短期NaCl胁迫对西伯利亚白刺幼苗Na~+、K~+分配和平衡的影响

[目的]为探究西伯利亚白刺盐适应机制。[方法]以1年生西伯利亚白刺水培幼苗为材料,研究不同浓度NaCl(0、200、300 mmol·L-1)胁迫24 h后根系Na~+、K~+离子流的动态变化(利用扫描离子选择微电极技术,SIET)及植株各器官中Na~+、K~+含量的静态变化(利用电感耦合等离子体光谱仪,ICP-OES)。[结果]表明:(1)短期NaCl胁迫显著提高了西伯利亚白刺根、茎、叶中Na~+含量,其中,叶中Na~+含量是根中的3倍以上;西伯利亚白刺根、茎、叶中K~+含量保持稳定或上升;(2)盐胁迫下,西伯利亚白刺根、茎、叶中K~+/Na~+呈下降趋势,其中,在200、300 mmol·L-1NaCl胁迫下,根中K~+/Na~+差异不显著;(3)离子流结果显示,NaCl胁迫显著提高了西伯利亚白刺根系Na~+的外流;对照和200 mmol·L-1NaCl胁迫下,K~+净流量分别为156、159 pmol·cm-2·s-1,差异不显著;300 mmol·L-1NaCl胁迫显著提高了K~+的内流,净流量为-370 pmol·cm-2·s-1。[结论]综合分析认为,西伯利亚白刺通过叶片对Na~+区隔,加强根系对Na~+的外排和K~+内流,进而维持植株根系K~+/Na~+的相对平衡,以此适应盐渍环境。     

Acridones of Vepris sclerophylla: their C-NMR data

The isolation and ¹³C-NMR data of four acridones from Vepris sclerophylla are reported.     

Measuring nitrogen fixation by <Emphasis Type="Italic">Sesbania sesban</Emphasis> planted fallows using <Superscript>15</Superscript>N tracer technique in Kenya

A field experiment was performed in eastern Kenya to estimate N₂ fixation by Sesbania sesban over an 18-month period using the ¹⁵N dilution method. The influence of three reference species, Senna spectabilis, Eucalyptus saligna and Grevillea robusta, on the estimates of N₂ fixation was also assessed. Percentage Ndfa (nitrogen derived from the atmosphere) was calculated based on foliar atom excess (FAE), above-ground atom excess (AAE) or whole tree atom excess (WAE) data. The differences in atom% ¹⁵N excess values between species and plant parts are presented and discussed. We recommend the use of several reference species for estimating %Ndfa and that the different results obtained should be carefully considered in relation to the issues being addressed. In this study, Senna was the most suitable of the three reference species because its N uptake pattern and phenology were very similar to those of Sesbania. When well established, the amount of N fixed by Sesbania accounts for more than 80% of its total N content, according to FAE-based estimates. We estimated the Ndfa by Sesbania after 18 months to between 500 and 600 kg ha⁻¹ , depending on whether FAE, AAE or WAE data were used and on the choice of reference species. The substantial accumulation of N in planted Sesbania highlighted its potential to increase the sustainability of crop production on N-limited soils. We consider the ¹⁵N dilution method to be appropriate for quantifying N₂ fixation in improved fallows in studies, similar to this one, of young trees with high N₂-fixing ability.     

Mixed-species plantations of Acacia mangium and Eucalyptus grandis in Brazil: 2: Nitrogen accumulation in the stands and biological N2 fixation

The sustainability of plantation forests is closely dependent on soil nitrogen availability in short-rotation forests established on low-fertility soils. Planting an understorey of nitrogen-fixing trees might be an attractive option for maintaining the N fertility of soils. The development of mono-specific stands of Acacia mangium (100A:0E) and Eucalyptus grandis (0A:100E) was compared with mixed-species plantations, where A. mangium was planted in a mixture at a density of 50% of that of E. grandis (50A:100E). N₂ fixation by A. mangium was quantified in 100A:0E and 50A:100E at age 18 and 30 months by the ¹⁵N natural abundance method and in 50A:100E at age 30 months by the ¹⁵N dilution method. The consistency of results obtained by isotopic methods was checked against observations of nodulation, Specific Acetylene Reduction Activity (SARA), as well as the dynamics of N accumulation within both species. The different tree components (leaves, branches, stems, stumps, coarse roots, medium-sized roots and fine roots) were sampled on 5–10 trees per species for each age. Litter fall was assessed up to 30 months after planting and used to estimate fine root mortality. Higher N concentrations in A. mangium tree components than in E. grandis might be a result of N₂ fixation. However, no evidence of N transfer from A. mangium to E. grandis was found. SARA values were not significantly different in 100A:0E and 50A:100E but the biomass of nodules was 20–30 times higher in 100A:0E than in 50A:100E. At age 18 months, higher δ¹⁵N values found in A. mangium tree components than in E. grandis components prevented reliable estimations of the percentage of N derived from atmospheric fixation (%Ndfa). At age 30 months, %Ndfa estimated by natural abundance and by ¹⁵N dilution amounted to 10–20 and 60%, respectively. The amount of N derived from N₂ fixation in the standing biomass was estimated at 62 kg N ha⁻¹ in 100A:0E and 3 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 16 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The total amount of atmospheric N₂ fixed since planting (including fine root mortality and litter fall) was estimated at 66 kg N ha⁻¹ in 100A:0E and 7 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 31 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The most reliable estimation of N₂ fixation was likely to be achieved using the ¹⁵N dilution method and sampling the whole plant.     

Structural changes in lignin of tropical woods during digestion by termite, <Emphasis Type="Italic">Cryptotermes brevis</Emphasis>

Wood samples of apitong (Dipterocarpus grandiflorua) and ilang-ilang (Ilang-Ilang C. dadloyi) and feces of termites [Cryptotermes brevis (Walker)] fed on these woods were collected from University of the Philippines, Los Baňos. Lignin of each sample was isolated by Björkman’s procedure. There was no significant difference in ¹H nuclear magnetic resonance (NMR) spectra or in the methoxyl content between Björkman lignins from original woods and termite feces. Differences were detected in the contents of aliphatic and unconjugated phenolic hydroxyl groups, suggesting minor structural changes of lignin during digestion by termites. In addition, the ratio of syringyl to guaiacyl nuclei of Björkman lignin from termite feces determined by ¹H NMR spectra was higher than those from the original woods. The molar ratio of syringyl to guaiacyl nuclei of termite feces was higher than those from the original woods as determined by alkaline nitrobenzene oxidation. These results suggest that the structural changes of lignin in the termite gut are due to the insignificant formation of C-C linkages in guaiacyl nuclei. It was concluded that there were minor changes in the structural features of lignin under mostly anaerobic conditions, in contrast to the significant changes that occur through biological modification under aerobic conditions.     

Elevation difference of Ca<Superscript>2+</Superscript> levels in young leaf cells of bromegrass and induced cold-tolerant enhancement under different controlled chilling temperatures

The changes of Ca2＋ levels in young leaf cells of bromegrass under different controlled chilling temperatures were inves- tigated by an antimonite precipitation cytochemical method. The main results were as follows： under 25/20℃ （day/night） tempera- ture and 14 h photoperiod, electron-dense Ca2＋ antimonite precipitates, indicators of Ca2＋ localization, were mainly localized in the vacuoles, cell walls and intercellular spaces; few Ca2＋ deposits were observed in the cytosol and nuclei. After a 3℃ chilling treatment for 3 h, many Ca2＋ precipitates appeared in the cytosol and nuclei, indicating that Ca2＋ influx had occurred in the cytosol and nuclei. When the 3℃ treatment was prolonged to 8 h, more Ca2＋ deposits appeared in the nuclei and cytosol, but the amount of Ca2＋ deposits in both the cytosol and nuclei decreased markedly after a 24 h treatment and most Ca2＋ deposits were returned to the vacuoles and intercellular spaces after an 8 d treatment. When bromegrass was exposed to 7℃ for 3 h, the Ca2＋ distribution in the cells had no visible changes, compared with that of the 25/20℃ grown control plants. However, when the chilling treatment of 7℃ was prolonged to 8 h, a Ca2＋ influx occurred, where many Ca2＋ deposits were observed in the nuclei and cytosol. More Ca2＋ deposits appeared in the nuclei and cytosol after a 24 h treatment, but the amount of Ca2＋ deposits in the cytosol and nuclei was reduced markedly after an 8 d treatment. After a 14 d treatment, the remaining low level of Ca2＋ was recovered in both the cytosol and nuclei and the Ca2＋ deposits were again located in the vacuoles and the intercellular spaces. The dynamics of subcellular Ca2＋ localization in young leaf cells of bromegrass during a 12℃ chilling treatment were similar to those of the 7℃ treatment. Besides, the results showed that the frost tolerance ofbromegrass exposed to 3℃ for 8 d increased by 6℃, for 7℃ and 8 d by 4℃ and for 12℃ and 14 d by 3℃, compared with the controls.     

Active root distribution pattern of <Emphasis Type="Italic">Hevea brasiliensis</Emphasis> determined by radioassay of latex serum

The active root distribution pattern of mature rubber (Hevea brasiliensis Muell. Arg.) up to a lateral distance of 250 cm from the tree and to a soil depth of 90 cm was studied in an oxisol by employing ³²P soil injection technique in Kerala, the state which accounts for 83% of rubber cultivation in India. The trees were aged 18 years and grown at a spacing of 4.9 × 4.9 m. The extent of absorption of applied ³²P by the tree from various placements was assessed by radio assay of leaf and latex serum. Latex serum registered higher counts and variability was less compared to leaf indicating the suitability of latex serum as a potential source for radio assay for ³²P studies in rubber. The results revealed that rubber is a surface feeder with 55% of the root activity confining to the top 10 cm of soil layer. Root activity declined with increasing depths and the concentration of physiologically active roots at 90 cm depth was only 6%. A more or less uniform distribution of root activity was noticed with respect to lateral distance indicating more extensive spread of lateral roots. Concentration of physiologically active roots in the surface layer suggests the possibility for competition under intercropped situation in mature plantations.     

Proton translocating ATPase mediated fungicidal activity of eugenol and thymol

Eugenol (1) and thymol (2) exhibit excellent fungicidal activity against pathogenic yeasts, including isolates resistant to azoles. The rapid irreversible action of compound-1 and compound 2 on fungal cells suggested a membrane-located target for their action. We investigated their effect on H⁺-ATPase mediated H⁺-pumping by various Candida species. Both compounds inhibit H⁺-ATPase activity at their respective MIC values — 500 and 100 μg/ml. Glucose stimulated H⁺-extrusion was also inhibited significantly by compound 1 and compound 2. Inhibition of H⁺-ATPase leads to intracellular acidification and cell death. Inhibition of cell growth and H⁺-efflux by test compounds suggests that their antifungal properties are related to their inhibitory effects on H⁺-ATPase.     

Natural abundance of <Superscript>15</Superscript>N in two cacao plantations with legume and non-legume shade trees

Natural abundance of ¹⁵N was sampled in young and mature leaves, branches, stem, and coarse roots of trees in a cacao (Theobroma cacao) plantation shaded by legume tree Inga edulis and scattered non-legumes, in a cacao plantation with mixed-species shade (legume Gliricidia sepium and several non-legumes), and in a tree hedgerow bordering the plantations in Guácimo, in the humid Caribbean lowlands of Costa Rica. The deviation of the sample ¹⁵N proportion from that of atmosphere (δ¹⁵N) was similar in non-legumes Cordia alliodora, Posoqueria latifolia, Rollinia pittieri, and T. cacao. Deep-rooted Hieronyma alchorneoides had lower δ¹⁵N than other non-N₂-fixers, which probably reflected uptake from a partially different soil N pool. Gliricidia sepium had low δ¹⁵N. Inga edulis had high δ¹⁵N in leaves and branches but low in stem and coarse roots. The percentage of N fixed from atmosphere out of total tree N (%N_f) in G. sepium varied 56–74%; N₂ fixation was more active in July (the rainiest season) than in March (the relatively dry season). The variation of δ¹⁵N between organs in I. edulis was probably associated to ¹⁵N fractionation in leaves. Stem and coarse root δ¹⁵N was assumed to reflect the actual ratio of N₂ fixation to soil N uptake; stem-based estimates of %N_f in I. edulis were 48–63%. Theobroma cacao below I. edulis had lower δ¹⁵N than T. cacao below mixed-species shade, which may indicate direct N transfer from I. edulis to T. cacao but results so far were inconclusive. Further research should address the ¹⁵N fractionation in the studied species for improving the accuracy of the N transfer estimates. The δ¹⁵N appeared to vary according to ecophysiological characteristics of the trees.     

Tracing the fate of mineral N compounds under high ambient N deposition in a Norway spruce forest at Solling/Germany

The fate of high and equally distributed ammonium and nitrate deposition was followed in a 72-year-old roofed Norway spruce forest at Solling in central Germany by separately adding ¹⁵NH₄⁺ and ¹⁵NO₃⁻ to throughfall water since November 2001. The objective was to quantify the retention of atmospheric ammonium and nitrate in different ecosystem compartments as well as the leaching loss from the forest ecosystem. δ¹⁵N excess in tree tissues (needles, twigs, branches and bole woods) decreased with increased tissue age. Clear ¹⁵N signals in old tree tissues indicated that the added ¹⁵N was not only assimilated to newly produced tree tissues but also retranslocated to old ones. During a period of over 3-year ¹⁵N addition, 30% of ¹⁵NH₄⁺ and 36% of ¹⁵NO₃⁻ were found in tree compartments. For both ¹⁵N tracers, 15% of added ¹⁵N was found in needles, followed by woody tissues (twigs, branches and boles, 7–13%) and live fine roots (7%). The recovery of ¹⁵NH₄⁺ and ¹⁵NO₃⁻ in the live fine roots differed with soil depth. The recovery of ¹⁵NH₄⁺ tended to be higher in the live fine roots in the organic layer than in the upper mineral soil. In the live fine roots in deeper soil, the recovery of ¹⁵NO₃⁻ tended to be higher than that of ¹⁵NH₄⁺. Soil retained the largest proportion of ¹⁵N, accounting for 71% of ¹⁵NH₄⁺ and 42% of ¹⁵NO₃⁻. Most of ¹⁵NH₄⁺ was recovered in the organic layer (65%) and the recovery decreased with soil depth. Conversely, only 8% of ¹⁵NO₃⁻ was found in the organic layer and 34% of ¹⁵NO₃⁻ was evenly distributed throughout the mineral soil layers. Nitrate leaching accounted for 3% of ¹⁵NH₄⁺ and 19% of ¹⁵NO₃⁻. Only less than 1% of the both added ¹⁵N was leached as DON. These results suggested that trees had a high contribution to the retention of atmospheric N and soil retention capacity determined the loss of atmospheric N by nitrate leaching.     

Myricanol and myricanone biosynthesis in <Emphasis Type="Italic">Myrica rubra</Emphasis>: incorporation of two molecules of 4-coumaric acid

After feeding experiments of Myrica rubra young shoots with 4-[8,9-¹³C₂]coumaric acid, mass spectrometric analyses revealed that the cyclic diarylheptanoids, myricanol and myricanone, were derived from two molecules of 4-coumaric acid. ¹³C Nuclear magnetic resonance analysis of myricanol isolated after administration of 4-[8,9-¹³C₂]coumaric acid demonstrated that the C-8 and C-9 atoms of 4-coumaric acid are incorporated into C-8, C-9, C-11, and C-12 of the corresponding myricanol. Part of this report was presented at the 56th Annual Meeting of the Japan Wood Research Society, Akita, August 2006     

Effectiveness and side effects of glue-traps to decrease damages caused by Byturus tomentosus in raspberry

Damages caused by the larvae of Byturus tomentosus (Coleoptera: Byturidae) are a big problem of European raspberry production. Under integrated pest management conditions in Switzerland, B. tomentosus is controlled by chemical-synthetic insecticides. In organic production, no corresponding insecticides are permitted. White sticky traps (type Rebell^® bianco) are used for monitoring purposes. Can glue-traps also be used for mass-trapping and damage control? In this study, the attractiveness for adult B. tomentosus of one yellow and several white glue-traps was compared by counting the trapped individuals. Trapped beneficial insects like honey bees, Coccinellidae, Syrphidae and Chrysopidae were also counted. The contamination of the traps caused by other non-target arthropods was measured by a computer-assisted method. The white sticky trap type Rebell bianco was the most attractive for B. tomentosus. The attractiveness for the beneficials was relatively low, except when too much glue was applied on the traps, then the attractiveness for honey bees increased significantly. In this study, traps, which were placed in high densities (17 traps per 100 m²), significantly decreased the damages caused by larvae by around 40%. The trapping method does not cause any residuals of pesticides on the fruits or soil. Therefore, the trapping method could be an alternative to control B. tomentosus, especially in organic production.     

Nitrogen-fixation dynamics in a cut-and-carry silvopastoral system in the subhumid conditions of Guadeloupe, French Antilles

This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system to increase soil fertility and insure sustainability. We analyzed the N₂ fixation pattern of the woody legume component (Gliricidia sepium), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass (Dichanthium aristatum). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied. Dinitrogen fixation, as estimated by the ¹⁵N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average, 76% of the N exports from the plot in tree pruning (194 kg [N] ha^–1 yr^–1) originated from N₂ fixation. Grass production averaged 13 Mg ha^–1 yr^–1 and N export in cut grass was 195 kg [N] ha^–1 yr^–1. The total N fixed by G. sepium, as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg [N] ha^–1 yr^–1. Carbon sequestration averaged 1.9 Mg [C] ha^–1 yr^–1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg [N] ha^–1 yr^–1, corresponding to 30% of N₂ fixation by the tree. Nitrogen released in nodule turnover (10 kg [N] ha^–1 yr^–1) and litter decomposition (40 kg [N] ha^–1 yr^–1) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground tree biomass than nodules. This revised version was published online in June 2006 with corrections to the Cover Date.     

Lignin characterization of triploid clones of Populus tomentosa Carr.

In order to understand the structural characteristics of lignin in triploid clones of Populus tomentosa and its changes in the processes of pulping and bleaching, milled wood lignin (MWL), lignin carbohydrate complex (LCC) and the residual lignin from kraft pulp (KP) and sulfite pulp (SP) were isolated and analyzed by Fourier transform infrared (FTIR) spectrum and ¹³C nuclear magnetic resonance (NMR). The most diagnostic peaks were assigned and the differences were discussed. The spectral patterns reveal that triploid P. tomentosa shows the specific features of hardwood from temperate areas, but in the spectrum of FTIR, the strength ratio of A 1270 cm⁻¹ to A1226 cm⁻¹ is 0.88, higher than the average of hardwood from temperate areas, which will make the lignin delignification more difficult during pulping and bleaching. The LCC from triploid P. tomentosa is mainly composed of xyloglucan and glucuronic acid, and other glucides have much lower ratio. In LCC FTIR, there are three peaks at 1 427, 1 329 and 1 046 cm⁻¹, indicating that both semi-cellulose and cellulose could exist in LCC, and that there might be relationships between cellulose and lignin. Compared with the residual lignin from KP and SP, the condensed structure in KP is more than that in SP.     

Effects of Ca^2＋concentrations on accumulations of mineral elements in the components of Pteroceltis tatarinowii

The bark ofPteroceltis tatarinowii is a raw material for manufacturing Xuan Paper. The effects of Ca²⁺ concentrations on the accumulation of mineral elements in the bark, leaf and root ofPteroceltis tatarinowii were studied under controlled conditions. The types of Hoagland nutrient solution with three Ca²⁺ concentrations levels (200, 400 and 600 μg·g⁻¹) and a control (without Ca²⁺ were designed to culturePteroceltis tatarinowii. After 6 months, contents of seven mineral elements including Ca, K, Mg, Mn, Zn, Cu and Na in the root, leaf and bark were analyzed. The results indicated that Ca accumulations content in the root, leaf and bark had positively relation with Ca²⁺ concentrations (200, 400, 600 μg·g⁻¹), and the order of the Ca content in the three components was root>leaf>bark. Ca content in the root treated with 600 μg·g⁻¹ Ca²⁺ concentrations was 5.5 times as high as that of the control, and about 1.4 times as high as that of the root treated in 200 and 400 μg/g Ca²⁺ concentrations respectively. On the contrary, K and Mg contents in the root, leaf and bark were negatively related to Ca²⁺ concentrations, especially in the bark, and their accumulation trend followed the order of leaf>root>bark. K content in the bark treated with 600 μg·g⁻¹ Ca²⁺ concentrations was 39.3% of that of the control, and was 79.0% and 91.8% of that of the bark treated with 200μg·g⁻¹ and 400μg·g⁻¹ Ca²⁺ concentrations respectively; Mg content in the bark treated with 600μg·g⁻¹ Ca²⁺ concentrations was 23.4% of that of the control, and was 27.1% and 35.4% of that of the bark treated with 200 and 400 μg·g⁻¹ Ca²⁺ concentrations respectively. Compared with the control, the general tendency of Mn, Zn and Cu content decreased with increasing of Ca²⁺ concentrations and their contents were in the order: root>leaf>bark. Based on the results of this study, the experiment has been useful for providing academic bases in improving the bark quality ofPteroceltis tatarinowii on non-limestone soil. Foundation item: This paper is supported by National Natural Science Foundation of China (No. 39970608). Biography: Fang Shengzun (1963), male, Professor in Stiiviculture, Nanjing Forestry University, Nanjing 210027, P.R. China. Responsible editor: Zhu Hong     

Recovery of N-urea 10 years after application to a Douglas-fir pole stand in coastal British Columbia

The long-term fate of fertilizer N in forest ecosystems is poorly understood even though such information is critical for designing better forest fertilization practices. We studied the distribution and recovery of ¹⁵N (4.934 atom% excess)-labelled fertilizer (applied as urea at 200 kg N ha⁻¹) 10 years after application to a 38–39-year-old Douglas-fir (Pseudotsuga menzeisii (Mirb.) Franco) stand in coastal British Columbia. The urea was applied in the spring (May 1982) or fall (November 1982). Sampling was conducted in October 1992, and we found that after 10 years, there were few differences between the fall and spring fertilizer applications in total N and ¹⁵N distribution within the tree and forest ecosystem. On average total fertilizer-N recovery was 59.4%; about 14.5% of the applied-N was recovered in the trees including coarse roots, with foliage containing 41% of the labelled-N recovered in the aboveground tree biomass. Tissue ¹⁵N remained mobile and could be transferred to new growth. Soil recovery was 39.8%, which had decreased from 57.0% at a previous 1-year sampling, with an average loss of 3.0% per year from the mineral soil and 3.7% from the litter layers. However, it appears that there was little continuing tree uptake. While short-term effects of fall vs. spring urea application were previously reported, there were no long-term effects on either stand productivity or fertilizer use efficiency, suggesting that if fertilization is properly done, timing of fertilization is not a critical issue in terms of maximizing fertilizer use efficiency for the coastal Douglas-fir forest we studied. Our results also highlight the high capacity of this ecosystem to retain externally applied inorganic N over the long-term, the importance of maximizing nitrogen uptake in the first year, and also of the continuing need to develop new approaches to overcome the generally low efficiency of forest N fertilization.     

Effects of enhanced ultraviolet-B radiation on water use efficiency, stomatal conductance, leaf nitrogen content and morphological characteristics of Spiraea pubescens in a warm-temperate deciduous broad-leaved forest

Spiraea pubescens, a common shrub in the warm-temperate deciduous forest zone which is distributed in the Dongling Mountain area of Beijing, was exposed to ambient and enhanced ultraviolet-B (UV-B, 280–320 nm) radiation by artificially supplying a daily dose of 9.4 kJ/m² for three growing seasons, a level that simulated a 17% depletion in stratospheric ozone. The objective of this study was to explore the effects of long-term UV-B enhancement on stomatal conductance, leaf tissue δ ¹³C, leaf water content, and leaf area. Particular attention was paid to the effects of UV-B radiation on water use efficiency (WUE) and leaf total nitrogen content. Enhanced UV-B radiation significantly reduced leaf area (50.1%) but increased leaf total nitrogen content (102%). These changes were associated with a decrease in stomatal conductance (16.1%) and intercellular CO₂ concentration/ air CO₂ concentration (C _i /C _a) (4.0%), and an increase in leaf tissue δ ¹³C (20.5‰), leaf water content (3.1%), specific leaf weight (SLW) (5.2%) and WUE (4.1%). The effects of UV-B on the plant were greatly affected by the water content of the deep soil (30–40 cm). During the dry season, differences in the stomatal conductance, δ ¹³C, and WUE between the control and UV-B treated shrubs were very small; whereas, differences became much greater when soil water stress disappeared. Furthermore, the effects of UV-B became much less significant as the treatment period progressed over the three growing seasons. Correlation analysis showed that enhanced UV-B radiation decreased the strength of the correlation between soil water content and leaf water content, δ ¹³C, C _i/C _a, stomatal conductance, with the exception of WUE that had a significant correlation coefficient with soil water content. These results suggest that WUE would become more sensitive to soil water variation due to UV-B radiation. Based on this experiment, it was found that enhanced UV-B radiation had much more significant effects on morphological traits and growth of S. pubescens than hydro-physiological characteristics. __________ Translated from Journal of Plant Ecology, 2006, 30(1): 47–56 [译自: 植物生态学报]     

Foliar Carbon Isotope Composition (δ 13C) and Water Use Efficiency of Different Populus deltoids Clones Under Water Stress

Foliar carbon isotope composition (δ ¹³C), total dry biomass, and long-term water use efficiency (WUE_L) of 12 Populus deltoids clones were studied under water stress in a greenhouse. Total dry biomass of clones decreased greatly, while δ ¹³C increased. Single-element variance analysis in the same water treatment indicated that WUE_L difference among clones was significant. Clones J₂, J₆, J₇, J₈, and J₉ were excellent with high WUE_L. Extremely significant δ ¹³C differences among water treatments and clones were revealed by two-element variance analysis. Water proved to be the primary factor affecting δ ¹³C under water stress. It showed that there was a good positive correlation between δ ¹³C and WUE_L in the same water treatment, and that a high WUE_L always coincided with a high δ ¹³C. δ ¹³C might be a reliable indirect index to estimate WUE_L among P. deltoids clones. Translated from Scientia Silvae Sinicae, 2005, 41(1) (in Chinese)     

Effects of paper mill sludge and weed control on competing vegetation and growth of young red pine

In September, 1988, a paper mill sludge from Georgia-Pacific Corporation's wastewater treatment facility in Port Edwards, WI., was applied to a 4- and 6-year-old red pine (Pinus resinosa Ait.) plantation. Sludge was applied using industrial spreaders at rates of 0, 10, 20 and 40 Mg ha^-1. Twenty-one months following treatment, above-ground biomass production of sedge (Carex spp.), the predominant understory component, was increased by as much as 85% from the 40 Mg ha^-1 rate relative to the control. The increase in dry matter production coincided with significant increases in above- and below-ground levels of N, P and K. Weed control performed in August, 1989, resulted in reduced levels of woody and herbaceous vegetation, without a concomitant effect on red pine performance. Possible reasons for this lack of response are discussed within this paper.     

Functional involvement of Ca(2+) and Ca(2+)-activated K(+) channels in anethol-induced changes in Ca(2+) dependent excitability of F1 neurons in Helix aspersa

The effects of anethol, the major component of anise oil, on the Ca²⁺-dependent excitability and afterhyperpolarization (AHP) in snail neurons were examined using intracellular recording. Anethol (0.5%) significantly broadened the spike, reduced the firing frequency and enhanced the AHP amplitude. In contrast, anethol (2%) significantly increased the firing frequency and decreased the AHP. Blockade of Ca²⁺ channels after anethol application depolarized the membrane potential and significantly reduced the firing rate. Furthermore, in the presence of anethol (0.5%) a significant decrease in the AHP was observed by Ca²⁺ channels blockage. Here, anethol-induced functional modification of Ca²⁺ and Ca²⁺-activated K⁺ channels is suggested.