章古台沙地松树人工林土壤无机氮、微生物生物量碳及微生物生物量氮

The dynamics of soil inorganic nitrogen （NH4^＋ -N and NO3^- -N） and microbial biomass carbon （Cmic） and nitrogen （Nmic） under 30-year-old fenced Pinus sylvestris L. var. mongolica Litvin （SF）, unfenced P. sylvestris L. var. mongolica Litvin （SUF）, and unfenced Pinus densiflora Siebold et Zucc. （DUF） plantations in the Zhanggutai sandy soil of China were studied during Apr. to Oct. 2004 by the in situ closed-top core incubation method. All mentioned C and N indices in each stand type fluctuated over time. The ranges of inorganic N, Cmic, and Nmic contents in the three stand types were 0.7-2.6, 40.0-128.9, and 5.4-15.2 μg g^-1, respectively. The average contents of soil NH4^＋ -N and Cmic under the three 30-year-old pine plantations were not different. However, soil NO3^ -N and total inorganic N contents decreased in the order of SUF ≥ SF ≥ DUF, the Nmic content was in the order of SF = SUF 〉 DUF, and the Cmic：Nmic ratio was in the order of SUF = DUF 〉 SF. Seasonal variations were observed in soil inorganic N, microbial biomass, and plant growth. These seasonal variations had certain correlations with microbe and plant N use in the soil, and their competition for NH4^＋ -N was mostly regulated by soil N availability. The influence of tree species on inorganic N and Nmic were mainly because of differences in litter quality. Lack of gazing decreased the Cmic：Nmic ratio owing to decreased carbon output and increased the ability of soil to supply N. The soil N supply under the P. sylvestris var. mongolica plantation was lower than under the P. densiflora plantation.     

科尔沁沙地东南部植被类型变化对土壤磷素状况的影响

In the past 50 years, large areas of the Horqin sandy land were afforested to prevent desertification. Although the afforestation policy appears successful, many people now doubt whether it is suitable to plant trees with high density on the poor soils in semiarid regions. Little is known about the impacts of afforestation on the sandy soil properties, although the evaluation of these impacts is fundamental to judge the rationality of afforestation policy. Soil phosphorus （P） fractions, acid phosphomonoesterase activities, and other soil chemical properties were compared among five adjoining typical ecosystems on poor sandy soils in southeastern Horqin sandy land. The ecosystems studied are natural elm savanna, degraded grassland, Mongolian pine （Pinus sylvestris var. mongolica） plantation, Chinese pine （Pinus tabulaeformis） plantation, and mixed plantation of Mongolian pine and poplar （Populus simonii）. The results showed that organic P dominated soil P （47%-65%） was the principal source of available P. The degradation of elm savanna to grassland significantly reduced soil pH and resulted in an overall reduction in soil fertility, although slightly increased labile inorganic P. Grassland afforestation had no significant influence on soil pH, organic carbon, and total N but significantly reduced total P. Impacts of grassland afforestation on soil P fractions depended on tree species. Natural elm savanna had higher soil P conserving ability than artificial plantations. Therefore, with the aim of developing a sustainable ecosystem, we suggested that vegetations with low nutrient demand （particularly P） and efficient nutrient cycling would be more suitable for ecosystem restoration in the semiarid region.     

红壤中重金属的复合污染及污染指数

A field experiment was conducted to study the effects of Pb,Cd,Cu,Zn and As coexisting in red soil on growth of rice (Oryza sativa L.) mung bean(Vigna rabiata(Linn.) Wilczek),alfalfa(Medicago sativa L.),Slash pine(Pinus elliottii Engelm.)and aspen(Populus L.).Results showed that rice,mung bean and alfalfa were significantly influenced by combined poollution of the heavy metals,the contents of Pb,Cd and As in rice grains greatly exceeded the National Standards for Food Hygiene of China.Heavy metals at a high concentration seriously retarded growth of mung bean and alfalfa,but not so obviously with slash pine and aspen.The composite index is suggested for evaluating the relativity of combined pollution with heavy metals in soil.     

Streamflow and Soil Moisture of Agroforestry and GrassWatersheds in Hilly Area

A study was conducted in a hilly area of Sichuan Province, Southwestern China, to compare the streamflow and soilmoisture in two upland watersheds with different land use patterns. One was an agroforestry watershed, which consistedmainly of trees with alder (Alnus cremastogyne Burkill) and cypress (Cupressus funebris Endl.) planted in belts or stripswith a coverage of about 46%, and the other was a grassland primarily composed of lalang grass (Imperata cylindricavar. major (Nees) C.E.Hubb.), filamentary clematis (Clematis filamentosa Dunn) and common eulaliopsis (Eulaliopsisbinata (Retz.) C. E. Hubb) with a coverage of about 440/o. Streamflow measurement with a hydrograph established atthe watershed outlet showed that the average annual streamflow per 100 mm rainfall from 1983 to 1992 was 0.36 and1.08 L s^-1 km^-2 for the agroforestry watershed and the grass watershed, respectively. This showed that the streamflowof the agroforestry watershed was reduced by 67% when compared to that of the grass watershed. The peak averagemonthly streamflow in the agroforestry watershed was over 5 times lower than that of the grass watershed and lagged byone month. In addition, the peak streamfiow during a typical rainfall event of 38.3 mm in August 1986 was 37% lowerin the agroforestry watershed than in the grass watershed. Results of the moisture contents of the soil samples from 3slope locations (upper, middle and lower slopes) indicated that the agroforestry watershed maintained generally highersoil moisture contents than the grass watershed within 0-20 and 20-80 cm soil depths for the upper slope, especially forthe period from May through July. For the other (middle and lower) slopes, soil moisture contents within 20-80 cm depthin the agroforestry watershed was generally lower than those in the grass watershed, particularly in September, revealingthat water consumption by trees took place mainly below the plow layer. Therefore, agroforestry land use types mightoffer a complimentary model for tree-annual crop water utilization.     

Toxicity of Cu and Cd in Soils and Detoxication by Additives

Results from laboratory experiments indicated that the concentrations and toxicities of both water-soluble and 0.1 M HCl-extractable Cu and Cd from soils were in the order of red soil> yellow brown earth> black earth. The toxicity of soil varied with the concentrations of metals. The form, concentration and toxicity of Cu and Cd in soils were determined by cation exchange capacity, content of organic matter and composition of clay minerals in the soil. Addition of CaCO3 could significantly decrease the concentration and toxicity of water-soluble and 0.1 M HCl-extractable Cu or Cd from the red soil, and could notably transform the Cu and Cd from the water-soluble or exchangeable form into the organic, free oxides-occluded or sulfic form.     

应用Wenner结构原理估计沙地松树人工林土壤含水量

To estimate the mean value of surface soil water content rapidly, accurately, and nonintrusively, field investigations on soil electrical resistivity （SER） with the Yokogawa 324400 earth resistivity meter and the surface （0-150 cm） soil water content （SWC） with time domain reflectometry （TDR）, together with the abiotic factors including soil texture, structure, and salinity concentrations were conducted in the Mongolian pine （Pinus sylvestris var. mongolica） plantations on a sandy land. The measurement of SER was based on the 4-probe Wenner configuration method. Relationships between the values of SWC and SER were obtained based on analysis of the abiotic factors of the research site, which play a key role in affecting the soil electrical resistivity. Results indicate that the SER meter could be used to estimate the mean value of SWC in the Mongolian pine plantations on the sandy land during the growing seasons. The bulky nature of the equipment simplified the cumbersome measurements of soil water content with the general methods. It must be noted that the Wenner configuration method could only provide the mean values of the SWC, and the soil texture, structure, temperature, and solute concentrations influenced the SER and further affected the estimation of the SWC by the SER meter. Therefore, the results of this study could be applied on a sandy land during the growing seasons only. However, the SWC of other soil types also may be obtained according to the individual soil types using the procedures of this study.     

Metal contamination in Nullah Dek water and accumulation in rice

Corn field experiments with two treatments, NP and NPK, where N in the form of urea, P in the form of calcium phosphate, and K in the form of KCl were applied at rates of 187.5, 33.3, and 125 kg ha^-1, respectively, on soils derived from Quaternary red clay were conducted in the hilly red soil region of Zhejiang Province, China. Plant grains and stalks were collected for determination of K content. Seven equations were used to describe the kinetics of K release from surface soil samples taken before the corn experiments under electric field strengths of 44.4 and 88.8 V cm^-1 by means of electro-ultrafiltration （EUF） and to determine if their parameters had a practical application. The second-order and Elovich equations excellently described K release; the first-order, power function, and parabolic diffusion equations also described K release well; but the zero-order and exponential equations were not so good at reflecting K release. Five reference standards from the field experiments, including relative grain yield （yield of the NP treatment/yield of the NPK treatment）, relative dry matter yield （dry matter of the NP treatment/dry matter of the NPK treatment）, quantity of K uptake in the NP treatment （no K application）, soil exchangeable K, and soil HNO3-soluble K, were used to test the effectiveness of equation parameters obtained from the slope or intercept of these equations. Correlations of the ymax （the maximum desorbable quantity of K） in the second-order equation and the constant b in the first-order and Elovich equations to all five reference standards were highly significant （P ≤ 0.01）. The constant a in the power function equation was highly significant （P 〈 0.01） for four of the five reference standards with the fifth being significant （P ≤ 0.05）. The constant b in the parabolic equation was also significantly correlated （P ≤ 0.05） to the relative grain yield and soil HNO3-soluble K. These suggested that all of these parameters could be used to estimate the soil K supplying capacity and the crop response to K fertilizer.     

高浓度CO2下长白松幼苗土壤和根系呼吸

The objectives of this study were to investigate the effect of higher CO2 concentrations （500 and 700 μmol mol^-1） in atmosphere on total soil respiration and the contribution of root respiration to total soil respiration during seedling growth of Pinus sylvestris vat. sylvestriformis. During the four growing seasons （May-October） from 1999 to 2003, the seedlings were exposed to elevated concentrations of CO2 in open-top chambers. The total soil respiration and contribution of root respiration were measured using an LI-6400-09 soil CO2 flux chamber on June 15 and October 8, 2003. To separate root respiration from total soil respiration, three PVC cylinders were inserted approximately 30 cm deep into the soil in each chamber. There were marked diurnal changes in air and soil temperatures on June 15. Both the total soil respiration and the soil respiration without roots showed a strong diurnal pattern, increasing from before sunrise to about 14：00 in the afternoon and then decreasing before the next sunrise. No increase in the mean total soil respiration and mean soil respiration with roots severed was observed under the elevated CO2 treatments on June 15, 2003, as compared to the open field and control chamber with ambient CO2. However, on October 8, 2003, the total soil respiration and soil respiration with roots severed in the open field were lower than those in the control and elevated CO2 chambers. The mean contribution of root respiration measured on June 15, 2003, ranged from 8.3% to 30.5% and on October 8, 2003, from 20.6% to 48.6%.     

Metal Contamination in Nullah Dek Water and Accumulation in Rice

A research study was carried out to determine the electrical conductivity （EC）, residual sodium carbonate （RSC）, sodium adsorption ratio （SAR）, pH and metals in metal-polluted irrigation water from a nullah and those in soils over a period of time, and the effect of metals on rice yield and metal concentrations in rice grain and straw. Two sites （I and If） were selected on the bank of Nullah Dek at Thatta Wasiran in Sheikhupura District （Pakistan）, with two rice varieties, Super Basmati and Basmati 385, at both sites. Water samples were collected during rice crop growth at 15-day intervals from August 3 to November 1, 2002. The results showed that Nullah Dek water had an EC 〉1.0 dS m^-1 and RSC of 2.78-4.11 mmolc L^-1, which was hazardous for crops, but the SAR was within the safe limit. Cu, Mn Cd and Sr were also within safe limits. The soil analysis showed that Site Ⅱ was free from salinity/sodicity, whereas Site Ⅰ was saline sodic. Among metals, Zn was sometimes deficient, Cu, Mn and Fe were adequate, and St, Ni and Cd were within safe limits in the soil at both the sites. After the rice crop harvest, concentrations of all metals tested were usually slightly increased, being higher in the upper soil layer than the lower. In addition, Basmati 385 produced higher rice grain and straw yield than Super Basmati. Chemical analysis of rice grain indicated the presence of Zn, Cu, Fe, Mn, Pb and Sr, whereas rice straw contained Zn, Cu, Fe, Mn and Sr, with Cd and Ni both being found in minute quantities.     

SOIL AND WATER CONSERVATION IN CHINA

Hydrologic Effect of Canopy Layer of Typical Vegetation in Ecological Rehabilitation Region in the Upper stream of Huangqian Reservoir
CHENG Chuan-min WANG Hua-wei CHEN He-nan（ 1. Tai＇ an Soil and Water Conservation Ecological Monitoring Station, Tai＇ an, Shandong 271000, China; 2. Forestry School of Shandong Agricuhural University, Tai＇ an, Shandong 271018, China）
It studies the hydrological effect of canopy layer of typical vegetation type in the ecological rehabilitation region of soil and water conservation in the upper stream of Huangqian Reservoir in Tai＇ an City of Shandong Province, by using the principle of forest hydrology and water balance and the method of fixed sample plot. The outcomes show that （1）under the conditions of P = 18 mm, the sequence of the canopy interception of different trees in the ecological rehabilitation region is Pinus tabulaeformis 〉 Pinus densiflora 〉 Platycladus orientalis 〉 Quercus acutissima 〉 Robinia pseudoacacia, but the similar law has not been found in the amount of stemflow and the throughfall in forest area, and the canopy interception of the coniferous forest is greater than that of the broadleaf forest.     

茄二十八星瓢虫对雷公藤和曼陀罗提取物的敏感性

为研究寄主植物对茄二十八星瓢虫药剂敏感性及体内酶活力的影响,采用浸渍法分别测定了取食茄子、马铃薯、番茄和龙葵的茄二十八星瓢虫幼虫(以下简称幼虫)对雷公藤和曼陀罗提取物的敏感性,用生化方法测定了雷公藤和曼陀罗提取物对幼虫体内乙酰胆碱酯酶(AChE)和主要解毒酶活性的影响。结果表明,雷公藤提取物对取食茄子、马铃薯、番茄和龙葵的幼虫LC50值分别为1.407 9 mg.L-1、1.595 8 mg.L-1、1.464 7 mg.L-1和1.109 7 mg.L-1,相对毒力指数为78.82、69.54、75.76和100;曼陀罗提取物对取食茄子、马铃薯、番茄和龙葵的幼虫LC50值分别为0.641 7 mg.L-1、0.610 3 mg.L-1、0.758 0 mg.L-1和0.488 3 mg.L-1,相对毒力指数为76.09、80.01、64.42和100;取食龙葵的幼虫对2种植物提取物的敏感性显著高于取食茄子、马铃薯和番茄的幼虫。取食4种寄主植物的幼虫体内靶标酶AChE和主要解毒酶谷胱甘肽-S-转移酶(GST)、羧酸酯酶(CarE)、多功能氧化酶(MFO)活力顺序均为茄子>马铃薯>番茄>龙葵。其中,取食番茄和龙葵的幼虫体内AChE和GST活力显著低于取食茄子和马铃薯的幼虫,取食马铃薯、番茄和龙葵的幼虫CarE活力显著低于取食茄子的幼虫,取食4种寄主植物的幼虫MFO活力差异达极显著水平。雷公藤和曼陀罗提取物对幼虫体内AChE和GST、CarE和MFO活性均有抑制作用。其中,对取食马铃薯幼虫的AChE活力抑制作用最强,其次为取食茄子和番茄的幼虫,对取食龙葵的幼虫抑制作用最低。雷公藤和曼陀罗提取物对取食龙葵幼虫CarE活力的抑制作用最强,而对取食马铃薯的幼虫MFO活力的抑制作用最强。寄主植物中的次生物质对解毒酶的诱导或抑制可能是引起药剂敏感性差异的主要原因。     

藻(Ziziphus spina-christi)体内外无性繁殖的方法

Christ‘s thorn (Ziziphus spina-christi L. Desf.) is ecologically and economically important in Iran. Since it is a crosspollinated plant with a wide range of genetic variability, an investigation was carried out to determine the best method for mass and clonal propagation. Three vegetative methods were examined, including 1) cutting, where shoots with a 22-25 cm length and three shoot diameters were treated with two culture media; 2) layering, where air layering and trench layering treatments consisted of three growth regulators at three levels of concentration; and 3) tissue culture with nodal segments bearing axillary buds that were removed from shoots of mature trees at different seasons. Several experiments were carried out to determine the best disinfectant chemical, the best culture method, the best season, the appropriate explant characteristics and media type. Rooting was successful only on the sandy beds for cuttings with more than 8.0 mm diameter. For the trench layering method, only one specimen in one replicate rooted a very small root, while for the air layering method, only seedlings with growth regulator treatments rooted successfully. The best season for explant harvesting was determined as mid summer, and among the disinfecting treatments, Ca(OCI)2 at a concentration of 0.5g kg^-1 for 20 minutes was the best. There were no significant differences for shoot weight and length with a Murashige and Skoog (MS) medium with and without a hormone.     

Delayed inoculation and competition of Rhizobium meliloti in annual Medicago species

Seed inoculation is frequently essential for annual Medicago establishment in Mediterranean dryland farming systems. As post-planting soil inoculation is often practiced when seed inoculation fails, the effect of delayed inoculation was investigated. Roots of Medicago rigidula (L.). All selection 716, and Medicago rotata Boiss. selection 2132, were initially pre-exposed to Rhizobium meliloti strains. Subsequently, roots were exposed to a secondary inoculum after 6, 48 and 168 h to simulate delayed inoculation. and subsequent establishment of others strains in the nodules were investigated. Combinations of highly effective and host compatible ICARDA strains (M15 and M53) and effective-ineffective strains (M15 and M28) were used to evaluate proportional nodulation responses. Plants were harvested after 6 weeks of growth. Nodules were assessed for distribution in the root system and for occupancy based on their differential resistance to kanamycin and streptomycin, and, in the case of ICARDA M28, on nodule characteristics. The strain ICARDA M15 was a better competitor than ICARDA M53 when applied in equal density in M. rotata, at zero time. While forming nodules with M. rigidula, ICARDA M53 was equally competitive under the same conditions. With ICARDA M15 as the primary inoculum, and ICARDA M53 delayed for 6, 48 and 168 h, the incidence of ICARDA M15 nodules increased on M. rigidula from 43% (at zero time) to 86, 94, and 97% and, on M. rotata, from 78% (at zero time) to 88%, 95%, and 98% for the three time delays, respectively. Pre-exposure of 2-day old M. rigidula seedlings to the ineffective strain ICARDA M28 as the primary inoculant was followed by significant nodule number increases (P 0.01) as compared with ICARDA M15. Nonetheless, when ICARDA M15 was the primary inoculum, M28 was able to produce about 35% of the nodules when applied at the 6 and 48 h time delays. However, with ICARDA M28 as the primary inoculum, followed by ICARDA M15, nodule occupancy of ICARDA M28 in M. rigidula increased from 40 (at zero time) to 75%, 80%, and 95% for the three time delays, respectively. The percentage of total nodulation by M28, applied at the three delay times, was markedly lower (10%, 5% and 1%, respectively) when M. rotata was pre-exposed to ICARDA M15. This suggested a host preference for ICARDA M15, even if applied as a late inoculum. Results indicate that the early events in the nodulation process of annual medics coupled with host-specificity factors are perhaps the most critical for competition among R. meliloti strains for nodule formation.     

设施条件下青菜间作大豆或芋艿控制斜纹夜蛾效果及对捕食性天敌多样性的影响

为探讨设施菜田间作控制害虫斜纹夜蛾(Spodoptera litura)的效果及对捕食性天敌多样性的影响,以在上海市浦东新区设施菜田设置的青菜间作大豆或芋艿为处理,以非间作设施青菜田为对照,对间作作物大豆或芋艿植株上诱集到的斜纹夜蛾幼虫和卵块进行了调查,并对各处理区和对照区青菜田捕食性天敌群落结构特征进行系统调查和分析。结果表明,在调查期内(7~9月),每100株大豆和芋艿诱集斜纹夜蛾幼虫分别为1 098.84±107.50头和1 260.78±126.16头,诱集斜纹夜蛾卵块数分别为17.45±1.31个和20.76±1.81个;与非间作青菜田相比,青菜田间作大豆或芋艿后斜纹夜蛾种群数量分别减少37.83%或45.89%;间作大豆或芋艿青菜田捕食性天敌分别隶属5目21科31种和5目21科32种,而非间作青菜田隶属5目19科26种;非间作青菜田捕食性天敌的优势种为拟环纹狼蛛(Lycosa pseudoamulata)和草间小黑蛛(Erigonidium graminicolum),而间作大豆或芋艿后天敌优势种群均为拟水狼蛛(Pirata subpiraticus)、拟环纹狼蛛(Lycosa pseudoamulata)和草间小黑蛛(Erigonidium graminicolum);间作大豆青菜田捕食性天敌的个体数量、丰富度、多样性指数分别为91.22±4.91头.100株?1、29.74±0.30、4.53±0.03,较非间作青菜田分别增加58.70%、25.27%、10.60%;间作芋艿青菜田捕食性天敌的个体数量、丰富度、多样性指数分别为92.09±5.03头.100株?1、29.96±0.35、4.54±0.03,较非间作青菜田分别增加60.21%、26.19%、11.00%。本研究结论可为上海地区发展设施青菜田间作大豆或芋艿种植模式提供参考依据。     

Genome sizes and ploidy levels in Mexican cactus pear species Opuntia (Tourn.) Mill. series Streptacanthae Britton et Rose, Leucotrichae DC., Heliabravoanae Scheinvar and Robustae Britton et Rose

The ploidy levels and amounts of DNA of 23 Opuntia species from Mexico were determined by flow cytometry. Four different ploidy levels (2n = 2x, 2n = 4x, 2n = 6x, 2n = 8x) with 2C-DNA amount ranging from 4.17 pg (Opuntia incarnadilla Griffiths) to 6.53 pg (Opuntia heliabravoana Scheinvar) were determined among the samples analyzed. Polyploidy is widespread (93%) among these Opuntia species. Opuntia heliabravoana Scheinvar was the sole diploid species. Opuntia leucotricha DC. (2C = 5.71 pg), Opuntia spinulifera Salm-Dyck (2C = 5.51 pg), Opuntia robusta Wendl. ex Pfeiff. var. larreyi (F. A. C. Weber) Bravo (2C = 4.98 pg), and Opuntia elizondoana E. Sánchez et Villase?or (2C = 5.29 pg) were tetraploids. Opuntia oligacantha C.F. F?rst. (2C = 5.33 pg), Opuntia incarnadilla Griffiths and Opuntia matudae Scheinvar (2C = 5.25 pg) were hexaploids. Opuntia zamundioi Scheinvar (2C = 4.35 pg), Opuntia lasiacantha Pfeiff. (2C = 4.88 pg), Opuntia hyptiacantha F.A.C. Weber (2C = 4.84 pg), Opuntia streptacantha Lem. ssp. streptacantha (2C = 4.64 pg) and Opuntia streptacantha Lem. subsp. aguirrana Scheinvar et A.␣Rodríguez (2C = 4.43 pg), Opuntia megacantha Salm-Dyck (2C = 5.01 pg), Opuntia joconostle F.A.C. Weber. ex Diguet (2C = 4.70 pg), Opuntia ficus-indica (L.) Miller (2C = 4.90 pg), Opuntia albicarpa Scheinvar (2C = 4.80 pg), Opuntia␣amarilla Griffiths (2C = 4.84 pg), Opuntia chavena Griffiths (2C = 4.70 pg), Opuntia cochinera Griffiths (2C = 5.10 pg), Opuntia fuliginosa Griffiths (2C = 4.64 pg), Opuntia pachona Griffiths (2C = 4.70 pg), Opuntia cretochaeta Griffiths (2C = 4.35 pg), Opuntia rzedowskii Scheinvar (2C = 4.77 pg), Opuntia robusta Wendl. ex Pfeiff. ssp. robusta (2C = 4.98 pg) and Opuntia robusta Wendl. ex Pfeiff. var. guerrana (Griffiths) Sánchez-Mejorada (2C = 5.05 pg) were all octoploids. The series Streptacanthae Britton et Rose showed a high level of ploidy with octoploid species except for Opuntia heliabravoanae Scheinvar (2n = 2x), Opuntia elizondoana E. Sánchez and Villase?or (2n = 4x) and O. matudae Scheinvar (2n = 6x). Opuntia spinulifera Salm-Dyck was determined to be as a tetraploid species. Series Leucotrichae DC. grouped tetraploid and hexaploid species. The monospecific series Heliabravoanae Scheinvar has one species: Opuntia heliabravoana Scheinvar diploid (2n = 2x). The monospecific series Robustae Britton et Rose seems to be a contradictory group; containing three varieties: Opuntia robusta Wendl. ex Pfeiff. ssp. robusta and Opuntia robusta Wendl. ex Pfeiff. var. guerrana (Griffiths) Sánchez-Mejorada as octoploid taxa and: Opuntia robusta Wendl. ex Pfeiff. var. larreyi (F.A.C. Weber) Bravo which is tetraploid. In earlier report Rafael del Castillo and Mario González-Espinosa (1988) indicate that the arborescent varieties of this species are diploid and the postrate variety tetraploid. Implications for botanical systematics, genetic resources and breeding are discussed.     

酸枣荆条耗水特征及其茎木质部解剖构造

[目的]研究酸枣和荆条耗水特征与其茎木质部解剖构造之间的关系,为中国北方干旱区造林树种的选择提供技术支持。[方法]采用热扩散式液流探针(TDP)法对酸枣和荆条的树干液流进行监测,并于监测完成后,采用切片法,观察其茎木质部解剖构造。[结果](1)不同季节2树种的耗水特征存在差异,与湿润季节相比,干旱季节两树种树干液流变化均具有较强的波动性,其日均液流速度和日均耗水量均较小;2树种相比,干旱季节时酸枣的最大液流速度、日均液流速度以及日均耗水量均显著大于荆条,而湿润季节与之相反。(2)就其茎木质部解剖构造而言,酸枣的导管形状大小比较均一,而荆条的导管形状大小参差不齐;酸枣的导管直径、长度、面积平均值及边材相对输导面积均小于荆条,而其导管密度大于荆条。(3)酸枣的相对输导率和脆性指数均小于荆条,说明酸枣的水分输导的有效性小于荆条,而其安全性和抗旱性大于荆条;另外,在湿润季节,二者的耗水特征主要取决于其水分输导的有效性,而在干旱季节,主要取决于其安全性和抗旱性,进而阐明了二者在不同季节表现出不同耗水差异的原因。[结论]与荆条相比,酸枣的茎解剖构造更有利于其在干旱季节维持较高的树干液流,进而得以正常的生长,因此更适合于干旱区造林。     

玫烟色拟青霉对小菜蛾幼虫的侵染过程及接菌方法对其致病力的影响

采用扫描电镜观察玫烟色拟青霉(Paecilomyces fumosoroseus)分生孢子在小菜蛾(Plutella xylostella)幼虫体表的萌发和侵染过程及玫烟色拟青霉孢子粉、孢子悬浮液和孢子培养液对小菜蛾幼虫的致病力.结果表明:小菜蛾幼虫体表嵴状突起结构区附着的孢子较多, 刺状突起结构区附着的孢子较少;刺状突起结构区附着的孢子萌发较早, 多数孢子在接菌后16 h开始萌发, 而嵴状突起结构区附着的孢子多数在20 h开始萌发, 在平缓结构区孢子萌发最迟.在嵴状突起结构区和刺状突起结构区, 多数孢子萌发后产生芽管, 直接以芽管侵入幼虫体壁, 少数形成附着胞侵染寄主.此外玫烟色拟青霉3种不同接菌方法对小菜蛾幼虫的侵染速率和致病力大小明显不同, 其中孢子培养液比孢子悬浮液和孢子粉对小菜蛾幼虫的侵染速率快, 接菌44 h虫体表现出明显的感病症状, 致死中时为3.18 d;孢子悬浮液和孢子粉处理的小菜蛾幼虫, 60 h虫体出现感病症状, 致死中时分别为4.20 d和4.34 d;而且致病力大小也存在明显差异, 接孢子粉的处理明显高于孢子悬浮液和孢子培养液, 小菜蛾幼虫6 d的死亡率达76.2%, 而其他两种处理小菜蛾幼虫6 d的死亡率仅为59.8%和58.5%.本研究结果表明, 小菜蛾幼虫的体表结构影响玫烟色拟青霉孢子在寄主体表的附着、萌发和侵入, 玫烟色拟青霉孢子粉对小菜蛾幼虫的致病力最强, 明显高于孢子悬浮液和孢子培养液.     

菲对秀丽隐杆线虫、中杆属和拟丽突属线虫毒性效应研究

采用悉生培养系统,研究不同浓度菲对秀丽隐杆线虫、拟丽突属与中杆属线虫的毒性效应,以及3种线虫对菲的去除作用。结果表明:(1)随着菲浓度的增加,3种线虫存活率逐渐降低。秀丽隐杆线虫在不添加菲的处理中,48 h内出现繁殖,而在添加菲的处理中,即使在最低浓度5 mg/L下,繁殖现象也会消失。中杆属与拟丽突属线虫由于世代时间较长,在本试验周期内均未出现繁殖现象。(2)暴露24 h时,比较不同浓度菲处理下线虫的相对死亡率,得到3种线虫的耐性依次为中杆属线虫≥秀丽隐杆线虫≥拟丽突属线虫,且随菲浓度的增加,秀丽隐杆线虫耐性水平逐渐降低;暴露48 h时中杆属线虫耐性依旧高于拟丽突属,而72 h时中杆属与拟丽突属线虫的耐性趋于一致。(3)3种线虫受菲胁迫后均失去头部正常摆动能力,且秀丽隐杆线虫与拟丽突属线虫体长随菲浓度的增加而逐渐降低。(4)不同种类线虫的添加均能促进菲的去除,不同线虫之间无显著差异。因此,菲会显著抑制3种线虫的存活率和生长发育,抑制秀丽隐杆线虫的繁殖。线虫的存活率受线虫种类、暴露时间、菲浓度及其交互作用的影响显著,其中中杆属线虫对菲的综合耐性最强,3种线虫均能促进溶液中菲的去除。