模拟增温和降水变化对半干旱区春小麦生长及产量的影响

为了探索和验证未来气候变化对半干旱区春小麦生产的影响,了解春小麦生长发育和产量对增温和降水变化协同响应的基本特征,利用开放式增温系统和水分控制装置,设置不同水分和温度梯度来模拟气候变化对半干旱区春小麦的影响。结果表明：正常和增加30%降水条件下,增温2.0℃使春小麦株高降低。在不增温和增温2.0℃条件下,增加30%降水使春小麦株高增加;正常和增加降水条件下,增温的叶面积指数比不增温的低。正常和增温条件下,水分对叶面积指数的影响规律性不是很明显;增温和增水协同条件下的株高、叶面积指数小于不增温和正常降水条件下的株高、叶面积指数;增温导致叶绿素含量降低,增温情况下增水会使叶绿素含量提高;正常和增加降水条件下,增温的干物质质量比不增温的低。正常和增温条件下,降水增多则有利于干物质质量的积累;营养生长阶段和生殖生长阶段,在正常和增加降水条件下,增温对叶的分配系数有负效应,增水为正效应。增温对茎的分配系数有正效应,增水为负效应。增温对穗的分配系数有负效应,增水为正效应;增加降水对春小麦的产量有正效应,而增温则不利于产量的提高,即便是在增加降水的情况下,增温还是对产量有不利的影响。研究结果为中国半干旱区春小麦对全球气候变化下的敏感性及适应性提供理论参考。     

夜间增温对水稻生长、生理特性及产量构成的影响

2015年6-11月,在大田条件下采用铝箔反光膜覆盖对水稻(南粳46)进行夜间增温试验。试验设置夜间增温(NW)和对照(CK)两个处理,在水稻主要生育期(分蘖期、拔节期、抽穗扬花期、灌浆期和成熟期)观测水稻分蘖数、叶绿素含量(SPAD值)、叶面积指数、光合作用和蒸腾作用参数以及产量构成(有效穗数、穗粒数和千粒重)。结果表明:(1)铝箔反光膜覆盖达到了夜间增温的目的,整个生育期夜间水稻冠层平均气温比对照提高0.4℃。(2)夜间增温条件下,水稻分蘖数比对照平均每株减少4.33个;各生育期叶片叶绿素含量(SPAD值)分别下降0.2%、2.75%、6.31%、10.77%和32.03%,而叶面积指数差异不大。(3)NW处理各生育期水稻叶片的光合和蒸腾作用参数,包括净光合速率、气孔导度和蒸腾速率均显著低于对照(P0.05)。(4)NW处理每穗粒数和有效穗数分别比对照低12.76%和19.02%,产量下降32.54%,千粒重增加3.93%。研究认为,夜间增温对水稻的生长及光合作用产生显著影响,在未来气候变化背景下,应进一步研究不同增温方式对水稻生产的影响及其模型模拟。     

增温对保护性耕作下冬小麦籽粒蛋白质含量的影响

冬小麦是世界主要粮食作物之一，气候变暖可能显著影响冬小麦籽粒蛋白质含量，但其影响机制还不明确。针对该问题，该研究在中国冬小麦主产区华北平原开展连续3 a（2017-2019）免耕（No Tillage，NT）和常规耕作（Conventional Tillage，CT）下的田间增温试验。结果表明，增温提前了冬小麦返青期，延长了冬小麦营养生长阶段时长，提高了冬小麦叶面积指数和群体净光合速率。2019年增温处理下冬小麦开花期茎叶氮素积累量提升了20.17%（CT）、99.21%（NT），花后茎叶氮素转移量提升了24.62%（CT）、134.21%（NT），茎叶氮素对籽粒的贡献率提升了2.43%（CT）、46.10%（NT）。增温影响了冬小麦产量构成，增温下冬小麦有效小穗数略减，部分年限千粒质量略增。NT处理增温增产，CT处理增温增产不明显，总的趋势为NT处理连续3 a平均产量低于CT处理。增温还显著提升了冬小麦籽粒蛋白质含量（P<0.05），连续3 a平均籽粒蛋白质含量提升了14.28%（CT）、17.39%（NT）。综上，研究表明增温会通过改变冬小麦生理特征显著促进氮素向籽粒转化，并且增温下冬小麦有效小穗数减少使得原本将进入更多籽粒中去的氮素都进入到最终有效籽粒中去，进而显著增加籽粒蛋白质含量。研究结果可为气候变化对冬小麦籽粒蛋白质含量的影响提供科学依据。     

气候变暖将显著降低引黄灌区春小麦产量和氮磷钾养分吸收

【目的】探索宁夏引黄灌区春小麦不同生育时期氮（N）、磷（P）、钾（K）养分吸收利用对气候变暖的响应机制,为预测气候变暖对干旱半干旱区春小麦生长的影响提供依据。【方法】试验于2018年3月在宁夏银北引黄灌区宁夏大学试验站进行。供试春小麦品种为‘宁春50号’,供试肥料为磷酸二铵和尿素。采用自动控制红外线辐射器进行野外增温,每个小区内分别设置一组红外灯管作为增温装置、一套自动控温电子设备与一组可移动温度传感器作为控温装置,增温装置直接连接控温装置以使增温梯度达到预设水平,增温时间为昼夜不间断增温。以春小麦冠层自然温度为对照温度 (增温0℃,CK),设置4个增温梯度 (0.5℃、1℃、1.5℃、2.0℃) 处理。于苗期、拔节、抽穗、灌浆、灌浆后10天、成熟期采集植株样品,测定叶、茎、穗的N、P、K养分含量,计算地上部各器官的养分累积吸收量、养分分配率和地上部植株养分累积量,并测定春小麦植株地上部干物重和产量。【结果】增温0.5℃,春小麦植株苗期干物重、拔节期地上部各器官N、P、K养分含量及养分累积吸收量均显著高于CK。增温1.0℃,苗期植株N、K含量和N素吸收量以及拔节期叶片的N、P、K含量显著高于CK,较对照提高3.2%～23.7%。增温1.5℃,仅苗期植株K含量显著高于CK,较对照提高22.2%。增温2.0℃,从苗期开始各项指标均显著低于CK。拔节期以后,除增温0.5℃春小麦K素含量与CK差异不显著外,其余指标均显著低于CK,春小麦成熟期小穗数、穗粒数、千粒重、产量均随温度的升高呈下降的趋势,增温2.0℃,分别较对照降低53.7%、24.1%、13.4%、21.7%。增温梯度越大,各指标下降的幅度越大。【结论】春小麦苗期温度升高0.5℃～1.0℃尚有利于拔节期前春小麦对N、P、K养分的吸收,但拔节期后增温超过1.0℃以上都会对N、P、K养分吸收产生显著负作用,导致使生育后期干物质的累积量减少,千粒重、穗粒数等降低,并最终导致产量和品质的下降。     

开花期复水对受旱冬小麦叶片状态和产量结构的补偿效应

以冬小麦"济麦22"为供试品种,于拔节-开花期设置4个水平的水分控制试验:在拔节前将各小区20cm土层土壤湿度控制在60%左右,拔节期(4月2日)按照正常补水量(75mm)的80%(W1)、50%(W2)、25%(W3)和0%(W4)进行一次性灌溉,之后不再补水,使各处理植株在不同时段受到不同程度的干旱胁迫;以正常灌溉管理的大田为对照(CK,土壤湿度保持在65%～75%)。然后于开花期(4月26日)统一复水至土壤湿度达90%,直至冬小麦成熟土壤湿度与CK保持一致。分别观测干旱胁迫和复水条件下冬小麦单株叶面积、叶片含水率、叶绿素含量、产量及产量结构等数据,研究复水对不同强度干旱胁迫下冬小麦生长发育的补偿效应。结果表明:拔节-开花期干旱处理后,冬小麦叶片含水率、叶面积和叶绿素含量均有不同程度的降低,干旱程度越重,降低幅度越大。复水后,W1、W2和W3处理叶片含水率和叶面积均能恢复至CK水平,恢复所需时间与胁迫程度正相关;叶绿素含量的恢复程度随胁迫程度的升高而降低。W4处理的复水补偿效应最弱,叶片含水率、叶面积和叶绿素含量均显著低于CK,降幅分别为8.7%、21.2%和32.3%。控水末期,4个干旱处理组中仅W4处理达特旱水平,可见,特旱水平下的胁迫将引起冬小麦叶片不可逆损伤,复水后仍无法恢复。干旱胁迫导致冬小麦产量和穗粒数呈减少趋势,不孕小穗率呈增加趋势,其变化幅度与干旱胁迫程度有关。与CK相比,各处理组冬小麦产量及不孕小穗率均有显著差异;对穗粒数而言,仅W3、W4处理达显著水平,降幅为20.0%和23.3%。花后复水各处理组的千粒重均能达到CK水平,表现出明显的补偿效应。由此可知,产量及产量构成要素中千粒重的复水补偿效应最明显,其次是穗粒数,产量和不孕小穗率最弱。     

模拟增温对半干旱雨养区春小麦物质生产与分配的影响

为了明确未来气候变化对半干旱区春小麦生产的影响,了解增温条件下春小麦不同生长阶段物质生产的响应特点以及光合产物在不同器官中的分配特征,利用开放式红外增温系统设置不同的温度梯度,即不增温（对照）、增温1和2℃,模拟田间增温对春小麦物质生产与分配的影响。结果表明：温度增加,春小麦发育加快,全生育期明显缩短,增温1和2℃,比对照分别缩短7和11 d;从各器官干物质生产来看,相对于对照,在增温1、2℃处理下,叶干物质质量在三叶期分别增加了11.23%和27.49%,在拔节期及其以后分别平均降低了20.12%和30.83%。茎干物质质量在拔节期及其以前分别平均增加了17.30%和30.30%,拔节期以后分别平均降低了13.19%和22.09%。根干物质质量在孕穗期及其以前分别平均增加了10.26%和23.30%,孕穗期以后分别平均降低了15.79%和26.05%。穗干物质质量分别平均降低16.43%和29.00%;增温处理下春小麦物质生产随时间的响应规律主要是由净同化率的变化所致;从各器官干物质分配来看,与对照相比,增温1、2℃处理下,春小麦叶和穗干物质质量占全株干物质质量的比例在整个生育期分别平均下降了8.32%、12.01%和0.56%、3.40%,且增温幅度越大,下降的越多。增温1、2℃处理下,茎和根干物质质量占全株干物质质量的比例在整个生育期分别平均增加了3.92%、6.25%和3.86%、8.71%,且增温幅度越大,增加的越多。结果为中国半干旱区春小麦对全球气候变化下的敏感性及适应性研究提供理论参考。     

秸秆颗粒还田对土壤养分和冬小麦产量的影响

为明确秸秆颗粒还田在农业生产中推广应用的可行性,在山东省冬小麦-夏玉米一年两熟种植区通过田间微区试验,研究了秸秆不还田(CK)、常规粉碎还田(CCSI)和秸秆颗粒还田(GSI)对耕层土壤养分含量、冬小麦群体茎蘖数、旗叶净光合速率、叶绿素含量、干物质积累及分配和小麦产量的影响。结果表明:与CK和CCSI处理相比,GSI处理显著提高土壤有机质、碱解氮和有效磷的含量;增加基本苗和分蘖成穗率,显著提高有效穂数13.23%和16.64%。同时,GSI处理显著提高灌浆期叶面积指数、旗叶叶绿素含量和净光合速率,改善开花后旗叶光合性能,促进地上部干物质积累及其向籽粒的转运。与CK和CCSI处理相比,GSI处理的开花后干物质向籽粒的转运量显著提高19.65%和14.75%,籽粒产量显著提高9.69%和10.71%。相关分析表明,穗粒数和千粒重对产量影响不显著,有效穂数的提高是秸秆颗粒还田增产的主要原因。因此,秸秆颗粒还田可作为一种安全有效的还田方式,在农业生产中推广应用。     

花前光照亏缺对水稻物质积累及生理特性的影响

以超级杂交稻“Ⅱ优航2 号”为试验材料, 大田条件下, 水稻拔节期~始穗期设置55%和85%两个遮光处理, 以全生育期自然光为对照, 对花前光照亏缺条件下水稻物质积累及生理特性进行研究。结果表明, 花前光照亏缺极显著地降低了水稻产量, 遮光55%和85%处理的产量比自然光对照分别降低48.25%和70.54%, 产量降低主要是由于单位面积有效穗数和穗粒数降低; 但结实率在各处理之间无显著差异; 生物产量和收获指数显著下降。花前光照亏缺抑制了花前物质的积累、运转率、对籽粒贡献率, 并随着强度增加, 受抑制程度加大。生理特性研究结果表明, 随光照亏缺程度增加, 水稻叶片硝酸还原酶活性、净光合速率和稻株伤流量受抑制程度增加, 丙二醛含量增加幅度加大。光照亏缺引起了功能叶片光合性能、膜系统及根系活力等功能的全面弱化、紊乱、衰变, 并引起光合产物运输受阻, 降低了叶面积扩展速率, 总叶面积减少, 净同化率下降, 从而导致水稻光合生产能力的下降, 干物质生产量减少, 最终导致水稻产量显著降低。     

提前喷施叶面肥对超级杂交晚稻抵御寒露风能力的影响

以超级杂交晚稻品种五丰优T025为材料,以叶面喷清水作对照（CK）,设置叶面喷施0.1%（P1）、0.3%（P3）和0.5%（P5）3个浓度的磷酸二氢钾溶液处理,研究双季晚稻抽穗扬花期遭遇低温条件下提前喷施磷钾肥对水稻叶温、产量和生理特性的影响。结果表明：低温期间,不同叶面肥处理叶片温度较对照均有所提高,其中P3处理增温效果最好。低温胁迫下各处理稻株叶片叶绿素含量和净光合速率均不同程度降低,以P3处理降幅最小,蒸腾速率、胞间CO2浓度及气孔导度等也均呈现类似变化特点;低温下各处理MDA含量均不同程度上升,其中以P3处理最低;叶片抗氧化酶活性低温来临后产生不同程度的变化,其中SOD活性、POD活性总体上表现为CK最高,P3最低,而CAT活性则以CK最低,P3最高;低温胁迫下喷施叶面肥处理均能不同程度提高黄熟期植株尤其是穗部干物质量,达到减缓产量降低的效果,其中以P3处理最佳,遭遇低温明显的2015年第二播期（7月1日播种）水稻产量比CK高14.04%;产量结构上,各处理单株有效穗数、每穗总粒数、结实率等均较CK明显改善。说明叶面喷施0.3%磷酸二氢钾是增强双季超级杂交晚稻抽穗扬花期低温抵御能力的有效措施。     

施硅对夜间增温条件下水稻生长和产量的影响

通过大田试验研究了施硅对夜间增温条件下水稻分蘖期、拔节期、抽穗期、灌浆期和成熟期植株分蘖数、叶面积指数、生物量和产量的影响。夜间增温设常温对照（CK）和夜间增温（NW）两个水平;施硅量设不施硅（Si0）和施钢渣硅肥（Si1,200kgSiO2·hm-2）两个水平。结果表明：（1）水稻冠层和5cm土层全生育期夜间增温处理平均温度分别提高1.21℃和0.41℃,夜间最低温度分别提高1.21℃和0.62℃,夜间最高温度分别提高1.20℃和0.28℃。（2）夜间增温使水稻成熟期植株分蘖数、叶面积指数、地上部生物量、地下部生物量和产量较对照分别减少10.81%、5.65%、8.20%、3.29%和4.45%;施钢渣硅肥可使各项指标较对照分别增加16.22%、11.18%、14.16%、6.51%和22.10%;夜间增温下施硅比不施硅各项指标分别增加16.67%、11.71%、12.56%、6.74%和20.90%。（3）与对照相比,夜间增温使水稻有效穗数、每穗实粒数、千粒重和结实率分别减少2.66%、12.72%、1.53%和2.06%;施用钢渣硅肥可分别较对照增加6.91%、15.49%、2.00%和4.48%;夜间增温下施硅比不施硅各项指标分别增加4.37%、22.50%、2.15%和3.31%。研究认为,施硅对夜间增温条件下水稻生长有显著影响,对产量的影响主要通过影响有效穗数和每穗实粒数实现。     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Einfluss der düngungsmethoden auf die entwicklung von zuckerrübenkrankheiten

Während neunjähriger (1994-2002) Untersuchungen in der Versuchsanstalt Ba?cyny (Fahlerde, Fall-Gleyboden, ausgebildet aus leichtem Lehmboden) wurde der Befall mit Krankheiten an der Zuckerrübe in Abhängigkeit von der Düngungsmethode bewertet. Folgende Methoden wurden angewendet: A - Mineraldünger, B - Stalldung und Mineraldünger, C - Stroh-, Gründung und Mineraldünger, D - Kompostdünger und Biopräparate (ökologische Düngung). Auf den Objekten A, B, C wurden bei konstanter Phosphor-Kalium-Düngung die Stickstoffgaben von 0 bis 180 kg.ha^?1 differenziert. Auf dem ökologischen Objekt D ohne Mineraldünger wurden statt Stickstoff die Biopräparate P₅₀₀ und P₅₀₁ verabreicht. Der geringste Befall von Krankheiten wurde an der Zuckerrübe auf jenem Objekt festgestellt, das mit Kompost und den Biopräparaten gedüngt worden war. Im Rahmen der konventionellen Düngungsmethoden wurde allgemein die höchste Intensität der Krankheiten an der mit Stroh, Gründung und Mineraldünger gedüngten Zuckerrübe beobachtet. Ausnahmen von dieser Regel bildete das Vorkommen von echtem Mehltau und Keimlingsfäule. Auf den Objekten A, B, C nahm die Intensität der Krankheiten mit der Steigerung der Stickstoffgabe zu. Auch die auf Objekt D verabreichten Biopräparate stimulierten die Entwicklung der Krankheiten. The effect of various fertilization methods on the diseases of sugar beet was estimated on the basis of nine-year studies (1994-2002) conducted in the Experimental Production Farm in Ba?cyny on loess-based, sedimentary-gley, light-clay soil. The following fertilization methods were applied: A - mineral fertilization, B - mineral and manure fertilization, C - straw, green manure and mineral fertilization, D - ecological compost and biodynamic preparations fertilization. In the objects A, B and C fertilized with phosphorus and potassium, various doses of nitrogen ranging from 0 to 180 kg/ha^?1 were used. In the ecological object D, where mineral fertilization was not used, biodynamic preparations P₅₀₀ and P₅₀₁ were applied instead of nitrogen. The lowest ratio of the diseases of sugar beet was observed in the object fertilized with the compost and biodynamic preparations. In view of the conventional fertilization methods, generally the highest incidence of diseases was noted in the sugar beet fertilized with straw, green manure and mineral fertilizers. The exception was the occurrence of powdery mildew and the black leg. In objects A, B and C the incidence of the diseases increased with the increase in nitrogen doses. The applied biodynamical preparations in the object D stimulated the development of diseases too.     

Prospects for control of Pythium damping-off of lettuce with Trichoderma,Gliocladium and Enterobacter spp.

Summary Damping-off of lettuce (Lactuca sativa) caused by Pythium ultimum was studied in pots containing a non-sterile potting mix in the glasshouse. Fifty P. ultimum sporangia g^-1 compost reduced the plant stand to 15% and shoot dry weight to 18%, but this reduction was totally prevented by applying Trichoderma harzianum at 2×10⁵ viable propagules g^-1 potting mix. Gliocladium virens and Enterobacter cloacae also alleviated the damping-off. E. cloacae did not adversely affect the action of the fungal antagonists. The co-existence of the bacterial and fungal antagonists was revealed on the root surface and inner surface of the testa by scanning electron microscopy, indicating the compatibility of the biocontrol agents.     

细菌、真菌及植物氮营养信号研究进展

氮素吸收代谢是所有生物生命活动的核心部分,因此,各种生物对氮的吸收与同化过程都有精细的调节。这种调节依赖于生物对体内氮素状况信号及体外（生长介质中）氮素信号的感受。过去几十年中,在细菌、真菌中已经对氮素营养信号有了较好的研究,而植物中则相对缓慢,但也有了一定的认识。本文重点比较细菌、真菌及植物中氮信号系统的组成,以期为进一步认识植物中的氮信号接受与转导系统提供启示。     

Aircraft operations near concentrations of birds in Antarctica: The development of practical guidelines

Aircraft operations have the potential to disturb and to impact negatively on bird life. A gradient of increasing behavioural response is evident in birds when exposed to increasing aircraft stimulus. The most major disturbance is likely to lead to impacts on the health, breeding performance and survival of individual birds, and perhaps bird colonies. A process of revision to policies on aircraft operations contained in management plans for a number of specially protected areas in Antarctica by the United Kingdom, accompanied by consultations made within the scientific community through the Scientific Committee on Antarctic Research (SCAR) and with operational interests through the Council of Managers of National Antarctic Programmes (COMNAP) resulted in new guidelines being adopted by the Antarctic Treaty Consultative Parties in June 2004. The principal recommendations of the guidelines are that bird colonies should not be overflown below 2000 ft (∼610 m) above ground level and landings within 1/2 nautical mile (∼930 m) of bird colonies should be avoided wherever possible. These guidelines are less stringent and less specific than those that were recommended by the SCAR specialist group on birds, and represent a compromise to accommodate operational needs. While the adoption of clear and consistent guidelines for the operation of aircraft in Antarctica is welcome in that this provides practical advice that is likely to reduce incidences of close aircraft/bird encounters, there remains insufficient knowledge of the interactions between aircraft and birds in Antarctica, and the consequent impacts on individual birds and on bird populations. It is important, therefore, that the guidelines adopted are considered interim, and should be kept under scrutiny with revisions made as new and improved research results appear.     

The abundance of heterocystous blue-green algae in rice soils and inocula used for application in rice fields

Summary Algal populations were quantified (as colony-forming units [CFU] per square centimetre) in 102 samples of rice soils from the Philippines, India, Malaysia and Portugal, and in 22 samples of soil-based inocula from four countries. Heterocystous blue-green algae (BGA) were present in all samples. Nostoc was the dominant genus in most samples, followed by Anabaena and Calothrix. In soils, heterocystous BGA occurred at densities ranging from 1.0 × 10² to 8.0 × 10⁶ CFU/cm² (median 6.4 × 10⁴) and comprised, on average, 9% of the total CFU of algae. Their abundance was positively correlated with the pH and the available P content of the soils. In soil-based inocula, heterocystous BGA occurred at densities ranging from 4.6 × 10⁴ to 2.8 × 10⁷ CFU/g dw (dry weight), comprising only a moderate fraction (average 13%) of the total algae. In most soils, the density of indigenous N₂-fixing BGA was usually higher than that attained by applying recommended rates of soil-based inoculum. Whereas research on the practical utilization of BGA has been mostly directed towards inoculation with foreign strains, our results suggest that attention should also be given to agricultural practices that enhance the growth of indigenous strains already adapted to local environmental conditions.Maître de Recherches ORSTOM (France), Visiting Scientist at IRRI