拉杰沙希大学校园药用植物菌根研究

Forty different medicinal plants were investigated for arbuscular mycorrhizal association in the Rajshahi University Campus in Bangladesh. The results indicated that 35 different plants were infected by AM (arbuscular mycorrhizal) fungi as found by trypan blue staining procedure. The percentage of root colonization by AM fungi varied from 13.3% to 100%. Mangifera indica and Morus indica have maximum percentage of colonization (100%). The intensity of root colonization were abundant in the plants belonging to the families Anacardiaceae, Asclepiadaceae, Moraceae, Leguminosae and Apocynaceae whereas the intensity of colonization of crop roots were moderate and poor belonging to Gramineae and Leguminosae. The presence of greater number of spore in soil was always associated with the incidence of abundant mycelia. In plant roots the formation of spore and mycelia was restricted by low pH. Number of mycorrhizal fungus spores ranged between 35 to100 per 100g air dried soil in different family respective soils. The frequency of mycorrhizal fungus infection showed positive correlation with soil pH, moisture, water holding capacity, texture, total nitrogen, organic carbon, phosphorus, calcium, potassium, and magnesium. Especially phosphorus and nitrogen in the soil greatly influenced the plant root infection by AM fungi.     

Effects of short-Term experimental warming on soil microbes in a typical alpine steppe北大核心CSCD

Aims Soil microbe plays key role in mediating terrestrial carbon cycles. It has been suggested that climate warming may affect the microbial community, which may accelerate carbon release and induce a positive feedback to soil climate warming. However, there is still controversy on how microbial community responds to experimental warming, especially in cold and drought environment. Methods We conducted an open top chambers (OTCs) experiment to explore the effects of warming on soil microbial community in an alpine steppe on Qinghai-Xizang Plateau. During the maximum of the growing seasons (August) of 2015 and 2016, we monitored the biomass and structure of soil microbial community in warming and control plots using phospholipid fatty acids (PLFA) as biomarkers. Important findings Short-Term warming treatment significantly increased the soil temperature by 1.6 and 1.6 C and decreased soil moisture by 3.4% and 2.4% (volume fraction) respectively, but did not alter either soil properties or normalized difference vegetation index (NDVI) during the growing season (from May to October) in 2015 and 2016. During the maximum of growing seasons (August) of 2015 and 2016, the magnitude of microbial biomass carbon (MBC) were 749.0 and 844.3 mg·kg-1, microbial biomass nitrogen (MBN) were 43.1 and 102.1 mg·kg-1, and the microbial biomass C:N ranged between 17.9 and 8.4. Moreover, all three showed no significant differences between warming and control treatments. The abundance of bacteria was the most in microbial community, while arbuscular mycorrhizal fungi was the least, and warming treatment did not alter the abundance of different microbial group and the microbial community structure. Nonetheless, our result revealed that warming-induced changes in MBC had significant positive correlation with changes in soil temperature and soil moisture. These patterns indicate that, microbial community in this alpine steppe may not respond substantially to future climate warming due to the limitation of soil drought. Therefore, estimation of microbial community response to climate change calls for consideration on the combined effect of warming and drought. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.     

CO2 flux dynamics and its limiting factors in the alpine shrub-meadow and steppe-meadow on the Qinghai-Xizang Plateau北大核心CSCD

Aims Alpine shrub-meadows and steppe-meadows are the two dominant vegetation types on the Qinghai-Xizang Plateau, and plays an important role in regional carbon cycling. However, little is known about the temporal- spatial patterns and drivers of CO2 fluxes in these two ecosystem types. Methods Based on five years of consecutive eddy covariance measurements (2004-2008) in an eastern alpine shrub-meadow at Haibei and a hinterland alpine steppe-meadow at Damxung, we investigated the seasonal and annual variation of net ecosystem productivity (NEP) and its components, i.e. gross primary productivity (GPP) and ecosystem respiration (Re). Important findings The CO2 fluxes (NEP, GPP and Re) were larger in the shrub-meadow than in the steppe-meadow during the study period. The shrub-meadow functioned as a carbon sink through the five years, with the mean annual NEP of 70 g C·m-2·a-1. However, the steppe-meadow acted as a carbon neutral, with mean annual NEP of -5 g C·m-2·a-1. The CO2 fluxes of steppe-meadow exhibited large variability due to the inter-Annual and seasonal variations in precipitation, ranging from a carbon sink (54 g C·m-2·a-1) in 2008 to a carbon source (-88 g C·m-2·a-1) in 2006. The differences in carbon budget between the two alpine ecosystems were firstly attributed to the discrepancy of normalized difference vegetation index (NDVI) because NDVI was the direct factor regulating the seasonal and inter-Annual NEP. Secondly, the shrub-meadow had higher carbon use efficiency (CUE), which was substantially determined by annual precipitation (PPT) and NDVI. Our results also indicated that the environmental drivers of CO2 fluxes were also different between these two alpine ecosystems. The structure equation model analyses showed that air temperature (Ta) determined the seasonal variations of CO2 fluxes in the shrub-meadow, with NEP and GPP being positively correlated with Ta. By contrast, the seasonal CO22 fluxes in the steppe-meadow were primarily co-regulated by soil water content (SWC) and Ta, and increased with the increase of SWC and Ta. In addition, the changes of Re during the growing season in two ecosystems were directly affected by GPP and soil temperature at 5 cm depth (Ts), while Re during non-growing season were determined by Ts. These results demonstrate that the synergy of soil water and temperature played crucial roles in determining NEP and GPP of the two alpine meadows on the Qinghai-Xizang Plateau. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.     

Characteristics of soil animal community in the subalpine/alpine forests of western Sichuan during onset of freezing

Seasonal freeze–thaw cycle is a common phenomenon in the subalpine/alpine forest region, and may have a significant influence on the structure and function of soil animal community. To understand the characteristics and dynamics of soil animal community as well as its response to repeated freeze–thaw events in this region during onset of freezing, a field experiment was conducted to investigate the composition, abundance, and diversity of soil fauna in primary fir (Abies faxoniana) forest, fir and birch (Betula albosinensis) mixed forest and secondary fir (A. faxoniana) forest, which were three representative forests in the subalpine and alpine forest region in western Sichuan. Soil samples were collected from November 3 to November 27, 2008, which was defined as onset of freezing based on the simultaneous monitoring of soil temperature. Soil macrofauna were picked up by hand in the fields. Mesofauna were separated and collected from the soil samples by Baermann and Tullgren methods, respectively. By preliminary identification, 40,942 individuals were collected, which belonged to 7 phyla, 15 classes and 25 orders in the three sampling forests. 16,557, 14,669 and 9716 individuals were found in primary forest, mixed forest and secondary forest, respectively. In comparison with the mineral soil layer, the soil organic layer had higher density and groups of soil fauna. Furthermore, following the repeated freeze–thaw events, density and groups of soil fauna experienced a distinct decrease in both soil organic layer and mineral soil layer, and this trend in soil organic layer was more significant in the primary forest, owing to higher intense and more frequent freeze–thaw cycles in soil organic layer of the primary forest. The results revealed that soil animals were sensitive bio-indicators to environmental changes, such as repeated freeze–thaw events and dry–wet cycle. Meanwhile, the results also implied that the dynamics of the structure and function of soil animal community during the onset of freezing was of ecological significance to understand the wintertime ecological process in soils.     

Water sources of dominant species in three alpine ecosystems on the Tibetan Plateau, China

Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope （δD and δ^18O） values of different components such as plant xylem water, precipitation and river water as well as soil water on the Tibetan Plateau in the summer of 2005. Four dominant species （Quercus aquifolioides, Pinus tabulaeformis, Salix rehderiana and Nitraria tangutorum） in three typical ecosystems （forest, shrub and desert） were investigated in this study. Stable isotope ratios of the summer precipitations and the soil water presented variations in spatial and temporal scales. δ^18O values of N. tangutorum xylem water were constant in the whole growth season and very similar to those of deep soil water. Water sources for all of the plants came from both precipitations and soil water. Plants switched rapidly among different water sources when environmental water conditions changed. Rainwater had different contributions to the plants, which was influenced by amounts of precipitation. The percentage of plant xylem water derived from rainwater rose with an increase in precipitation. Water sources for broad-leaved and coniferous species were different although they grew in the same environmental conditions. For example, the broad-leaved species Q. aquifolioides used mainly the water from deep soil, while 92.5% of xylem water of the coniferous species P. tabulaeformis was derived from rainwater during the growth season. The study will be helpful for us to fully understand responses of species on the Tibetan Plateau to changes in precipitation patterns, and to assess accurately changes of vegetation distribution in the future.     

Characteristics of soil animal community in the subalpine/alpine forests of western Sichuan during onset of freezing

Seasonal freeze–thaw cycle is a common phenomenon in the subalpine/alpine forest region, and may have a significant influence on the structure and function of soil animal community. To understand the characteristics and dynamics of soil animal community as well as its response to repeated freeze–thaw events in this region during onset of freezing, a field experiment was conducted to investigate the composition, abundance, and diversity of soil fauna in primary fir (Abies faxoniana) forest, fir and birch (Betula albosinensis) mixed forest and secondary fir (A. faxoniana) forest, which were three representative forests in the subalpine and alpine forest region in western Sichuan. Soil samples were collected from November 3 to November 27, 2008, which was defined as onset of freezing based on the simultaneous monitoring of soil temperature. Soil macrofauna were picked up by hand in the fields. Mesofauna were separated and collected from the soil samples by Baermann and Tullgren methods, respectively. By preliminary identification, 40,942 individuals were collected, which belonged to 7 phyla, 15 classes and 25 orders in the three sampling forests. 16,557, 14,669 and 9716 individuals were found in primary forest, mixed forest and secondary forest, respectively. In comparison with the mineral soil layer, the soil organic layer had higher density and groups of soil fauna. Furthermore, following the repeated freeze–thaw events, density and groups of soil fauna experienced a distinct decrease in both soil organic layer and mineral soil layer, and this trend in soil organic layer was more significant in the primary forest, owing to higher intense and more frequent freeze–thaw cycles in soil organic layer of the primary forest. The results revealed that soil animals were sensitive bio-indicators to environmental changes, such as repeated freeze–thaw events and dry–wet cycle. Meanwhile, the results also implied that the dynamics of the structure and function of soil animal community during the onset of freezing was of ecological significance to understand the wintertime ecological process in soils.     

Environmental conditions in high mountain lakes containing toxic benthic cyanobacteria

In glacial lakes on an alpine pasture in Switzerland, benthic cyanobacteria produced microcystin, a cyclic hepatotoxic heptapeptide. The cyanobacteria formed dense mats on sediments and submerged stones. The mats consisted mainly of Oscillatoria limosa, Phormidium konstantinosum (= Oscillatoria tenuis) and Tychonema granulatum (= Oscillatoria granulata). In order to characterize the ecological conditions of these cyanobacteria, nutrient concentrations were determined, and an automatic data acquisition station was installed in one of the lakes. It continuously recorded air temperature, global irradiance, precipitation, atmospheric pressure, wind speed and direction; as well as temperature, pH, oxygen content and conductivity of the lake water. The nutrient situation in the lakes was mainly influenced by the erosion of the gneissic catchment by glacial meltwater and by precipitation. In the glacial lakes, the concentrations of calcium, iron, magnesium, sodium and sulphate increased throughout the summer season. Conductivity values of 4–110 μS cm^-1 represent generally low nutrient concentrations. Nevertheless, iron concentrations of up to 20 μM occurred. Biomass, expressed as protein concentration, as well as the microcystin content of the cyanobacterial mats varied within one season and between different years (1994 and 1995). In one cyanobacterial mat community, biomass and microcystin concentrations were highest at the same time, in an other one the microcystin content was maximal three weeks after the highest biomass concentration was reached. Our observations suggest that biomass and toxin production in the mats were strongly influenced by mechanical stress, temporary desiccation and high irradiation. This revised version was published online in July 2006 with corrections to the Cover Date.     

The influences of arboraceous layer on spatial patterns and morphological characteristics of herbaceous layer in an arid plant community

The objectives of this study were to examine the effects of arboraceous layer on the spatial pattern and morphological characteristics of herbaceous layer in Elaeagnus angustifolia–Achnatherum splendens community in Ningxia Hui Autonomous Region, China. The analyses of community composition and structural characteristics as well as the investigation of soil moisture and salinity showed that different life forms of plants differ in the soil depth at which they absorb and utilize soil moisture. Wavelet analysis showed that there were differences between the spatial patterns of A. splendens in the canopy-projected regions and other regions, and the intrinsic scales were detected. The results from the buffer analysis showed that the control of arboraceous layer on the herbaceous layer on the spatial patterns and the morphological characteristics were influenced not only by canopy shading but also by other causes such as distribution patterns of roots as the morphological characteristics did not monotonically change with distance.     

Carbon Sequestration in Two Alpine Soils on the Tibetan Plateau

Soil carbon sequestration was estimated in a conifer forest and an alpine meadow on the Tibetan Plateau using a carbon- 14 radioactive label provided by thermonuclear weapon tests （known as bomb-^14C）. Soil organic matter was physically separated into light and heavy fractions. The concentration spike of bomb-^14C occurred at a soil depth of 4 cm in both the forest soil and the alpine meadow soil. Based on the depth of the bomb-^14C spike, the carbon sequestration rate was determined to be 38.5 g C/m^2 per year for the forest soil and 27.1 g C/m^2 per year for the alpine meadow soil. Considering that more than 60% of soil organic carbon （SOC） is stored in the heavy fraction and the large area of alpine forests and meadows on the Tibetan Plateau, these alpine ecosystems might partially contribute to ＂the missing carbon sink＂.     

扁蓄总黄酮提取方法的比较

The factors which effected the extraction of total flavones from Polygonum aviculare L.var.aviculore were discuseed with respects to solvent,concentration and the extracting temperature.The rutin was used as a standard compound,the total flavones extracted by the different extracting procedure were quantitated by measurement of absorbance at 510 nm.The results show that 80℃ and 35% alcohol are optimal and the extracting rate of the total flavones in as high as 4.349%.     

Effects of nitrogen addition on root dynamics in an alpine meadow,Northwestern Sichuan北大核心CSCD

Aims Our aim was to characterize the effects of nitrogen (N) addition on plant root standing crop, production, mortality and turnover in an alpine meadow on the Northwestern plateau of Sichuan Province, China. Methods A N addition experiment was conducted in an alpine meadow on the Northwestern plateau of Sichuan Province since 2012. Urea was applied at four levels: 0, 10, 20 and 30 g·m-2·a-1, referred to as CK, N10, N20 and N30. Root samples in surface (0-10 cm) and subsurface layers (10-20 cm) were observed using Minirhizotron from May 10th to Sept. 27th in 2015. The root standing crop, production, mortality and turnover rate were estimated using WinRHZIO Tron MF software. Repeated-measure ANOVA, one-way ANOVA and Pearson correlation were performed to analyze the effect of N addition on soil and root characteristics. Important findings N addition significantly increased soil available N content and decreased soil pH value, but did not alter soil total N and SOM contents under all treatments. N addition did not exhibit any significant effects on the mean root standing crop and cumulative root production in the 0-10 cm, but significantly reduced mean root standing crop and cumulative root production in 10-20 cm soil layer by 195.3 and 142.3 g·m-2 (N10), 235.8 and 212.1 g·m-2 (N20) and 198.0 and 204.4 g·m-2 (N30), respectively. The cumulative root mortality was significantly decreased by 206.1 g·m-2 in N10 treatment and root turnover rate was significantly increased with 17% for N30 treatment at the 0-10 cm soil depth, but the cumulative root mortality and root turnover rate was not significantly different at 10-20 cm soil depth. In addition, cumulative root production, mortality and turnover rate in 0-10 cm soil layer were significantly correlated with the soil available N content, whereas no significant associations were observed in 10-20 cm soil. Taken together, these results demonstrate that N addition alters the soil N availability and thus induces the root dynamics and changes in root distribution as well as C allocation in alpine meadow. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.     

Different Patterns of Changes in the Dry Season Diameter at Breast Height of Dominant and Evergreen Tree Species in a Mature Subtropical Forest in South China

Information on changes in diameter at breast height （DBH） is important for net primary production （NPP） estimates, timing of forest inventory, and forest management. In the present study, patterns of DBH change were measured under field conditions during the dry season for three dominant and native tree species in a monsoon evergreen broad-leaved forest in the Dinghushan Biosphere Reserve. For each tree species, different patterns of DBH change were observed. In the case of the fast-growing tree species Castanopsis chinensis Hance, large diurnal fluctuations occur, with a peak DBH in the early morning （around 05：00 h） that decreases to a minimum by about 14：00 h. Both Schima superba Gardn. et Chemp and Cryptocarya chinensis （Hance） Hemsh exhibited less diurnal swelling and shrinkage. Diurnal fluctuations for these species were observed on a few occasions over the period of observation. Graphical comparisons and statistical analysis of changes in DBH with meteorological variables indicate that for different trees, the different changes in DBH observed responded to different meteorological variables. Large stem changes were found to occur for Ca. chinensis trees that were associated with variations in solar radiation. However, both S. superba and Cr. chinensis were found to be less sensitive to solar radiation. Changes in the DBH of these two species were found to be controlled mainly by soil temperature and soil moisture. During the later dry season, with a lower soil temperature and soil moisture, all three tree species stopped growing and only negligible shrinkage, expansion, or fluctuation occurred, suggesting that the optimum time to measure tree growth in the Dinghushan Biosphere Reserve is the later dry season.     

Effects of external stimuli on the pacemaker function of the sinoatrial node in sodium channel gene mutations models

Loss of function and gain of function mutations of the sodium channel were investigated using an intact two-dimensional rabbit sinoatrial node (SAN) and atrial cell model. The effects of three external stimuli (acetylcholine secretion by the vagal nerve, acid-base concentration, and tissue temperature) on cardiac pacemaker function and conduction were studied. Our results show that these two groups of mutations have different effects on pacemaker function and conduction. Furthermore, we found that the negative effects of these mutations could be altered by external stimuli. The bradycardic effects of mutations were magnified by an increase in acetylcholine level. Changes in acid-base concentration and tissue temperature increased the ability of the SAN to recover its pacemaker function. The results of this study increase our understanding of sodium channel disorders, and help to advance research on the treatment of these conditions.     

Potential impacts of climate warming on active soil organic carbon contents along natural altitudinal forest transect of Changbai Mountain

Understanding soil carbon fractions and their responses to the global warming is important for improving soil carbon management of natural altitudinal forest ecosystem. In this study, the contents of soil total organic carbon (SOC), soil labile organic carbon (LOC), and microbial biomass carbon (MBC) in soil upper layers (0–20 cm) were measured along a natural altitudinal transect in the north slope of Changbai Mountain. The results showed that under natural conditions the contents of SOC and LOC were largest in Betula ermanii forest (altitude 1996 m), moderate in spruce-fir forest (altitude 1350 m), and smallest in Korean pine mixed broad-leaf tree forest (altitude 740 m). MBC contents in different forest ecosystems decreased in the order of Betula ermanii forest, Korean pine mixed broad-leaf tree forest, and dark coniferous forest. In addition, the responses of SOC, LOC, and MBC to soil warming were conducted by relocating intact soil cores from high- to low-elevation forests for one year. As expected, the soil core relocation caused significant increase in soil temperature but made no significant effect on soil moisture. After one year incubation, soil relocation significantly decreased SOC contents, whereas the contents of LOC, MBC, and the ratios of LOC to SOC and MBC to SOC increased.     

Potential impacts of climate warming on active soil organic carbon contents along natural altitudinal forest transect of Changbai Mountain

Understanding soil carbon fractions and their responses to the global warming is important for improving soil carbon management of natural altitudinal forest ecosystem. In this study, the contents of soil total organic carbon (SOC), soil labile organic carbon (LOC), and microbial biomass carbon (MBC) in soil upper layers (0–20 cm) were measured along a natural altitudinal transect in the north slope of Changbai Mountain. The results showed that under natural conditions the contents of SOC and LOC were largest in Betula ermanii forest (altitude 1996 m), moderate in spruce-fir forest (altitude 1350 m), and smallest in Korean pine mixed broad-leaf tree forest (altitude 740 m). MBC contents in different forest ecosystems decreased in the order of Betula ermanii forest, Korean pine mixed broad-leaf tree forest, and dark coniferous forest. In addition, the responses of SOC, LOC, and MBC to soil warming were conducted by relocating intact soil cores from high- to low-elevation forests for one year. As expected, the soil core relocation caused significant increase in soil temperature but made no significant effect on soil moisture. After one year incubation, soil relocation significantly decreased SOC contents, whereas the contents of LOC, MBC, and the ratios of LOC to SOC and MBC to SOC increased.     

Human-induced environmental changes influence habitat use by an ungulate over the long term

Habitat use and preferences may be subject to spatial and temporal changes. However, long-term studies of species-habitat relationships are the exception. In the prese nt research, I on g-term trends in habitat use by an alpine ungulate, the Tatra chamois Rupicapra rupicapra tatrica, were analyzed. We exami ned how envir on mental changes attributable to climate cha nge, removal of sheep, and habituation to hikers, which took place over the last half-century have changed the spatial distribution of animals. Data on the localities of groups sighted between 1957 and 2013 during autumnal population surveys were used to evaluate habitat associations: these were correlated with year, group size, population size, and climatic conditions. The results indicate that the Tatra chamois is tending, over the long term, to lower its altitude of occurrenee, reduce its average distance to hiking trails, and stay less often on slopes with a southerly aspect. These trends are in dependent of group size, population size, and the weather conditions prevailing during observations, though not for altitude, where increases in air temperature are related to finding chamois at higher elevations. The proportion of alpine meadows and slope in the places used by chamois is correlated with population size, while the proportion of areas with trees and/or shrubs is correlated with group size and air temperature, though long-term changes were not evident for these variables. To the best of our knowledge, this work is the first to document Iong-term trends in habitat use by ungulates. It shows that a species' ecology is influe need by huma n-in duced cha nges: abandonment of pasturage, high-mountain tourism, and climate changes, which constitute the most probable reasons for this aspect of behavioral evolution in the Tatra chamois.     

连作土灭菌对葡萄根际土壤微生物群落功能的影响

In order to explore the correlation between soil microbial community function and plant growth, using 30 year continuous cropping soil of grapevines as research object, we studied the effects of sterilization of continuous cropping soil at different temperatures on the growth of grapevines and the microbial community function of rhizosphere soil. The results showed that plant height and stem diameter of grapevines grown in continuous cropping soil were lower than those in the other treatments. With the increasing sterilization temperature, the plant height and stem dia meter of grapevines increased. The ratio of bacteria to fungi in rhizosphere soil increased with the increasing sterilization temperature. The activity of rhizosphere microbes using carbon source was in order of continuous cropping soil sterilized at 100 ℃ > non continuous cropping soil > continuous cropping soil sterilized at 60 ℃ > continuous cropping soil. The regression analysis showed that amino acid (carbon source) in Biolog ECO plate had a significant correlation with microbial metabolic activity of rhizosphere soil. PCA analysis showed that lysine in root exudate had a highest contribution to the variance of principal components in each treatment, and it may play an important role in the obstacle of continuous cropping of grapevines.     

Thermal Cycling Effect on the Wear Resistance of Bionic Laser Processed Gray Iron

Thermal fatigue and wear both seriously affect the service life of some working parts. Environmental temperature will modify the surface conditions and influences the result of wear. In this research, to come close to working conditions, specimens were tested by a combination of thermal cycles and wear. Different cycles of thermal fatigue was carried out first on the gray iron specimens and subsequently wear test was performed to evaluate the effect of these thermal fatigue cycles. In this case, bionic laser processing was used to enhance the wear performance. The results indicated that bionic laser processing reduces the negative effects from thermal fatigue, such as grain fragmentation and oxidation. Because the initiation and growth of cracks as well as oxidation are suppressed in bionic processed areas. Bionic specimens exhibit high wear resistance compared with the common one. The process described can be considered as an effective method to improve the performance of gray iron in combined thermal fatigue and wear service conditions.     

Functional response and predation of Nabis kinbergii （Hemiptera. Nabidae） to Plutella xylostella （Lepidoptera. Plutellidae）

The functional response of adult Nabis kinbergii （Hemiptera： Nabidae） to density of diamondback moth Plutella xylostella （Lepidoptera： Plutellidae） was investigated under laboratory conditions. Holling＇ s （1959） type Ⅱ model was found to be a good fit for the observed functional response of this predator. The numbers of P. xylostella consumed increased with temperature from 15℃ to 35℃. The maximum number of prey killed was observed at 35℃, with average of 10.3 and 8.3 forth instar larvae consumed by adult females and males of N. kinbergii, respectively. The predation of N. kinbergii on P. xylostella increased with successive immature stages. The number of prey consumed by predators decreased as the body size of prey increased. An average of 131 eggs or 95 larvae of P. xylostella were killed by a single of female adult in 24 hours at 24＂C. The pupae of P. xylostella were observed to be eaten by fifth instar nymphs and adults N. kinbergiiin numbers of less than an average of 0.7 pupae per predator in 24 hours at 24＂C. Predation preference by N. kinbergii was also investigated. The number of P. xylostella and Myzus persicae killed by female N. kinbergii was not significantly different, but males killed significantly more P. xylostella than M. persicae. Both eggs and larvae of P. xylosteUa were killed in significantly greater number than those of Pieris rapae in the same feeding arena.     

Transcriptional silencing and developmental reactivation of cry1Ab gene in transgenic rice

One transgenic rice line lacking CrylAb expression product was screened in the progenies of Agrobacterium-transformed transgenic rice variety Zhong 8215 with a cry1Ab gene under field releasing conditions by using GUS histochemical assay and Western blot. Molecular hybridization results revealed that the crylAb gene was silenced in the transgenic rice variety Zhong 8215 and two copies of ubiquitin promoter were integrated into the rice genome. The silencing of crylAb gene in transgenic rice was found to be due to the methylation of the ubiquitin promoter as revealed by methylation analysis. Meanwhile, different concentrations of demethylation reagent 5-azacytidine combining with different treatment time were employed to treat the silenced transgenic rice seeds. The results indicated that 5-azacytidine could reactivate 8%-30% of the silenced transgenic rice plants and the expression level of the reactivated cry1Ab transgene could reach as high as 0.147% of the total soluble protein. Treatment with low con