不同处理方法对美国截叶胡枝子种子发芽的影响

美国截叶胡枝子的硬实率很高,发芽率只有17.3%.经过种子预处理,如采用不同温度下浸种、98%浓硫酸浸泡、机械破皮和机械破皮结合热水浸种等处理,结果表明,机械破皮后用60℃热水浸种处理的效果最好,发芽势和发芽率分别达到64.0%和74.3%;其次是机械破皮,平均发芽率达到50%;浓硫酸浸种可以显著提高种子发芽势,浓硫酸浸种5min效果最好,发芽率达到44.7%;热水浸种的处理效果不佳,最好的90℃热水浸种处理发芽率也仅有26.7%.     

不同处理方法对美国截叶胡枝子种子发芽的影响

截叶胡枝子(Lespedezacunecta)是原产于亚洲东部的一种多年生的豆科植物,在我国南方地区野生分布很广。它具有耐瘠、耐旱、耐酸、耐热、固土能力强、适应性广等特性,在国外也颇受重视。我国于1983年从美国引种,通过对其生物学和生态学特性、经济性状和栽培技术研究证明,引进的美国截叶胡枝子在人工栽培条件下,表现出良好的经济性状,是南方草地改良的希望种子。但是在生产中,由于其硬实的存在,使得种子的发芽率很低,往往造成出苗困难和草地建植缓慢,甚至出现严重缺苗断垄的现象,直接影响田间产量,限制了它的进一步推广应用。试验采用不同处…     

不同处理方法对美国截叶胡枝子种子发芽的影响

美国截叶胡枝子的硬实率很高,发芽率只有17.3%。经过种子预处理,如采用不同温度下浸种、98%浓硫酸浸泡、机械破皮和机械破皮结合热水浸种等处理,结果表明,机械破皮后用60℃热水浸种处理的效果最好,发芽势和发芽率分别达到64.0%和74.3%;其次是机械破皮,平均发芽率达到50%;浓硫酸浸种可以显著提高种子发芽势,浓硫酸浸种5min效果最好,发芽率达到44.7%;热水浸种的处理效果不佳,最好的90℃热水浸种处理发芽率也仅有26.7%。     

Phytoplasma identity and disease etiology

ABSTRACT Many plant diseases believed to be caused by phytoplasmas were described before phytoplasma groups were delineated through molecular analyses. It is now possible to assess the relationships between phytoplasma identity or classification and specific plant diseases. Data were consistent with the hypothesis of a common ancestral origin of pathogenicity genes in many phytoplasmas and a limited repertoire of plant responses to certain pathogen signals. Observations also were consistent with the hypotheses that the botanical host ranges of some phytoplasmas reflect specificities in transmission by vectors and vector feeding preferences; phytoplasma-insect vector relationships are keys to understanding evolutionary divergence of phytoplasma lineages; small differences in a highly conserved phytoplasma gene may be regarded as potential indicators of separate gene pools; the reliability of a diagnosis based on symptoms must be learned empirically (i.e., through case study for each syndrome); and some discrete diseases can be ascribed to phytoplasma taxa at the 16S rRNA group level, whereas others are clearly associated with phytoplasma taxa below this level.     

不同退化程度高寒草甸植物物种多样性与生态系统多功能性关系

为探究高寒草甸不同退化程度生态系统多功能性的变化,本研究综合考虑了植物物种多样性和多种生态系统功能如生产力、养分循环和固存能力、土壤涵养水分能力等,运用降维因子分析的方法计算了生态系统多功能性,综合分析了植物物种多样性与生态系统功能和多功能性间的关系。结果表明：高寒草甸退化显著降低了Margalef指数、Shannon-weiner指数、Simpson指数和Pielou指数(P<0.05),各生态系统功能趋于恶化。高寒草甸退化导致生态系统多功能性的下降,综合统计量结果为轻度退化(21.9955)＞中度退化(8.7295)＞重度退化(—30.7245)。植物物种多样性与生态系统多功能性之间均存在正相关关系,其中Simpson指数与生态系统多功能性指数拟合的结果最好,说明高寒草甸生态系统多功能性受植物物种多样性的制约。本研究可为青藏高原草地退化及恢复的过程和机理研究提供理论依据。     

Diversity of Glomale Mycorrhizal Fungi in Maize/Sesbania Intercrops and Maize Monocrop Systems in Southern Malawi

The study investigated diversity and frequency of occurrence of glomale (Arbuscular- or Vesicular Arbuscular-) mycorrhizal fungi on three farming systems in a drought prone and nitrogen deficiency site in southern Malawi. The farming systems comprised of two agroforestry systems of Sesbania sesban (L) Merr intercropped with maize and Sesbania macrantha E Phillips & Hutch. intercropped with maize and a maize monocrop systems without fertilizer, with nitrogen, phosphorus and a combination of nitrogen and phosphorus. Species diversity and species frequency of occurrence were examined in soil samples obtained in the dry and wet seasons. Twelve glomale mycorrhizal species were recorded, four species being in the genus Acaulospora, four in Glomus, two in Gigaspora and two in Scutellospora. Species diversity in the two agroforestry systems were not significantly (p ≤ 0.05) different but had lower species diversity than maize monocrop with only Sesbania macrantha intercropped with maize significantly (p ≤ 0.05) lower. Species diversity was significantly increased by the inorganic nitrogen fertilizer. Inorganic phosphorus fertilizer had no effect. The study shows that the occurrence and persistence of glomale species are influenced by agroforestry combinations, and that the spores of most species are tolerant to dry conditions. Only four species responded to fertilizer application with the occurrence of spores of some species high and some low. Management practices have great implication in the persistence of spore propagules of glomale species. The order Glomale was revised in 2001 and upgraded to a phylum Glomeromycota.     

Modelling interactions amongst people and forest resources at the landscape scale

FLORES, the Forest Land Oriented Resource Envisioning System, is a framework to facilitate quantitative modelling of ecological, economic and social issues at the landscape scale. This issue ofSmall-scale Forest Economics, Management and Policy describes the evolution of FLORES from a concept to a series of models calibrated for diverse locations, and documents the lessons learned. The idea to construct and use landscape-scale models of the forest frontier, based on simulating household decisions and land use at a spatial scale close to the field level, arose from a desire to add rigour to land-use policy research at CIFOR, the Center for International Forestry Research (Vanclay 1995). This simulation modelling approach to addressing interdisciplinary issues, where people are strongly interacting with forest resources, became known as FLORES, the Forest Land Oriented Resource Envisioning System (Vanclay 1998). Muetzelfeldtet al. (1998) constructed a simple prototype of a FLORES model to illustrate the concept and demonstrate the ability of a system-dynamics modelling environment to animate such a model (Muetzelfeldt and Taylor 1997, 2001, Muetzelfeldt and Massheder 2003). In 1999, FLORES became a reality, when 50 scientists from diverse disciplines met in Bukittinggi, Indonesia to construct the first FLORES model styled on this prototype (CIFOR 1999, Vanclayet al. 2003). The research reported in this special issue was made possible by generous financial support from the Department for International Development (UK), the European Community, the Asian Development Bank (under RETA 5812) and the Center for International Forestry Research. The views expressed herein are those of the authors alone. We would like to thank the following people who have assisted in the production of this special issue by acting as anonymous referees for these and other papers: Andy Warner, Brendan Moran, Bruno Verbist, Chris Dake, Chris Legg, Doug Sheil, Euan Mason, Francois Bousquet, Frank Vanclay, Geoff Slaughter, James Gambiza, John Herbohn, John Poulsen, Jungho Suh, Mike Spilsbury, Paul Phillips, Paul van Gardingen, Phil Norman, Philip Nyhus, Roger Wheate, Ross Sigley, Steve Harrison and Tom Evans. Thanks also to the editorial staff, especially Steve Harrison, John Herbohn and Jungho Suh, for making this special issue possible.