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1.
Dirk Schories 《Aquatic Ecology》1995,29(3-4):341-347
For the last two decades dense mats of species of the filamentous green algaeEnteromorpha spp. have regulary occurred on tidal flats of Köningshafen Bay (island Sylt, North Sea, FRG). In calm areas overwintering of adult plants or plant fragments is a common process to guarantee the mass development during the next season. In contrast, the distribution ofEnteromorpha on exposed sandy tidal flats depends on recruitment by juvenile stages. In 1993Enteromorpha spore settlement was recorded regularly in the field. Polyethylene dishes were placed in the field and left for a period of seven days and lateron cultivated in the laboratory to checkEnteromorpha germling development. During summer 1993 — at a minimum distance of 200 m to the nearest adultEnteromorpha populations — a total of at least 82×106 spores m–2 settled. During winter the number of spores attached to the collecting dishes was close to zero and the adjacent sand flats were free of any visibleEnteromorpha plants. In further experiments it was shown that the development ofEnteromorpha juveniles in the next spring depended on the overwintering capacity of spores. More than 2×106 spores m–2 attached to large sand grains and other substrata (e.g. Hydrobia ulvae) survived the winter. In a laboratory experiment several species ofEnteromorpha were able to survive in total darkness for at least 10 months. 相似文献
2.
R S English J S Lampel TJ Vanden Boom 《Journal of industrial microbiology & biotechnology》1998,21(4-5):219-224
The introduction of plasmid DNA into germinating spores of an industrially improved strain of Saccharopolyspora erythraea was accomplished by electroporation. Various parameters affecting the efficiency of electroporation were examined. The most
critical factor was the extent of spore germination. Electrocompetence was limited to a 4-h period following the initial emergence
of the germ tube. Electroporation efficiencies as high as 2 × 105 CFU μg−1 of plasmid DNA were obtained using electrocompetent germlings. The optimal field strength was 12–14 kV cm−1 with a pulse duration of 15–20 ms. Electrocompetent germlings were stored at −80°C without a significant decrease in transformation
efficiency. The utility of this protocol was demonstrated by isolating a propionyl-CoA carboxylase mutant through targeted
gene disruption and replacement.
Received 3 April 1998/ Accepted in revised form 28 September 1998 相似文献
3.
Fengjuan Zhao Ziguo Zhao Aihua Wang Jidong Liu Delin Duan 《Journal of applied phycology》2010,22(2):195-202
Morphological and culture studies of germlings derived from carpospores of Chrysymenia wrightii (Harvey) Yamada were carried out under various treatments combining temperature and irradiance. Basal, main, and tip branches
were applied for inducing callus-like tissue. Focus was on how carpospores develop into germlings, how callus-like tissues
are induced from explants, and how temperature and irradiance affect carpospore germination and discoid crust growth. Results
show that carpospore development can be divided into three stages: division stage, discoid crust stage, and erect juvenile
germling stage. Discoid crusts, even more than ten, might coalesce into a big discoid crust, and then developed into germlings.
Filamentous fronds, formed on the rims of discoid crusts, exhibited in self-existence or co-existence form with germlings,
could form spherical tufts if cultured separately. Filamentous callus-like tissues appeared on the tip branches after 13 days.
PES is suitable for filament induction and culture, and filaments have potential use in germplasm preservation and vegetative
propagation. Temperature (10, 15, 20, 25°C) and irradiance (8 and 36 μmol photons m−2 s−1) significantly influenced carpospore germination rate and discoid crust diameter. Carpospores germinated normally under 36 μmol
photons m−2 s−1, 15~25°C, and maximum growth of discoid crusts was at 25°C, 36 μmol photons m−2 s−1; 10°C and 8 μmol photons m−2 s−1 did not favor carpospore germination or discoid crust growth. 相似文献
4.
Han Gil Choi Ki Hoon Lee Hyun Il Yoo Pil Jun Kang Young Sik Kim Ki Wan Nam 《Journal of applied phycology》2008,20(5):729-735
The effects of temperature, irradiance, and daylength on Sargassum horneri growth were examined at the germling and adult stages to discern their physiological differences. Temperature–irradiance
(10, 15, 20, 25, 30°C × 20, 40, 80 μmol photons m−2s−1) and daylength (8, 12, 16, 24 h) experiments were carried out. The germlings and blades of S. horneri grew over a wide range of temperatures (10–25°C), irradiances (20–80 μmol photons m−2s−1), and daylengths (8–24 h). At the optimal growth conditions, the relative growth rates (RGR) of the germlings were 21% day−1 (25°C, 20 μmol photons m−2s−1) and 13% day−1 (8 h daylength). In contrast, the RGRs of the blade weights were 4% day−1 (15°C, 20 μmol photons m−2s−1) and 5% day−1 (12 h daylength). Negative growth rates were found at 20 μmol photons m−2s−1 of 20°C and 25°C treatments after 12 days. This phenomenon coincides with the necrosis of S. horneri blades in field populations. In conclusion, we found physiological differences between S. horneri germlings and adults with respect to daylength and temperature optima. The growth of S. horneri germlings could be enhanced at 25°C, 20 μmol photons m−2s−1, and 8 h daylength for construction of Sargassum beds and restoration of barren areas. 相似文献
5.
Ziguo Zhao Fengjuan Zhao Jianting Yao Jingmei Lu Put. O. AngJr. Delin Duan 《Journal of applied phycology》2008,20(5):925-931
Morphology and culture studies on germlings of Sargassum thunbergii (Mertens et Roth) Kuntze were carried out under controlled laboratory conditions. Growth characteristics of these germlings
grown under different temperatures (from 10 to 25°C), irradiances (from 9 to 88 μmol photons m−2 s−1), and under blue and white light conditions are described. The development of embryonic germlings follows the classic “8
nuclei 1 egg” type described for Sargassaceae. Fertilized eggs spent 5–6 h developing into multicellular germlings with abundant
rhizoids after fertilization. Under conditions of 20°C, 44 μmol photons m−2 s−1 and photoperiod of 12 h, young germlings with one or two leaflets reached 2–3 mm in length after 8 weeks. Temperature variations
(10, 15, 20, 25°C) under 88 μmol photons m−2 s−1 significantly influenced the growth rate within the first week, although this effect became less obvious after 8 weeks, especially
at 15 and 20°C. Variation in germling growth was highly significant under different irradiances (9, 18, 44, 88 μmol photons
m−2 s−1) at 25°C. Low temperature (10°C) reduced germling growth. Growth of germlings cultured under blue light was lower than in
white light. Optimal growth of these germlings occurred at 25°C and 44 μmol photons m−2 s−1. 相似文献
6.
Summary The soil water potential (inferred from vapor pressure measurements by thermocouple psychrometry) influenced both chlamydospore
germination and continuing growth of germlings ofFusarium roseum f. sp.cerealis ‘Culmorum’ the same way in two different soils. Chlamydospore germination in both Ritzville silt loam (RSL) and Palouse silt
loam (PSL) amended with about 2,500 ppm C (as glucose) and 250 ppm N (as ammonium sulfate) was 40–50 per cent in 24 hours
at water potentials down to −50 to −60 bars. Some germination occurred by 72 hours at −80 to −85 bars in both soils but not
at lower potentials.
At a potential of −10 bars or higher, germ tubes lysed or converted into new chlamydospores within 48–72 hours after germination,
whereas at lower potentials germlings branched and appeared to grow for at least 6 days.
Bacterial numbers/g of RSL, 24 and 72 hours after adding nutrients, were 200 to 300 times greater in soil at water potentials
of −5 bars or more than in comparably treated soil at about −14 to −17 bars or less. Markedly reduced bacterial activity appeared
to coincide with a water potential of about −9 to −10 bars. When streptomycin and neomycin (300 ppm each) were mixed into
the soil in addition to nutrients, the survival of germlings of Culmorum was greatly enhanced, even in soil at potentials
of less than −1 bar. Indications were that soil water potentials of −10 bars or more favored bacterial activity, and that
this in turn repressed growth of germlings of Culmorum.
Culmorum infections of below-ground parts of wheat are serious primarily in drier soils, possibly because the fungus escapes
bacterial antagonism but can still extract water for growth.
Cooperative investigations, Crops Research and the Water and Soil Conservation Research Divisions, Agricultural Research Service,
U.S. Department of Agriculture and the Agricultural Experiment Stations of Idaho, Montana, Oregon, Utah, and Washington. Scientific
Paper No.3152, College of Agriculture, Washington State University, Pullman. 相似文献
7.
Killing of wild-type spores of Bacillus subtilis by t-butyl hydroperoxide, cumene hydroperoxide and peracetic acid was not through DNA damage, as shown by the absence of mutations
in the survivors and the identical sensitivity of spores of strains with or without a recA mutation. In contrast, B. subtilis spores (termed α−β−) lacking the DNA protective α/β-type small, acid-soluble spore proteins (SASP) were more sensitive to t-butyl hydroperoxide and cumene hydroperoxide, and their killing was in large part through DNA damage, as shown by the high
frequency of mutations in the survivors and the greater sensitivity of α−β− recA spores. Analysis of t-butyl hydroperoxide-treated spores showed that generation of DNA damage in α−β− spores was more rapid than in wild-type spores; α/β-type SASP also protected against DNA strand breakage in vitro caused by t-butyl hydroperoxide. α/β-Type SASP appeared to play no role in protection of spores from killing by peracetic acid; wild-type
and α−β− spores exhibited identical peracetic acid sensitivity and their killing by this agent appeared to be not through DNA damage.
Received 17 December 1996/ Accepted in revised form 13 March 1997 相似文献
8.
Lubomír Adamec 《Biologia》2008,63(4):515-520
Basic respiration characteristics were measured in turions of six aquatic plant species differing greatly in their ecological
and overwintering characteristics both before and after overwintering, i.e., in dormant and non-dormant state: non-carnivorous
Hydrocharis morsus-ranae and Caldesia parnassifolia and carnivorous Aldrovanda vesiculosa, Utricularia australis, U. ochroleuca, and U. bremii, and in non-dormant winter apices of three Australian (sub)tropical populations of Aldrovanda and of two temperate North American Utricularia species, U. purpurea and U. radiata. Respiration rate of autumnal (dormant) turions at 20°C ranged from 0.36 to 1.3 μmol O2 kg−1 (FM) s−1 and, except for U. bremii, increased by 11–114% after overwintering. However, this increase was statistically significant only in two species. Respiration
Q10 in dormant turions ranged within 1.8–2.6 and within 2.3–3.4 in spring (non-dormant) turions. Turions of aquatic plants behave
as typical storage, overwintering organs with low respiration rates. No relationship was found between respiration rate of
turions and overwintering strategy. In spite of their low respiration rates, turions can usually survive only from one season
to another, due to their limited reserves of respiratory substrates for long periods. Contrary to true turions, respiration
rates in non-dormant winter apices both in Australian Aldrovanda populations and temperate U. radiata and U. purpurea, in sprouting turions, and growing shoot apices of Aldrovanda were high and ranged from 2.1 to 3.1 μmol kg−1 (FM) s−1, which is comparable to that in aquatic plant leaves or shoots. 相似文献
9.
On sedimentary tidal flats in the Wadden Sea near the Island of Sylt, the periwinkleLittorina littorea occurred preferentially on clusters and beds of mussels and on shell beds (100 to 350 m−2), achieved moderate densities on green algal patches or mats (20 to 50 m−2), and remained rare on bare sediments (<5 m−2). Green algae covering>10% of sediment surface appeared in summer on approximately one third of the tidal zone, mainly in
the upper and sheltered parts and almost never on mussel and shell beds. In feeding experiments,L. littorea ingested more of the dominant alge,Enteromorpha, than ofUlva, irrespective of whether or not algae were fresh or decaying. The tough thalli ofChaetomorpha were hardly consumed. Snails feeding onEnteromorpha produced fecal pellets from which new growth ofEnteromorpha started. In the absence of periwinkles,Enteromorpha developed on mussels and the attached fucoids. Experimentally increased snail densities on sediments prevented green algal
development, but the snails were unable to graze down established algal mats. It is concluded that natural densities ofL. littorea hardly affect the ephemeral mass development of green algae on sediments. However, where the snails occur at high densities,
i.e. on mussel beds, green algal development may be prevented. 相似文献
10.
Seasonal activities of the digestive enzyme trypsin were measured between August 1998 and May 1999 to study different nutritional
strategies of the two copepods Pseudocalanus minutus and Oithona similis in the Arctic Kongsfjorden (Svalbard) using a highly sensitive fluorescence technique. Stage-, depth- and season-specific
characteristics of digestive activity were reflected in the trypsin activity. P. minutus females and stage V copepodids (C) had highest trypsin activities in spring during reproduction (197.5 and 145.7 nmol min−1 ng C−1, respectively). In summer stages CIII–V and in autumn stages CIV and V had high activities (80–116 nmol min−1 ng C−1) in the shallow layer (< 100 m) presumably as a consequence of prolonged feeding before descending to overwintering depth.
Trypsin activities at depth (> 100 m) in summer and autumn were low in stages CIII and CIV (29–60 nmol min−1 ng C−1) and in winter in all stages in both layers (20–43 nmol min−1 ng C−1). Based on low trypsin activity, males most likely did not feed. In O. similis, the spring phytoplankton bloom did not significantly affect trypsin activity as compared to the other seasons. O. similis CV and females had high trypsin activities in summer in the deep stratum (304.5 nmol min−1 ng C−1), which was concomitant with reproductive processes and energy storage for overwintering. In autumn, stage CV and female
O. similis had significantly higher activities than stage CIV (130–152 versus 78 nmol min−1 ng C−1), which is in accordance with still ongoing developmental and reproductive processes in CVs and females. Comparisons of both
species revealed different depth-related responses emphasizing different nutritional preferences: the mainly herbivorous P. minutus is more actively feeding in the shallow layer, where primary production occurs, whereas the omnivorous O. similis is not as much restricted to a certain depth layer, when searching for food. P. minutus had lower levels of trypsin activity during all seasons. In contrast to P. minutus, higher enzyme activities in males of O. similis suggest that they continue to feed and survive after fertilization of females. 相似文献
11.
Xiaowen Zhang Hongxia Wang Yuze Mao Chengwei Liang Zhimeng Zhuang Qingyin Wang Naihao Ye 《Journal of applied phycology》2010,22(2):173-180
For the last 2 years, vast accumulations of the unattached filamentous green alga, Enteromorpha prolifera, have occurred during summer along the coastal region of the Yellow Sea, China. However, algae do not seem to occur after
the end of the fertile season. It has been suggested that banks of microscopic forms of the algae, primarily spores, function
as a survival mechanism for this opportunistic alga. Therefore, in this study, field surveys and laboratory cultures were
conducted to determine if somatic cells were serving as a propagule bank to enable the algae to survive through periods of
unfavorable conditions. Laboratory experiments demonstrated that somatic regeneration was one of the most important approaches
by which E. prolifera colonized and flourished in the study area. Indeed, at least 19.32% of somatic cells from the filamentous segments could
survive for 2 months under various temperatures (0, 5, 10, 15, 20, and 30°C at an irradiance of 60 μmol photons m−2 s−1) and irradiances (darkness, 5 10, 15, 20 and 30 μmol photons m−2 s−1 at a temperature of 20°C). Additionally, greater than 35.85% of the somatic cells could survive at 0°C or in darkness for
2 months, and no less than 15.99% of these cells resumed growth when the temperature and irradiance were adjusted to the normal
levels (20°C and 60 μmol photons m−2 s−1). Furthermore, the results of field surveys revealed that viable E. prolifera was widespread in high quantities in the sediment of the Yellow Sea when the macroalga was absent. Taken together, the results
of this study suggest that somatic cells may act as an overwintering stage for the annual spring bloom of E. prolifera. These findings should be useful in future studies conducted to behavior of somatic cells in green tide as well as in the
management of future spring blooms of E. prolifera. 相似文献
12.
Chengzhang Liao Yiqi Luo Lifen Jiang Xuhui Zhou Xiaowen Wu Changming Fang Jiakuan Chen Bo Li 《Ecosystems》2007,10(8):1351-1361
Whether plant invasion increases ecosystem carbon (C) stocks is controversial largely due to the lack of knowledge about differences
in ecophysiological properties between invasive and native species. We conducted a field experiment in which we measured ecophysiological
properties to explore the response of the ecosystem C stocks to the invasion of Spartina alterniflora (Spartina) in wetlands dominated by native Scirpus mariqueter (Scirpus) and Phragmites australis (Phragmites) in the Yangtze Estuary, China. We measured growing season length, leaf area index (LAI), net photosynthetic rate (Pn), root
biomass, net primary production (NPP), litter quality and litter decomposition, plant and soil C and nitrogen (N) stocks in
ecosystems dominated by the three species. Our results showed that Spartina had a longer growing season, higher LAI, higher Pn, and greater root biomass than Scirpus and Phragmites. Net primary production (NPP) was 2.16 kg C m−2 y−1 in Spartina ecosystems, which was, on average, 1.44 and 0.47 kg C m−2 y−1 greater than that in Scirpus and Phragmites ecosystems, respectively. The litter decomposition rate, particularly the belowground decomposition rate, was lower for Spartina than Scirpus and Phragmites due to the lower litter quality of Spartina. The ecosystem C stock (20.94 kg m−2) for Spartina was greater than that for Scirpus (17.07 kg m−2), Phragmites (19.51 kg m−2) and the mudflats (15.12 kg m−2). Additionally, Spartina ecosystems had a significantly greater N stock (698.8 g m−2) than Scirpus (597.1 g m−2), Phragmites ecosystems (578.2 g m−2) and the mudflats (375.1 g m−2). Our results suggest that Spartina invasion altered ecophysiological processes, resulted in changes in NPP and litter decomposition, and ultimately led to enhanced
ecosystem C and N stocks in the invaded ecosystems in comparison to the ecosystems with native species. 相似文献
13.
Summary Snails and nematodes, the potential cyanobacterial grazers, differ in their choice for cyanobacterial diet. Snails prefer
non-mucilaginous forms while nematodes prefer mucilaginous forms. Such differences in feeding choice between the cyanobacteria
suggests that it may not be possible to select strains of diazotrophic cyanobacteria that are resistant to all grazers. The
potential consumption of cyanobacteria at an average field density of 20,000 snails ha−1 was estimated to be about 50 kg (fresh weight) ha−1 day−1. Dorylamus sp. was most dominant nematode associated with cyanobacterial consumption. Phytoextracts of neem (Azadirachta indica), bel (Aegle marmelos) and tobacco (Nicotiana tabacum) were effective in controlling these cyanobacterial grazers. The minimum concentration of neem, bel and tobacco phytoextract
in water for 100 % mortality of snails were 0.1, 2.0 and 0.05%, respectively. However, trepellent level was only 0.01% for
neem and tobacco phytoextract. Complete mortality of nematode (Dorylamus spp.) required a higher concentration level (2%) even in the most effective tobacco phytoextract. Lower levels of phytoextract
(0.1%) were found to stimulate growth and nitrogen fixation of cyanobacteria. Application of these plant biomasses resulted
in significant increase in cyanobacterial acetylene-reducing activity (ARA) and rice yield and a significant decrease in snail
and nematode population. Augmentation of cyanobacterial acetylene-reducing activity was two to three times higher in comparison
to the control in both the years of experimentation. Rice yield also increased between 3.8 and 58.5% over the control, depending
on the quantity and nature of plant biomass. Tobacco waste was significantly superior in comparison to neem and bel biomass
as carrier of cyanobacterial culture. 相似文献
14.
Nobuhiko Ohga 《Ecological Research》1992,7(3):341-353
Herbaceous lomas in the Peruvian coastal desert, of South America establish in spring, and its habitat is limited to the southern
or southwestern slopes along the coast that are affected by thick fog. The time of appearance, the duration and the thickness
of the fog vary greatly from year to year, so the lomas can grow only in habitats with enough water to, sustain seed germination
and plant growth. This paper studies the species composition and density of the buried seed population, of the herbaceous
lomas of Loma Ancon in order to clarify the mechanisms of the lomas' establishment. The mean number of species with viable
seeds was about, 12 spp. m−2 and that of dead seeds was about 22 spp. m−2. The dominant species wereSolanum tuberiferum, S. pinnatifidum andNolana humifusa, both in viable and dead seeds. Viable seed density was about 5000–8000 seeds m−2, which is comparable with the seed densities of other herbaceous communities. Dead seed density was about 15000–27000 seeds
m−2, or nearly three times the viable seed density, because the rate of decomposition was slow in the extremely dry conditions.
The net increase of viable seeds by seed production was estimated at about 5000 seeds m−2 in 1980, and the increase in the number of dead seeds was 2200 seeds m−2. 相似文献
15.
In order to provide a better understanding of the dynamics of phytoplankton in the coastal regions of high latitudes, a study
was carried out to estimate the dynamics of carbon biomass of autotrophic and heterotrophic algal groups over the austral
spring-summer 1997/1998 period. At a fixed station located in the central basin (Paso Ancho) of the Straits of Magellan (53°S),
surface water samples were collected at least once a week from September 1997 (early spring) to March 1998 (late summer).
Quantitative analysis of biomass of phytoplankton was estimated from geometric volumes, using non-linear equations, and converted
to biomass. The pattern of chlorophyll a showed a strong temporal variability, with maximum values (mean 2.8 mg m−3) at the austral spring phytoplankton increase or bloom (October/November) and minimum values during early spring (September:
<0.5 mg m−3) and summer (January/March: 0.5–1.0 mg m−3). During the spring bloom, diatoms made up to 90% of the total phytoplankton carbon (0.01–189 μg l−1), followed by a maximum of thecate dinoflagellates (0.08–34 μg l−1), and sporadic high biomass of phytoflagellates during summer. Heterotrophic algal groups such as Gymnodinium and Gyrodinium spp. dominated (70%, in the 5- to 25-μm size range) shortly before the main diatom bloom, and small peaks were observed within
spring and early summer periods (0–0.4 μg l−1). Phytoflagellates dominated earlier (spring) with higher carbon biomass (8 μg l−1) and post-bloom periods (summer) when carbon biomass ranged between 1 and 4 μg l−1.
Accepted: 6 September 2000 相似文献
16.
T. S. Zakharenkova A. A. Aver’yanov T. D. Pasechnik V. P. Lapikova C. J. Baker 《Russian Journal of Plant Physiology》2010,57(5):615-619
Effects of reactive oxygen species (ROS) on the release of putative elicitors from spores of rice blast causal fungus Magnaporthe grisea (Hebert) Barr were studied. While studying the influence of exogenous ROS, the spores were germinated for 5 h in the presence
of 50 μM H2O2 and then treated with catalase to decompose hydrogen peroxide. The spore germination fluid was then boiled to inactivate
catalase. When the resulting diffusate was applied onto rice (Oryza sativa L.) leaves, it caused necroses and stimulated superoxide (O2−) production. Both effects were observed with the resistant rice cultivar but not with the cultivar susceptible to the fungal
strain. The susceptible cultivar did not acquire resistance to challenge with fungal spores, which were applied one day after
the treatment. The fractionation of the spore diffusate showed that both low- and high-molecular compounds (mol wt < 3 kD
and >3 kD, respectively) should be present in combination to induce O2− production by leaves. The diffusates from spores germinated in water also caused necroses and stimulated O2− generation, though to a weaker extent than diffusates from spores germinated in H2O2. The effect of diffusates from spores germinated in water was abolished by catalase or superoxide dismutase added initially
to the spore suspension. The results suggest that germinating spores of M. grisea are able to release elicitors and this ability depends on ROS formation by spores. Presumably, the yield of elicitors is
increased additionally if fungus M. grisea is stressed or subjected to exogenous ROS. The described phenomena may be involved in incompatibility mechanisms. 相似文献
17.
Carla V. Giordano Aranzazú Guevara Hernán E. Boccalandro Carmen Sartor Pablo E. Villagra 《Plant Ecology》2011,212(7):1123-1134
Prosopis flexuosa trees dominate woodlands in the Central Monte Desert (Mendoza, Argentina), with <200 mm rainfall, exploiting the water table
recharged by Andean rivers, and also growing in dunes with no access to the water table. Prosopis woodlands were extensively logged during development of the agricultural oasis, and surface and groundwater irrigation could
lower the depth of the water table in the future. We evaluated tree populations with decreasing access to the water table:
valley adult trees, valley saplings, and dune adult trees, in order to assess their ecophysiological response to water table
accessibility. High and seasonally stable pre-dawn leaf water potentials (−2.2 ± 0.2 to −1.2 ± 0.07 MPa) indicated that valley
adults utilize larger and more stable water reservoirs than valley saplings and dune adults (−3.8 ± 0.3 to −1.3 ± 0.07 MPa),
with higher midday leaf conductance to water vapor (valley adults ~250; dune adults <60 mmol m−2 s−1), potentially higher CO2 uptake, and increased radial growth rate (valley adults 4.1 ± 0.07; dune adults 2.9 ± 0.02 mm year−1). Trees with poor access to the water table exhibited drought tolerance responses such as midday stomata closure, leaflet
closure, and osmotic adjustment. Stomata density decreased in response to drought when leaf expansion was restricted. The
combination of phreatophytism and drought tolerance would enlarge P. flexuosa habitats and buffer populations against changes in rainfall dynamics and water table depth. 相似文献
18.
Zhenhua Huo Xingming Yang Waseem Raza Qiwei Huang Yangchun Xu Qirong Shen 《Applied microbiology and biotechnology》2010,87(2):527-536
Bioorganic fertilizer containing Paenibacillus polymyxa SQR-21 showed very good antagonistic activity against Fusarium oxysporum. To optimize the role of P. polymyxa SQR-21 in bioorganic fertilizer, we conducted a study of spore germination under various conditions. In this study, l-asparagine, glucose, fructose and K+ (AGFK), and sugars (glucose, fructose, sucrose, and lactose) plus l-alanine were evaluated to determine their ability to induce spore germination of two strains; P. polymyxa ACCC10252 and SQR-21. Spore germination was measured as a decrease in optical density at 600 nm. The effect of heat activation
and germination temperature were important for germination of spores of both strains on AGFK in Tris–HCl. l-Alanine alone showed a slight increase in spore germination; however, fructose plus l-alanine significantly induced spore germination, and the maximum spore germination rate was observed with 10 mmol l−1
l-alanine in the presence of 1 mmol l−1 fructose in phosphate-buffered saline (PBS). In contrast, fructose plus l-alanine hardly induced spore germination in Tris–HCl; however, in addition of 10 mmol l−1 NaCl into Tris–HCl, the percentages of OD600 fall were increased by 19.6% and 24.3% for ACCC10252 and SQR-21, respectively. AGFK-induced spore germination was much more
strict to germination temperature than that induced by fructose plus l-alanine. For both strains, fructose plus l-alanine-induced spore germination was not sensitive to pH. The results in this study can help to predict the effect of environmental
factors and nutrients on spore germination diversity, which will be beneficial for bioorganic fertilizer storage and transportation
to improve the P. polymyxa efficacy as biological control agent. 相似文献
19.
High yields of protoplasts have been obtained from vegetative thalli of three species ofEnteromorpha by enzymatic degradation of the cell wall. Several commercial and crude enzymes prepared from the digestive system and hepatopancrease
of abalone and top-shell were tested at different concentrations and combinations to evaluate the yield. Commercial enzymes
in combination with either abalone or top-shell crude enzymes, consistently produced a high yield of protoplasts from all
three species. High regeneration rate (85–95%) occurred in the protoplasts cultured at a density greater than 1.72 × 103 cells cm−2 at 20 and 25°C. Light intensities tested in the present study did not affect protoplast wall formation and regeneration.
Protoplasts, after regenerating the cell wall, followed different types of developmental patterns under identical culture
conditions. In one type some cells underwent repeated cell divisions and formed a round and oval shaped hollow thallus with
a single layer of cells. In the second type many cells underwent one or two cell divisions (occasionally no division) and
soon matured and discharged many motile spores, which on germination grew into normal plantlets. In the third type some cells
divided irregularly to form a mass of callus-like cells (exceptE. prolifera). Culture medium supplemented with either mannitol, sorbitol, dextrose, saccharose or NaCl at higher concentrations (> 0.4
M) inhibited cell division and further differentiation in all species.
author for correspondence 相似文献
20.
Lay CY Mykytczuk NC Niederberger TD Martineau C Greer CW Whyte LG 《Extremophiles : life under extreme conditions》2012,16(2):177-191
Lost Hammer (LH) spring is a unique hypersaline, subzero, perennial high Arctic spring arising through thick permafrost. In
the present study, the microbial and geochemical characteristics of the LH outflow channels, which remain unfrozen at ≥−18°C
and are more aerobic/less reducing than the spring source were examined and compared to the previously characterized spring
source environment. LH channel sediments contained greater microbial biomass (~100-fold) and greater microbial diversity reflected
by the 16S rRNA clone libraries. Phylotypes related to methanogenesis, methanotrophy, sulfur reduction and oxidation were
detected in the bacterial clone libraries while the archaeal community was dominated by phylotypes most closely related to
THE ammonia-oxidizing Thaumarchaeota. The cumulative percent recovery of 14C-acetate mineralization in channel sediment microcosms exceeded ~30% and ~10% at 5 and −5°C, respectively, but sharply decreased
at −10°C (≤1%). Most bacterial isolates (Marinobacter, Planococcus, and Nesterenkonia spp.) were psychrotrophic, halotolerant, and capable of growth at −5°C. Overall, the hypersaline, subzero LH spring channel
has higher microbial diversity and activity than the source, and supports a variety of niches reflecting the more dynamic
and heterogeneous channel environment. 相似文献