Characterization and Role of Glucose-6-phosphate Dehydrogenase of Populus suaveolens in Induction of Freezing Resistance

Glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) was purified from the leaves of 8-week-old Populus suaveolens cuttings. The enzyme activity in the absence and presence of reduced dithiothreitol (DTTred) was determined. The results show that the G6PDH activity is not inactivated by pre-incubation with DTTred, indicating that the purified enzyme probably presented in cytosol of P suaveolens. The catalytic characteristics and kinetic parameters of cytosolic G6PDH purified from P.suaveolens cuttings were also studied. The results show that G6PDH is characterized by Km value of 360/amol.L^-1 for G6P and 16μmol.L^-1 for NADP, a pH range of 7.3-8.9, and the maximum activity around pH 8.2. The enzyme activity is inhibited by various metabolites such as NADPH, NADH, GTP, UTP, ATP, AMP, ADP, CoA, acetyl CoA, fructose-6-phosphate (F6P), erythrose-4-phosphate (E4P), ribose-5-phosphate (R5P) and 3-phosphoglycerate (3-PG) (all at 1 mmol‘L i except for NADPH and NADH)to different extents. NADPH is the most effective inhibitor of enzyme activity, with an inhibition of 72.0%. The addition of metal ions such as MgC12, CaC12 and KC1 (all 1.0 mmol.L^-1) to the standard reaction mixture has no remarkable influence on the cytosolic G6PDH activity. However, CdCl2 (1.0 mmol.L-1) causes high inhibitory effect on the enzyme activity. To explore the role of G6PDH on the enhancement of freezing resistance induced by freezing acclimation, the changes in the cytosolic G6PDH activity and freezing resistance (expressed as LTs0) of P. suaveolens cuttings during freezing acclimation at -20℃ were investigated. The results reveal that freezing acclimation decreases LTs0 of cuttings, and increases the activity of cytosolic G6PDH compared with control ones,while 2 d of de-acclimation at 25 ~C result in a decrease in cytosolic G6PDH activity, and caused an increase in LT50. Furthermore,the change in cytosolic G6PDH activity is found to be closely correlated to the degree of freezing resistance of cuttings during freezing acclimation. It is suggested that cytosolic G6PDH may be involved in the induction of freezing resistance of cuttings.     

The role of antioxidant system in freezing acclimation-induced freezing resistance of Populus suaveolens cuttings

We investigated the changes in the contents of H2O2, malonaldehyde (MDA) and endogenous antioxidants, the activities of protective enzymes and some critical enzymes involved in the ascorbate-glutathione (ASA-GSH) cycle as well as freezing resistance (expressed as LT50) and correlations mentioned above, in detail using Populus suaveolens cuttings. The purpose was to explore the physiological mechanism of the enhancement of freezing resistance induced by freezing acclimation at –20°C, and to elucidate the physiological mechanisms by which trees adapt to freezing. The results showed that freezing acclimation enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), monodehydroascorbate reductase (MDAR), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR). And it increased the contents of reduced ascorbate (ASA), reduced glutathione (GSH), dehydroascorbate (DHA) and oxidized glutathione (GSSG). However, H2O2 and MDA contents and LT50 of cuttings were decreased. LT50 in cuttings was found to be closely correlated to the levels of SOD, POD, CAT, APX, DHAR, MDAR, GR, H2O2, MDA, ASA, GSH, DHA and GSSG during freezing acclimation. This suggested that the enhancement of freezing resistance of cuttings induced by freezing acclimation may relate to the distinct increase for the levels of SOD, POD, CAT, APX, DHAR, MDAR, GR, ASA, GSH, DHA, and GSSG. In addition, the observed levels of APX, DHAR, MDAR, GR, ASA, DHA, GSH and GSSG were higher than those of SOD, POD and CAT during freezing acclimation. It indicated that a higher capacity of the ASA-GSH cycle is required for H2O2 detoxification, and growth and development of cuttings. Based on the obtained results, it can be concluded that the ASA-GSH cycle plays an important role in enhancement of freezing resistance of P. suaveolens cuttings during freezing acclimation.     

Comparison of G6PDH Activity and LT50 Between P.tomentosa and P.suaveolens During Freezing Acclimation

The differences of glucose-6P dehydrogenase(G6PDH) activity and freezing resistance induced by freezing acclima-tion between cuttings of freezing-sensitive P.tomentosa and freezing-resistant P.suaveolens were compared for exploring the role of G6PDH on the enhancement of freezing resistance induced by freezing acclimation.After 5d of freezing acclimation at -3℃ ,the LT50 of P.tomentosa has deereased from -6.2℃ incontrol cuttings to -14.3℃ in freezing acclimated ones,and the increase of LT50 of P.tomentosa has decreased from -6.2℃ in control cutting to -14.3℃ in freezing acclimated ones,and the increase of G6PDH activity was observed in freezing acclimated cuttings as compared with control ones.Whereas,when P.suaveolens was freezing acclimated at -20℃ for 5d,the LT50 has decreased from -27.1℃ in control cuttings to -43.5℃ in freezing acclimated ones,and the activity of G6PDH increased considerably.In addition,the increase of LT50 and the decrease of G6PDH activity resulting from 2d of deacclimation at 25℃ were found in two kinds of freezing acclimated cuttings.It is concluded that the increase in the activity of G6PDH may associate with the inherited freezing resistance of species and the enhancemen of freezing resistance of cuttings,and may play an important role in the antifreeze process under freezing temperature,which would provide the basis for the study on the molecular mechanism of freezing resistance in P.suaveolens and the cloning of gene associated with freezing resistance.     

Effects of elevated CO2 concentrations on photosynthesis, dark respiration and RuBPcase activity of three species seedlings in Changbai Mountain

Two-year-old seedlings ofPinus koraiensis, Pinus sylvestriformis andFraxinus mandshurica were treated in open-top chambers with elevated CO₂ concentrations (700 μL·L⁻¹, 500 μL·L⁻¹) and ambient CO₂ concentrations (350 μL·L⁻¹) in Changbai Mountain from June to Sept. in 1999 and 2001. The net photosynthetic rate, dark respiration rate, ribulose-1,5-bisphosphate carboxlase (RuBPcase) activity, and chlorophyll content were analyzed. The results indicated the RuBPcase activity of the three species seedlings increased at elevated CO₂ concentrations. The elevated CO₂ concentrations stimulated the net photosynthetic rates of three tree species exceptP. sylvestriformis grown under 500 μL·L⁻¹ CO₂ concentration. The dark respiration rates ofP. koraiensis andP. sylvestriformis increased under concentration of 700 μL·L⁻¹ CO₂, out that ofF. mandshurica decreased under both concentrations 700 μL·L⁻¹ and 500 μL·L⁻¹ CO₂. The seedlings ofF. mandshurica decreased in chlorophyll contents at elevated CO₂ concentrations. Foundation item: This paper was supported by the National Natural Science Foundation of China (No. 30070158). Knowledge Innovation Item of Chinese Academy of Sciences (KZCX2-406) and “Hundred Scientists” Project of Chinese Academy of Sciences. Biography: Zhou Yu-mei (1973-) Ph. Doctor, Assistant Research fellow Institute of Applied Ecology. Chinese Academy of Sciences. Shenyang 110016. P.R. China. Responsible editor: Song Funan     

Ecophysiological responses and carbon distribution ofPinus koraiensis seedlings to elevated carbon dioxide

The net CO₂ assimilation rate, stomatal conductance, RuBPcase (ribulose 1,5-biphosphate carboxylose) activity, dry weight of aboveground and belowgroud part, plant height, the length and diameter of taproot ofPinus koraiensis seedlings were measured and analyzed after six-week exposure to elevated CO₂ in an open-top chamber in Changbai Mountain of China from May to Oct. 1999. Seedlings were planted in four different conditions: on an open site, control chamber, 500 μL·L⁻¹ and 700 μL·L⁻¹ CO₂ chambers. The results showed that the total biomass of the seedlings increased whereas stomatal conductance decreased. The physiological responses and growth to 500 μL·L⁻¹ and 700 μL·L⁻¹ CO₂ varied greatly. The acclimation of photosynthesis was downward to 700 μL·L⁻¹ CO₂ but upward to 500 μL·L⁻¹ CO₂. The RuBPcase activity, chlorophyll and soluble sugar contents of the seedlings grown at 500 μL·L⁻¹ CO₂ were higher than that at 700 μL·L⁻¹ CO₂. The concentration 500 μL·L⁻¹ CO₂ enhanced the growth of aboveground part whereas 700 μL·L⁻¹ CO₂ allocated more carbon to belowground part. Elevated CO₂ changed the carbon distribution pattern. The ecophysiological responses were significantly different between plants grown under 500 μL·L⁻¹ CO₂ and 700 μL·L⁻¹ CO₂. Foundation Item: This paper was supported by Chinese Academy of Sciences. Biography: HAN Shi-jie (1956-), male, Ph. Doctor, Professor in Laboratory of Ecological Process of Trace Substance in Terrestrial Ecosystem, Institute of Applied Ecology, Chinese Academy of Sciences. Responsible editor: Chai Ruihai     

High level expression of glucose-6-phosphate dehydrogenase gene <Emphasis Type="Italic">PsG6PDH</Emphasis> from <Emphasis Type="Italic">Populus suaveolens</Emphasis> in <Emphasis Type="Italic">E. coli</Emphasis>

In order to investigate the functions of the gene PsG6PDH and the mechanisms underlying freezing tolerance of Populus suaveolens, the recombinant expression vector pET-G (pET30a-G6PDH), which contained full encoding region of PsG6PDH gene, was established. The recombinant was identified by lawn-PCR and double enzyme digestion and then transformed into expression host XA90 and induced by isopropyl-â-D-thiogalactoside (IPTG) to express 100 kD polypeptide of G6PDH fusion protein. The results showed that the expressed amount of the fusion protein culminated after 1 mmol&#8226;L^–1 IPTG treatment for 4 h and that pET-G product was predominately soluble and not extra-cellular secreting.     

Cloning and sequence analysis of a glucose-6-phosphate dehydrogenase gene <Emphasis Type="Italic">PsG6PDH</Emphasis> from freezing-tolerant <Emphasis Type="Italic">Populus suaveolens</Emphasis>

A 1207 bp cDNA fragment (PsG6PDH) was amplified by RT-PCR from cold-induced total RNA of the freezing-tolerant P. Suaveolens, using primers based on the highly conserved region of published plant glucose-6-phosphate dehydrogenase (G6PDH) genes. The sequence analysis showed that PsG6PDH coding region had 1 101 bp and encoded 367 predicted amino acid residues. Moreover, the nucleotide sequence of PsG6PDH showed 83%, 82%, 79%, 79% and 78% identity, and the derived amino acid sequence shared 44.2%, 44.7%, 42.0%, 40.5% and 43.9% identity with those of the Solanum tuberosum, Nicotiana tabacum, Triticum aestivum, Oryza sativa and Arabidopsis thaliana, respectively. The results show that PsG6PDH is a new member of G6PDH gene family and belongs to the cytosolic G6PDH gene. This is the first report on cloning of the G6PDH gene from woody plants.     

外源糖溶液和高浓度CO2处理对白桦叶片糖和蛋白质含量的影响

3年生白桦同时接受3种外源糖溶液(蔗糖、果糖、葡萄糖)和3种高浓度CO2(700、1400、2100μL·μL-1CO2)处理.处理1个月后,测定了叶片的总糖、蔗糖、果糖和蛋白质含量.结果表明:在700μL·L-1和1400μL·L-1 CO2下,外源糖溶液增加了叶片的可溶性糖和蛋白质含量,其中外源蔗糖的效果最好:外源糖溶液与2100μL·L-1CO2结合,会抑制叶片积累总糖和蛋白质:在700μL·L-1和1400μL·L-1CO2下,喷施葡萄糖、果糖的叶片在蛋白质含量上没有明显差别:同700、1400μL·L-1CO2相比,除喷施果糖植株外,2100μL·L-1 CO2明显增加了叶片的总糖、蔗糖、果糖和蛋白质含量:在喷施同种外源糖溶液的情况下,叶片的糖含量与CO2浓度呈正相关性.图6参7.     

Response of seedlings growth ofPinus sylvestriformis to atmospheric CO2 enrichment in Changbai Mountain

The biomass and ratio of root-shoot ofPinus sylvestriformis seedlings at CO₂ concentration of 700 μL·L⁻¹ and 500 μL·L⁻¹ were measured using open-top chambers (OTCs) in Changbai Mountain during Jun. to Oct. in 1999. The results showed that doubling CO₂ concentration was benefit to seedling growth of the species (500 μL·L⁻¹ was better than 700 μL·L⁻¹) and the biomass production was increased in both above-ground and underground parts of seedlings. Carbon transformation to roots was evident as rising of CO₂ concentration. This project is supported by Chinese Academy of Sciences Responsible editor: Chai Ruihai     

An efficient method for clonal propagation and in vitro establishment of softwood shoots from epicormic buds of teak (Tectona grandis L.)

Softwood shoots were produced from 40 cm long stem segments placed horizontally in flat trays containing sterilized sand under natural light or shade conditions for subsequent rooting and micropropagation studies in teak (Tectona grandis L.). Higher number of shoots (6.17) per log was produced under natural light as compared to shade conditions. Forcing was also better in natural light as compared to shade in terms of shoot length, number of nodes or leaves. For rooting, 2–4 cm long softwood shoots were excised and treated with either indole-3-butyric acid (IBA) or α-naphthyl acetic acid (NAA) at 0, 1000, 2000 or 3000 μmol·L^–1 each or with combinations (1000 + 1000, 2000 + 2000 or 3000 + 3000 μmol·L^–1) and then placed in flat trays containing autoclaved sand at 25 ± 2ºC in 16 h photoperiod at 35 µmol·m^–2·s^–1. After 28 days, softwood cuttings treated with IBA + NAA (3000 + 3000 μmol·L–1) had highest rooting percentage (89.3%) with 5.5 mean roots. Shoot apex and nodal explants of softwood cuttings were pretreated with 0.1% (w/v) ascorbic acid, boric acid, activated charcoal, citric acid, glutamine or polyvinylpolypyrollidone (PVP) for 24 h to remove phenolic compounds before surface disinfestation. Glutamine (Gl) and PVP were equally effective resulting in 60% establishment of shoot apices on MS medium supplemented with 10 μmol·L–1 6-benzylaminopurine (BAP) + 5 μmol·L–1 NAA. Using shoot apices, highest (42.80) number of multiple shoots with 54.33 mm shoot length were obtained on MS + BAP (8.8 μmol·L–1) + IBA (2 μmol·L–1) after 45 days. Shoots were successfully rooted and acclimatized to greenhouse     

Effects of Thidiazuron,basal medium and light quality on adventitious shoot regeneration from <Emphasis Type="Italic">in vitro</Emphasis> cultured stem of <Emphasis Type="Italic">Populus alba</Emphasis>×<Emphasis Type="Italic">P. berolinensis</Emphasis>

The effect of Thidiazuron （TDZ）, basal media and light quality on adventitious shoot regeneration from in vitro cultured stem of Populus albaxP berolinensis were determined to establish a high efficiency shoot regeneration system from stem explants of P. alba~P berolinensis. Stems ofPopulus alba~P berolinensis were collected from cultured shoots in vitro derived from dormancy buds of 3-year-old seedlings. The stem explants were cultured on MS medium containing 0.02-mg·L-1NAA （naphthaleneacetic acid）, and 0.1, 0.3, 0.5 and 1.0 mg·L-1 concentrations of TDZ to determine the effect of TDZ on shoot regeneration. Three basal media, i.e. MS, woody plant medium （WPM） and B5, were used to test their influences of different media on adventitious shoot regeneration. Green, red, blue and yellow plastic films in comparison with florescent light as control were used to observe their effects on shoot regeneration. The results showed that differ- ent concentrations of TDZ had an evident influence on shoot regeneration. Lower concentration of TDZ （0.1 mg·L-1） resulted in more ad- ventitious shoot regeneration and higher concentration of TDZ （〉0.1 mg·L-1） inhibited shoot regeneration. Among different media, MS medium exhibited a high efficiency for shoot regeneration, followed by WPM medium, while B5 medium inhibited shoot regeneration. Normal light and yellow light exhibited better effects on shoot regeneration, compared with other light.     

Embryo culture and rapid propagation of Syringa

Embryo of lilacs (Syringa L) culture in vitro and the rapid propagation were studied. The orthogonal experiments, including the selection of basal medium, embryo age and other factors such as sugar, benzyladenine (BA), naphthalene acetic acid (NAA) and glutamine (Gln), were carried out. The results indicated that the optimal medium for embryo culture was Monnier medium supplemented with NAA (0.001 mg.L^-1), BA (0.1 mg.L^-1), sugar (50 g.L^-1), and Gin (400 mg.L^-1), with a germination rate of 91.7% at least; the optimal embryo age was 50 d; and Gln had significant effects on the germination rate of embryo.Moreover, the optimal medium for subculture was MS BA (2 mg.L^-1) NAA (0.001 mg.L^-1) Gln (0.5 mg.L^-1), with the propagation coefficient of 3.6 at least.     

温度对大叶桃花心木(Swietenia macrophylla King)幼苗叶片的光合影响

本文研究了大叶桃花心木（Swietenia macrophylla King）一年生幼苗在经过夜温处理后的光响应曲线和在饱和光强下的CO2反应曲线.结果表明:在大气CO2浓度下,叶片的最佳光合作用温度在25-31℃之间,而在饱和CO2浓度下为31-35℃.在25℃以下光合速率开始降低,主要是由于羧化效率的降低,而当温度超过31℃时,光合速率下降,是因为羧化效率的降低和呼吸速率的增加.CO2浓度对光合的促进作用在低温下受到抑制,这意味着未来在CO2浓度增高的情况下,高浓度的CO2对热带常绿植物光合的促进在冬天低温情况下表现不十分明显.图4参23.     

Stomatal response ofPinus sylvestriformis to elevated CO2 concentrations during the four years of exposure

Four-year-oldPinus sylvestriformis were exposed for four growing seasons in open top chambers to ambient CO₂ concentration (approx. 350 μmol·mol⁻¹) and high CO₂ concentrations (500 and 700 μmol·mol⁻¹) at Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences at Antu Town, Jilin Province, China (42°N, 128°E). Stomatal response to elevated CO₂ concentrations was examined by stomatal conductance (g _s), ratio of intercellular to ambient CO₂ concentration (c _i/c _a) and stomatal number. Reciprocal transfer experiments of stomatal conductance showed that stomatal conductance in high-[CO₂]-grown plants increased in comparison with ambient-[CO₂]-grown plants when measured at their respective growth CO₂ concentration and at the same measurement CO₂ concentration (except a reduction in 700 μmol·mol⁻¹ CO₂. grown plants compared with plants on unchambered field when measured at growth CO₂ concentration and 350 μmol·mol⁻¹CO₂). High-[CO₂]-grown plants exhibited lowerc _i/c _a ratios than ambient-[CO₂]-grown plants when measured at their respective growth CO₂ concentration. However,c _i/c _a ratios increased for plants grown in high CO₂ concentrations compared with control plants when measured at the same CO₂ concentration. There was no significant difference in stomatal number per unit long needle between elevated and ambient CO₂. However, elevated CO₂ concentrations reduced the total stomatal number of whole needle by the decline of stomatal line and changed the allocation pattern of stomata between upper and lower surface of needle. Foundation Item: This research was supported by National Basic Research Program of China (2002CB412502), Project of Key program of the National Natural Science Foundation of China (90411020) and National Natural Science Foundation of China (30400051). Biography: ZHOU Yu-mei (1973-), female, Ph. Doctor, assistant research fellow, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan     

Dissolved organic carbon and nitrogen in precipitation, throughfall and stemflow fromSchima superba andCunninghamia lanceolata plantations in subtropical China

Despite growing attention to the role of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in forest nutrient cycling, their monthly concentration dynamics in forest ecosystems, especially in subtropical forests only were little known. The goal of this study is to measure the concentrations and monthly dynamics of DOC and DON in precipitation, throughfall and stemflow for two plantations ofSchima superba (SS) and Chinese fir (Cunninghamia lanceolata, CF) in Jianou, Fujian, China. Samples of precipitation, throughfall and stemflow were collected on a rain event base from January 2002 to December 2002. Upon collection, all water samples were analyzed for DOC, NO₃ ⁻−N, NH₄ ⁺−N and total dissolved N (TDN). DON was calculated by subtracting NO₃ ⁻−N and NH₄ ⁺−N from TDN. The results showed that the precipitation had a mean DOC concentration of 1.7 mg·L⁻¹ and DON concentration of 0.13 mg·L⁻¹. The mean DOC and DON concentrations in throughfall were 11.2 and 0.24 mg·L⁻¹ in the SS and 10.3 and 0.19 mg·L⁻¹ in the CF respectively. Stemflow DOC and DON concentrations in the CF (19.1 and 0.66 mg·L⁻¹ respectively) were significantly higher than those in the SS (17.6 and 0.48 mg·L⁻¹ respectively). No clear monthly variation in precipitation DOC concentration was found in our study, while DON concentration in precipitation tended to be higher in summer or autumn. The monthly variations of DON concentrations were very similar in throughfall and stemflow at both forests, showing an increase at the beginning of the rainy season in March. In contrast, monthly changes of the DOC concentrations in throughfall of the SS and CF were different to those in stemflow. Throughfall DOC concentrations were higher from February to April, while relatively higher DOC concentrations in stemflow were found during September–November period. Foundation item: This study was supported by the Teaching and Research Award program for MOE P.R.C. (TRAPOYT). Biography: Guo Jian-fen (1977-), female, Ph. Doctor in College of Life Science, Xiamen University, Xiamen 361005, P.R. China. Responsible editor: Zhu Hong     

Photosynthetic response ofPinus sylvestriformis to elevated carbon dioxide and its influential factor analysis

The photosynthetic response of 12-year oldPinus sylvestriformis to elevated CO₂ and its influential factors were tested and analyzed in the forest region of Changbai Mountain in 1999. Trees grown at the natural condition were controlled at three levels of CO₂ concentration (350 μL·L⁻¹, 500 μL·L⁻¹ and 700 μL·L⁻¹) by CO₂ rich settlement designed by us. Net photosynthetic rates (NPR), temperature, relative humidity, stomatal conductance, intercellular CO₂ concentration and photosynthetic active radiation (PAR) were measured at 6:00, 8:00, 10:00, 14:00, 16:00 and 18:00 hours a day. Experimental results showed that the NPR ofPinus sylvestriformis increased by 32.6% and 123.0% at 500 μL·L⁻¹ and 700 μL·L⁻¹ CO₂ concentration respectively, compared to ambient atmospheric CO₂ concentration (350 μL·L⁻¹). The relations between NPR and influential factors, including temperature, relative humidity, intercellular CO₂ concentration and photosynthetic active radiation, were analyzed respectively by regression analysis at different CO₂ concentrations. Foundation Item: This project was supported by Chinese Academy of Sciences. Biography: WANG Chen-rui (1970-), male, Assistant Research Fellow in Institute of Applied Ecology, Chinese Academy of Sciences. Responsible editor: Chai Ruihai     

In vitro propagation of a medicinal plant: Tripterygium wilfordii Hook f.

In this study a reliable protocol was developed for the establishment of commercial in vitro cultures of Tripterygium wilfordii Hook f.. Juvenile shoots from one-year-old elite plants were used as the source of explants. New axillary shoots were obtained after 30 days of culture on a MS medium supplemented with BAP (2.0 mg·L^–1) and NAA (0.1 mg·L^–1). The optimal multiplication medium was a modified MS medium supplemented with BAP (1.0 mg·L^–1) and NAA (0.1 mg·L^–1). This yielded a multiplication rate of 2.4 for each subculture. Slightly more than 92% of shoots rooted when cultured on a modified MS medium containing IBA (0.2 mg·L^–1) and acti-vated charcoal (0.5 mg·L^–1). Activated charcoal promoted both a strong and a high rooting rate during the rooting phase. Plantlets were transferred to pots for a short acclimatization stage in a greenhouse where 95% of the plantlets survived. This highly reproduci-ble procedure can be adopted for large-scale propagation of T. wilfordii.     

Effects of soil moisture and temperature on CH4 oxidation and N2O emission of forest soil

Soil samples were taken from depth of 0–12 cm in the virgin broad-leaved/Korean pine mixed forest in Changbai Mountain in April, 2000. 20 μL·L⁻¹ and 200 μL·L⁻¹ CH₄ and N₂O concentration were supplied for analysis. Laboratory study on CH₄ oxidation and N₂O emission in forest soil showed that fresh soil sample could oxidize atmospheric methane and product N₂O. Air-dried soil sample could not oxidize atmospheric methane, but could product N₂O. However, it could oxidize the supplied methane quickly when its concentration was higher than 20 μL·L⁻¹. The oxidation rate of methane was increased with its initial concentration. An addition of water to dry soil caused large pulse of N₂O emissions within 2 hours. There were curvilinear correlations between N₂O emission and temperature (r²=0.706, p<0.05), and between N₂O emission and water content (r²=0.2968, p <0.05). These suggested temperature and water content were important factors controlling N₂O emission. The correlation between CH₄ oxidization and temperature was also found while CH₄ was supplied 200 μL·L⁻¹ (r²=0.3573, p<0.05). Temperature was an important factor controlling CH₄ oxidation. However, when 20 μL·L⁻¹ CH₄ was supplied, there was no correlation among CH₄ oxidization, N₂O emission, temperature and water content. Foundation item: This paper was supported by Chinese Academy of Sciences. Biography: ZHANG Xiu-jun (1960-), female, Ph. Doctor, lecture in Laboratory of Ecological Process of Trace Substance in Terrestrial Ecosystem, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110015, P.R. China. Responsible editor: Song Funan     

Effect of elevated ambient CO2 concentration on water use efficiency ofPinus sylvestriformis

Pinus sylvestriformis is an important species as an indicator of global climate changes in Changbai Mountain, China. The water use efficiency (WUE) of this species (11-year old) was studied on response to elevated CO₂ concentration at 500±100 μL·L⁻¹ by directly injecting CO₂ into the canopy under natural condition in 1998–1999. The results showed that the elevated CO₂ concentration reduced averagely stomatal opening, stomatal conductance and stomatal density to 78%, 80% and 87% respectively, as compared to normal ambient. The elevated CO₂ reduced the transpiration and enhances the water use efficiency (WUE) of plant. The project was supported by Chinese Academy of Sciences Responsible editor: Chai Ruihai     

Somatic embryogenesis and histological analysis from zygotic embryos in Vitis vinifera L. ＇Moldova＇

We examined the somatic embryogenesis from and histological studies of zygotic embryos of seeds in European Grape ＇Moldova＇ （Vitis vinifera U ＇Moldova＇）. Primary calli were initiated on Nitsch and Nitsch （NN） medium supplemented with 1.0 mg·L^-1 2,4-D and 0.5 mg·L^-1 6-BA. Embryogenic calli were produced upon transfer to a NN medium with 0.5 mg·L^-1 6-BA and 2 mg·L^-1 NAA and somatic embryos were obtained on a half strength MS medium without plant growth regulators. During the somatic embryo germination, an addition of 1.0 mg·L^-1 6-BA in the medium could accelerate somatic embryos to develop into normal plants and increase the conversion rate from 0 to 43.3%. Histological studies of embryogenic calli and somatic embryos demonstrated dynamic changes of proteins and starch grains. The developmental processes of somatic embryos were similar to those of zygotic embryos, including typical epiderma, cotyledon primordium and vascular tissue.