Midday depression of net photosynthesis in the tropical rainforest tree Eperua grandiflora: contributions of stomatal and internal conductances,respiration and Rubisco functioning

High midday temperatures can depress net photosynthesis. We investigated possible mechanisms underlying this phenomenon in leaves of Eperua grandiflora (Aubl.) Benth. saplings. This tropical tree establishes in small gaps in the rainforest canopy where direct sunlight can raise midday temperatures markedly. We simulated this microclimate in a growth chamber by varying air temperature between 28 and 38 degrees C at constant vapor pressure. A decrease in stomatal conductance in response to an increase in leaf-to-air vapor pressure difference (deltaW) caused by an increase in leaf temperature (Tleaf) was the principal reason for the decrease in net photosynthesis between 28 and 33 degrees C. Net photosynthesis decreased further between 33 and 38 degrees C. Direct effects on mesophyll functioning and indirect effects through deltaW were of similar magnitude in this temperature range. Mitochondrial respiration during photosynthesis was insensitive to Tleaf over the investigated temperature range; it thus did not contribute to midday depression of net photosynthesis. Internal conductance for CO2 diffusion in the leaf, estimated by combined gas exchange and chlorophyll fluorescence measurements, decreased slightly with increasing Tleaf. However, the decrease in photosynthetic rate with increasing Tleaf was larger and thus the difference in CO2 partial pressure between the substomatal cavity and chloroplast was smaller, leading to the conclusion that this factor was not causally involved in midday depression. Carboxylation capacity inferred from the CO2 response of photosynthesis increased between 28 and 33 degrees C, but remained unchanged between 33 and 38 degrees C. Increased oxygenation of ribulose-1,5-bisphosphate relative to its carboxylation and the concomitant increase in photorespiration with increasing Tleaf were thus not compensated by an increase in carboxylation capacity over the higher temperature range. This was the principal reason for the negative effect of high midday temperatures on mesophyll functioning.     

Variation in the decay resistance of larch to fungi

? Decay resistance of larch (Larix sp.) to fungi was evaluated on heartwood samples belonging to 3 species (L. decidua, L. kaempferi and their hybrid), 3 races of European larch (polonica, sudetica and alpine), 13 wood lots (populations) and 313 trees.

? Larch wood appeared, on average, as moderately durable although a high variability was observed. At the sample level as well as at the mean individual tree level, durability ranged from class 1 to 5 according to EN 350-1 standard. At the population level, larch wood varied from ‘durable’ to ‘slightly durable’. Genetics played a major role in decay resistance at the species, provenance and tree levels. Environmental factors such as the position of heartwood samples and the age of trees were also identified as a source of variability.

? The most durable wood was not necessarily from old native alpine stands of European larch: some young larches from faster growing lowland origins also produced durable wood.

? Genetic improvement of larch wood durability appeared therefore likely by the selection of the best populations for decay resistance as well as from the selection of individuals.

     

Strength,decay and termite resistance of oriented kenaf fiberboards

The development of oriented fiberboards made from kenaf (Hibiscus cannabinus L.) and their suitability as a construction material has been investigated. Three different types of boards consisting of five layers with individual orientations were prepared using a combination of low molecular weight and high molecular weight phenol-formaldehyde (PF) resin for impregnation and adhesion purposes. Additional boards with the same structure were prepared using high molecular weight PF resin only. The mechanical properties of the boards have been examined as well as their resistance against fungal decay and termite attack. All kenaf fiberboards showed elevated mechanical properties compared with medium-density fiberboard made from wood fibers, and showed increased decay and termite resistance. Differences in the decay and termite resistance between the board types were caused by the presence of the low molecular weight PF resin for the impregnation of the fibers. No significant difference was found for the mechanical properties. The effect of the PF resin for impregnation was much clearer in fungal decay resistance than for termite resistance; however, fiber orientation had no effect on both decay and termite resistance of the specimens.     

Polymerisation of added coniferyl alcohol by inherent xylem peroxidases and its effect on fungal decay resistance of Norway spruce

It is known that active peroxidase isozymes exist in mature wood of Norway spruce (Picea abies L. Karst.) and that they remain active for years and are found even in the heartwood (in Scots pine), where all cellular activity has ceased. This peroxidase activity was utilised in the impregnation of wood blocks with a natural monolignol, coniferyl alcohol and hydrogen peroxide. The hypothesis was that the internal wood peroxidases would oxidise the added monolignol and bind it stably into the cell wall matrix, which could hinder fungal decay. Since coniferyl alcohol is not very soluble in water, the impregnation was done under vacuum with an acetone–water solution containing 10% coniferyl alcohol and 0.4 mM H₂O₂ at room temperature (ca. 0.02 g of coniferyl alcohol was added to 1 g of wood). After impregnation, dimers of coniferyl alcohol and free coniferyl alcohol were found in acetone extracts with GC–MS analysis. Penetration of coniferyl alcohol and non-extractable reaction products were studied from the wood blocks with FTIR PAS technique. The wood samples treated were also subjected to a fungal decay test with Coriolus versicolor. This treatment hindered fungal decay in a 60-day experiment and led to a dry weight loss of 8.8% in comparison with 19.9% in the control. The reactions of coniferyl alcohol and H₂O₂ in the presence of peroxidases are discussed as well as the use of monolignols to increase wood decay resistance.     

毛竹和重组竹腐朽前后的表面颜色及耐腐性能

以毛竹和重组竹为研究对象,用绵腐卧孔菌(PV)、密粘褶菌(GT)两种褐腐菌和彩绒革盖菌(CV)、变色栓菌(TV)两种白腐菌进行腐朽试验,比较分析了毛竹和重组竹腐朽前后表面视觉性质及其质量损失差异。结果发现:毛竹和重组竹颜色均发生了显著变化,主要表现为明度(L~*)降低,色度值(C)、红绿轴色品指数(a~*)和黄蓝轴色品指数(b~*)显著增大,其中绵腐卧孔菌对毛竹及重组竹的色差影响最大。重组竹(耐绵腐卧孔菌)能达到Ⅰ级强耐腐水平;毛竹(耐绵腐卧孔菌)和重组竹(耐密粘褶菌和彩绒革盖菌)达到了Ⅱ级耐腐水平;毛竹(耐密粘褶菌、彩绒革盖菌和变色栓菌)和重组竹(耐彩绒革盖菌)为Ⅲ级稍耐腐水平。整体来看,重组竹对白腐菌和褐腐菌的耐腐效果好于毛竹。绵腐卧孔菌虽然对毛竹和重组竹的降解能力最弱,但对其颜色变化的影响却最大。扫描电镜可观察到彩绒革盖菌通过毛竹导管壁上的纹孔进入薄壁细胞、伴胞等,同时通过分泌木质素酶导致其细胞壁降解。     

Leachability,decay, and termite resistance of wood treated with metaborates

The formation of insoluble metaborates in wood was investigated by impregnating the wood with borax and metallic salts, after which their properties (e.g., leachability in running water and biological resistance) were evaluated. The solubility of three metaborates in acidic solutions was also evaluated. Double-diffusion treatment was carried out to form the precipitates of metaborates in sapwood specimens of Japanese cedar (Cryptomeria japonica) at room temperature. Water-saturated wood specimens were first impregnated by a saturated borax solution and then diffuse-penetrated with Zn²⁺, Ca²⁺, or Pb²⁺ solution. The precipitates of the three metaborates in the wood proved to be insoluble or hardly soluble in water by the leaching test. With the decay test using a brown-rot fungus (Fomitopsis palustris) and a white-rot fungus (Trametes versicolor) and with the termite test using a virulent subterranean termite (Coptotermes formosanus), the metaborate-treated woods showed generally good decay and termite resistance with negligible mass loss of the specimens. Particularly, the lead metaborate formed in the wood provided superb biological resistance against decay and termite attacks. In addition, the precipitates of these metaborates were found to be soluble in acidic solution, suggesting a way to remove these chemicals from wood when disposing of waste materials.     

Fungal decay resistance of wood impregnated with parahalophenyl para-tolyl sulfonamides

Summary We are investigating wood decay biocides that are both effective in protecting wood from decay and more environmentally compatible than other biocides. A series of halophenyl sulfonamides were synthesized and characterized by infrared and neuclear magnetic resonance spectroscopy. Wood impregnated with these compounds was tested for resistance to decay as well as water leaching. Wood impregnated with para-iodophenyl or para-fluorophenyl para-tolyl sulfonamides resisted decay by brown- and white-rot fungi. For wood impregnated with para-iodophenyl para-tolyl sulfonamide, threshold retention with the brown-rot fungus Gloeophyllum trabeum was 9.1 mmol/ 100 g solution for unleached blocks. For leached blocks, weight loss was very high (24.6%), which indicated that threshold retention will be substantially higher than 9.1 mmol/100 g solution. With the white-rot fungus Coriolus versicolor, threshold retentions were 2.9 and 5.6 mmol/100 g solution, respectively, for unleached and leached blocks. Leaching of the blocks treated with the iodo compound slightly decreased resistance to decay by C. versicolor. For wood impregnated with parafluorophenyl para-tolyl sulfonamide, threshold retentions with both G. trabeum and C. versicolor were very close to 9.0 and 9.2 mmol/100 g solution, respectively, for leached and unleached blocks. Leaching had a little effect on resistance to decay by both fungi. Wood impregnated with parachlorophenyl or bromophenyl para-tolyl sulfonamide was ineffective in resisting decay by both fungi.     

Wood colour variation in sapwood and heartwood of young trees of Tectona grandis and its relationship with plantation characteristics, site, and decay resistance

? Wood colour of Tectona grandis produced from fast-growth plantations is highly variable and the causes of this variation are relatively unknown.

? With the purpose of understanding the colour variation, different fast-growth plantations were sampled with different growth rates, tree ages, and sites.

? Wood colour was measured with a CIELab system, where three variables are estimated: coordinate L* for lightness, coordinate a* defines redness and coordinate b* defines yellowness.

? Results showed only a negative correlation between L* and a*. L* and a* were negatively and positively respectively correlated with pith distance in heartwood, but not for b*. No correlations were found between L* and b* in sapwood and plantation characteristics, while a* was positively correlated with age and height of tree and growth rate. In heartwood, tree age and diameter at breast height were correlated with all colour parameters, but tree height and plantation density were correlated with a* and b*. Cluster site had correlation with L*. Multiple correlation analysis showed that the heartwood is increasing darker (L*) and redder (a*) when the trees are older and bigger. Correlation coefficient shown that sapwood and heartwood with lighter colour (L*) is less resistance to fungal attack, but redness colour (a*) increasing decay resistance.

     

菊花水培扦插生根试验

用不同浓度的吲哚丁酸、萘乙酸和生根粉对菊花基部进行处理,测定了不同处理的生根情况,结果表明：生根粉、吲哚丁酸20mg／L和萘乙酸20mg／L生根效果较好,以生根粉表现最好,效果较为显著。从生产角度上来看,生根粉应为首选。     

Mechanical properties,components and decay resistance of Populus davidiana bioincised by Coriolus versicolor

The experiment was conducted to improve the decay resistance of wood by increasing the wood preservatives uptake and penetration depth by bioincising with Coriolus versicolor. The mechanical properties of bioincised Populus davidiana sapwood were measured. The changes of wood components(lignin, cellulose and hemicellulose) were analyzed by FTIR. The staining treatment using potassium permanganate was to measure the preservatives uptake and penetration depth in wood specimens. The decay resistance of bioincised specimens impregnated with IPBC and CA was assessed against C.versicolor and Gloeophyllum trabeum using bioincised P.davidiana sapwood and untreated controls. The results showed that the mechanical properties of the bioincised specimens were changed with the incubation time and mass loss. The mechanical strength was decreased after 17 days compared to that of the specimens bioincised 13 days.The bioincised specimens demonstrated the deeper penetration depth than the un-bioincised specimens. It was significant correlation(P 0.01) between penetrationdepth and incubation time. The average value of the penetration depth of the bioincised specimens was deeper than the control groups by 158.7%. By FTIR analysis, the biodegradation ability of C. versicolor to decay cellulose and hemicellulose was weaker than that of lignin. The bioincising treatment significantly increased the wood uptake of IPBC and CA, and reached the maximum uptake value at 17 and 13 days, respectively. Summarily, the bioincising pretreatment can obviously improve the wood decay resistance against C. versicolor and G. trabeum following by introducing the IPBC and CA.     

Structure-activity relationships of some congeners of 4-phenyl-3-butenoic acid against aspen decay and stain fungi

Phellinus tremulae is the most important decay fungus on Populus tremuloides. In forest industries using aspen wood chips, two blue-stain fungi Ophiostoma crassivaginatum and Ophiostoma piliferum cause considerable reduction in the value of the end product. Thirty-eight homologues and analogues of 4-phenyl-3-butenoic acid were studied against P. tremulae, O. crassivaginatum, and O. piliferum. Varied inhibition of the in vitro growth of these fungi was observed at 1–1000 μg/ml. The wood-chip colonization by P. tremulae was not affected by the six most active compounds at 1 μg/ml, however, at 10 and 100 μg/ml the growth of P. tremulae on wood chips was totally arrested. 4-Phenyl-3-butenoic acid and 4-phenyl-3-butynoic acid prevented blue-stain development on wood chips at 1 μg/ml.     

Dihydrochalcones and coumarins of Esenbeckia grandiflora subsp. brevipetiolata

Six furoquinolines and five coumarins have been isolated from the roots of Esenbeckia grandiflora subsp. brevipetiolata. The leaves yielded two dihydrochalcones and two flavonol rhamnosides. One of the coumarins (5-senecioyl-xanthotoxin) and the dihydrochalcones are novel compounds and their structures were elucidated by spectroscopic methods. The comparison with the dihydrochalcones previously isolated from another subspecies, E. grandiflora subsp. grandiflora is also provided.     

A comparative study on stability and decay resistance of some environmentally friendly fire-retardant boron compounds

Environmental concern accelerated development of new wood preservatives having low mammalian toxicity in addition to high protective effectiveness. PHN 130 and PHN 130 G have been developed recently by KOHMIX Ltd. in Japan as environmentally safe, fire-proof boron containing compounds. Beyond their proved fire-proof properties, stability of loaded chemical in wood at humid service conditions and decay resistance are required to be known for effective and broad use of these compounds in wood preservation. Results indicated that PHN imparted complete decay resistance to wood against brown- and white-rot fungi Tyromyces palustris and Coriolus versicolor, respectively. Protection efficacy of PHN also continued despite severe weathering conditions provided that impregnation is done by an undiluted solution. PHN 130 G appeared more effective than PHN 130 in this respect. However, both compounds were leachable from treated wood regardless of retention level or physical restriction of water access into wood by compression.This revised version was published online in April 2005 with a corrected date of receipt of the article.

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木材天然耐腐性室内试验标准方法的研究

采用三种培养基、两种白腐菌、两种褐腐菌对马尾松、毛白杨的天然耐腐性进行了试验。结果表明:砂子锯屑培养基法对采绒革盖菌(Corjolus versicolor)和绵腐卧孔菌(Poiraplacenta)的生长较快,对木材腐朽力,即重量损失较明显。     

抗虫基因及其在杨树育种上的应用

概述了抗虫基因的特性、抗虫机理及其在杨树抗虫育种中的应用，指出了杨树抗虫基因工程存在的问题，并提出其解决对策。     

木材液相乙酰化处理及处理材尺寸稳定性和耐腐性的研究

本文论述了马尾松、白桦和青杨三种木材的液相乙酰化条件及各种乙酰化木材的尺才稳定性和耐菌腐能力。以乙酸酐和二甲苯为处理液,反应的最佳条件是:温度120℃,时间7到11小时,乙酸酑与二甲苯配比1:1。当处理试样的增重到15%时,抗收缩率可达60%以上。增重为11.75—17.98%的不同处理试块,其耐菌腐能力可提高3—34倍。     

园林绿化树种——八宝树病虫害调查研究

为了及时准确掌握八宝树病虫害种类及危害程度、发生发展规律,制定切实可行的有效防治措施,对广西林科院内八宝树病虫害进行调查,发现虫害20种,描述了主要害虫(包括严重危害和中等危害)的危害情况、形态特征,研究了主要害虫的生物学特性。