荒漠河岸林生态系统的结构分析

在以塔里木河为中心的荒漠河岸林生态系统中，植物种类及生活型单一；动物种群不够丰富，荒漠环境下的微生物种群在河岸林风沙土中，细菌，放线菌及真菌数量分别占63.1%,26.8%和10.1%，在柽柳根际土壤中，细菌及放线菌分别占96.74%和3.26%，而胡杨根际土壤中则全部为真菌，生物种群的这种特点，决定了荒漠生态系统中生态过程的特殊性，生产用水及生态用水的矛盾长期得到解决，造成了天然植被衰退，土壤干旱，盐渍化，沙漠化发展，加之大风及沙尘暴频繁，生态环境脆弱特征明显，以胡杨为建群种的荒漠生态系统的组成群落十分多样，随着系统内的水文，土壤，植被，地形及气候条件的相应更替，群落的结构及组成也自然要随之变化，最终一种生态系统将为不同群落生态系统所替代，以水资源为中心，大力营造生态工程，优化系统结构，实午动态监测与管理，实现荒漠河岸林生态系统的可持纽发展。     

提高果品品质的途径和措施

本文从品种、生态条件、栽培技术和采后商品化处理等方面分析了对果品品质的影响,提出了选用优良品种、坚持"适地适栽"、加强栽培管理和采后商品化处理等提高果品品质的途径及相应的对策和措施.     

不同栽培方式对生菜产量及品质的影响

采用土壤栽培、有机生态型无土栽培、无机耗能型无土栽培三种栽培方式，进行生菜三次采收四层立体栽培试验。结果表明：采用有机生态型无土栽培进行生菜分次采收立体栽培，可有效降低产品中硝酸盐含量，提高根冠比和相对生长速率，变一次性收获为三次采收，可使每盘产量提高30％以上，变平面栽培为4层立体栽培，使温室复种指数提高4倍。     

日光温室黄瓜栽培CO_2浓度的消长规律初探

近 3a(年 )的研究结果表明 :日光温室内CO2 浓度有明显的季节变化和日变化。在整个生长期内因通风时间和通风量的不同 ,日光温室内的CO2 浓度 11月和 3月较高 ,5月较低。各时期日变化基本相同 ,但变化幅度因季节而异 ,上午随Pn的逐渐增大而下降 ,中午 12 :0 0～ 14 :0 0时降至最低 ,下午又随Pn的减小而缓慢回升。叶片的光合作用、呼吸作用和土壤呼吸是影响日光温室内CO2 浓度日变化的主要因素。有机肥施用量对室内土壤呼吸和日光温室CO2 浓度有较大影响 ,在有机肥充足的条件下 ,室内CO2 浓度基本满足黄瓜光合作用的需要 ,无须补施 ,如果在作物生长期间再定时随水向土壤中冲施有机肥 ,效果就更好     

杨梅属植物共生结瘤固氮研究进展

杨梅属35个种中有28个种能与Frankia放线菌共生结瘤固氮。根据有关文献从杨梅属植物共生固氮根瘤及其内生放线菌的形态结构、杨梅属植物根瘤内生放线菌的分类地位、杨梅属植物共生固氮放线菌的生理生化特性、环境条件对杨梅属植物根瘤共生固氮的影响以及分子生物学方法在杨梅属植物根瘤共生固氮放线菌中的应用等方面作了较为详细的阐述。     

气调及温度对杂拟谷盗发育和繁殖的影响

杂拟谷盗Tribolium confusum Jacquelin du Val是重要储藏物害虫之一,主要危害面粉。笔者研究了气调及温度对杂拟谷盗生长发育和繁殖的影响,旨在弄清杂拟谷盗在低氧、低药(双低)环境中的生物学及生态学特性,为有效地控制该虫提供理论依据。 1 材料与方法采用两种气调环境5％O_2、12％CO__2(CA_1)和9％O_2、16％CO_2(CA_2)以及非气调环境     

Indole-3-acetic acid biosynthesis in <Emphasis Type="Italic">Aciculosporium take</Emphasis>, a causal agent of witches' broom of bamboo

 Aciculosporium take (Ascomycota; Clavicipitaceae) is a causal agent of witches' broom of bamboo plants. The symptoms of this disease are believed to be induced by plant hormones, particularly auxins. Indole-3-acetic acid (IAA) was identified in cultures of this fungus in an l-tryptophan-supplemented liquid medium. IAA production was confirmed on 30 isolates of A. take from various hosts and locations at levels up to 1 mg/l. The biosynthetic pathway of IAA in A. take culture was examined by analyzing intermediate products and by feeding experiments. The results showed that the indole-3-pyruvic acid pathway (l-tryptophan → indole-3-pyruvic acid → indole acetaldehyde → IAA) was the dominant pathway in A. take. Received: June 3, 2002 / Accepted: July 25, 2002     

Inconspicuous restraint of rice seedling growth by root-infecting fungi in soil of a rice paddy field

 Rice seedling growth, estimated by plant height and root development and discoloration, was better in pasteurized soil than in unpasteurized soil obtained from a flooded rice field. Rice seedlings also grew better in sterilized soil modified by adding roots harvested from the pasteurized soil than in soil modified by adding roots harvested from the unpasteurized soil. The results demonstrate that seedling growth in the rice field soil was inhibited by soil microorganisms, even though no typical symptoms such as seedling blight or damping-off appeared. Pythium aristosporum is suggested to be involved in the inhibition. Thus, it appears that inconspicuous restraint of rice seedling growth could occur in soils of rice paddy fields. Received: May 20, 2002 / Accepted: October 16, 2002 Acknowledgments The authors thank Dr. T. Ichitani, former professor at Osaka Prefectural University, for providing an isolate of Pythium aristosporum for comparison, and Mr. Mitsuaki Sato of Akita Prefectural College of Agriculture for technical assistance.     

对锰害敏感性不同的两个苹果品种枝条中锰的积累与分布

 以对苹果粗皮病抗性不同的两个苹果品种富士(感病) 和乔纳金(抗病) 为材料,通过田间采样、室内盆栽模拟,结合组织化学、显微鉴定和X- 射线微区分析,研究了枝条内锰的累积、分布与粗皮病抗性的关系。结果表明,锰在韧皮部的含量高于木质部,感病品种含量高于抗病品种;粗皮病病斑部位存在氧化锰沉淀,韧皮部锰的局部累积和分布与病斑的分布相一致;锰在感病品种的枝条横截面上存在局部累积现象,而在抗病品种上分布较均匀。