克服树木种子休眠的方法

树木种子休眠是植物为了种的生存，适应环境，在长期生长发育过程中形成的特性。树木种子的休眠从休眠程度上分为：强迫休眠和长期休眠。引起长期休眠的因素很多，如种皮的机械障碍、含有抑制物质、生理后熟、综合因素的影响。无论哪种休眠都极大影响种子的发芽。在播种育苗或在室内检验种子的品质都需采取措施，克服种子的休眠，促进种子的发芽，不同树种采取的措施也不尽相同。克服种子休眠的方法称为催芽。在实验和实践中总结出以下几种催芽方法：一、浸入催芽法此方法主要是通过不同温度的水在一定时间内浸种，使种子的种皮软化、通气、…     

天女花种子处理与苗木年生长过程的研究

天女花种子休眠为生理休眠，种皮的机械约束对种子休眠有一定的影响，但不起决定作用，休眠原因在于种胚未完成分化。通过试验，找到了打破种子休眠的方法。观测了苗木的年生长过程，划分了生育阶段。     

林木种子休眠研究评述

种子休眠,是指在充分满足各种发芽条件时,有生命力的种子一时不能发芽或发芽困难的自然现象。处于休眠的种子,种皮坚硬、含水量低,细胞内养分处于难溶态,代谢活动较低。一般将种子休眠划分为三个类型:即强迫休眠、生理休眠和综合休眠。种子生理休眠的机理包括:种果皮的抑制;植物激素的作用;种子的二次休眠;综合因素造成的休眠;分子变化等方面。     

种胚先期休眠机制猜想与理论探索

注意到黄熟采集的榆钱忌暴晒和提前采集的霸王种子播种后分2次出苗现象。提出解释认为,种胚先期成熟,并被赋予生理休眠特性以免种子整体成熟前萌发。进而分析认为,种胚内合成脱落酸一类抑制物质诱导并维持自身先期休眠。最后从不同种子休眠类型进化角度分析指出,种胚先期休眠是种子休眠的核心和基础。     

钟萼木种子生理休眠特性的初步研究

通过对钟萼木（BretschneiderasinensisHemsl）种子进行各种处理，然后进行发芽试验．以及直接将新采集的种子和离体胚进行发芽试验，并进行生物鉴定（白菜籽发芽试验），研究了钟萼木种子生理休眠特性及打破休眠的方法．结果表明，种胚、内种皮及胚乳内的抑制物质虽可引起种子休眠，但引起种子休眠的主要原因是种子内缺乏萌发促进物质和酶活性低；用30kg／100mL的赤霉素溶液浸种24h或低温（5℃）层积60d，可解除种子休眠，萌发率由8．00％可提高到87．00％～96．00％，低温层积后适宜的萌发温度为30℃，25℃，20℃，其次是变温条件（昼30℃，夜20℃）；将种子置于聚乙烯薄膜袋内低温（5℃）干藏120d，也可解除休眠．低温干藏120d后再层积20d，解决休眠的效果最佳，如此处理置床后第三天即开始发芽，9d完成萌发过程，萌发率达94．00％．     

林木种子休眠与萌发机制研究进展

种子休眠是由外界环境因素或者种子自身遗传特性诱导产生的,是具有生活力的种子在有利环境下仍不能萌发的现象。种子休眠与萌发是2种既相互区别又相互联系的发育状态,具有休眠特性的种子只有休眠解除才可能萌发,种子休眠在一定程度上决定其发芽所需的环境。为了对种子休眠与萌发现象有更全面的认识,本文在收集国内外林木种子休眠、休眠解除及萌发研究文献的基础上,总结了常见林木种子休眠产生的原因以及休眠类型划分系统,探讨休眠产生的机制,阐述内源激素调控种子休眠、阐述光信号调控种子休眠、Ca~(2+)调控种子休眠、基因控制种子休眠、细胞膜变论等学说;概述了种子通过层积处理、物理方法、化学方法以及激素等解除休眠的方法;种子恢复吸胀则表示已进入萌发阶段,其伴随着形态、生理生化及分子层面的复杂变化。同时讨论当前研究的薄弱之处,并提出应对种子休眠与萌发的启动转录、基因调控、遗传表达等分子调控机制展开更深入的研究,以期为林木种子休眠解除与萌发机制方面的研究提供依据,为林木种子贮存、苗木繁育、种植推广及开发利用等提供参考。     

华南五针松种子休眠生理的初步研究

华南五针松(Pinus Kwangfungensis Hand)种子的胚分化明显且发育完善,但种子具生理休眠特性。种子内部酶的活性低,是引起种子休眠的主要原因,外种皮存在的抑制物质,种皮的透水、透气性差对种子休眠也有一定的影响。低温(5℃)层积60天能有效地解除种子休眠,最适的萌发条件是在光照下30℃(日)/20℃(夜)变温。     

枫杨种子休眠与萌发特性研究

为了确定枫杨种子的休眠原因及其打破休眠的方法,以枫杨成熟种子为材料,对种子透水性、种子浸提物的生物抑制作用、种子催芽处理效果以及种子在不同温度下的萌发能力进行研究。结果表明:枫杨种子种皮透水性良好,种子浸提液中存在发芽抑制物质,抑制物质的存在是造成种子休眠的主要原因。直接埋藏和混雪后埋藏解除枫杨种子休眠的效果不理想;低温层积解除种子休眠效果较好,层积时间达到120d时种子萌发率可以达到89%。温度显著影响枫杨种子的萌发,25℃的恒温条件下种子萌发能力显著高于其它温度条件。结论:枫杨种子不存在物理休眠,属于生理休眠类型,种子需要低温层积处理120d打破休眠,解除休眠种子的适宜萌发温度是25℃。     

南京椴种子贮藏及发芽试验

对南京椴种子的休眠机理和发芽条件进行了探讨。共设定2个处理：剪破种皮、热水处理（40℃）和3种贮藏方法：室内混沙堆藏、露天坑藏、自然贮藏进行试验。结果表明，剪破种皮、热水处理都没有发芽，说明南京椴种子的体眠不是种皮限制所引起的。3种贮藏方法的种子都要经过长达近440d的时间，让种子历经低温-高温-低温的变温阶段，均能不同程度地打破种子的休眠，因而认为南京椴种子休眠属于生理休眠。3种贮藏方法种子的发芽率分别为5．23％、4．98％和2．66％。     

毛果含笑种子休眠的原因及其休眠的破除

毛果含笑为分布于云南的珍贵绿化观赏树种,其种子具有休眠习性。为解决毛果含笑种子的有效繁殖问题,从种子的形态结构,种皮的透水性、种子中的萌发抑制物质测定,种子的生活力测定及其种子萌发试验等方面,对毛果含笑种子休眠的原因及破除方法进行了研究。结果表明:种胚发育不完全和种子所含的萌发抑制物质是导致毛果含笑种子休眠的主要原因。毛果含笑种皮具有较好的透水性,与其休眠的关系不大,由此可认为毛果含笑种子的休眠类型为形态生理休眠;用蒸馏水浸泡或赤霉素液浸泡种子均可有效破除毛果含笑种子休眠,促进其萌发。     

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。     

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.     

Key Habitats in the Norwegian Production Forest: A Case Study

This study investigated the forest history, structural characteristics, the presence of fungal species suggested to indicate ecological continuity in old-growth forest, and the species composition of saproxylic beetles in 30 old forest ''woodland key habitats'' (WKHs), and compared them with production forest in the same age-class in south-eastern Norway. No statistically significant differences in forest characteristics, community of saproxylic beetles or number of red-listed beetles were found between the WKHs and the production forest, probably owing to a combination of profound long-term logging and a lack of will to delineate sufficiently large WKHs in the one area with significantly less forestry impact. The study indicates the advantage of including forest history information in WKH selection where such data exist, and the importance of restoring habitats in heavily exploited forest landscapes.