Effects of vegetation cover on recruitment of Ulmus pumila L. in Horqin Sandy Land,northeastern China

Understanding the effects of vegetation cover on seedling survival is helpful for promoting vegetation restoration in environmentally fragile zones. This study was conducted in the desertified, moving sand dunes of Horqin Sandy Land, Inner Mongolia, northeastern China. We hyphothesized that(1) seed density(i.e., number/m2) increases as vegetation cover increases, and(2) there will be more surviving seedlings in locations with higher vegetation covers. Total vegetation cover and initial densities of seeds, germinated seeds and surviving seedlings of Ulmus pumilia were evaluated under various vegetation covers in trying to clarify the effects of vegetation cover on the early stages of the plant life history. In agreement with the first hypothesis, initial seed densities were greater(P<0.05) under higher vegetation covers. The relationship between vegetation cover and initial seed density was represented by a quadratic regression, where a threshold occurred with a vegetation cover of 36%(P<0.05). The higher total vegetation covers, however, did not result in increased densities of germinated seeds(P>0.05), which on average represented 16.7% of initial seed densities. Even more, three months after the study initiation, total vegetation covers were similar(P>0.05) at all positions in the dunes, and they determined a similar number(P>0.05) of surviving seedlings at those positions(i.e. the second hypothesis had to be rejected). The mean number of seed- lings that survived at all positions was only 4.5% of germinated seeds. The number of surviving elm seedlings(0 to 1.7 seedlings/m2) under various vegetations covers(12.2% to 20.8%) at all dune positions by late summer would most likely not contribute to vegetation restoration in the study area.     

人工老化对刺槐种子活力的影响

刺槐种子在高温、高湿模拟条件下人工加速老化1～6d,随着老化时间的延长,其生活力和活力指标均发生明显变化.老化5d后,种子丧失活力,发芽率为0.在老化过程中,电导率和过氧化物酶活性随老化程度的增大而明显增大.     

进一步履行好种子管理职能

随着国办发[2006]40号《关于推进种子管理体制改革、加强市场监管的意见》和省办发[2006]134号实施意见的发布,宣告了长期以来种子行业政、企不分,站、司一体旧体制的结束,标志着我国种业的市场化、法制化进入了新的历史时期。伴随种业市场的全面开     

曲靖市种子管理体制改革的探索与实践

根据《种子法》和国务院办公厅《关于推进种子管理体制改革加强市场监管的意见》（国办发[2006]40号）及云南省人民政府办公厅云政办发[2006]174号、曲靖市人民政府曲政发[2006]119号等文件的精神,曲靖市9个县（市）区和市级种子管理体制改革工作任务按时完成,并取得较好的成绩,总体达到农业部农办发[2007]7号关于印发《种子管理体制改革验收方案》通知中的验收标准。     

关于如何实施种子放心工程问题

在“放心农资下乡进村”活动中,种子放心工程的核心是建立种子专业服务网络,实行种子配送、信息传递、网上订购、技术推广一体化,减少环节,降低价格,提高效率。这一工程的实施,对于加强种子市场管理、规范种子生产经营行为、提高种子专业服务水平具有重要意义。     

良种体系——现代农业的起跑器

发展现代农业是新农村建设的首要任务。现代农业是先进科技的农业,其发展要靠多种因素推动,但种子是现代农业最重要的科技载体,在现代农业发展中起着基础性和先导性作用。本文结合江苏农业发展实际,阐述了建设良种体系在农业发展中的重要作用,围绕现代农业发展要求,提出了突破良种体系建设的几点思考和建议。     

种业市场渠道中的串货现象与应对策略

随着种业市场竞争的加剧,市场营销中的窜货现象最使经营者头疼。窜货即产品越区销售,也叫倒货、冲货。它往往导致市场秩序混乱,使种业生产公司与经销商关系恶化,从而破坏原有的销售网络,导致最终双方销售额和利润的降低。     

Effects of Ultra-drying on Viability and Physiological Characteristics of Platycladus orientalis Seed from Arid and Semiarid Areas of Northwest China

In order to supply quality seed for vegetation restoration in arid and semiarid areas of Northwest China, the effects of Platycladus orientalis seed storage under ultra-drying and accelerated aging were studied. The seeds were dried from 6.8% to 5.1%, 4.4%, 3.7% and 2.2% MC, respectively, in a desiccator with the silica gel. The germination energy, germination percentage, germination index and vigor index of the seed were investigated. After ultra-drying, groups of seeds were carried on the accelerated agin...