辽宁省菜田生态系统组分优势值与系统优势度分析

辽宁省菜田生态系统组分优势值与系统优势度分析周宝利，葛晓光李宁义（沈阳农业大学园艺系，１１０１６１）（沈阳市城建中专，１１００１３）ＡｎａｌｙｓｉｓｏｎＳｕｐｅｒｉｏｒｉｔｙＶａｌｕｅａｎｄＤｏｍｉｎａｎｃｅＤｅｇｒｅｅｏｆＶａｒｉｏｕｓＣｏｍｐｏｎ...     

Reproductive characteristics that favor invasiveness in Leonotis nepetifolia (L.) R. Br.

Reproductive systems are life attributes important in defining the demography and genetic constitution of invasive alien species populations. We describe the phenology, floral behavior and floral visitors in Mexican populations of Leonotis nepetifolia considered invasive in America, Asia and Oceania. The mating system was determined through pollination experiments and, with a morphological analysis of flowers (outcrossing index, OCI) and pollen/ovule ratio, the breeding system was evaluated. Germination of 1 and 2-year-old seeds was tested to assess the potential characteristics of germination. Leonotis nepetifolia was reproductive for 7 months (June to December) and tended towards a specific season during autumn. Anthesis lasted 36 hr with protogyny and no hercogamy, with floral visitors of Apodiformes, Hymenoptera, Lepidoptera and Thysanoptera. Pollination experiments indicated a mixed mating system, whereas the OCI and the pollen/ovule ratio pointed towards a facultative xenogamous breeding system. Seed production was high (1,445 ± 132 seeds/plant); the seeds had potential longevity and were neutral photoblastic. One-year-old seeds germinated slightly later ( = 2.6 ± 0.11 days) than 2-year-old seeds ( = 1.9 ± 0.02 days), both synchronously (IS_1yr = 0.88 ± 0.03 and IS_2yr = 0.82 ± 0.02). Germination percentage for 1-year-old seeds was lower (55.33 ± 4.40%) than that of 2-year-old seeds (94.18 ± 0.59%), suggesting a potential longevity of the seeds in an optimal environment. Reproductive characteristics, such as wide reproductive period, mixed breeding system, copious seed production, seeds with potential longevity, and quick and synchronic germination in different light conditions, favor the invasive capacity of Leonotis nepetifolia.     

Biology and host preference of Selitrichodes neseri: A potential biological control agent of the Eucalyptus gall wasp,Leptocybe invasa

Selitrichodes neseri (Hymenoptera: Eulophidae) is a parasitoid of the invasive gall-forming wasp Leptocybe invasa (Hymenoptera: Eulophidae), which has caused serious damage to Eucalyptus plantations in many parts of the world. S. neseri is a recently discovered parasitoid considered to be a potentially important biological control agent of L. invasa. The aim of this study was to provide the first basic data on the biology of S. neseri, which is essential for its application in biological control. S. neseri was shown to be a biparental ectoparasitoid. Observation from dissected galls indicated that the parasitoid developed on late larvae, pupae and callow adults, although development did occur in a range of gall ages. Observed nominal parasitism in captivity ranged from 9.7% to 71.8%. Adult S. neseri specimens, fed with honey-water and galled Eucalyptus leaves, survived an average of 26 days at 26 °C. The average developmental time from oviposition to emergence was 19.3 days ± 0.2 days. There was no pre-oviposition period. A single female produced a maximum of thirty-nine offspring, with a maximum of ten per day. Dissection of the ovaries showed that twelve ovarioles were present. The sex ratio of S. neseri observed in this study was 1:3.43 males:females. Galls of native insects most closely related to L. invasa and to galls of similar morphology to L. invasa-induced galls, were not suitable for S. neseri oviposition. S. neseri showed considerable potential as a biological control agent of L. invasa due to its relatively short developmental time, long adult life span when supplemented with carbohydrates, ability to utilize a range of gall ages and the fact that it has a high level of host specificity.     

A search for quantitative trait loci for ovulation rate in cattle

Seventy-seven polymorphic microsatellites were analysed in offspring of three elite sires that were part of the foundation of an experimental population selected for twinning rate at the US Meat Animal Research Center, Clay Center, Nebraska. All females were assessed for ovulation rate by rectal palpation of corpora lutea over 8–10 consecutive oestrous cycles from approximately 12 to 18 months of age, and associations between ovulation rate and sire allele were examined in each of the three sire groups. A preliminary analysis was performed using selectively genotyped daughters of each sire. Markers found significant or approaching significance were also genotyped in all daughters, sons and granddaughters of these sires. A test of marker associations limited to the granddaughter data provided an independent confirmation of marker effect and significance relative to the initial test with daughter data. Putative ovulation rate quantitative trait loci were detected on chromosomes 7 and 23. Marker UWCA20 on chromosome 7 was associated with an effect in excess of one phenotypic standard deviation and accounted for approximately 10% of phenotypic variation ovulation rate. Marker CYP21 (steroid 21-hydroxylase) on chromosome 23 was associated with an effect of slightly less than half a phenotypic standard deviation and accounted for approximately 4% of phenotypic variation.     

Effect of light on abscisic acid content in photosensitive Scots pine (Pinus sylvestris L.) seed

Dormancy-breaking treatment of the photosensitive Scots pine (Pinus sylvestris L.) seed by white light incubation or a 15-min exposure to red light decreased the abscisic acid content prior to radicle protrusion. Incubation in the dark or exposure to red light followed by a 5-min far-red light irradiation did not cause as great a decrease in abscisic acid content nor was the dormancy relieved. The ability of the far-red light to keep the ABA level high and to prevent germination gradually disappeared as the length of the dark period between the red and far-red treatments was increased to 24 h. ABA was quantified on a gas chromatograph with an electron capture detector.     

Temperature thresholds for germination in 20 short‐range endemic plant species from a Greenstone Belt in southern Western Australia

• The study of climate‐driven effects on seed traits such as germination has gained momentum over the past decade as the impact of global warming becomes more apparent on the health and survival of plant diversity.
• Seed response to warming was evaluated in a suite of short‐range endemic species from the biodiverse Greenstone Belt of southern Western Australia. The temperature dimensions for germination in 20 woody perennials were identified using small unreplicated samples over 6 weeks on a temperature gradient plate (constant and fluctuating temperatures between 5 and 40 °C). These data were subsequently modelled against current and forecast (2070) mean monthly minimum and maximum temperatures to illustrate seasonal changes to germination timing and final percentage germination.
• All but one species attained full germination in at least one cell on the gradient plate. Modelling of the data suggested only minimal changes to percentage germination despite a forecast rise in diurnal temperatures over the next 50 years. Nine species were predicted to experience declines of between <1% and 7%, whilst 11 species were predicted to increase their germination by <1% to 3%. Overall, the speed of germination is predicted to increase but the timing of germination for most species shifts seasonally (both advances and delays) as a result of changing diurnal temperatures.
• The capacity of this suite of species to cope with warmer temperatures during a critical early life stage shows a degree of adaptation to heterogeneous environments. Predicting the effects of global change on terrestrial plant communities is crucial to managing and conserving plant diversity.

     

Stress integrated tests and cytological analyses reveal Brassica villosa subsp. drepanensis seed quality decrease upon long-term storage

Under stress integrated germination test (SIGT), seeds undergo osmo-saline stresses, which enable to detect differences in vigour of long-term stored seeds with high germination percentage (G%). The quality of Brassica villosa subsp. drepanensis seeds stored in a genebank (at ? 20°C for 16 years) was compared with seeds at harvest by standard germination tests (GT), SIGT and cytogenetic analysis. No differences were detected in G% and mean germination time under GT. Conversely, SIGT performed with NaCl ? 0.9 MPa osmotic potential did not influence G% at harvest but reduced that of stored seeds, SIGT at ? 1.4 MPa reduced G% of both. Cytogenetic analysis showed reduction of mitotic index, appearance of chromosomal aberrations and smaller nucleoli in stored seeds compared with harvest seeds germinated in water. SIGT at ? 0.9 MPa had no effect on mitotic index, but increased chromosome aberrations and nucleoli number. SIGT at ? 1.4 MPa inhibited G% of harvest and stored seeds, reduced mitoses in harvest and completely prevented it in stored seeds. The results indicate that GT does not faithfully reflect the quality of stored seeds, with misinterpretation of their vigour, whereas SIGT and cytogenetical parameters are sensitive, reliable and inexpensive methods for early prediction of genetic erosion in germplasm banks.     

Assessment of biofilm formation by Scedosporium apiospermum,S. aurantiacum,S. minutisporum and Lomentospora prolificans

Reported herein is the ability of Scedosporium apiospermum, S. aurantiacum, S. minutisporum and Lomentospora prolificans conidia to adhere, differentiate into hyphae and form biofilms on both polystyrene and lung epithelial cells. To different degrees, all of the fungi adhered to polystyrene after 4 h, with a predominance of those with germinated conidia. Prolonged fungi–polystyrene contact resulted in the formation of a monolayer of intertwined mycelia, which was identified as a typical biofilm structure due to the presence of a viable mycelial biomass, extracellular matrix and enhanced antifungal resistance. Ultrastructural details were revealed by SEM and CLSM, showing the dense compaction of the mycelial biomass and the presence of channels within the organized biofilm. A similar biofilm structure was observed following the co-culture of each fungus with A549 cells, revealing a mycelial trap covering all of the lung epithelial monolayer. Collectively, these results highlight the potential for biofilm formation by these clinically relevant fungal pathogens.