北京石灰性草甸土冬小麦营养元素生物循环的特点与锰、锌肥效应

 本文用盆钵试验研究京郊石灰性草甸土冬小麦养分生物循环的结果表明：小麦对不同养分吸收、携出和归还数量的差异很大。根据随籽粒携出和以根茬归还的比例特点,可将养分划分为三种类型：1)低归还高携出型(N、P、K);2)低携出高归还型(Ca、Fe);3)中归还中携出型(Mg、Mn、Cu、Zn)。施锰增加植株对氮和锰的吸收及钾和锰随籽粒的携出;施锌则降低植株对锰的吸收和随籽粒携出的钾、钙、镁、铁、锰量。锰肥和锌肥有拮抗作用。     

Effect of temperature and photoperiod on diapause development in a Douglas fir seed chalcid, Megastigmus spermotrophus

Douglas fir seeds infested by diapausing larvae of a chalcid, Megastigmus spermotrophus, were transferred under different temperature and photoperiod regimes at various dates during autumn and winter. Both winter diapause and prolonged diapause were compared to the diapause patterns observed in control lots kept under natural conditions. The results showed that exposure to low temperatures in autumn and winter is required for the completion of diapause development. Median adult emergence dates and the date of transfer of larvae to 20°C were negatively correlated. The frequency of prolonged diapause of larvae transferred to 20°C decreased significantly after November. When larvae were submitted to different constant temperatures, the longer the daylength, the higher and faster the reactivation. These results suggest that chalcid larvae can perceive daylength through the seed coat. This phenomenon is probably related to the fact that most of the infested seeds falling in autumn are usually covered by a layer of leaf litter during the winter. Received: 14 June 1996 / Accepted: 24 February 1997     

Seasonal trends in intestinal nematode infection and medicinal plant use among chimpanzees in the Mahale Mountains, Tanzania

A longitudinal study of nematode infection in chimpanzees was conducted between 1989 and 1994 on the M group chimpanzees of the Mahale Mountains National Park, Tanzania during two annual dry and rainy season periods and a third rainy season. Chemical and physical antiparasite properties of medicinal plant use against the strongyle nematodeOesophagostomum stephanostomum have recently been reported at Mahale. Here, the incidence of nematode infections were analyzed for seasonal trends to elucidate the possible influence of parasite infection on previously reported seasonality of medicinal plant use and to test the hypothesis that the use of these plants is stimulated byO. stephanostomum. The number of chimpanzees infected byO. stephanostomum was significantly higher in the rainy season than in the dry season of both 1989–1990 and 1991–1992. However, the incidence ofTrichuris trichura andStrongyloides fuelleborni showed no seasonality. Reinfection of individuals byO. stephanostomum occurred in synchrony with annual variation in rainfall: there was a sharp rise in the occurrence of new infections per individual within one to two months after the beginning of the first heavy rains of the season. This pattern coincides with the reproductive cycle of this nematode species.O. stephanostomum (95%) infections were associated significantly more frequently with medicinal plant use than eitherT. trichiura (50%) orS. fuelleborni (40%) infections. These observations are consistent with previous reports for the increased use of these plants during the rainy season and are consistent the hypothesis that medicinal plant use is stimulated byO. stephanostomum infection.     

冠层温度与冬小麦农田生态系统水分状况的关系

1　引　　言通过表面温度遥感监测作物和土壤水分一直是一个共同关注的问题,而该问题解决的一个基础是冠层温度与农田土壤湿度和作物水分状况的关系的研究.国内这方面的研究起步于80年代并已取得一些结果[1～3].但主要集中在冠层空气温度差与农田土壤湿度的关系上,对于冠层温度     

冬小麦群体叶片气孔导度差异性分析

对冬小麦 (Triticum aestivum L.)两个品种 3个生育期测定和分析了群体叶片的气孔导度。结果表明 ,近轴面气孔导度比远轴面的大 ,二者之比呈近似正态分布 ,最大概率出现约为 1 .5,该比值在冠层垂直方向变化不显著 ,但随季节而变 ,抽穗期最大。叶片气孔导度从冠层顶部向下迅速递减 ,递减系数约为 0 .57,且各层日变化大致平行。冠层上部气孔活跃 ,导度日变化明显 ,下部日变化不大。同一叶片的气孔导度由近轴面的叶基 ,经由其叶中、叶尖 ,翻过尖点 ,再从远轴面的叶尖经叶中向叶基递减。对近轴面叶中、叶尖气孔导度与该面平均气孔导度相关系数较大 ,而对远轴面叶中、叶基气孔导度与该面气孔导度相关系数较大 ,据此建议测定近轴面气孔导度时 ,应以叶中、叶尖部位为最佳点 ,而测定远轴面气孔导度时 ,应以叶中、叶基部位为最佳点     

A case of unusually early postpartum resumption of estrous cycling in a young female chimpanzee in the wild

A case of unusually early postpartum resumption of estrous cycling (<7 months) was recorded for a young, presumably primiparous female in the M group of chimpanzees (Pan troglodytes schweinfurthii) in the Mahale Mountains National Park, western Tanzania. The female showed estrous cycling while lactating her infant, and mated with young and low-ranking males as well as with the alpha male.     

The use of tracers to estimate the exposure of beneficial insects to direct pesticide spraying in cereals

A fluorescent spray tracer was used to measure the profile of spray deposits through winter-wheat crop canopies and upon beneficial insects, placed in fixed positions which approximated to their natural distributions. Tracer deposition profiles were recorded on a series of occasions between G.S. 47 to G.S. 90. Deposition levels declined through the canopy on each occasion but the proportion of the spray reaching the ground varied between growth stages. Deposition rates upon insects followed the same trends but insects on the aerial parts of the plant received a higher volume of tracer per unit area than the part of the crop that they were placed upon. Insects placed on the ground received a dose equivalent to their ground area. For a given distribution of insects, these data permit direct spray exposure to be estimated. The general application of the method to a wide range of crops, to the calculation of risk indices, to the standardisation of field tests and to the development of selective spray placement methods are discussed.     

Photoinhibition of photosynthesis under natural conditions in ivy (Hedera helix L.) growing in an understory of deciduous trees

We investigated to what extent south-exposed leaves (E-leaves) of the evergreen ivy (Hedera helix L.) growing in the shadow of two deciduous trees suffered from photoinhibition of photosynthesis when leaf-shedding started in autumn. Since air temperatures drop concomitantly with increase in light levels, changes in photosynthetic parameters (apparent quantum yield, _i and maximal photosynthetic capacity of O₂ evolution, P_max; chlorophyll-a fluorescence at room temperature) as well as pigment composition were compared with those in north-exposed leaves of the same clone (N-leaves; photosynthetic photon flux density PPFD< 100 mol · m^–2 · s^–2) and phenotypic sun leaves (S-leaves; PPFD up to 2000 mol · m^–2 · s^–1).In leaves exposed to drastic light changes during winter (E-leaves) strong photoinhibition of photosynthesis could be observed as soon as the incident PPFD increased in autumn. In contrast, in N-leaves the ratio of variable fluorescence to maximum fluorescence (F_V/F_Mm) and _i did not decline appreciably prior to severe frosts (up to -12° C) in January. At this time, _i was reduced to a similar extent in all leaves, from about 0.073 mol O₂ · mol^–1 photons before stress to about 0.020. Changes in _i were linearly correlated with changes in f_v/f_m (r = 0.955). The strong reduction in F_V/F_M on exposure to stress was caused by quenching in F_M. The initial fluorescence (F₀), however, was also quenched in all leaves. The diminished fluorescence yield was accompanied by an increase in zeaxanthin content. These effects indicate that winter stress in ivy primarily induces an increase in non-radiative energy-dissipation followed by photoinhibitory damage of PSII. Although a pronounced photooxidative bleaching of chloroplast pigments occurred in January (especially in E-leaves), photosynthetic parameters recovered completely in spring. Thus, the reduction in potential photosynthetic yield in winter may be up to three times greater in leaves subjected to increasing light levels than in leaves not exposed to a changing light environment.Abbreviations and Symbols F₀, F_M initial and maximal fluorescence yield when all PSII centres are open and closed - F_V variable fluorescence (F_M-F₀) - P_max maximal photosynthetic capacity at 1000 umol · m^–2 · s^–1 PPFD and CO₂ saturation - PPFD photosynthetic photon flux density - _i apparent quantum yield of photosynthetic O₂ evolution - E-leaves, N-leaves shade leaves exposed, not exposed to drastic light changes during winter - S-leaves sun leaves from an open ivy stand Dedicated to Professor Otto Härtel on the occasion of his 80th birthdayThis work was supported by the Austrian Fonds zur Förderung der wissenschaftlichen Forschung.     

Cranial capacity estimations of the FrankfurtPan troglodytes verus collection

Cranial capacity measurements of 18 individuals (9 ♂, 9 ♀) of a total collection of 277Pan troglodytes verus skulls were taken using four different methods:- two conventional filling methods and two mathematical methods. The two mathematical analyses normally used in hominids, were for the first time specifically modified forPan. The results probably present a more accurate estimation of total cranial capacity inPan and specifically inPan troglodytes verus (352 cm³) than previously available. Sexual differences related to this trait were also measured. Regardles of the methods used,Pan troglodytes verus seems to manifest the smallest cranial capacity of all subspecies ofPan.     

Dental pathologies in ten free-ranging chimpanzees from Gombe National Park, Tanzania

The dental remains of ten adult chimpanzees from Gombe National Park, Tanzania, were examined for enamel attrition, caries, abscesses, periodontal disease, and tooth loss. Age was the underlying factor in the development of dental pathology, in that enamel wear was present to some extent in all ten but was uniformly severe only in the three for whom estimated age at death was 39-43 years. In turn, enamel wear appears to have been the direct cause of abscess development, periodontal disease, and tooth loss. Periodontal disease was commonly expressed as alveolar resorption, particularly around the premolars and molars. This involvement was variable in all except the two youngest. Some interesting wear patterns were evident in the form of deep grooves in the upper incisors and dramatic notching of the lower canines. These patterns, and enamel attrition in general, were attributed to normal mastication and to various stripping activities. Only one carious lesion was observed, in a male with an estimated age of 26 years. An accurate assessment of the actual prevalence of caries was obscured by enamel wear and tooth loss in the older individuals.