Modification of softwood kraft pulp with carboxymethyl cellulose and cationic surfactants

An elemental chlorine-free (ECF)-bleached soft-wood kraft pulp was treated first with a carboxymethyl cellulose (CMC, degree of substitution 0.3, 1% on pulp) and then with alkyltrimethylammonium bromides (alkyl chain lengths of C₁₀ to C₁₆). Surprisingly, the treatment with dodecyltrimethylammonium bromide (C₁₂TAB) markedly increased the internal and tensile strengths of the handsheets prepared from the modified pulp. Environmental scanning electron microscopy (ESEM) showed that these properties could be partly explained by the “rope/gum-like” bridges that were formed between the fibers.     

Ultrastructural and cytochemical investigations of pathogen development and host reactions in susceptible and partially-resistant carrot roots infected by Pythium violae, the major causal agent for cavity spot

Two carrot genotypes, cultivar Nanco and line 24, susceptible and partially- resistant respectively to cavity spot, were compared ultrastructurally and cytochemically 24 h, 48 h and 72 h after root inoculation with a virulent Pythium violae isolate. The extent of pathogen ingress and the response of the host differed markedly with the two genotypes. In cv Nanco, growth of fungal hyphae was predominantly intracellular and was accompanied by pronounced damage; by 48 h after inoculation, pericycle and the first cell layers of the phloem parenchyma were invaded, resulting in host wall dissolution and cytoplasm aggregation. The growth of P. violae in line 24 was limited to the pericycle, even up to 72 h after inoculation; fungal colonization was accompanied by retraction of cytoplasm and in the appearance of granular or fibrillar material in the host cell lumen. Some affected host cells were filled with structureless osmophilic material. In cultivar Nanco, invading fungal hyphae were unaffected; by contrast in line 24, the cytoplasm of invading hyphae, particularly those inside the cell host, was disorganised and structureless. Infection and host response in the two cultivars were studied with two specific labels: Aplysia gonad lectin (AGL), a polygalacturonic acid-binding lectin, and an exoglucanase complexed to colloidal gold were used to locate pectin and cellulosic -(1,4)-glucans respectively in infected tissues. The decrease of cytochemical labeling beyong fungal penetration showed clearly hydrolysis of pectin and cellulose in cell walls of the cv Nanco. By contrast, the cell wall of line 24 remained largely intact, although, unlabeled amorphous and electron-dense material was observed inside the wall. Fibrillar or electron dense material commonly observed in infected tissue of line 24 apparently did not contain pectic or cellulosic substances. Moreover, material observed in host cells or fungal hyphae was also free of labeling. The origin and the chemical composition of these compounds as well as their possible role in the defence mechanisms of carrot against P. violae are discussed.     

新型秸秆分解菌的筛选和酶活性研究

取江苏省泰州市的农田土壤和木材厂腐烂的木材,经过刚果红染色和滤纸条培养基的反复筛选,筛选出能降解纤维材料的7种菌,通过生化鉴定和纤维素酶活力的测定,菌种分别是白腐真菌、绿色木霉、纤维单胞菌、肋生菌、单胞菌、黑曲菌、节杆菌等。     

玉米叶片纤维素含量与冠层光谱特征的研究

以株型相近的高赖氨酸玉米“中单9409”、粮饲兼用型玉米“中原单32”和高油玉米“高油115”为供试材料,研究了不同生育时期和冠层中不同高度叶片中纤维素、半纤维素含量的差异及其冠层水平的光谱响应。结果表明：在相同栽培密度和施肥水平下,不同品玉米品种叶片的纤维素、半纤维素含量存在差异,其中以中、上层叶片相差较大,不同品种间同层叶片纤维素含量相差可达34.9%,下层叶片相差较小。通过对同步获取的冠层近红外光谱与叶片中纤维素、半纤维素含量进行相关分析,分别筛选出1420、1450、1490、2100和2270 nm可作为反演纤维素含量的特征波长;而2270、2280和2340 nm可作为反演半纤维素含量的特征波长,达到了显著或极显著水平。     

青枯菌胞外酶对木麻黄的致病作用研究

对三个致病性不同的木麻黄青枯菌ＰｓｅｕｄｏｍｏｎａｓｓｏｌａｎａｃｅａｒｕｍＥ．Ｆ．Ｓｍｉｔｈ产生的胞外酶活性测定显示,聚半乳糖醛酸酶（果胶酶）活性在各菌株之间无明显差别,但纤维素酶活性差别明显,并随菌株的致病性上升而增加,菌株致病性与酶活性具有高度正相关（ｒ＝０．９６）。     

川陈皮素-羧甲基纤维素钠复合涂膜对黄瓜保鲜效果的影响

以"绿箭一号"黄瓜为试材,研究了不同质量分数的川陈皮素-羧甲基纤维素钠复合涂膜材料对黄瓜的保鲜效果,以期在贮藏过程中减少其营养物质的损失。结果表明:与对照(蒸馏水)组相比,川陈皮素-羧甲基纤维素钠复合涂膜材料能有效降低黄瓜的失重率,减慢了黄瓜水分的散失;延缓了黄瓜中叶绿素的分解;减少了黄瓜中维生素C、可溶性固形物的分解及丙二醛(MDA)的累积,并降低了多酚氧化酶(PPO)活性。当川陈皮素添加量为2 g·L-1时,黄瓜有较佳的保鲜效果,可将其贮藏期延长至18 d,该研究可为黄瓜的贮藏保鲜方法提供参考依据。     

Microbial N-dealkylation of atrazine: Effect of exogeneous organic substrates and behaviour of the soil microflora

It has been demonstrated that atrazine side-chain mineralisation could be substantially stimulated by addition of carbon-containing substrates such as cellulose, green manure, straw or sawdust in the presence of NH₄⁺ nitrogen but poorly affected by amendments with glucose. Cellulose has the most beneficial effect. For that substrate it has been shown that (i) simultaneous application of the organic amendment and atrazine results in kinetics for side-chain dealkylation showing a lag phase which is reduced or even eliminated by preliminary incubation with the amendment, (ii) rate and extent of mineralisation of the ethylamino side chain are significantly accelerated by decreasing the C/N ratio of the amendment. By comparison, mineralisation of the isopropylamino side chain is not appreciably affected by a change in the value of the C/N ratio as far as atrazine is applied within a two- to three-week period following the organic treatment after which a small deficit in N supply has a definite beneficial effect on mineralisation. Cellulose and, to a lesser extent, straw induce a biphasic change in bacterial number with more numerous and/or active atrazine degraders being predominantly found in the later-developing bacterial community. The fungal microflora is relatively unaffected by all types of carbon substrates but glucose and, unexpectedly, by atrazine at high ratio of application. Activation of atrazine mineralisation seems to be a co-metabolic process which is kinetically controlled by the rate of release from polymerised C substrates of easily available and readily metabolisable low-molecular-weight co-substrates. Transient production of glucose as an end-product of cellulose depolymerisation might induce catabolic repression of dealkylation enzyme systems and be responsible for a lag in atrazine side-chain mineralisation. © 1998 Society of Chemical Industry     

沙柳与柠条混合原料碱性过氧化氢法分离的纤维素特性研究

分析了沙柳(Salix psamm ophila)与柠条(Caragana korshinskiiKom.)质量比为1∶1的混合原料的化学组成,在NaOH 18%(质量分数)、反应温度165℃、H2O23%(质量分数)、反应时间90 m in、液固比4∶1(mL∶g)的条件下降解木质素与半纤维素,分离纤维素,计算纤维素制备物的得率及粘度。采用GC、HPLC、FT-IR及13C NMR分析了纤维素制备物的特性,结果表明,碱性过氧化氢法能高效降解大部分木质素,得到的纤维素制备物中残余木质素含量较低(酚醛和酚酸总量为4.39%),纤维素纯度较高(葡萄糖含量84.68%),纤维素结晶度可能升高。     

南方型黑杨无性系木材材性的研究

在48个7—8年生南方型黑杨无性系对比试验林中,选择生长量达中等以上水平的19个新、老无性系,开展木材基本密度、纤维素含量、纤维形态的分析研究。纤维素含量和纤维长度在19个无性系中无显著差异,基本密度只在中汉17等几个无性系间有显著差异。基本密度和纤维长度在不同年龄间都存在显著差异。1～3年生的纤维长度在0．9mm以下,属短纤维;4—7年生的纤维长度在0．91mm以上,达到中级纤维长度标准。因此,杨树纸浆材超短轮伐期可以确定为3a或3a以上。