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1.
Water relations and root activities of Buchloe dactyloides and Zoysia japonica in response to localized soil drying 总被引:5,自引:0,他引:5
Effects of localized soil drought stress on water relations, root growth, and nutrient uptake were examined in drought tolerant
‘Prairie’ buffalograss [Buchloe dactyloides (Nutt.) Engelm.] and sensitive ‘Meyer’ zoysiagrass (Zoysia japonica Steud.). Grasses
were grown in small rhizotrons in a greenhouse and subjected to three soil moisture regimes: (1) watering the entire 80-cm
soil profile (well-watered control); (2) drying 0–40 cm soil and watering the lower 40 cm (partially dried); (3) and drying
the entire soil profile (fully dried). Drying the 0–40 cm soil for 28 days had no effect on leaf water potential (Ψ
leaf
) in Prairie buffalograss compared to the well-watered control but reduced that in Meyer zoysiagrass. Root elongation rate
was greater for Prairie buffalograss than Meyer zoysiagrass under well-watered or fully dried conditions. Rooting depth increased
with surface soil drying; with Prairie buffalograss having a larger proportion of roots in the lower 40 cm than Meyer zoysiagrass.
The higher rates of water uptake in the deeper soil profile in the partially dried compared to the well-watered treatment
and by Prairie buffalograss compared to Meyer zoysiagrass could be due to differences in root distribution. Root 15N uptake for Prairie buffalograss was higher in 0–20 cm drying soil in the partially dried treatment than in the fully dried
treatment. Diurnal fluctuations in soil water content in the upper 20 cm of soil when the lower 40 cm were well-watered indicated
water efflux from the deeper roots to the drying surface soil. This could help sustain root growth, maintain nutrient uptake
in the upper drying soil layer, and prolong turfgrass growth under localized drying conditions, especially for the deep-rooted
Prairie buffalograss.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Nocturnal increases in water potential (ψ) and water content (θ) in the upper soil profile are often attributed to root water efflux, a process termed hydraulic redistribution
(HR). However, unsaturated liquid or vapor flux of water between soil layers independent of roots also contributes to the
daily recovery in θ (Δθ), confounding efforts to determine the actual magnitude of HR. We estimated liquid (J
l) and vapor (J
v) soil water fluxes and their impacts on quantifying HR in a seasonally dry ponderosa pine (Pinus ponderosa) forest by applying existing datasets of ψ, θ and temperature (T) to soil water transport equations. As soil drying progressed, unsaturated hydraulic conductivity declined rapidly such that
J
l was irrelevant (<2E−05 mm h−1 at 0–60 cm depths) to total water flux by early August. Vapor flux was estimated to be the highest in upper soil (0–15 cm),
driven by large T fluctuations, and confounded the role of HR, if any, in nocturnal θ dynamics. Within the 15–35 cm layer, J
v contributed up to 40% of hourly increases in nocturnal soil moisture. While both HR and net soil water flux between adjacent
layers contribute to θ in the 15–65 cm soil layer, HR was the dominant process and accounted for at least 80% of the daily
recovery in θ. The absolute magnitude of HR is not easily quantified, yet total diurnal fluctuations in upper soil water content
can be quantified and modeled, and remain highly applicable for establishing the magnitude and temporal dynamics of total
ecosystem water flux. 相似文献
3.
Biodegradation of glyphosate in sod-podzol soil by both the indigenous micro flora and the introduced strain Ochrobactrum anthropi GPK 3 was studied with respect to its sorption and mobility. The experiments were carried out in columns simulating the vertical
soil profile. Soil samples studied were taken from soil horizons 0–10, 10–20, and 20–30 cm deep. It was found out that the
most of the herbicide (up to 84%) was adsorbed by soil during the first 24 h; the rest (16%) remained in the soluble fraction.
The adsorbed glyphosate was completely extractable by alkali. No irreversible binding of glyphosate was observed. By the end
of the experiment (21st day), glyphosate was only found in extractable fractions. The comparison of the effect of the introduced
O. anthropi GPK 3 and indigenous microbial community on the total toxicant content (both soluble and absorbed) in the upper 10 cm soil
layer showed its reduction by 42% (21 mg/kg soil) and 10–12% (5 mg/kg soil), respectively. Simultaneously, 14–18% glyphosate
moved to a lower 10–20 cm layer. Watering (that simulated rainfall) resulted in a 20% increase of its content at this depth;
6–8% of herbicide was further washed down to the 20–30 cm layer. The glyphosate mobility down the soil profile reduced its
density in the upper layer, where it was available for biodegradation, and resulted in its concentration in lower horizons
characterized by the absence (or low level) of biodegradative processes. It was shown for the first time how the herbicide
biodegradation in soil can be increased manifold by introduction of the selected strain O. anthropi GPK 3. 相似文献
4.
Elzbieta Krolak Jerzy Kwapulinski Agnieszka Fischer 《Radiation and environmental biophysics》2010,49(2):229-237
The vertical 137Cs profile of forest and wasteland soils was analyzed in the south of the Podlasie Lowland area (Eastern Poland) about 20 years
after the Chernobyl accident. In addition, the concentration of 40K in soils of the investigated area was measured. Below the litter layer (mean thickness 3 cm), the soil samples were collected
up to a depth of 12 cm and then divided into three layers: 0–3, 3–7, 7–12 cm. The behavior of 137Cs and 40K isotopes in soils was analyzed depending on the depth from which the soil samples were collected, as well as on the content
of organic carbon, pH of soil and its granulometric composition. It was established that the density of 137Cs in the litter layer equals 2.17 kBq m−2; it is the highest in layer 0–3 cm where it equals 3.44 kBq m−2, and it decreases with the depth to the value of 0.76 kBq m−2 in layer 7–12 cm. No similar pattern was observed in wasteland soils. The concentrations of 40K in forest and wasteland soils did not change significantly with depth. 相似文献
5.
N fertilizer recommendatons are based on the Nmin content in the useable soil layer. However, for spinach, information from the literature differs for both depth of useable
soil layer and N fertilizer recommendations. The objectives of these experiments were to study the importance of different
soil zones for N supply to spinach and to kohlrabi, and to examine the relationship between N supply in the useable soil layer
and yield of spinach.
Field experiments with both crops showed that about 80% of total root length was in the upper 0–15 cm soil layer and less
than 5% below 30 cm. Spinach roots were present in the 15–30 cm layer only during the last 2 weeks before harvest, whereas
kohlrabi roots penetrated this layer already 4 weeks before harvest. Placement of NO3 below 30 cm depth did not influence root distribution. The top layer contributed about 80% to total N uptake for both crops.
The 15–30 cm soil layer can maximally contribute 40–50 kg N ha-1. It is concluded that N fertilizer recommendations for both crops should be based on the Nmin content of the 0–30 cm soil layer.
Maximum yield of spinach (300 dt f.m. ha-1) was obtained at 150 kg N supply ha-1. The nitrate residue was 50 kg N ha-1 at 0–30 cm in this treatment. It is argued that the nitrate residues at harvest could be decreased by delaying the harvest
for a few days, at slightly suboptimal N supply. 相似文献
6.
Guomo Zhou Shunyao Zhuang Qiufang Xu Hua Qin Minghung Wong Zhihong Cao 《The Botanical review》2011,77(3):296-303
Area of bamboo forest (Phyllostachys praecox) has rapidly increased in southern China during the last 20 years due to its high economic value. Aims of this study were
to analyse the temporal and spatial variations of soil organic matter (SOM) in heavily winter mulched bamboo stands and to
estimate potential for carbon sequestration. Total of 60 soil profiles with 0–15 years of bamboo plantation were sampled from
three towns in Lin’an County. Results showed that with increased plantation years, SOM decreased slightly at the beginning
(1–5 years), and then rose up steadily. Based on the average of the three locations, the highest SOM content of 75.82 g/kg
was the surface layer (0–10 cm) of the 15 years. As plantation year increased, the variation of SOM in the surface layer (0–10 cm)
was represented by a parabolic shape, and in the second layer (10–20 cm), it was a similar mode, but less vigorous. Soil organic
carbon (SOC) storage significantly increased during 5 to 15 years after it reached full production, and the calculated annual
SOC increment in 0–40 cm soil profile was about 6.3 t C/ha/year. Therefore, extended Phyllostachys praecox forests can be considered as one option for countering CO2 emissions and regional climate change. 相似文献
7.
Throughout a 13 year period, the Throughfall Displacement Experiment sustained both increased (+33; wet) and decreased (−33%;
dry) throughfall into an upland oak forest in Tennessee. Organic (O) horizon carbon (C) stocks were measured at several occasions
before, during and after the experiment and mineral soil C stocks before and after the experiment. In the O horizon, higher
C stocks were observed in the dry treatment compared to the ambient and wet, attributable to a combination of enhanced litter
inputs and reduced decomposition. No precipitation treatment effects on mineral soil C stocks were found to a depth of 60 cm.
Conversely, long-term reductions in surface mineral soil C stocks were surprisingly high for all treatments (3.5–2.7% C in
the 0–15 cm layer and from 0.6 to 0.5% in the 15–30 cm layer) over the duration of the experiment. A clear explanation for
this temporal trend in C storage was not readily apparent. 相似文献
8.
The fate of sheep urine sulphate in the soil and its plant uptake was monitored using 35S-labelled sulphate-S in undisturbed pasture microplots in two glasshouse experiments. The extent of macropore flow of simulated
urine immediately following a sheep urination was also investigated at 5 pasture sites in the field.
Immediately following urination to pasture microplots in the glasshouse, the amounts of urinederived 35S recovered in the 0–2.5, 2.5–7.5, 7.5–15 and 15–30 cm soil layers were 38, 28, 18 and 9%, respectively. In the field study
on 5 contrasting soils, a similar pattern was found with 55–70, 20–35 and 13–20% of simulated urine being recovered in the
0–5, 5–10 and 10–15 cm soil layers, respectively. There was insignificant loss below 15 cm. If urine had moved via simple
displacement in these soils the wetting front would have reached only 2.0–2.5 cm in depth suggesting that significant downward
movement of urine via macropore flow occurs after urination.
In a 15-day period following urine application to a pasture soil there was a rapid rate of incorporation of 35S into organic forms, while between 15 and 64 days the rate of incorporation declined. After 7 days, 27% of added 35S had been incorporated into organic forms with 19% being C-bonded S and 8% Hl-reducible S. This rapid incorporation was attributed
to the large and active microbial biomass present in the rhizosphere. Since urine application depressed pasture growth, due
to ‘urine burn’, less than 10% of applied 35S was absorbed by pasture plants over a 64-day period. A second experiment using microplots of contrasting soil types, confirmed
that the majority of the 35S incorporated into the organic form was present as C-bonded S. Results showed that of the 35S remaining in the 0–2.5 cm layer 35 days after application, 20–40% was present as sulphate, 10–20% as Hl-reducible S and
50–60% as C-bonded S. Plant uptake of S accounted for only 7–12% of applied 35S over the 35-day period. 相似文献
9.
Fate of polycyclic aromatic hydrocarbons (PAH) in the rhizosphere and mycorrhizosphere of ryegrass 总被引:5,自引:0,他引:5
Polycyclic aromatic hydrocarbons (PAH) can be degraded in the rhizosphere but may also interact with vegetation by accumulation
in plant tissues or adsorption on root surface. Previous studies have shown that arbuscular mycorrhizal (AM) fungi contribute
to the establishment and maintenance of plants in a PAH contaminated soil. We investigated the fate of PAH in the rhizosphere
and mycorrhizosphere including biodegradation, uptake and adsorption. Experiments were conducted with ryegrass inoculated
or not with Glomus mosseae P2 (BEG 69) and cultivated in pots filled with soil spiked with 5 g kg−1 of anthracene or with 1 g kg−1 of a mixture of 8 PAH in a growth chamber. PAH were extracted from root surfaces, root and shoot tissue and rhizosphere soil
and were analysed by GC-MS. In both experiments, 0.006 – 0.11‰ of the initial extractable PAH concentration were adsorbed
to roots, 0.003 – 0.16‰ were found in root tissue, 0.001‰ in shoot tissue and 36 – 66% were dissipated, suggesting that the
major part of PAH dissipation in rhizosphere soil was due to biodegradation or biotransformation. With mycorrhizal plants,
anthracene and PAH were less adsorbed to roots and shoot tissue concentrations were lower than with non mycorrhizal plants,
which could contribute to explain the beneficial effect of AM fungi on plant survival in PAH contaminated soils.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
Rafael E. Coopman Fernanda P. Fuentes-Neira Verónica F. Briceño Hernán M. Cabrera Luis J. Corcuera León A. Bravo 《Trees - Structure and Function》2010,24(2):247-259
Nothofagus nitida (Phil.) Krasser (Nothofagaceae) regenerates under the shade. Nonetheless, older seedlings are commonly found at full sun.
We tested the hypothesis that light capture and photochemical and non-photochemical energy dissipation of both photosystems
PSI and PSII adjust with ontogeny and brighter environment. Light energy partitioning in both photosystems was studied in
seedlings of different developmental stages (small 9.7 cm, tall 36 cm) under contrasting light environments (8–200 and 1,800–2,043 μmol
photons m−2 s−1) in the Chilean evergreen temperate forest. Higher A
max, dark respiration, and light compensation and saturation points in sun seedlings of both developmental stages were accompanied
by higher rates of electron transport. These seedlings also showed a high fraction of open PSII reaction centres and similar
non-photochemical quenching at high-light in both photosystems, showing no effect of developmental stage in these parameters.
Conversely, light capture, total thermal dissipation after photoinhibition, active down-regulation of antenna efficiency,
and state transitions were higher in smaller seedlings than in taller ones. These changes maintain photostasis, preventing
photodamage, while favouring a more oxidized quinone pool. There is an independent effect of seedling development and light
acclimation on this transition from shade to sun during early ontogeny. This transition reflects short-term responses of the
photosynthetic apparatus to light and longer term responses that depend on seedling developmental stage. 相似文献
11.
Elevated Atmospheric CO2 Alters Soil Microbial Communities Associated with Trembling Aspen (Populus tremuloides) Roots 总被引:4,自引:0,他引:4
Global atmospheric CO2 levels are expected to double within the next 50 years. To assess the effects of increased atmospheric CO2 on soil ecosystems, cloned trembling aspen (Populus tremuloides) seedlings were grown individually in 1 m3 open bottom root boxes under either elevated (720 ppm, ELEV) or ambient CO2 (360 ppm, AMB). After 5 years, soil cores (40 cm depth) were collected from the root boxes and divided into 0–20 cm and 20–40
cm fractions. ELEV treatment resulted in significant decreases in both soil nitrate and total soil nitrogen in both the 0–20
cm and 20–40 cm soil fractions, with a 47% decrease in soil nitrate and a 50% decrease in total soil nitrogen occurring in
the 0–20 cm fraction. ELEV treatment did not result in a significant change in the amount of soil microbial biomass. However,
analysis of indicator phospholipid fatty acids (PLFA) indicated that ELEV treatment did result in significant increases in
PLFA indicators for fungi and Gram-negative bacteria in the 0–20 cm fraction. Terminal restriction fragment length polymorphism
(T-RFLP) analysis was used to analyze the composition of the soil bacterial communities (using primers targeting the 16SrRNA
gene) and the soil fungal communities (using primers targeting the intergenic transcribed spacer region). T-RFLP analysis
revealed shifts in both bacterial and fungal community structure, as well as increases in both bacterial and fungal species
richness with ELEV treatment. These results indicated that increased atmospheric CO2 had significant effects on both soil nutrient availability and the community composition of soil microbes associated with
aspen roots. 相似文献
12.
Shifting sources of soil labile organic carbon after termination of plant carbon inputs in a subtropical moist forest of southwest China 总被引:1,自引:0,他引:1
Labile organic carbon (LOC) is a critical component of soil organic carbon (C) because of its intimate association with soil
heterotrophic respiration and role in the decomposition of resistant soil organic matter. In a subtropical moist evergreen
broad-leaved forest of southwest China, we examined changes of LOC and its potential turnover time, microbial biomass C (MBC),
and soil microbial activity of the organic and the 0–10 cm mineral soil layers with aboveground plant litter and belowground
root treatments. In February of 2004, removal of organic layer, root-trenching, and tree-girdling treatments were applied
alone and in combination to manipulate plant-C inputs. In 2006, root-trenching and tree-girdling treatments did not significantly
change LOC in the organic layer. In the 0–10 cm mineral soil layer, LOC increased substantially due to tree-girdling treatment,
especially in the plots of tree-girdling and the combinations of three treatments, but this increase was absent in 2007. Soil
MBC in these two layers generally did not change markedly after plant-C inputs manipulations except significant increase under
tree-girdling treatment in 2006. The potential turnover times of LOC increased in all plots with the plant-C inputs manipulations.
The lack of influence of plant-C inputs manipulations on LOC pools is likely due to high total soil organic C here, while
insignificant changes of MBC suggest the soil microbes are not C limited in this forest. The changes of the potential turnover
time of LOC imply that the sources of LOC have been shifted from fresh plant litter or root exudates to old soil organic C.
Our results suggest that LOC recently derived from plants is preferred by microbes when available, but microbes can also use
LOC from soil organic matter when fresh plant C is not available. 相似文献
13.
Changes in soil carbon flux and carbon stock over a rotation of poplar plantations in northwest China 总被引:2,自引:0,他引:2
Forest soil is a major component of terrestrial ecosystems for carbon sequestration and plays an important role in the global
carbon cycle. Soil carbon flux and soil carbon pools were investigated in a poplar plantation chronosequence over a rotation
in northwest China. Based on continuous field observation in 2007, the results showed that mean soil CO2 efflux rate was 5.54, 4.81, and 3.93 μmol CO2 m−2 s−1 for stands of 2-, 8-, and 15-year-old, respectively, during the growing season. Significant differences in soil respiration
of three age classes were mainly because soil temperature, carbon allocation, and fine root growth changed greatly with stand
age. Multiple regression analysis suggested that soil temperature and fine root biomass in the upper layer could explain 78–85%
of the variation in soil respiration. Mineral soil C stock at 0–40 cm depth was 55.77, 55.09, and 58.14 t ha−1 in the 2-, 8-, and 15-year-old stands, respectively. The average rate of soil C sequestration was 0.13 t ha−1 year−1 following afforestation on former crop lands. Although the plantations had similar management practices and soil types since
their establishment, many biotic and abiotic factors such as root biomass and turnover rate, soil condition of the plantations
had undergone marked changes at different development stages, which could result in the remarkable differences in soil carbon
flux and storage over a rotation. Our results highlight the importance of the development stage within a rotation of poplar
plantation in assessment of soil carbon budget. 相似文献
14.
Summary The effect of cropping systems of wheat-maize (WM), wheat-rice (WR), wheat-groundnut (WG), gram-bajra (GrB), potato-guara
(PGu), and raya-mash (RaMa) in combination with treatments of dummy (uncultivated area) and applied Zn 0.0 (Zn0), 2.8 (Zn1), 5.6 (Zn2) 11.2 (Zn3) kg/ha was studied on the transformation of labile Zn fractions: exchangeable (Exch.), adsorbed (TAd) [weakly (WAd), moderately
(MAd), strongly (SAd)], and organic matter (OM) in different layers of sandy loam soil. The added Zn stayed largely in the
0–30 cm layer and was associated with the WAd- and OM-Zn fractions. About 70% of the total labile Zn (PAv) remained in the
WAd- and OM-Zn, that is, 33 and 39% in 0–15 cm layer, and 33–39% and 31–36% in 16–150 cm layer. All the Zn fractions in 0–15
cm layer, and only of WAd in 16–30 cm layer, significantly increased with rates of Zn addition. These were also significantly
higher in Zn1–3 than Zn0 and dummy treatments because of the residual Zn.
Diverse effects of cropping systems on soil properties, residual Zn, and labile Zn fractions were found. The influence was
strong in 0–15 cm layer decreasing gradually with soil depth due largely to differences in Zn requirement, crop intake of
various Zn fractions and the cultural practices of the systems. All the crops and rotations appreciabilly responded to Zn
application. Uptake of Zn by crops markedly and successively increased with increasing rates of Zn application. The WR caused
a significant increase in soil organic matter whereas WR and WM in CaCO3. The WR, WM and GrB resulted in a decrease in pH while WG and GrB in CaCO3. The RaMa and PGu maintained much higher residual Zn than other systems. The systems which caused the maximum decrease in
Zn fractions were: cereal-cereal (WM) in Exch. legume-millet (GrB) in all the adsorbed, PAv and the Zn associated with CaCO3, vegetable-legume (PGu) also in MAd and SAd; and cereal-legume (WG) in OM and PAv. Hence GrB, WG and WM in that order will
cause the deficiency of Zn much earlier than the other systems due to greater use and or transformation of WAd- andOM-Zn.
Such effects were least under RaMa because it increased the WAd-, MAd- and OM-Zn. 相似文献
15.
With the widespread introduction and invasion of exotic plants there is a need for studies that quantify alterations of basic
ecosystem structure and function. Ecosystem invasion by Melaleuca quinquenervia significantly altered both above- and belowground ecosystem components in this study. We measured the quantity and nutrient
concentration of the litterfall, litter layer, and soil; microbial biomass pools; and rates of potentially mineralizable nitrogen
and soil oxygen demand. Annual litterfall was 4.9 times higher in the non-invaded sites and contained 1.9 times more phosphorus
than invaded sites. Non-invaded plots contained a larger litter layer compared to invaded plots: 2.4 ± 1.2 kg m−2 and 0.62 ± 0.3 kg m−2
, respectively. Lower nutrient concentration and quantity of the litter layer in the invaded plots led to changes in the aboveground
storage of nutrients. In the invaded plots there was four times less carbon, seven times less nitrogen, and ten times less
phosphorus stored in the organic litter layer compared to the non-invaded plots. Microbial biomass nutrient pools were consistently
lower at both the 0–5 cm and 5–15 cm depth in the invaded soils compared to non-invaded soils, indicating a plant mediated
change. Although M. quinquenervia altered microbial community structure, microbial activities were not different between invaded and non-invaded plots at either
depth as measured by rates of soil oxygen demand and potentially mineralizable nitrogen. These changes may affect both native
plant growth and water quality, and may act to promote and maintain site dominance by M. quinquenervia. 相似文献
16.
Inland Antarctic terrestrial ecosystems and biodiversity are poorly understood in comparison with Antarctic coastal regions.
Microorganisms, as primary colonists, are integral to Antarctic soil ecosystem development, essential for pedogenesis and
structuring the soil, and providing the nutrients necessary for the subsequent establishment of macroorganisms. This study
analysed the microbial communities present in polygon soils of Coal Nunatak (Alexander Island, at the southern limit of the
maritime Antarctic). Soils were analysed across three polygons (centre and margins) and at three depths (0–1, 1–2, 2–5 cm).
Cyanobacterial communities were characterised using two complementary molecular biological approaches, temperature gradient
gel electrophoresis and clone library analysis. The three polygons exhibited conspicuous differences in community composition,
both between different polygons and spatially (horizontally and vertically) within a single polygon. Comparison of our data
with that from previous studies using classical culture and morphological identification techniques clearly shows the need
for more intensive research on patterns of microbial diversity in terrestrial habitats throughout the Antarctic. The majority
of the 17 cyanobacterial genera identified at Coal Nunatak are thought to have ubiquitous distributions, while none are known
only from the Antarctic. Three of the genera present are also known to be capable of being lichen photobionts. 相似文献
17.
Symptoms of fairy rings caused by Lepista sordida have been reported on Zoysiagrass (Zoysia spp.) turf maintained at fairway height (2 cm), but not on bentgrass (Agrostis spp.) maintained at putting green height (0.5 cm). The mycelia of this fungus inhabit primarily the upper 0–2 cm layer of
the soil extending into the thatch. To compare conditions for the mycelial growth in Z. matrella turf to those in A. palustris turf, we examined the effects of nutrients, temperature, water potential, and pH in the field as well as in the laboratory.
Greater growth of the mycelia was observed in medium that included hot water extracts from soil of the 0–1 cm zone in Z. matrella turf compared to that from A. palustris. The upper soil layer in Z. matrella turf contained more organic matter from clippings than that in A. palustris. The temperature and water potential of the 0–2 cm soil zone in Z. matrella turf were also more favorable for the mycelial growth. The soil pH values of this zone in Z. matrella turf were less favorable compared to A. palustris but within the range for accelerating mycelial growth.
Part of this study was presented orally at the 46th meeting of the Mycological Society of Japan in 2002 相似文献
18.
The effect of chemical additives (acetosyringone, AS; L-cysteine, CYS; dithiothreitol, DTT; glutathione, GSH; cellulase, CEL;
pectinase, PEC) and light regimes (16/8 light/dark photoperiod, 16L/8D; continuous light, 24L; continuous dark, 24D) applied
during cocultivation procedure of pea explants with Agrobacterium tumefaciens on transformation efficiency was studied. A hypervirulent strain of A. tumefaciens EHA 105 with two plasmids, namely pGT89 and pBIN19, both carrying reporter gus-int gene, and bar or nptII selectable marker gene, respectively, was used for genetic transformation of cotyledonary node explants of three dry seed
pea cultivars Adept, Komet and Menhir. The focus was laid on cocultivation step (48 h) of transformation protocol. After chemical
or physical treatments, transient GUS expression was recorded 20 days after cocultivation as a measure of successful transformation,
using a four category scale (0 – without GUS expression, 1 – weak, 2 – medium and 3 – strong GUS expression) for calculation
of IGE (Intensity of GUS Expression). Of the tested chemical cocultivation additives, 100 μM AS and 50 mg CYS significantly
improved GUS expression (IGE value), while DTT, GSH and both macerating enzymes (CEL, PEC used either separately or in combination)
either had no positive effect or were even negative. There were no statistically significant differences between the light
regimes tested. Nevertheless, cocultivation in 24L, without chemical additives, reproducibly resulted in the highest frequency
of explants scored in category 3 of GUS expression (followed by 24D and 16L/8D treatment). However, application of 100 μM
AS reverted this trend. Cv. Adept yielded higher transformation frequencies than cvs. Menhir and Komet. Plasmid pGT89 produced
a higher IGE value than pBIN19. Based on our results, the improved cocultivation step for pea consists of 48 h cocultivation
at 20 ± 2°C, with 50 mg l−1 CYS and 100 μM AS, 16L/8D photoperiod (or without AS in continuous light). 相似文献
19.
The growth of forest species in soil development chronosequences becomes increasingly phosphorus (P)-limited with time, as
P is weathered, eroded and leached from soil. Foliar nitrogen (N) concentrations also tend to decrease with soil age when
vegetation may be limited in both N and P. Here we report on soil development in temperate rain forests along three New Zealand
chronosequences that have minimal pollution and disturbance from human activities, at Franz Josef, Waitutu and Central Volcanic
Plateau, and on factors influencing soil net N mineralization (aerobic; 56 days) and foliar N and P concentrations. Except
in very young soils (<500 years), at least 85% of total-P in mineral soil (0–10 cm) was transformed to organic-P. In each
chronosequence, total-P declined with time, and foliar N:P ratios (mass) generally increased from 8 to 15–18, suggesting P
was more limiting than N in the oldest soils of the chronosequence. There was a negative relationship between net N mineralization
and C:N ratio for mineral soil. For the FH (organic) layer, net N mineralization had the strongest relationships with total-N
concentration (positively) and C:organic-P ratio (negatively); however, relationships varied with forest group, suggesting
that other factors were also important. Foliar P of kamahi (Weinmannia racemosa Linn. f.), a dominant canopy species, was related to soil organic-P, suggesting mineralization was an important process for
tree nutrition.Foliar N was positively related to N concentration in the FH layer, but was not significantly related to any
measured property in mineral soil, possibly because of the wide range of soils. The consistent declines in both soil and foliar
P across the contrasting chronosequences strongly suggest that vegetation becomes progressively P-limited during long-term
ecosystem development. 相似文献
20.
Krzysztof J. Rakowski 《Trees - Structure and Function》1997,11(4):248-253
Eastern white pine (Pinus strobus L.) seedlings were pretreated with 12 h photoperiod to induce dormancy. Dormant plants were fumigated with 0.5 ppb (0.4 μg
m–3) or 2.0 ppb (1.6 μg m–3) hydrogen fluoride (HF) for 2 – 28 days. Plasma membranes were isolated from needles of treated and control seedlings to
determine their chemical composition and ATPase activity. For all analyses, only those plants which did not show needle necrosis
were selected. The amount of plasma membrane phospholipid expressed on a plasma membrane protein basis was higher after 2
days in the 0.5 ppb HF treatment as compared to controls. After 2 days of 2.0 ppb HF treatment as well as after 8 and 28 days
of both HF treatments phospholipid to protein ratios in fluoride treated seedlings were lower as compared to control levels.
A decrease in sterol levels could be observed after 2 days in both HF treatments. A large increase in the ratio of sterols
to proteins was observed in plasma membranes of eastern white pine seedlings treated with 0.5 ppb HF for 28 days. Increased
sterol to phospholipid ratios were observed after 8 and 28 days in 0.5 ppb and after 2 and 8 days of 2.0 ppb HF treatment.
A decrease in ATPase activity was observed after 8 days with both fluoride treatments. Drastic increase of ATPase activity
was observed after 28 days of HF treated plants. Observed changes of sterol and phospholipid levels after only 2 days of fumigation
suggest early fluoride effects on plasma membrane composition during plant dormancy.
Received: 25 October 1995 / Accepted: 24 May 1996 相似文献