of tussock grass on the germination in R. lycioides (20.4±8.0%) and S. tenacissima (41.3±5.7%) while the corresponding figures for bare ground were 0%. These results suggest that the recovery of potential vegetation in this ecosystem is not possible or, at least, is very slow because the residual shrub patches do not generate a sufficient number of seeds able to disperse to favorable germination microsites. S. tenacissima may act as facilitator of seedling recruitment if there is a supply of diaspores. 相似文献
38.
骆驼蓬属（Peganum L.）种子氨基酸组成及其系统学意义 总被引：5，自引：0，他引：5
本文分析了我国西北地区骆驼蓬属植物种子中总氨基酸和游离氨基酸的组成。结果表明：均以天冬氨酸、苏氨酸、丝氨酸、谷氨酸、缬氨酸、精氨酸和脯氨酸为主要组成。其中，苏氨酸含量最高。分别达２８．６３％和２６．１５％。在一定意义上反映了该分类群的同源性和遗传稳定性。多裂骆驼蓬在精氨酸和亮氨酸的含量上与骆驼蓬有较显著差异，为该种的独立提供了又一佐证。不同生境下，多裂骆驼蓬种子中游离脯氨酸含量随干旱胁迫减弱而降低 相似文献
39.
This is a reply to Ortega-Baes’ et al. (2010) survey of 25 Argentinean species of cacti evaluated for vivipary. We argue that the sample size and geographic area of the species investigated is insufficient to totally exclude the putative commonness of this condition in the Cactaceae. We indicate possible reasons why they did not find viviparous fruits in their survey. Failure to detect vivipary in cacti of NW Argentina may be correlated with limited taxonomic sampling and geographic region in addition to intrinsic and extrinsic plant factors, including different stages of fruit and seed development and genetic, ecological, and edaphic aspects, which, individually or in concert, control precocious germination. We uphold that viviparity is putatively frequent in this family and list 16 new cases for a total of 53 viviparous cacti, which make up ca. 4% incidence of viviparism in the Cactaceae, a substantially higher percentage than most angiosperm families exhibiting this condition. The Cactaceae ranks fourth in frequency of viviparity after the aquatic families of mangroves and seagrasses. We suggest the re-evaluation of cactus vivipary, primarily as a reproductive adaptation to changing environments and physiological stress with a secondary role as a reproductive strategy with limited offspring dispersal/survival and fitness advantages. 相似文献
40.
The medium-scale spatial patterns of soil seed banks (SSBs) and extant vegetation and the roles of abiotic factors are poorly understood. We selected the dry Minjiang River valley of southwest China to investigate SSB structure and corresponding extant vegetation in a medium-scale size (200-230 km long, 3-4 km wide) at eight sites across the valley using a germination method and field surveys. We found that, there was low seed density and species number in SSB and less coverage and litter thickness for community in extant vegetation at central sites compared with transitional sites across the dry valley; Quercus spp. occurred frequently in extant vegetation at transitional sites, while Caryopteris spp., Jasminum spp., Rabdosia parvifolia, Sophora davidii, Campylotropis spp., and Bauhinia faberi var. Microphylla was present frequently at central sites; Carex spp. and Artemisia spp. occurred frequently in SSB at transitional sites, while Ajania spp., Poa spp., and Fagopyrum caudatum was present more frequently at central sites. Hierarchical cluster analysis and Kendall’s correlation showed that the spatial variation of both SSB and extant vegetation had significant correlation with rainfall and air evaporation. 相似文献