天山云杉体细胞胚的成熟及萌发条件

【目的】建立天山云杉体细胞胚成熟及萌发阶段的适宜培养条件,为该树种的体细胞胚大规模繁殖和工厂化生产提供基础。【方法】以天山云杉成熟合子胚为外植体所诱导形成的胚性愈伤组织为材料,通过14个株系、4种成熟培养基、接种量(100、150、200mg的新鲜胚性愈伤组织)、ABA浓度(1.9、3.8、7.6、19、38μmol·L^-1)等体细胞胚成熟培养条件,以及对不同起源(体细胞胚、合子胚和种子)的幼苗形态特征的比较,筛选出最优的天山云杉体细胞胚成熟与萌发条件。采用SPSS18.0等统计软件对体细胞胚进行统计分析。【结果】1)天山云杉14个株系诱导体细胞胚的结果表明,不同株系在同一成熟培养基上诱导体细胞胚的数量存在差异;其中4个株系及其接种量对体细胞胚形成数量影响的结果表明,不同株系及其接种量诱导体细胞胚的数量也存在差异,当接种量为100mg时,T36株系的体细胞胚诱导数量最高,为3470±546个,显著高于其他接种量和株系(P<0.05)。2)在4种不同成熟培养基上,均形成了成熟的体细胞胚,在1/2BLG+30g·L^-1麦芽糖培养基上形成的体细胞胚数量高于其他培养基,分别为2044个(T6株系)和2282个(T36株系),且与其他培养基差异显著(P<0.05)。3)不同ABA浓度对天山云杉体细胞胚诱导数量的影响无显著性差异(P>0.05),在ABA浓度为1.9~38μmol·L^-1时,其体细胞胚平均诱导数量为2850~2913个,其中以7.6μmol·L^-1ABA的浓度处理效果较好,平均获得2913个正常体细胞胚,高于其他处理。4)将不同起源(体细胞胚、合子胚和成熟种子)萌发的小植株进行对比,结果表明,体细胞胚和合子胚幼苗发育阶段基本一致,但合子胚的幼苗比体细胞胚的幼苗约大1倍,但二者间差异不显著(P>0.05);体细胞胚与合子胚子叶的平均数量一致,二者无显著差异(P>0.05),多数幼苗子叶数量为7~8个。【结论】天山云杉体细胞胚成熟阶段的适宜培养条件为胚性愈伤组织接种量100mg,1/2BLG培养基添加7.6μmol·L^-1的ABA及75%PEG4000、30g·L^-1麦芽糖,并添加750mg·L^-1的L-谷氨酰胺或50mg·L^-1L-天冬酰胺。不同株系在诱导体细胞胚的数量上存在差异。体细胞胚再生植株与合子胚植株在形态上相似。研究结果可为天山云杉体细胞胚的大规模繁殖和工厂化生产提供基础。     

培养基成分对黑松体胚发育成熟的影响

【目的】对日本抗性黑松体细胞胚成熟的影响因子进行研究,探究各因素在体细胞胚发生过程中的作用,为进一步提高体细胞胚发生的质量和数量提供理论依据。【方法】胚性细胞团在固体增殖培养基上继代生长10天,使用灭菌(75%乙醇擦拭、紫外灭菌30 min)的电子天平称量1 g胚性细胞团,采用50 mL无菌量筒(紫外灭菌30 min)量取30 mL培养液中于100 mL的三角瓶中,将1 g胚性细胞团转至100 mL的三角瓶中,手动搅拌至细胞团分散,置于90 r·min^-1摇床上,25℃黑暗培养7～8天。随后,取3 mL沉淀悬浮细胞进行继代增殖,每星期继代增殖一次至胚性细胞全部均匀散落于培养液。将继代4次的胚性细胞充分摇匀,取2 mL(鲜质量约200 mg)胚性悬浮细胞喷洒在不同组分麦芽糖(30、45、60 g·L^-1)、脱落酸(ABA)(0、5、10、20、30、50 mg·L^-1)、聚乙二醇(PEG8000)(0、50、75、100、125、150 g·L^-1)、活性炭(AC)(1、2、3 g·L^-1)、琼脂(琼脂6、8、10、12 g·L^-1,植物凝胶2、2. 5、3、3. 5 g·L^-1)以及麦芽糖、ABA、PEG 3因素的组合固体成熟培养基上。【结果】以#1337为材料的体细胞胚成熟发育过程中,麦芽糖45 g·L^-1,获得的体细胞胚数量显著增多。ABA浓度为5～20 mg·L^-1,体细胞胚数量呈显著上升趋势,ABA为20 mg·L^-1时,获得的体细胞胚最多。125 g·L^-1PEG8000为体胚发生最佳浓度; AC 2 g·L^-1时,胚性细胞形成结构完整、数量较多的成熟体胚;成熟培养基中添加琼脂粉,培养基不能凝固,植物凝胶更适合作为成熟培养基凝固剂。3 g·L^-1植物凝胶为抗性黑松体胚发育成熟的最佳浓度。在设计的9种成熟培养基组合中(胚性细胞#1337、#1537、#1637),胚性细胞产生体细胞胚最多的成熟培养基组合为麦芽糖45 g·L^-1、ABA 10 mg·L^-1、PEG8000 125 g·L^-1。在不同的麦芽糖、ABA和PEG组合中,不同无性系生产体细胞胚数量呈现出不同的变化趋势:胚性细胞系#1337体胚发育成熟的最佳组合为麦芽糖45 g·L^-1+ABA 10 mg·L^-1+PEG 125 g·L^-1;#1537和#1637体胚发育成熟的最佳组合为麦芽糖30 g·L^-1+ABA 10 mg·L^-1+PEG 125 g·L^-1;在3个无性系中PEG的极差最大,对抗性黑松体细胞胚发育成熟的影响最大。【结论】抗性黑松体胚发育成熟过程中,麦芽糖45 g·L^-1、ABA20～30 mg·L^-1、PEG8000 125 g·L^-1、AC 2 g·L^-1和植物凝胶3 g·L^-1对体细胞胚成熟都具有促进作用。30 g·L^-1麦芽糖、10 mg·L^-1ABA、125 g·L^-1PEG为抗性黑松体胚发育成熟的最佳组合。     

马尾松胚性细胞团诱导体系优化

【目的】马尾松胚性细胞团诱导率低一直限制着马尾松体细胞胚胎发生体系的实践应用,探讨了影响马尾松胚性细胞团诱导的几个关键因子及其效应,以期提高胚性细胞团诱导率,优化胚性细胞团诱导发生体系。【方法】以包含未成熟胚的雌配子体为外植体,LP培养基为基本培养基,探讨家系基因型、激素组合、培养基碳源及氮源等因子对马尾松胚性细胞团诱导的影响。【结果】家系基因型对马尾松胚性细胞团诱导有显著性影响,家系平均诱导率最高达17.5%,最低为0;3组激素组合的诱导率无显著差异,其中1.5 mg/L 2.4-D+1.0 mg/L 6-BA处理获得较高诱导率(14.85%);不同碳源类型及水平处理下(麦芽糖、蔗糖、葡萄糖),各家系的最佳诱导反应呈现家系与碳源类型及水平的交互效应,其中k1家系在30 g/L蔗糖处理中可获得最高诱导率(40%),而k3家系则在30 g/L葡萄糖处理中获得最高诱导率(22%),综合4个家系在不同碳源水平处理下的综合诱导效应,在30 g/L蔗糖处理中获得的平均诱导率最高(18.51%);调整培养基中的氨硝比(NH4+/NO3-)有助于胚性细胞团诱导,其氨硝比(NH4+/NO3-)的合适比例范围为0.2～0.4,平均诱导率可达14.23%,而单一性降低NH4+浓度至1/2LP浓度水平或增加培养基中NO3-浓度至3/2 LP浓度水平,诱导率分别可提高到17.86%和15.48%。【结论】马尾松胚性细胞团诱导有显著的家系效应,需选择诱导敏感型家系为实验材料来源;调整诱导培养基中碳源类型与浓度水平,同时考虑培养基中的氨硝比,对优化胚性细胞团诱导有积极作用,推荐30 g/L蔗糖为碳源,并调整培养基中的氨硝比(NH4+/NO3-)范围0.2～0.4,可提高胚性细胞团诱导率。研究结果可为提升胚性细胞团诱导率建立稳定的马尾松胚性细胞团诱导体系提供研究参考和技术支撑。     

国外竹类植物组织培养研究最新进展

组织培养技术已经成为竹类植物快速繁殖的重要手段之一。文章概述了近10年来国外在竹类植物组织培养研究方面的最新进展,包含了基于固体、液体培养基所开展的以芽繁芽、愈伤组织诱导、体细胞胚胎发生等途径的繁殖研究,以及细胞悬浮培养与种质保存、次生代谢物质诱导与分离等应用研究。对外植体的选择与消毒、组培种苗产权保护和试管开花与转基因育种等进行了讨论。     

热激启动子控制的FT基因诱导杨树早期开花体系的优化

为实现杨树早期开花,缩短育种周期,利用农杆菌介导的转化方法,探讨影响热激启动子控制的FT1基因转化白杨派杂种无性系的因素,优化其转化条件,并实现FT1基因的转化,采用热激诱导方法诱导2～3个月大的转基因植株早期开花。结果表明:叶盘转化前的预培养、菌液浓度、侵染时间及共培养时间对卡那霉素抗性植株再生率的影响均达到极显著水平;叶盘在愈伤组织诱导培养基上暗培养6天,然后用活化至OD600=0.5的菌液侵染60min,再在愈伤组织诱导培养基上共培养2天,该条件下FT1基因转化白杨派杂种的卡那霉素抗性植株再生率可达29.84%;37℃每天1h持续热激3周可使FT1基因顺利表达,促进转基因植株开花;热激植株大小是影响转基因植株热激诱导开花的限制因素,低于20cm的植株不能诱导开花;热激诱导可产生相对较多的正常花器,但花器变异仍然十分广泛。     

群众杨39无性系耐盐悬浮细胞系的建立和体细胞变异体完整植株的诱导*

本试验以群众杨３９号为试材，通过耐盐胁迫悬浮培养建立耐盐悬浮细胞系，经愈伤组织成功培育出耐ＮａＣｌ３．０‰～３．５‰的群众杨体细胞变异体的完整植株。实验表明，ＭＳ培养基附加０．４５ｍｇ／Ｌ２，４－Ｄ、０．３ｍｇ／ＬＮＡＡ和０１ｍｇ／ＬＫｉｎｅｔｉｎｅ的Ｍ４培养基能较好地获得松脆、易分散的愈伤组织。液体以ＭＳ培养基只附加０．５ｍｇ／Ｌ２，４－Ｄ的ＬＭ３为最好，附加氨基酸有益于悬浮细胞的正常生长。还对悬浮培养细胞的有关参数进行了测定。耐盐悬浮细胞培养实验结果表明ＮａＣｌ对细胞生长有抑制作用，并随着ＮａＣｌ升高而加强。对获得的耐３‰～６‰各水平ＮａＣｌ悬浮细胞经高密度植板，都能形成愈伤组织。耐盐愈伤组织诱导只获得耐３‰～４‰ＮａＣｌ的不定芽，高于４‰ＮａＣｌ未能诱导出不定芽，说明高浓度ＮａＣｌ对芽组织分化有明显的抑制作用。不定根分化对ＮａＣｌ反应非常敏感，只在耐３‰和３．５‰ＮａＣｌ浓度培养基诱导出不定根。     

外源激素对日本落叶松体细胞胚发生不同阶段的影响

【目的】探究外源激素对日本落叶松体细胞胚发生不同培养阶段的影响,优化日本落叶松的体细胞胚发生条件并提高体细胞胚的质量,为研究外源激素调控落叶松体细胞胚发生的生理机制提供数据支持,为落叶松的规模化繁育和遗传改良奠定基础。【方法】首先确定生长曲线的延迟期、对数期和平台期,然后根据生长曲线,采用正交设计研究胚性胚柄团在2,4-D 0.15、0.30、0.50 mg·L-1、6-BA 0、0.15、0.30 mg·L-1和ABA 0、0.50、1.00 mg·L-1浓度下培养7天、14天、21天的鲜质量增长情况和14天的体胚发生能力,采用析因设计研究悬浮细胞在2,4-D 0.15、0.30、0.50 mg·L-1和6-BA 0、0.15、0.30 mg·L-1浓度下培养7天、14天、21天的细胞鲜质量增长情况和14天的体胚发生能力,结合鲜质量增长和体胚发生能力2种结果确定胚性胚柄团增殖和悬浮细胞生长的最佳激素浓度。最后,以不含GA3、IAA的体细胞胚诱导培养基为对照,分别研究了GA3和IAA 0、10、20、30、40 mg·L-1对体细胞胚发生的影响。【结果】7、14、21天分别处于日本落叶松胚性胚柄团增殖和悬浮细胞生长的延迟期、对数期和平台期。在胚性愈伤组织增殖阶段,2,4-D、6-BA、ABA对胚性胚柄团增殖和体胚发生能力的影响显著(P0.05),最佳的激素浓度是2,4-D 0.15 mg·L-1+ABA0.50 mg·L-1;在悬浮培养阶段,2,4-D、6-BA组合对悬浮细胞生长和体胚发生能力的影响显著(P0.05),最佳激素浓度是2,4-D 0.15 mg·L-1+6-BA 0.15 mg·L-1; GA3、IAA对成熟子叶胚的数量的影响均显著(P0.05),10～20 mg·L-1GA3或IAA时成熟子叶胚数量显著升高,而更高的GA3或IAA浓度将会抑制体胚发生。【结论】外源激素可有效调控日本落叶松的体细胞胚发生,适宜增殖阶段胚性胚柄团增殖和体胚发生能力保持的激素组合为2,4-D 0.15 mg·L-1+ABA 0.50 mg·L-1,适宜悬浮培养阶段细胞生长和体胚发生能力保持的激素组合为2,4-D 0.15 mg·L-1+6-BA 0.15 mg·L-1,添加GA3或IAA 10～20 mg·L-1可以显著提高成熟子叶胚的数量。     

樟树对土壤中PAHs的修复及其影响因子

采用室内盆栽实验,利用柴油设置2 g·kg-1(L1),10 g·kg-1 (L2)和50 g·kg-1 (L3)模拟PAHs浓度梯度,对盆栽的1年生樟树幼苗对PAHs的修复机制及影响因子进行研究.结果表明:(1)不同浓度PAHs污染(L1、L2、L3)水平下,樟树幼苗土壤中PAHs的去除率分别为85.86％、91.95％、80.80％,均高于无植物处理.(2) PAHs在樟树不同器官中的积累浓度不同.中、低浓度污染处理水平(L2、L1)下,樟树各器官对PAHs的积累作用均表现为:叶＞根＞干;高浓度污染处理水平(L3)下则表现为根＞叶＞干.不同污染处理(L1、L2、L3)水平下,樟树吸收累积作用修复PAHs污染土壤的贡献率分别为64.26％、22.81％、11.39％.(3)随着PAHs污染浓度的增大,樟树不同部位生物浓缩系数逐渐减小.叶和根是樟树富集PAHs的主要部位.(4)5cm土壤温度和多酚氧化酶是影响樟树修复PAHs污染土壤的关键因子,真菌、放线菌数量和磷酸酶活性可以作为土壤PAHs污染评价的生物指标.研究结果可为南方城市PAHs污染修复优良绿化树种的筛选提供理论依据.     

米良一号猕猴桃的组织培养研究

米良一号猕猴桃外植体在不同激素的MS培养基上培养．结果表明：①诱导培养基以MS 1．0mg／L ZT为好，材料不经转移可直接分化出丛生芽，ZT浓度在1．5mg／L以上时，对愈伤组织形成有抑制作用，且在1．5mg／L ZT的同时．加0．5mg／L 6-AB，这2种细胞分裂素超量后的抑制作用是累加的，致使抑制作用加剧无芽茎段褐化死亡；②出芽周期长短与茎段年龄和有芽无芽有关，成熟茎段出芽早，幼嫩茎段出芽迟，有芽茎段出芽早，无芽茎段出芽迟，幼嫩的无芽茎段出芽虽晚30d左右．但由愈伤组织形成的丛芽多得多；③米良一号生根能力不强，出芽后不经生根诱导不能生根，1／2MS 1．0mg／L IBA 30g／L蔗糖，有较好的诱导生根作用；④叶片培养再生率正交实验结果表明生长素优先因子顺序为ZT、6-BA、NAA、TDZ，叶的最佳诱导分化培养基为MS 10mg／LBA 0．2mg／L NAA 1．0mg／L TDZ。     

无机盐与激素混合对土沉香结香的诱导

【目的】探明无机盐与激素混合配比对土沉香结香的影响,揭示其结香机制,为促进土沉香结香奠定基础。【方法】以10年生土沉香为材料,采用均匀试验设计,以NaCl、FeSO_4、CaCl_2、茉莉酸甲酯和乙烯利为诱导因子,每个因子3个水平,共5种处理,分别在诱导处理后0.5、1、3、6、10个月取样,测定淀粉、可溶性糖、醇溶性浸出物含量以及木芯变色范围;利用光学显微镜观察切片组织化学变化,扫描电镜观察组织结构内含物变化。【结果】1)随诱导时间增加,各处理淀粉含量先降低后升高,降至最低值时间不同;可溶性糖含量先升高后降低,各处理均在第6个月达到峰值;2)各处理射线薄壁细胞、轴向薄壁细胞和导管内油脂类物质含量随诱导时间增加不断积累;3)木薄壁细胞内侵填物质通过导管-薄壁细胞间半具缘纹孔进入相邻导管内积累至完全堵塞;4)各处理在木芯变色横向宽度上诱导效果不佳,而在纵向上诱导效果较好、变色较长,其中处理2(0.5%NaCl+1.5%FeSO_4+0.1%CaCl_2+0.01%茉莉酸甲酯+0.05%乙烯利)诱导10个月的纵向变色长度达77.0 cm;5)随诱导时间增加,各处理醇溶性浸出物含量不断增加,且差异显著。【结论】1) 5种诱导处理中,以0.5%NaCl+1.5%FeSO_4+0.1%CaCl_2+0.01%茉莉酸甲酯+0.05%乙烯利诱导效果最好,处理10个月时醇溶性浸出物含量最高,达19.07%;2)促进土沉香结香的主要诱导因子为NaCl和乙烯利,其中乙烯利起主导作用,理论上诱导土沉香结香的最佳因子组合为0.16%NaCl+0.21%乙烯利;3)结香油脂首先在薄壁细胞内形成,随后在导管和薄壁细胞内积累,导管内油脂物质积累与薄壁细胞内淀粉含量变化有关,淀粉转化为可溶性糖的能力越强,油脂积累越多,越有利于结香。     

论法治与德治的辩证统一

法治既是一种治国方式和手段,也是人民行使管理国家、管理社会的权利的途径.德治的核心内容是要建立社会主义的道德体系和弘扬优秀的民族精神.法治和德治既有区别,又有联系,是辨证统一的.法治、德治的辩证统一是贯彻"三个代表"重要思想和建设中国特色社会主义的内在要求.     

Indentation of wood by wedges

Summary The deformation processes involved in wedge indentation of wood are described. The behaviour of wood is compared to that of an elastic-plastic solid and that of a cellular body. It approximates towards the former when its density is high and towards the latter when its density is low. The hardness of wood is examined as a function of density and of wedge angle.We wish to thank the University Grants Committee and the New Zealand Forest Service for supporting this work     

Penetration of hardwoods by liquids

Summary Oven dry highly evacuated sticks of the sapwood of various hardwoods, 40 cm long by 1.0 to 1.2 cm in the radial and tangential directions, took up water to the extent of 44 to 82% of saturation by capillary flow in one minute. Heartwood sticks took up 15 to 38% of saturation in one minute. The initial rapid penetration was followed by a penetration in which the take up increase directly with the square root of elapsed time. In this range, the slope of toluene take up plots was about twice that of the water take up. This is close to the theoratical value on the basis of viscous flow control. The linear portion of the plots is followed by a curvilinear decrease in rate of take up to a final equilibrium value. Water take ups approached 100% of the theoretical values.Times to 0.99 of theoretical filling with water varied from 9 minutes for tupelo gum sapwood to 14.6 to 17.3 days for white oak heartwood. Complete filling with toluene was never attained. Diffuse porous hardwoods filled to the extent of 93.5 to 96.5% of saturation. Ring porous oaks filled to the extent of 88 to 92%, the lower values being for heartwood. Edge coating of the sapwood of yellow poplar and yellow birch with epoxy glue reduced the rate of penetration only slightly. End coating reduced the rate to a higher degree. Moisture gradients in the fiber direction for tyloses-free hardwoods were negligible at various stages of penetration, indicating that filling of the vessels was practically instantaneous. White oak heartwood gave an initial longitudinal gradient followed by a negligible gradient, indicating that longitudinal penetration is primarily through the lumen of the fibers rather than continously through the vessels. Longitudinal penetration was calculated to be 31.5 times as deep as transverse penetration in 100 minutes and 33.3 times as deep in 25 minutes for white oak heartwood. The ratios are of the same order of magnitude as for Loblolly pine. In both cases the ratios are smaller than values calculated from the fiber dimensions alone as ray cell penetration and cross grain effects tend to lower the ratios.Paper No. 3947 of the Journal Series of North Carolina State University Agricultural Experiment Station, Raleigh, N. C.     

Suppression of debris movement by forests and damage to forests by debris deposition

 Forest buffer zones have recently been introduced in an attempt to suppress debris movement caused by mass wasting. There are, however, many questions left unsolved regarding the role of forests in suppressing debris movement and damage to forests by debris deposition. A number of debris avalanches occurred in southern Fukushima Prefecture and Hiroshima Prefecture in August 1998 and June 1999, respectively. Suppression of debris movement by forests and damage to forests by debris deposition were investigated in this study using aerial photographic interpretation and topographic analysis. Of the debris avalanches delineated in the Fukushima and Hiroshima areas, 282 and 84 sites, respectively, were forested, and 43 and seven sites, respectively, were nonforested. Topographic parameters, land use, and forest type at each site were surveyed by aerial photographic interpretation and topographic analysis. Suppression of debris movement by forest vegetation was confirmed by higher equivalent coefficients of friction and shorter average deposition zone length (about 28% and 55% shorter in the Fukushima and Hiroshima areas, respectively) in forested sites compared with nonforested sites. While previous studies suggested that the width of the forest zone required to prevent sediment outflow by surface erosion increases with increasing slope gradient, no clear relationship was found in this study. While the length of deposition zone of debris material (this study) is strongly affected by the dynamic solid friction coefficient and fluid friction of debris material, the length of deposition zone of the outflow of surface wash (past studies) is mainly affected by the tractive force of water flow. Among the 65 trees that remained at the terminus of deposition zones at five sites, 36 were alive and 29 were dead. Damage to the forest increases with increasing thickness of deposits and decreases with increasing tree diameter. Such results are useful for designing forest buffer zones. Received: June 18, 2001 / Accepted: August 21, 2002 Correspondence to:Y. Ishikawa     

Inhibition by pulp juice and enhancement by ingestion on germination of bird-dispersedPrunus seeds

To evaluate what prevents seed germination and why ingestion by birds enhances germination, we carried out germination experiments using bird-dispersed seeds of twoPrunus species (Prunus sargentii andP. ssiori) in the laboratory. Germination of seeds with following four treatments was compared: “Ingested seeds” excreted after feeding of fruits to birds; “Extracted seeds” deliberately extracted from the fruit pulp; “Juiced seeds” which were supplemented with the juice of the pulp after seeds had been deliberately extracted from the pulp; and “Intact seeds” in untreated whole fruits. Many ingested (27%, 23% inP. sargentii, 18% inP. ssiori) and extracted seeds (24% inP. sargentii, 17% inP. ssiori) germinated, and difference in germination percentages between ingested and extracted seeds were not significant, for eitherPrunus species. The Juiced seeds rarely germinated (2% inP. sargentii, 6% inP. ssiori), and seeds within intact fruits did not germinate. These results suggest that the fruit pulp and the juice of the pulp inhibit germination and the seeds could germinate without ingestion by birds once they had been manually extracted from pulp. Therefore, it is considered that bird ingestion enahnces germination by removing pulp, especially juice of the pulp, in these twoPrunus species.     

Deviations of kerf by handsaws III: the bend of saw blade by unsymmetrical set

To clarify the inducing mechanism of kerf deviation caused by unsymmetrical set of the handsaw, we hypothesized that the moment on the bottom edge of the saw blade, which is generated by the unsymmetrical set on handsaw teeth, bends the saw blade and this deformation should be one factor of the kerf deviation. To verify this hypothesis, the bend of a saw blade was examined by experiment and by calculation. In the experiments, a model tooth was attached to an actual handsaw. In the calculations, a saw model with a rectangular prism as the model tooth was analyzed by the finite element method. Loads were applied on the model tooth or the rectangular prism. From both the experiments and the calculations, the following results were obtained: (1) the deformation of the handsaw was caused by the unsymmetrical set in the length direction and the height direction of the saw blade; (2) the deformation and the inclination of the blade was larger at the front part of the saw than at the butt part; and (3) comparing the saw handle fixing conditions, the kerf deviation in the sawing line was supposed to be larger in the free handle condition and that kerf deviation in the depth direction was larger in the fixed handle condition. Based on the above results, it is apparent that one of the kerf deviation mechanisms originated from unsymmetrical set on the saw teeth. Part of this report was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, Japan, August 2004.     

Quantification by allometric equations of carbon sequestered by Tectona grandis in different agroforestry systems

Non destructive methods for quantification of carbon seques-tration in tropical trees are inadequately developed. We described a stan-dardized method for estimating carbon stock in teak (Tectona grandi...     

Surface checking of wood is increased by photodegradation caused by ultraviolet and visible light

The aim of this research was to test the hypothesis that exposure to solar radiation increases the checking of wood exposed to the weather, and to examine the causes and spectral dependency of such an effect. Lodgepole pine decking samples were exposed outdoors under filters, which blocked selected regions of the solar spectrum while allowing other weathering factors to act on samples. Surface checking in samples was quantified after 12, 24 and 36 weeks of exposure, and the chemical and micro-structural changes occurring at weathered wood surfaces were examined. Check numbers and dimensions were greater in samples exposed under a filter to the full solar spectrum than in samples exposed under filters that blocked the transmission of UV, visible or infrared radiation. Samples that were shielded from more energetic wavelengths developed less checking and also showed less delignification at the exposed wood surfaces. Checks developed at the margins of rays and propagated at the interface between adjacent tracheids, close to the middle lamella. We conclude that exposure to UV and visible light increases the tendency of wood to check during exterior exposure. Our findings point to a link between changes in cell micro-structure as a result of photodegradation of lignin and the development of visible checks in wood exposed outdoors.