水稻旱作对其生长量和经济产量的影响

1998～1999年，研究了水稻旱作条件下，不同生育时期受水分胁迫后对作物生长量的影响。结果表明：不同指标对水分胁迫时期的敏感性不一，植株高度对抽穗期水分胁迫最敏感；单株绿叶面积和单株地上部干重对幼穗分化后期水分胁迫最敏感；根系干重和根冠比对幼穗分化前期水分胁迫最敏感；幼穗分化后期水分胁迫对经济产量影响程度最大，无效分蘖期水分胁迫对产量影响程度最小。     

黑河流域水资源开发利用现状及存在问题分析

本文根据有关资料对黑河流域水资源的数量、分布与变化特征进行了较为详细的阐述 ,并且从可持续发展的内涵出发 ,分析了该地区水资源开发利用中出现的问题及对策。结果表明 ,黑河流域水资源开发利用中所出现的种种问题固然与西北内陆地区气候干旱等先天不利条件有很大的关系 ,但最主要的原因还是人类对水资源的开发利用不当所造成的。因此 ,必须改变传统的以牺牲生态环境为代价的经济发展模式 ,社会经济发展应充分考虑流域水资源的制约条件。     

乌鲁木齐区域水资源利用中的生态经济问题及其调控对策

本文在考察乌鲁木齐区域水资源利用现状的基础上 ,从生态经济学的角度总结和分析了该区域水资源利用中存在的问题 ;针对问题 ,提出了相应的调控对策。     

土壤水分研究进展及简要评述

回顾了土壤水分研究的进程及取得的一些成就：从最初的形态学观点到现在的能量观点；从简单研究逐步发展为一门学科，再到多学科交叉；研究方法日趋理论化同时注重应用，理论与实践相结合；研究手段的多样化；研究领域的扩展等等。同时指出了当前土壤水研究存在的一些问题，并对未来土壤水研究进行了展望。     

中国风水侵蚀交错区分布特征分析

风水侵蚀交错带的研究 ,对景观、土地覆盖 /土地利用、全球变化等研究具有重要意义。论文以GIS技术为支撑 ,定量计算出我国风水侵蚀带。在分布特征上 ,主要分布我国北方地区 ,其中以西部沙漠 ,北部山脉沿线为重 ,这种分布与气候、地貌分界有明显联系。 49.6 %风水侵蚀复合带的降水量小于 2 0 0mm。风水侵蚀复合带的土地利用主要以草地为主 ,占 41.8% ,其次为耕地。两种类型的分布 ,草地以与其它土地利用类型交错分布为主 ;而耕地是有重心的分散分布。风水侵蚀复合带的总体侵蚀要强于全国水平。     

Alternative Route of Infection for Bacterial Seedling Blight of Rice Caused by Burkholderia plantarii

Burkholderia plantarii , the pathogen of bacterial seedling blight of rice, was detected in paddy water. Its concentration rose in July and August. The bacterial concentration in the paddy water was always higher along levees than at distances more than 5 m from levees. Confirmed to be released into water when graminaceous weeds were immersed, B. plantarii survived for at least 4 days at 30°C. B. plantarii was splashed at least 30 cm upward by rain splash in the field. Harvested seeds, which had been sprayed with B. plantarii released from graminaceous weeds at the flowering stage, retained the bacteria. Bacterial seedling blight occurred when the seeds were then sown in nursery boxes. These results indicated that graminaceous weeds growing on levees of paddy fields are a source of infection of the disease and that rice seeds are infected through the paddy water. Received 23 May 2002/ Accepted in revised form 1 September 2002     

Observations of Phytophthora spp. in Water Recirculation Systems in Commercial Hardy Ornamental Nursery Stock

Samples of water and sediment were taken from drains, reservoirs and wells from four commercial hardy ornamental nurseries with water recirculation systems. The samples were taken on seven different dates throughout a single year from August 1994 to July 1995. The samples were screened for Phytophthora species using five different methods: direct plating, three bait tests (using lupin seedlings, apples and Rhododendron leaves) and a DAS-ELISA (double-antibody sandwich enzyme-linked immunosorbent-assay) with two antisera. In the nurseries with old water recirculation systems, Phytophthora species were detected in the drains and in the reservoirs. In the nursery with a new recirculation system, the pathogens were only present in the drains. None of the water samples from wells in any of the nurseries were contaminated. Phytophthora species were present in the water as well as in the sediment samples from drains and reservoirs. They were detected in the water recirculation systems irrespective of the season. The number of isolates increased about sevenfold between late summer and spring. At least 12 different Phytophthora species were identified: some isolates were previously unrecorded species. The epidemiology of the pathogens in outdoor water recirculation systems as well as the importance of the results for commercial nurseries is discussed.     

Variation in the development of secondary dormancy in oilseed rape genotypes under conditions of stress

Summary A substantial amount of seed is left in the fields before and during harvest of oilseed rape. Although this crop exhibits little or no primary dormancy, the absence of certain environmental cues that promote germination of imbibed seeds induces secondary dormancy. The work reported investigated the extent to which environmental stress conditions, including osmotic stress, low oxygen stress and anaerobiosis, induce secondary dormancy in oilseed rape, and examined the variation in development of secondary dormancy between and within genotypes. Osmotic stress was most effective in inducing dormancy. Anaerobic treatment produced very few dormant seeds, as did an atmosphere low in oxygen and high in nitrogen. The development of secondary dormancy under osmotic stress varied considerably between and within genotypes. Dormancy ranged from almost zero to about 60% for winter genotypes and about 85% for spring types. Within genotypes, variations occurred between seed lots and years of harvest. Temperature variations affected the percentage of dormant seeds. More dormant seeds were likely to be produced with incubation under water stress at 20 °C than at 12 °C. In winter genotypes, fewer dormant seeds were produced when incubation temperature and germination test temperatures differed. Thus, incubating at 20 °C and 12 °C, followed by germination tests at 20 °C and 12 °C, respectively, produced most dormant seeds. Also, in the winter genotypes, the potential development of secondary dormancy was positively correlated with the pattern and speed of germination of untreated seeds.     

黑河干流中游地区耗水量变化的历史分析

黑河流域水资源极其匮乏 ,加之地区上的配置不均衡和中游地区水土资源的过度开发导致了黑河下游严重生态环境问题 ,已影响到我国北方广大地区生态环境质量 ,受到国家的高度重视和全社会的广泛关注。黑河水资源开发利用主要集中在中游地区 ,该区是全国重要的商品粮、蔬菜和经济作物生产基地之一 ,耗水量占流域耗水量的 85 %以上 ,是黑河的主要耗水区和径流利用区。本文利用黑河上游控制站莺落峡站和中游控制站正义峡站水文资料 ,分析了黑河中游耗水量的变化 ,结果表明 :2 0世纪 80年代以前黑河中游耗水量在 4.2 0× 10 8m3 左右 ,比较稳定 ;进入 2 0世纪 80年代以来耗水量明显增加 ,80年代耗水量比 40年代末期至 70年代增加了 2 .0× 10 8～ 2 .5×10 8m3 左右 ;90年代耗水量又比 80年代增加了 1.6 0× 10 8m3 左右。 80年代以来流域耗水量呈明显增加的趋势 ,这是以人类活动影响为主的结果