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991.
992.
993.
Changes in the isozyme profiles of peroxidases (POX, EC 1.11.1.7), glutamate oxaloacetate transaminase (GOT, EC 2.6.1.1) and esterases (EST, EC 3.1.1.1) have been studies in leaves of Chenopodium foetidum S. treated with ethrel. Different systems for administration of the ethrel led to different responses. In intact plants, treatment of the complete surface of leaves or local administration by pricking the leaves induced senescence and wilting as well as quick changes, characteristic of ageing, in the isozyme patterns of the treated leaves. Isolated leaves treated with ethrel in vitro also showed a senescence response, but this was followed by a necrosis that displayed an isozyme pattern highly similar to that of necrotic lesions induced by plum pox virus (PPV) infection. An accelerated senescence process seems to be involved in the induction of changes in the isozyme patterns of expression during the hypersensitive response of Chenopodium foetidum to PPV infection, and ethylene could participate in this process. However, other factors may also be required for necrotization. 相似文献
994.
Philippe Christe Anders Pape Mller Guillermo Gonzlez Florentino De Lope 《Journal of avian biology》2002,33(3):321-325
The intensity of parasite infections often increases during the reproductive season of the host as a result of parasite reproduction, increased parasite transmission and increased host susceptibility. We report within‐individual variation in immune parameters, hematocrit and body mass in adult house martins Delichon urbica rearing nestlings in nests experimentally infested with house martin bugs Oeciacus hirundinis and birds rearing nestlings in initially parasite‐free nests. From first to second broods body mass and hematocrit of breeding adult house martins decreased. In contrast leucocytes and immunoglobulins became more abundant. When their nests were infested with ectoparasites adults lost more weight compared with birds raising nestlings in nests treated with pyrethrin, whereas the decrease in hematocrit was more pronounced during infection with blood parasites. Neither experimental infestation with house martin bugs nor blood parasites had a significant effect on the amount of immune defences. 相似文献
995.
Ellie R. Paine Elizabeth A. Brewer Matthias Schmid Guillermo Diaz-Pulido Philip W. Boyd Catriona L. Hurd 《Journal of phycology》2023,59(4):738-750
Release of dissolved organic carbon (DOC) by seaweed underpins the microbial food web and is crucial for the coastal ocean carbon cycle. However, we know relatively little of seasonal DOC release patterns in temperate regions of the southern hemisphere. Strong seasonal changes in inorganic nitrogen availability, irradiance, and temperature regulate the growth of seaweeds on temperate reefs and influence DOC release. We seasonally surveyed and sampled seaweed at Coal Point, Tasmania, over 1 year. Dominant species with or without carbon dioxide (CO2) concentrating mechanisms (CCMs) were collected for laboratory experiments to determine seasonal rates of DOC release. During spring and summer, substantial DOC release (10.06–33.54 μmol C · g DW−1 · h−1) was observed for all species, between 3 and 27 times greater than during autumn and winter. Our results suggest that inorganic carbon (Ci) uptake strategy does not regulate DOC release. Seasonal patterns of DOC release were likely a result of photosynthetic overflow during periods of high gross photosynthesis indicated by variations in tissue C:N ratios. For each season, we calculated a reef-scale net DOC release for seaweed at Coal Point of 7.84–12.9 g C · m−2 · d−1 in spring and summer, which was ~16 times greater than in autumn and winter (0.2–1.0 g C · m−2 · d−1). Phyllospora comosa, which dominated the biomass, contributed the most DOC to the coastal ocean, up to ~14 times more than Ecklonia radiata and the understory assemblage combined. Reef-scale DOC release was driven by seasonal changes in seaweed physiology rather than seaweed biomass. 相似文献
996.
Luis Delgado Blanca A. Trejo Carlos Huitrón Guillermo Aguilar 《Applied microbiology and biotechnology》1993,39(4-5):515-519
Aspergillus sp. CH-Y-1043 synthesizes pectin lyase when grown on citrus pectin at 37° C. Production is favoured by increased esterification degree of the pectin used as carbon source. This enzyme displays higher activity at pH values of 8.5–8.8 and temperatures of 40–45° C. The optimal substrate for the enzyme was highly esterified pectin and no enzymatic activity was registered on polygalacturonic acid. The activity is stimulated by, though not dependent on, divalent cations (Ca2+, Mg2+, Mn2+, Ba2+ and Co2+) and inhibited by Zn2+, and it is not sensitive to the addition of EDTA. The enzyme is very stable when exposed to pH variations: at 4° C it preserves more than 95% of its activity at pHs ranging from 2.0 to 10.0, and at 30° C stability is preserved at pHs ranging from 4.0 to 8.0. At a constant pH of 5.0, the enzyme conserves its stability at temperatures ranging from 4 to 50° C and at pH 8.0 sensitivity to temperature increased. The results on the endo-exo nature of the enzyme suggest that this is an exo-pectin lyase.
Correspondence to: G. Aguilar 相似文献
997.
Ariel Arencibia Pedro R. Molina Gustavo de la Riva Guillermo Selman-Housein 《Plant cell reports》1995,14(5):305-309
Summary We describe an efficient procedure for genetic transformation of commercial sugarcane varieties POJ 2878 and Ja 60-5. The transformation protocol is based on electroporation of a plasmid conferring GUS activity into cell clusters isolated from embryogenic calli. Six to eight weeks after electroporation, Ja 60-5 plants regenerated from electroporated tissues were tested and confirmed to be transgenic using histochemical glucuronidase and Southern hybridization analysis. Electroporation of intact cells is an efficient and reproducible method for sugarcane transformation and may also be useful for transformation of other plants.Abhrevations GUS
-glucuronidase
- CAT
chloramphenicol acetyl transferase
- PCV
packed cell volume
- PCR
polymerase chain reaction
- DTT
dithiotreitol
- Hepes
N-2-Hydroxyethylpiperazine-N'-2-ethanesulfonic acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- NOS
nopaline synthase
- 4-MUG
4-methylumbelliferyl -D-glucuronide 相似文献
998.
Characterization of a small eutrophic Antarctic lake (Otero Lake, Cierva Point) on the basis of algal assemblages and water chemistry 总被引:2,自引:0,他引:2
Otero Lake is the main water body of Cierva Point, Danco Coast (SSSI No. 15). During the 1992/1993 and 1994/1995 seasons,
abiotic parameters and the structure and dynamics of the phytoplankton were studied. Algal assemblages from the phytoplankton,
from algal clumps encased in the lake ice and from the benthic algal felt were compared. Low Jaccard similarity indices between
these three assemblages suggest different survival strategies. The higher species richness of phytoplankton when studied during
the whole summer also suggests that external propagule inputs can heavily influence the structure of this community. High
levels of phosphate, nitrate and ammonium throughout the study periods indicate that they do not limit summer growth of the
phytoplankton community. Blooms of Chlamydomonas subcaudata Wille are apparently characteristic. This group of features define Otero Lake as a highly eutrophic water body, in which
outflow seems to be the main cause of phytoplankton loss during summer.
Received: 23 December 1996 / Accepted: 29 August 1997 相似文献
999.
Guillermo E. Napolitano Jacqueline E. Richmond Arthur J. Stewart 《Soil & Sediment Contamination》1998,7(6):709-724
Petroleum hydrocarbons from 20 soils from refineries or other industrial sites were extracted with a mixture of chloroform and methanol (1:1, v/v), and the extracts were analyzed by thin layer chromatography with flame ionization detection (TLC/FID). The TLC/FID procedure has been used widely in biological and medical research but generally has been underutilized in environmental chemistry. The analysis method involved spotting a small volume of sample extract (typically 1 to 3?µl) on ten silica-coated quartz rods, and chromatographically separating constituents in the spots using solvent systems of increasing polarities (hexane, toluene, and dichloromethane + methanol). We achieved complete separation of saturated hydrocarbons, aromatic hydrocarbons, resins, and asphaltenes from the hydrocarbon-contaminated soils with this method. Analysis of the separated constituents by TLC/FID also allowed quantification of aromatic and aliphatic hydrocarbons without interference from soil biogenic lipids. A simplified version of the method permitted excellent separation of aliphatics +aromatics (forming a single peak) from resins and asphaltenes. The procedure is rapid (complete analysis of ten samples in about 1?h after extraction). Thus, the method seems well suited for synoptic surveys or screening and characterizing numerous samples prior to using more detailed and costly analyses. 相似文献
1000.
A destructive disease affecting tank-cultivated Ulva rigida C. Agardh. was characterized by green spots, initially located at the base of the thalli, that spread through the host thallus and gradually caused perforations of the frond. The endophytic filamentous green alga Acrochaete geniculata (Gardner) O'Kelly was identified as the causative agent of the disease. The effects of this infection on the host varied from minor injuries to gross frond destruction. Advanced stages of infection resulted in frond wrinkling and severe tissue loss. These symptoms were caused by a primary compaction of the host cells due to a direct effect of the endophyte followed by secondary bacterial infections that became part of the degradative process initiated by the algal pathogen. Co-cultivation of healthy and diseased fronds resulted in transfer of the infection within 2 weeks; however, attempts to infect the host in the laboratory with actively reproducing suspensions of the endophyte were unsuccessful. 相似文献