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991.
992.
甘肃秦王川灌区土壤盐分特征及次生盐渍化预测 总被引:1,自引:0,他引:1
在秦王川灌区水文地质条件和土壤盐分含量特征调查研究的基础上,采用有限差分法建立了预测模型,对灌溉实施后1~5年间地下水位及其埋深变化进行了预测。结果表明,地下水位呈普遍抬升趋势,可导致约2000ha土地产生次生盐渍化。如果不及时采取防治措施,土壤次生盐渍化面积还会进一步扩大。 相似文献
993.
骆驼黄杏幼树的光合特性 总被引:7,自引:1,他引:6
采用红外线CO2气体分析仪对骆驼黄杏幼树光合特性进行了测定分析,结果表明,骆驼黄杏的光饱和点为1500~1700μmol·m(-2)·s(-1),光补偿点为60μmol·m(-2)·s(-1),属于喜光树种。净光合速率的日变化呈双峰曲线,最大值出现在上午9时30分,次峰值出现在下午5时,“午休”现象明显。净光合速率的年周期变化为双峰曲线,最高峰出现在6月24日,净光合速率(以CO2计)为25.7μmol·m(-2)·s(-1),次高峰出现在9月5日,峰值明显低于第一次。 相似文献
994.
Biological Control of Bipolaris sorokiniana on Tall Fescue by Stenotrophomonas maltophilia Strain C3
ABSTRACT Stenotrophomonas maltophilia strain C3 was evaluated for control of leaf spot on tall fescue (Festuca arundinacea) caused by Bipolaris sorokiniana. In growth chamber experiments, C3 inhibited conidial germination on leaf surfaces and reduced lesion frequency and percent diseased leaf area compared with nontreated controls. The amount of leaf spot suppression was related to the C3 dose applied. The highest dose tested, 10(9) CFU/ml, prevented nearly all B. sorokiniana conidia from germinating on treated leaf surfaces and provided nearly complete suppression of lesion development. When colloidal chitin was added to C3 cell suspensions of 10(7) or 10(8) CFU/ml, biocontrol efficacy was significantly increased over C3 applied alone, whereas addition of chitin to a C3 cell suspension of 10(9) CFU/ml had no effect. In field experiments, application of C3 to tall fescue turf resulted in significant reductions in infection frequency and disease severity compared with nontreated controls. Strain C3 applied at 10(9) CFU/ml was more effective than C3 applied at 10(7) CFU/ml, and amendment of the lower dose with colloidal chitin enhanced its efficacy. Populations sizes of C3 established on foliage in a growth chamber and in the field were directly related to dose applied. Chitin amendments did not affect C3 population size. 相似文献
995.
本文在考虑现有森林各龄级的蓄积及其连年生长率的两个前提下,对能保证永续利用的最大收获量求算方法作了初步的探讨。虽然解决问题的方法归结为非线性目标规划问题,但在编制电算程序时,由于用的是从高龄级到低龄级的试算循环比较法,因而比非线性目标规划程序简短得多,电算时所占的内存空间和耗费的机时也少得多。 相似文献
996.
安哥拉山羊与建昌黑山羊及其杂种后代的DNA指纹分析 总被引:5,自引:0,他引:5
以 (CA/GATA/TCC) 5探针 ,HinfI酶切 ,研究安哥拉山羊和建昌黑山羊及安哥拉山羊与建昌黑山羊级进杂交的F2 、F3的DNA指纹图谱。结果 ,在供试山羊中 ,个体平均检出 1 8.2± 0 .4条谱带 ,安哥拉山羊、F2 、F3的鉴别机率分别为 1 .38× 1 0 - 12 ,1 .1 8× 1 0 - 13,0 .50× 1 0 - 10 ;群体内相似系数安哥拉山羊为0 .4 539,F2 为 0 .4 0 77,F3为 0 .61 1 1 ;亲子鉴定的父权概率W =0 .9889;安哥拉山羊与建昌黑山羊比较 ,2 .3kb和 8.6kb谱带为安哥拉山羊的特异谱带 相似文献
997.
葡萄叶片光合速率日间降低内外因调控的研究 总被引:17,自引:2,他引:15
土壤水分充足时,葡萄日间光合速率的下降主要归因于CO2叶肉阻力的升高;光照、叶温和大气湿度可以影响气孔对CO2的阻力,但主要通过影响叶肉阻力来影响光合速率。‘巨峰’和‘长相思’葡萄具有不同的光合作用光响应曲线及其特征参数。 相似文献
998.
999.
Flow cytometric assessment of ethylene glycol monoethyl ether on spermatogenesis in rats 总被引:1,自引:0,他引:1
Yoon CY Hong CM Cho YY Chung YH Min HK Yun YW Lee BJ Yang KH Lee YS Kim CK 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2003,65(2):207-212
The effects of ethylene glycol monoethyl ether (EGEE) on testicular cell populations in rats were investigated by a flow cytometric method. Rats were administered by gavage with EGEE at the various doses of 0 (saline alone), 100, 200, 400, and 800 mg/kg body weight/day for 4 weeks. The treatment of EGEE caused decreases in the weight of testis and epididymis and in the number of testicular cells. Histopathologically, exfoliation of germ cells into the tubular lumen was observed at the doses of above 200 mg/kg. The treatment of EGEE at the dose of 400 mg/kg caused moderate testicular degeneration. A significant depletion of haploid cells and a disproportionate ratio of diploid and tetraploid cells were observed as determined by flow cytometric analysis. These results indicate that the toxic effect of EGEE on the male reproductive system may be strongly associated with the disproportion of testicular germ cells. 相似文献
1000.
Zhang Q Lin J Pereira S 《Animal health research reviews / Conference of Research Workers in Animal Diseases》2003,4(2):63-71
Thermophilic Campylobacter species, including Campylobacter jejuni and Campylobacter coli, are responsible for foodborne campylobacteriosis in humans and are increasingly resistant to fluoroquinolone (FQ) antimicrobials. The therapeutic use of FQ antimicrobial agents in food animal production, particularly in poultry, has become a concern for public health, because the practice may promote the emergence of FQ-resistant Campylobacter that can be transmitted to humans through the food chain. Recent studies have indicated that Campylobacter displays a hypermutable phenotype in response to in vivo treatment with FQ antimicrobials, resulting in the rapid emergence of resistant mutants. Distinct from other Gram-negative bacteria, the acquisition of FQ resistance in Campylobacter does not require stepwise accumulation of gyrA mutations and overexpression of efflux pumps, and is mainly mediated by single-step point mutations in gyrA in the presence of a constitutively expressed multidrug efflux pump, CmeABC. The simplicity of the resistance mechanisms may facilitate the rapid adaptation of Campylobacter to FQ treatment. The FQ-resistant Campylobacter mutants derived from chickens do not show a fitness cost in vivo and are ecologically competitive in the colonization of chickens even in the absence of antimicrobial selection pressure. These findings suggest that FQ-resistant Campylobacter may continue to persist regardless of antimicrobial usage, and highlight the need for extra effort to prevent the occurrence and spread of FQ-resistant Campylobacter in animal reservoirs. 相似文献