西南鸢尾种子萌发特性研究

为揭示西南鸢尾（Iris bulleyana）种子休眠特性，以野生西南鸢尾种子为试验材料，对种子活力、种子吸水性、萌发抑制物及光照和温度对种子萌发率的影响进行研究；采用低温层积、GA3及温水浸泡等方法，探索打破西南鸢尾种子休眠的方法。结果表明，西南鸢尾种子种皮吸水良好，92 h吸水率达125%；温度对种子萌发影响较大，30℃较适宜种子萌发；种皮醇提液明显抑制白菜（Brassica pekinensis）种子萌发。低温层积可促进种子萌发，4℃低温层积60天时，种子萌发率达63.33%。西南鸢尾种子种皮含有醇溶性萌发抑制物，是其种子产生生理休眠的主要原因之一；4℃低温层积60天可有效打破种子休眠，GA3和温水浸泡处理均不能打破休眠。     

银杏外种皮提取物对植物种子萌发及幼苗生长的影响

以萝卜和黄瓜种子为试验材料,研究了不同质量浓度的银杏外种皮提取物溶液对2种植物种子萌发及幼苗生长的影响。结果表明:提取物溶液在一定质量浓度范围内对萝卜、黄瓜种子萌发及幼苗生长具有显著抑制作用。当质量浓度20~100 g/L时对萝卜种子萌发具有显著的抑制作用,0.1~100 g/L时对萝卜根、茎生长显著抑制;当质量浓度0.02~25 g/L时对黄瓜种子萌发、根生长具有显著的抑制作用。     

种子发芽抑制物的解除

当具有活力的种子处在适宜的萌发条件中而不能正常地萌发时,则称种子处在休眠状态。引起种子休眠的原因很多,其中包括胚未成熟、肿皮对空气或水的不透性、胚的机械阻碍、对光温的特殊要求以及发芽抑制物的存在等,其中发芽抑制物的存在是一个重要原因。这里主要从抑制物存在部位、种类、解除抑制的方法以及研究发芽抑制物的实际意义几个方面来阐述一下对发芽抑制物进行研究的必要性。1 抑制物存在部位 抑制物主要存在于果实、种子的胚乳、种皮、胚及子叶中。例如,梨、苹果、番茄、甜瓜和柑桔的果肉中都含有抑制物。甜菜的种子其种皮含有发芽抑制物,因此,种子经浸泡和漂洗后才能萌发。菜豆的子叶中存在发芽抑制物。抑制育尾萌发的因子存在于胚乳中,在鸢尾成熟时出现的抑制物迫使胚不能继续生长,必须把胚乳完全剥离后,胚才能萌发;用水漂洗常可促进萌发。     

野生黄瑞香种子的休眠机制与破除方法

【目的】祁连山野生的黄瑞香生长在海拔2 500~2 600 m左右的半荫半阳的缓坡地带,为适应祁连山寒冷的冬季和凉爽的夏季气候,黄瑞香种子具有较强的休眠特性。探寻破除黄瑞香种子休眠的方法,可为其种子人工繁殖提供理论依据与技术支持。【方法】采用种子萌发抑制物的生物学鉴定、激素溶液浸种、低温层积、干藏等不同处理方法对黄瑞香种子的休眠类型、休眠原因及其破眠方法进行研究。【结果】1)新采收的黄瑞香种子生活力为84.6%,但不萌发,具有显著的休眠现象。种子吸水过程符合Logistic曲线,其种皮对种子吸水无严重阻碍作用。2)黄瑞香种子种皮和胚的醇提液、水提液对白菜种子的发芽率和胚根长均有不同程度的抑制作用。外种皮的水提液对白菜种子萌发和胚根长的抑制作用在相同浓度条件下比醇提液明显;种胚的醇提液和水提液在0.1,0.15 g·m L~(-1)的浓度下完全抑制白菜种子萌发,在0.05 g·m L~(-1)浓度下种胚的水提液对白菜种子萌发和胚根长的抑制作用显著低于醇提液;内种皮的醇提液在低浓度条件时已对白菜种子的萌发和胚根的伸长产生极其明显的抑制作用,但内种皮的水提液无论浓度高低对白菜种子的萌发抑制作用均较小。这些结果说明黄瑞香种子外种皮中存在的水溶性萌发抑制物、种胚中溶于有机溶剂和水的萌发抑制物、内种皮中溶于有机溶剂的萌发抑制物的共同作用是其种子休眠的主要原因。3)黄瑞香种皮的电镜结构显示未处理的种子的种皮表面细胞排列较规则紧密,种皮中长柱状细胞构成栅栏组织;经5℃温度条件下层积90天后,种皮表面已出现较多的"蚁穴"状孔洞,有利于种子萌发。【结论】将新采收的黄瑞香种子进行GA3和6-BA溶液浸种、低温干藏和暖温干藏处理,均不能有效提高黄瑞香种子的萌发,经5℃湿沙层积90天后黄瑞香种子萌发率近80%。新采收的黄瑞香种子为综合性休眠。     

珍稀濒危植物金丝李种子的萌发特性

【目的】揭示珍稀濒危植物金丝李种子的萌发特性和幼苗适宜生长条件,分析种子萌发过程中金丝李的致危因素,为其保护、引种驯化和高效种苗繁育提供理论支撑。【方法】从温度、光照、水分、基质、埋深和不同种群等可能影响其萌发的生态因子和种皮、种子质量等生物学特征研究其萌发特性,探讨金丝李种子萌发条件,推测其濒危机制。【结果】金丝李种子萌发缓慢且极不整齐;带内果皮和去种皮均会延缓种子的萌发,但对萌发率无影响,种皮对其萌发不存在抑制作用;25、32℃和室温条件下种子能萌发,32℃下能明显加快其萌发进程和生长速度,而18和37℃下种子均不萌发;种子在持续光照、持续黑暗、周期性光照条件下均能萌发,周期性光照下萌发速度最快、最整齐,但3种光条件下萌发率无显著差异,其为光中性种子;播种在河沙和泥炭土基质里的萌发率最高,在黏质壤土或石山土里萌发缓慢且萌发率较低,在泥炭土和蛭石基质里幼苗地上和地下部分生长均较好;40%~60%含水量的石山土较适宜萌发,80%含水量下萌发时滞较长,而20%含水量下种子不能萌发;播种在相同深度下时,以河沙为基质相比以石山土为基质,种子的发芽势和发芽率较高,且随着埋深增加,发芽势和发芽率均降低,以河沙为基质埋深0.5 cm的处理萌发速度最快、最整齐;在弄岗、安宁和胡润种群的种子中,胡润种群的萌发率最低,萌发速度最慢,弄岗种群的幼苗较细长,胡润种群幼苗较粗矮且根系较发达;4 g、4~5 g和5 g 3个质量级种子的萌发参数和幼苗生长量大多差异不显著,种子质量对金丝李种子萌发和幼苗生长无显著影响;已萌发的种子被摘除芽和根后再次播种,仍能萌发,其具有再生能力。【结论】金丝李种子存在休眠,萌发对温度的适应范围较窄,对基质通气透水性反应敏感,其种子的再生能力可防止种子成苗失败,加强它的生存能力,但其萌发及幼苗生长缓慢,不利于种群空间资源的迅速占据,加上种子萌发对土壤透气和水分要求较高可能是导致其种群衰落,成为濒危的重要原因。     

北美鹅掌楸种子外种皮发芽抑制物研究

北美鹅掌楸(Liriodendron tulipifera L.)种子具有深休眠习性。以其种皮浸提液作为白菜种子的萌发液，结果表明浸提液对白菜种子的萌发没有影响，但对幼苗和根系生长有一定的抑制作用，表明北美鹅掌楸种子的休眠不是由外种皮引起的。     

山杏种子后熟生理及萌发条件的研究

测定了去除内果皮的山杏种子不同温度浸水处理的吸水性、温度对去除胚尖处种皮和不去种皮种子萌发的影响；萌发过程中种子内可溶性糖含量的动态变化；激素对种子萌发的影响及萌发期间种子内ａ-淀粉酶活性和过氧化氢酶活性的变化。结果表明，５０℃低温浸种２４ｈ可达山杏萌发所需水分条件及活力指数；层积处理以２～５℃效果最好；ＧＡ３在适宜浓度下能打破休眠，促进种子发芽、茎根伸长和幼苗生长；种子萌发期间可溶性糖含量呈不断增加趋势，ａ-淀粉酶活性不断增强；层积后种子内ａ-淀粉酶活性显著增强。     

紫楠种子的休眠与萌发特性

【目的】探究紫楠种子休眠原因,确定其休眠类型,找到解除种子休眠的方法和适合紫楠种子萌发的最佳温度条件,为其苗木培育提供理论与技术支持。【方法】通过测定紫楠种皮的透水性、透气性、种子内含萌发抑制物,探究种子休眠的原因,通过低温层积处理研究打破紫楠种子休眠的方法,通过设置15℃、20℃、25℃、30℃、35℃恒温、日30℃夜20℃、日25℃夜15℃变温共7个温度处理研究适宜种子萌发的温度。【结果】1)新鲜种皮对种子具有明显的吸水障碍和呼吸障碍,去皮种子的吸水率是完整种子的1.92倍,去皮种子的呼吸速率是完整种子的2.24倍,对种子萌发具有抑制作用;2)紫楠种子的水浸提液和甲醇浸提液能显著抑制大白菜种子萌发和幼苗生长,由此可以说明紫楠种子具有水溶性和醇溶性的内源抑制物;3)低温层积能够打破紫楠种子的休眠,随着低温层积时间的延长,种子发芽提早,发芽速度加快,发芽率提高,低温层积100 d的种子发芽率显著高于其他处理,高达98.89%。GA3浸种对解除种子休眠的效果不理想;4)温度对紫楠种子的发芽率的影响较大,25℃的恒温条件下种子萌发的能力高于其他的温度处理。【结论】紫楠种子种皮造成的透水性透...     

海桑种子发芽条件的研究

对影响海桑种子发芽的因子即光照、温度、海水盐度和pH值进行了研究．结果表明：海桑种子为需光种子，种子萌发需有光敏素的参与．缺乏光照是造成种子发芽率低和不整齐的主要原因，播种前将种子在湿润状态下用700lx的光照射24～36h或用体积分数为10－3的外源赤霉素（GA3）溶液浸泡36h，即可显著提高发芽率和发芽势；实验室发芽适宜温度为30～40℃，最适为35℃；海水盐度在10‰以下有利于海桑育苗，最适盐度为2．5‰；酸碱度对种子发芽影响不大，种子在pH为4～11时均可正常萌发生长．     

光照、水分、基质对江南油杉种子萌发的影响

为了揭示江南油杉(Keteleeria fortunei var.cyclolepis)种子萌发对环境的适应性,设置光照、水分、基质等环境条件对江南油杉种子萌发进行胁迫研究。结果表明:光照对江南油杉种子萌发无显著性影响,种子萌发率为81.67%~83.33%,对幼苗生长具有一定影响;在持续黑暗胁迫条件下江南油杉幼苗均为黄化苗;间歇性光照对江南油杉种子萌发和幼苗生长均无显著影响。江南油杉种子在10%水分条件下不能萌发;在25%~30%水分条件下萌发效果最好,萌发率为75.00%左右;当基质中水分小于25%时江南油杉种子不能萌发或萌发效果不好,幼苗生长较差;当基质中水分大于30%时种子萌发和幼苗生长受到抑制。江南油杉种子在滤纸基质条件下萌发效果最好,种子萌发率为83.33%;在细沙基质条件下幼苗生长最好,胚芽长22.42 mm,胚根长53.08 mm。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.