旱地春玉米草纤维膜覆盖的农田生态效应

试验研究了草纤维膜旱地农田春玉米及其对土壤理化性状，土壤温度和水分状况及作物生长发育的影响，结果表明，草纤维膜覆盖在改善土壤结构、调节土壤温度、蓄水保墒、促进作物生长发育等方面效果明显，是解决我国北方旱农地区干旱缺水与土壤瘠薄缺肥的有效途径之一。     

稻草还田与施钾效果研究

采用田间小区试验研究了稻草还田对水稻生长发育、产量及土壤培肥的影响，结果表明：在洞庭湖贫钾地区，稻草还田能显著促进晚稻生长发育，提高结实率，增加千粒重。同时还可以提高土壤有机质含量，有利于培肥地力。在稻草还田的条件下，施用适量钾肥，对晚稻生长的促进作用和培土作用更加显著。     

植物的镍素营养

本文从分析土壤中镍的来源着手，探讨镍营养对植物生长发育的影响和镍污染及其危害，提出实践中不能盲目提倡依靠增施镍肥来促进作物生长发育，提高产量。     

南阳烟区土壤部分矿质元素的含量与分布

镁、硫、铁、锌、硼、铜、锰等矿质元素是烟草生长发育所必需的营养元素，在烟株生长发育过程中起着不可替代的作用。这些矿质元素供应不足或过多时，烟叶的正常生长发育受阻，产量和质量降低。为了摸清南阳烟区不同区域植烟土壤中的矿质元素分布状况，从2002年开始对南阳烟区植烟土壤中的镁、硫、铁、锌、硼、铜、锰等矿质元素进行了取样分析研究。     

日光温室番茄气候空间分布特征

为指导日光温室同时考虑温度和辐射两个因素进行环境管理,依据气候空间理论,应用气候空间图的方法分析了番茄吸收来自环境的辐射与温度的关系。在晴天环境下,对日光温室内番茄群体的气候空间进行了研究,得到了其气候空间图。结果表明日光温室番茄气候空间随气温变化分3个区间段,气温小于16.7℃时和大于28.3℃时,吸收辐射与黑体辐射偏差较大,数据波动也较大;并且低于适宜温度时比高于适宜温度时偏离更大。而在接近番茄生长发育的适宜温度的16.7～28.3℃环境下,番茄吸收辐射更接近理想的黑体辐射;番茄的气候空间变化趋势与D.M.Gates研究得到的北美红雀气候空间辐射极限图相类似,不同的是,番茄群体吸收的太阳辐射会低于理想的黑体所能吸收的辐射。     

冬小麦根系生长规律及土壤环境条件对其影响的研究

通过两年田间实测取样和盆栽试验对冬小麦根系的生长发育与在土壤中的分布规律以及环境条件如肥、水、耕作措施对根系生长发育的影响进行了研究，并建立了根系生长及其在土壤上分布的数学模型。     

GIS支持下的巴西陆稻IAPAR-9再生稻合理布局气候区划

根据巴西陆稻IAPAR-9生长发育对气候条件的要求,结合其在广西的引种试验结果,分析确定了广西种植巴西陆稻再生稻的气候区划指标;利用数理统计分析方法,建立气候区划指标的空间推算模型,并采用GIS技术推算出广西lkm×lkm网格点上的有关气候要素值,利用GIS的空间分析和多层复合方法,对广西的巴西陆稻再生稻进行气候区划,为广西巴西陆稻再生稻的合理布局提供科学依据。     

补光光源对AM真菌生长发育的影响

温室条件下，研究不同补光光源对丛枝菌根(Arbuscular mycorrhizae,AM)真菌Glomus mosseae生长发育的影响。结果表明：不同补光光源的光谱不同，对菌根共生体生长发育的影响不同，以农艺钠灯作为补光光源处理的宿主植物的光合速率及可溶性糖含量高于其它两种光源处理，综合比较菌根长度、根外菌丝量及孢子数三项指标，以农艺钠灯作为补充光源对真菌G. mosseae的生长发育最为有利。金属卤灯、荧光灯两处理宿主植物中氮、磷浓度高于农艺钠灯处理，可能对菌根真菌的生长发育有不利影响。因此，工厂化AM菌剂生产中，如果需要补充光照，应以农艺钠灯作为补光光源。     

氨累积对植物生长发育的效应

氨在大气和土壤中的层积影响植物呼吸，光合和无机营养，对植物生长发育有毒害作用。     

河北省冬小麦生育期气象条件定量评价模型

运用模糊数学理论，分别建立了气温、降水量和日照时数对河北省冬小麦生长发育适宜程度的隶属函数模型，据此模型分别计算了逐句的平均气温、降水量和日照时数对冬小麦生长发育的隶属度，运用一元积分回归方法确定各旬的权重系数，进而计算各发育期内光、温、水对冬小麦生长发育的隶属度，达到定量评价冬小麦生育期气象条件的目的。2005年度（2004．10—2005．06）和2006年度（2005．10—2006．06）对所建模型进行验证应用，得出：温度和日照的隶属度较高，而降水隶属度较低且变化幅度较大，说明评价年的温度和日照条件能够满足冬小麦生长发育，自然降水偏少是冬小麦产量形成的限制因素。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.     

Short-term variation in the concentration of selected ions within individual tropical rainstorms

Rainwater was collected at the campus of the University of Brunei Darussalam in Bandar Seri Begawan, Brunei Darussalam, using a funnel-in-bottle sampler. Polypropylene bottles were changed at intervals during rainstorm events. The pH and conductivity were determined immediately after collection on aliquots of the sample. Samples were refrigerated at 5°C for subsequent chemical analysis. Analyses for Na, Mg, Ca, Zn and Fe were carried out by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES); Cu and Mn were analysed by graphite furnace atomic absorption spectroscopy (GFAAS); K was analysed using flame atomic emission spectroscopy (FAES); and Cl^–, NO₃ ^– and SO₄ ^2– were analysed by ion chromatography (IC). Concentration versus time profiles are reported for three rainstorm events. All ions exhibited a decrease in concentration during the rainstorm. The first sample contained the highest concentration of ions, consistent with a first-flush effect. The contribution of the initial stages of the shower to the total quantity of ion deposited during the entire rainstorm is quite overwhelming; in many cases 20 to 30% of the mass was deposited in less than 5% of rainstorm duration. On the other hand, the pH and conductivity variation during rainstorms did not exhibit a consistent pattern.     

Leaf litter selection by detritivore and geophagous earthworms

Summary Litterbag experiments with 10 different kinds of leaf litter showed that detritivore (Lumbricus species) and geophagous (Aporrectodea species) earthworms prefer certain litter types over others, since different numbers of worms were found below the litter after 50–52 days of exposure in a pasture. The detritivores preferred Fraxinus, Tilia, and predecomposed Ulmus and Fagus litter to Fagus litter and paper, while geophages preferred Tilia litter to Alnus and Ulmus litter, so that the two groups of earthworms showed different preferences. The detritivores seemed to be more selective than the geophages. The palatability of the litter was examined in relation to the C: N ratio, the lignin concentration and the initial and final polyphenol concentration. The numbers of detritivores were significantly correlated with the C: N ratio and the final polyphenol concentration, so that selection of litter seems to be related to palatability. The numbers of geophages were not significantly correlated with any of the parameters for palatability. The disappearance of litter after 50–52 days appeared to be due to detritivore activity, since the numbers found below the litter were positively and significantly correlated with the litter disappearance. There was no significant correlation with geophage activity. This indicates that detritivores use litter as food, and therefore influence the composition of the litter layer.     

The 5S rRNA gene diversity in the genus <Emphasis Type="Italic">Secale</Emphasis> and determination of its closest haplomes

We analyzed 127 rDNA sequences (5S DNA units) obtained from 23 seed accession samples from more or less 10 taxa in wild and cultivated rye, genus Secale L. The sequences fell into two known groups, here assigned to two unit classes, viz. long R1 and short R1 (designations to reflect on R haplome of rye). The different taxa could not be fully differentiated based on the 5S DNA units. We searched for 5S DNA sequences from known unit classes most closely similar to the long R1 and the short R1. One set with the long R1 unit class contained sequences of the long P1 unit class from Agropyron (P haplome) and from Kengyilia (StYP haplome), long J1 from Thinopyrum (J haplome), whereas the set with the short R1 included the long S1 from Pseudoroegneria (St haplome) and Kengyilia (StYP haplome), the short J1 from Thinopyrum (J haplome) and the short V1 from Dasypyrum (V haplome). Each of the two sets was analyzed separately by maximum likelihood (ML) phylogenetic analysis from which we were able to infer that the 5S DNA units of Secale differentiated in a non-clock fashion and followed the HKY substitution model in the gene tree with the long R1 unit class and the HKY + G in the gene tree with the short R1 unit class. A complementary Bayesian analysis yielded identical tree topologies to the ML ones for each of the two sequence sets. In the tree with the long R1 units the long P1 and long J1 unit classes were closest to the long R1 unit class, whereas in the tree with the short R1 units the long S1 and short J1 unit classes were closest to the short R1 unit class, indicating possibly a close relationship between the St, J and R haplomes.     

Nematode succession and microfauna-microorganism interactions during root residue decomposition

The quality of plant material affects the vigor of the decomposition process and composition of the decomposer biota. Root residues from hairy vetch (Vicia villosa Roth), rye (Secale cereale L.) and vetch+rye, packed in litterbags were placed in pots of soil at 15 C and the content of the bags was analyzed after 2, 4, 8 and 12 weeks. Bacterial biomass did not differ between residues with contrasting composition. Among bacterivores groups of nematodes that require high bacterial production dominated in fast decomposing resources whereas flagellates with smaller requirements prevail in slower decomposing resources. Biomass of bacterial feeding nematodes correlated positively with early phase (0-2 wk) decomposition that increased in the order: rye< vetch+rye<vetch. Bacterial biomass therefore seems to be under top-down (predation) control during early decomposition. In contrast, the fungal biomass differed between resources with highest values for rye. Moreover, this increase in fungal biomass occurred later during succession and was correlated with decomposition activity for rye in that period. Fungal biomass therefore seems to be under bottom-up (resource) control. The composition of the nematode assemblages (composed of 25 taxa) showed a clear relationship to initial plant resource quality as well as decomposition phase. Early successional microbivorous nematodes vary according to resource quality with demanding bacterivores+predators (Neodiplogasteridae) dominating in vetch and less demanding bacterivores (Rhabditidae) and fungivores (Aphelenchus) being equally common in vetch and rye. Later in the succession (2-4 wk) bacterivorous Cephalobidae and fungivorous Aphelenchoides prevailed similarly on the different root materials whereas bacterivorous protozoa and the amoebal fraction thereof dominated in rye. At week 12 no species dominated the nematode assemblages that were similar between the resources. The differences between nematode assemblages among plant resources at 2 week were similar to the results of a field study sampled after 6 weeks with the same soil and plant resources. This lends support to the relevance of the successional patterns observed in this incubation study.     

Cycling of extracellular DNA in the soil environment

Upon entering the soil environment, extracellular DNA is subjected to dynamic biological, physical, and chemical factors that determine its fate. This review concerns the fate of both recombinant and non-recombinant sources of DNA. A schematic of DNA cycling coupled with genetic transformation is presented to understand its behavior in soil. Extracellular DNA may persist through cation bridging onto soil minerals and humic substances, be enzymatically degraded and restricted by DNases of microbial origin, and/or enter the microbial DNA cycle through natural transformation of competent bacteria. Lateral gene transfer may disseminate DNA through the microbial community. An understanding of DNA cycling is fundamental to elucidating the fate of extracellular DNA in the soil environment.