A comparative study of the metabolic effects of hypertrehalosemic hormone and 1,2,3,4,5,6-hexachlorocyclohexane (γ-HCH) in the American cockroach, Periplaneta americana

Several effects of hypertrehalosemic hormone (Peram-HTH) have been compared with the action of 1,2,3,4,5,6-hexachlorocyclohexane (γ-HCH) in the cockroach, Periplaneta americana. The data show that both agents stimulate respiration while maintaining an R.Q. of approximately 1. The action of γ-HCH differs from that of Peram-HTH-I in that it promotes oxidation of large amounts of soluble carbohydrate. Recent studies show that Peram-HTH-I has an equally potent stimulatory effect on lipid deposition in the fat body and on the release of trehalose from the same tissue. It is of interest that γ-HCH not only increases triacylglycerol accumulation in the fatγ body but that this effect is more pronounced if the γ-HCH is applied to the ventral surface of the mesothorax. γ-HCH also depleted whole body glycoprotein and glycolipid whereas Peram-HTH-I had no effect on glycoprotein but increased that of glycolipid. It is clear that γ-HCH causes complex disruptions to the metabolism of the insect, many of which are related to the release of hormones. The study supports the idea that certain actions of γ-HCH are mediated through the release of Peram-HTH-I.     

Carbon and nitrogen budgets of nematodes in arable soil

Summary The amounts of C and N that pass through the nematode biomass in four cropping systems, barley without and with N fertilization, grass ley and lucerne, has been estimated. The nematodes were sampled at the field site of a Swedish integrated research project Ecology of Arable Land: The Role of Organisms in Nitrogen Cycling. The nematode biomass was lower (200 mg dry weight m^–2) in the annual (barley) than in the perennial (grass and lucerne, 350 mg dry weight m^–2) crops. For respiration, the nematodes used 4–71 O₂m^–2 year^–1 corresponding to C liberation of 1.3%–2.0% of the carbon input to the soil. A higher relative contribution by bacterial-feeding nematodes to the C and N fluxes and a higher turnover rate of the nematode biomass is an indication of more rapid nutrient circulation in the annual than in the perennial cropping systems.     

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     

雪藏二次干湿交替法对油松种苗生理生化效应研究

对油松种子用雪藏二次干湿交替、一般雪藏和温水浸种三种方法处理后,有关生理生化指标及幼苗抗逆性变化测定,表明雪藏二次干湿交替法处理的种子其呼吸强度、氨基酸含量、幼苗体内叶绿素含量以及幼苗抗旱性、抗寒性和抗高温性等均显著或极显著地优于另两种处理方法。该研究为针叶树种子处理中推广应用雪藏二次干湿交替法提供了理生化方面的理论依据。     

Establishment of macro-aggregates and organic matter turnover by microbial communities in long-term incubated artificial soils

The study of interactions between minerals, organic matter (OM) and microorganisms is essential for the understanding of soil functions such as OM turnover. Here, we present an interdisciplinary approach using artificial soils to study the establishment of the microbial community and the formation of macro-aggregates as a function of the mineral composition by using artificial soils. The defined composition of a model system enables to directly relate the development of microbial communities and soil structure to the presence of specific constituents. Five different artificial soil compositions were produced with two types of clay minerals (illite, montmorillonite), metal oxides (ferrihydrite, boehmite) and charcoal incubated with sterile manure and a microbial community derived from a natural soil. We used the artificial soils to analyse the response of these model soil systems to additional sterile manure supply (after 562 days). The artificial soils were subjected to a prolonged incubation period of more than two years (842 days) in order to take temporally dynamic processes into account. In our model systems with varying mineralogy, we expected a changing microbial community composition and an effect on macro-aggregation after OM addition, as the input of fresh substrate will re-activate the artificial soils. The abundance and structure of 16S rRNA gene and internal transcribed spacer (ITS) fragments amplified from total community DNA were studied by quantitative real-time PCR (qPCR) and denaturing gradient gel electrophoresis (DGGE), respectively. The formation of macro-aggregates (>2 mm), the total organic carbon (OC) and nitrogen (N) contents, the OC and N contents in particle size fractions and the CO₂ respiration were determined. The second manure input resulted in higher CO₂ respiration rates, 16S rRNA gene and ITS copy numbers, indicating a stronger response of the microbial community in the matured soil-like system. The type of clay minerals was identified as the most important factor determining the composition of the bacterial communities established. The additional OM and longer incubation time led to a re-formation of macro-aggregates which was significantly higher when montmorillonite was present. Thus, the type of clay mineral was decisive for both microbial community composition as well as macro-aggregation, whereas the addition of other components had a minor effect. Even though different bacterial communities were established depending on the artificial soil composition, the amount and quality of the OM did not show significant differences supporting the concept of functional redundancy.     

水稻中抗品种抗褐稻虱机制的研究

褐稻虱在中抗水稻品种上的刺探频率低于抗级品种。虽然褐稻虱在中抗品种上能正常取食,但同化利用率较低。中抗品种受害后,无论是植株损害系数、光合作用强度降低程度或产量损失率均显著较感虫品种的少,说明了受害后较之感虫品种具有较强的补偿能力。另外,水稻品种受害后呼吸强度均较健株的明显降低。     

Soil nitrogen cycling under litter and coarse woody debris in a mixed forest in New York State

Coarse woody debris (CWD) could alter N availability and transformations in the underlying soil and therefore contribute to spatial heterogeneity and influence ecosystem loss of N. We measured soil N concentrations and transformations in soil beneath CWD and beneath a litter layer at a mixed forest in NY State. We found that total and microbial biomass N was lower and that microbial biomass C-to-N ratio was higher in soil beneath CWD. Rates of N₂O production and denitrification enzyme activity were reduced beneath CWD. These results suggest that CWD is an important controller of spatial heterogeneity in N dynamics and may influence the magnitude of N loss in temperate forests.     

月季切花开花和衰老进程中乙烯变化类型初探

以１４个生产用月季切花品种为试材，测定了开花和衰老过程中花朵的乙烯生成量和呼吸强度变化动态。结果表明：（１）乙烯生成量在萨蔓莎、天使、默西德斯、加布里拉和雅典娜５个品种表现为蕾期较低，随外层花瓣展开逐渐增大，在盛开期达到高峰，然后降低，变化动态类似于跃变型切花和跃变型果实；唐娜小姐品种在整个开花和衰老进程中一直保持在较低水平，类似于非跃变型切花和果实的变化动态；坦尼克、黄金时代、金徽章、金牌、红衣主教、红成功、玛丽娜等品种在蕾期较低，随着开花进程逐渐增大，至盛花后期花朵露心时仍在增加，类似于末期上升型果实的变化特点。（２）上述３个类型月季品种的呼吸强度在瓶插期间的变化趋势一致，即花蕾期相对较低，花朵充分展开前迅速升高并出现高峰，然后降低，呈现典型的呼吸跃变类型，同时，萨蔓莎和天使呼吸跃变高峰的出现都比类似乙烯跃变高峰的出现提前１～２天。说明月季切花乙烯生成量与呼吸强度的变化动态有很大不同     

Ethylene production and decomposition in soils

Six soils differing in texture and use were investigated for their ability to produce and decompose ethylene. In addition, changes in methane and CO₂ concentrations were monitored. The effects of organic amendments and different water tensions were studied, and a method using low concentrations of acetylene as an inhibitor of ethylene degradation was tested. Possible reduction of acetylene to ethylene was identified by the use of CO or NH₄ ⁺-N, of which the latter turned out to be the more reliable method. This reduction only occurred in a grassland soil. Under aerobic soil conditions, gross ethylene production rates of up to 4.7pmol g^–1 h^–1 could be measured. Highest ethylene production and lowest ethylene decomposition was detected in a spruce forest soil. Fine textured soils produced more ethylene than coarse textured soils. Amended soils produced more ethylene at –100kPa and –5kPa than at 0kPa water tension. Ethylene decomposition was most effective in soils from deciduous woodlands and reached rates of up to 137pmol g^–1 h^–1. Parallels between ethylene and methane decomposition were observed. The addition of 5mgg^–1 glucose and 1mgg^–1 methionine not only promoted ethylene production but also inhibited ethylene decomposition. Received: 4 April 1997     

大气[CO2]和温度升高对农作物生理及生产的影响

全球大气[CO2]和气温升高是全球气候变化对农作物产量影响最为重要的两个因子。本文着重介绍了[CO2]和温度升高对农作物光合作用、呼吸作用、蒸腾作用、产量、品质等方面影响的研究进展。研究表明随着[CO2]升高,作物光合速率及蒸腾速率有上升趋势,呼吸作用和气孔导度下降,产量有所提高,品质将会降低,但研究仍有不确定性。随着[CO2]变化,不同光合途径(C3、C4)作物的响应不一致且存在短期和长期效应。普遍认为大气温度升高抑制作物光合作用,作物产量下降。现有的研究多采用模型或模拟试验的方法研究气候变化对作物产量的影响,但研究发现模型研究结果与模拟试验研究结果有差异,不同学者对产量的评估结果也不一致。最新研究认为温度对作物产量影响成非线性,当温度高于关键温度后产量会迅速下降。现阶段大部分模拟试验均在气室中研究,与野外实际情况差异较大,结论仍需进一步验证。目前尚缺乏对作物模型结果的实验验证。