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1.
Isa A. M. Yunusa Sue E. Thomson Keith P. Pollock Lu Youwei Donald J. Mead 《Plant and Soil》2005,275(1-2):195-206
In order to understand how radiata pines respond to declining supply of soil-water in agroforestry systems, we monitored water
potential in xylem (ψ
x
), osmotic potential (ψ) and relative water content (q) for fascicles at pre-dawn and at mid-day for 3-year-old trees that were raised from either seedlings (Seedling) or from
tissue culture (TC3 and TC4), and grown either alone (Control) or over lucerne (Medicago sativa) pasture (Lucerne). Water relations at dawn were mostly similar for all the pines, except late in the season when ψ was lower,
bulk turgor pressure (P), deduced as the difference between ψ
x
and ψ, was higher, for TC3 than for the other two pines. At mid-day, Seedling often had higher ψ
x
and ψ, but because of its poor osmotic adjustment (OA) had lower P, than either TC3 or TC4. The cell walls were more elastic in Seedling with modulus of elasticity (e) of 6.5 MPa compared with 8.1 MPa for both TC3 and TC4, while loss of turgor was estimated to occur at ψ
x
of −1.45 MPa for Seedling, −1.38 MPa for TC3 and −1.35 MPa for TC4. All trees irrespective of their origin had higher ψ
x
, P, CO2 assimilation (A), and stomatal conductance (g
s
), but lower ψ, in Control than in Lucerne in which the soil profile was consistently drier. The trends in ψ
x
, ψ, q and A did not reflect the known differences in dry weight of trees, P was in the order TC3 > TC4 > Seedling, consistent with previously reported tree weights. Both TC3 and TC4 had higher P, due to their larger OA, than Seedling, although the latter had higher A. Thus ψ
x
and A that are routinely measured may not always adequately explain differences in growth amongst pines; it is advisable that ψ
be determined to allow deductions of P be made when using water relations to analyse plant growth. 相似文献
2.
Seasonal leaf water relations characteristics were studied in fully irrigated spring barley (Hordeum distichum L. cv. Gunnar) fertilized at low (50 kg K ha−1) or high (200 kg K ha−1) levels of potassium applied as KCl. The investigation was undertaken from about 14 days before anthesis until the milk ripe
stage in leaves of different position and age. Additionally, the effects of severe water stress on leaf water relations were
studied in the middle of the grain filling period in spring barley (cv. Alis). The leaf water relations characteristics were
determined by the pressure volume (PV) technique.
Water relations of fully irrigated plants were compared in leaf No 7 with the water relations of slowly droughted plants (cv.
Alis). Leaf osmotic potential at full turgor (ψ
π
100
) decreased 0.1 to 0.3 MPa in droughted leaves indicating a limited osmotic adjustment due to solute accumulation. The leaf
osmotic potential at zero turgor (ψ
π
0
) was about −2.2 MPa in fully irrigated plants and −2.6 MPa in droughted plants. The relative water content at zero turgor
(R0) decreased 0.1 unit in severely droughted leaves. The ratio of turgid leaf weight to dry weight (TW/DW) tended to be increased
by drought. The tissue modulus of elasticity (ε) decreased in droughted plants and together with osmotic adjustment mediated
turgor maintenance during drought. A similar response to drought was found in low and high K plants except that the R0 and ε values tended to be higher in the high K plants. Conclusively, during drought limited osmotic adjustment and increase
in elasticity of the leaf tissue mediated turgor maintenance. These effects were only slightly modified by high potassium
application.
The seasonal analysis in fully irrigated plants (cv. Gunnar) showed that within about 14 days from leaf emergence ψ
π
100
decreased from about −0.9 to −1.6 MPa in leaf No 7 (counting the first leaf to emerge as number one) and from about −1.1
to −1.9 MPa in leaf No 8 (the flag leaf) due to solute accumulation. A similar decrease took place in ψ
π
0
except that the level of ψ
π
0
was displaced to a lower level of about 0.2 to 0.3 MPa. Both ψ
π
100
and ψ
π
0
tended to be 0.05 to 0.10 MPa lower in high K than in low K plants. R0 was about 0.8 to 0.9 and was independent of leaf position and age, but tended to be highest in high K plants. The TW/DW ratio
decreased from about 5.5 in leaf No 6 to 4.5 in leaf No 7 and 3.8 in leaf No 8. The TW/DW ratio was 4 to 10% higher in high
K than in low K plants indicating larger leaf cell size in the former. The apoplastic water content (Va) at full turgor constituted about 15% in leaf No 7. ε was maximum at full turgor and varied from about 11 to 34 MPa. ε tended
to be higher in high K plants. Conclusively, in fully watered plants an ontogenetically determined accumulation of solutes
(probably organic as discussed) occurred in the leaves independent of K application. The main effect of high K application
on water relations was an increase in leaf water content and a slight decrease in leaf ψπ.
The effect of K status on growth and drought resistance is discussed. 相似文献
3.
We have investigated nucleotide polymorphism at theβ-esterase gene cluster including theEst-6 gene andψEst-6 putative pseudogene in four samples ofDrosophila melanogaster derived from natural populations of southern Africa (Zimbabwe), Europe (Spain), North America (USA: California), and South
America (Venezuela). A complex haplotype structure is revealed in bothEst-6 andψEst-6. Total nucleotide diversity is twice inψEst-6 as inEst-6; diversity is higher in the African sample than in the non-African ones. Strong linkage disequilibrium occurs within theβ-esterase gene cluster in non-African samples, but not in the African one. Intragenic gene conversion events are detected withinEst-6 and, to a much greater extent, withinyEst-6; intergenic gene conversion events are rare. Tests of neutrality with recombination are significant for theβ-esterase gene cluster in the non-African samples but not significant in the African one. We suggest that the demographic history (bottleneck
and admixture of genetically differentiated populations) is the major factor shaping the pattern of nucleotide polymorphism
in theb-esterase gene cluster. However there are some ’footprints’ of directional and balancing selection shaping specific distribution of
nucleotide polymorphism within the cluster. Intergenic epistatic selection betweenEst-6 andψEst-6 may play an important role in the evolution of theβ-esterase gene cluster preserving the putative pseudogene from degenerative destruction and reflecting possible functional interaction
between the functional gene and the putative pseudogene.Est-6 andyEst-6 may represent an indivisible intergenic complex (‘intergene’) in which each single component (Est-6 orψEst-6) cannot separately carry out the full functional role. 相似文献
4.
A simple model was developed to characterize the daily water potential dynamics (Ψx of sun and shade leaves of three forest tree species (Quercus cerris, Acer campestre andCarpinus betulus) under anticyclonic weather types. Input data used for this-model were the vapour pressure deficit (d) and the soil moisture content (w.). The model is usable for the calculation of the actual Ψx-values with a probable error 0.18 –0.28 MPa and limits the maximum and minimum Ψx-values which may occur with the particular tree species. The model makes it possible to establish for each species the regime, determined byd andw, at which the water potential of the leaves reacts most sensitively to the changes of the environmental parameters. 相似文献
5.
Ambient temperature and water availability regulate seasonal timing of germination. In fire-prone landscapes, the role of
fire-related cues in affecting the range of temperatures and water potentials (ψs) across which germination can occur is poorly
known, especially in non-Mediterranean landscapes. We examined interactive effects of temperature (15 or 25°C), ψ (0 to −0.9 MPa),
and fire-related cues (heat and smoke) on germination for seeds of three shrub species from fire-prone southeastern Australia.
Incubation temperature affected germination of untreated seeds of Kunzea
ambigua and Kunzea capitata (Myrtaceae) (reduction at 25°C), but germination was uniformly low in Epacris obtusifolia (Ericaceae). Decreasing ψ reduced germination across both incubation temperatures. Fire cues increased germination at both
incubation temperatures and across ψs, although in Kunzea the increase was smaller and occurred over a narrower range of ψs at 25°C. Hydrotime analysis suggested that fire cues reduced
the amount of water necessary for germination of Kunzea seeds. Post-fire germination of the three study species may occur during the warm season, although it is reduced and confined
to wet periods for the two Kunzea species. Warm season germination of the study species is consistent with a trade-off between the increased risk of failure
of a cohort of seedlings, and benefits of early establishment of a cohort that may survive in an environment with aseasonal
rainfall. 相似文献
6.
Experiments were carried out to investigate the effects of different degrees of water stress on cowpea in the presence and
absence of Bradyrhizobium spp. inoculation and to evaluate physiological responses to stress. The soil used was Yellow Latosol, pH 6.3 and the crop
used was cowpea (Vigna unguiculata (L.) Walp.) cv. ‘IPA 204’. Stress was applied continuously by the control of matric potential (ψ
m
) through a porous cup. The lowered soil ψ
m
had a direct effect on the N2 fixation, but the strains Bradyrhizobium introduced by inoculation in the cowpea plants were superior to the indigenous strain demonstrating the importance of inoculation
in the stressed plants. At the more negative ψ
m
plants inoculated with the strains EI 6 formed associations of greater symbiotic efficiency which helped the cowpea plants
to withstand drought stress better than the strain BR 2001 and the uninoculated control. The leghaemoglobin concentration
was not inhibited in the drought-stressed plants at ψ
m
-70 kPa when inoculated with the strain EI 6, which confered a differential degree of drought resistance in plants. The ψ
w
declined in the stressed plants reaching values of -1.0 MPa which was sufficient to cause disturbance in nodulation and biomass
production.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
7.
Water potential (ψw) and water saturation deficit (WSD), and several reflectance (R) indexes were assessed in an aerophytic lichen Umbilicaria hirsuta (Sw. ex Westr.) Hoffm. The water index (WI, R900/R970) and normalized difference vegetation index, NDVI [(R900-R680)/(R900+R680)] were strongly correlated both with the ψw and the WSD of lichen thalli. No significant changes during desiccation were found in structural independent pigment index,
SIPI [(R800-R445)/(R800-R680)]. Sensitivity of the spectral detection of water status was rather small at high hydration level (WSD < 25 %, or ψw > −1 MPa), but this is not much limiting its value and potential use, because physiological processes in lichens are usually
inhibited at much lower values of ψw than in leaves of vascular plants. 相似文献
8.
Steven C. Grossnickle 《Trees - Structure and Function》1993,7(3):148-155
Summary Shoot water relations, summer gas exchange response and morphological development of western hemlock [Tsuga heterophylla (Raf.) Sarg.] and western red cedar (Thuja plicata Donn) seedlings were monitored over the first growing season on a coastal reforestation site in British Columbia. In March, osmotic potential (s) at saturation [s(sat)] was –1.98 MPa and turgor loss point [s(tlp)] –2.38 MPa for western hemlock, while western red cedar had –1.45 MPa s(sat) and –1.93 MPa s(tlp). Seasonally s increased through June and then decreased through September, with western hemlock –0.15 to –0.50 MPa lower than western red cedar. Maximum bulk modulus of elasticity (max) for western hemlock was 29.3 MPa in March, decreased to 15.0 MPa in June and increased to 25.0 MPa from July through September, while western red cedar max was 10.6 MPa in March and around 8.0 MPa thereafter. Utilized turgor (T
util) for western hemlock was <40% from March through May, 69 to 78% from June through August and 96% in September, while western red cedar T
util was 68 to 73% during March and April, 84 to 96% from May through August and 100% in September. Maximum CO2 assimilation rate (A) of western red cedar was more than double western hemlock, and for both species A declined in a linear fashion with increasing vapour pressure deficit (D). Maximum foliage conductance (g
wv) declined in a concave manner as D increased in both species, with western red cedar values 50 to 67% greater than western hemlock. Maximum daily g
wv declined in a concave manner as predawn shoot water potential (pd) decreased, with maximum daily g
wv 1.8 to 3.6 times greater in western red cedar than western hemlock, when pd was –0.25 and –1.4 MPa, respectively. Western red cedar, compared to western hemlock, had a greater increase in A as g
wv increased. Eight months after planting, western red cedar seedlings had twice the root growth, measured as root dry weight and root number, of western hemlock. 相似文献
9.
Ken C. Hodgkinson 《Oecologia》1992,90(4):467-473
Summary Plant water relations and shoot growth rate of shrubs resprouting after fire or unburnt were measured in a semi-arid poplar box (Eucalyptus populnea) shrub woodland of eastern Australia. In vegetation unburnt for about 60 years, the dawn xylem water potential (x) of the dominant shrub species was about-1.0 MPa when the soil was wet and-8.0 MPa when the soil was very dry. At any one time, the dominant shrub species,Eremophila mitchellii, E. sturtii, Geijera parviflora andCassia nemophila, were similar in x butAcacia aneura andDodonaea viscosa were consistently higher in x than this group when the soil was moist and lower when the soil was dry. The dominant tree species,Eucalyptus populnea andE. intertexta, appeared to have access to additional water beneath the hardpan which is located 60–80 cm below the surface. When shrubs were under extreme water stress (x of-8 MPa), the trees had a x of-3 to-3.6 MPa. Following a fire, both x and leaf stomatal conductance (g
s) of resprouting shrubs were higher for about 5 years than comparable-aged unburnt vegetation, with relative differences in x increasing with drought stress. Elongation rate of resprouts was positively linked to prefire shrub height in 3 of 4 species. However, shrubs resprouting after high intensity fires had substantially higher rates of shoot elongation than after low intensity fires which were in turn higher than for foliar expansion of unburnt shrubs. It is concluded that the growth rate of resprouting shrubs is primarily determined by physiological/ morphological factors associated with plant size but is also assisted by greater availability of water and possibly nutrients for a period after fire. 相似文献
10.
Dehydration-induced alterations in growth and osmotic potential of callus from six tepary bean lines varying in drought resistance 总被引:1,自引:0,他引:1
Growth and osmotic potential of calli induced from leaf- and root-derived tissues of six tepary bean lines (Phaseolus acutifolius) varying in drought resistance were assessed in vitro after polyethylene glycol-induced (10%, PEG-10,000) dehydration. Calli of resistant teparies were characterized by low initial osmotic potential (ψs) and relative growth rate (RGR) on medium lacking PEG (−0.30 MPa). However, calli of both resistant and sensitive lines were similar in dry matter percent (DM). Presence of PEG in the medium (−0.58 MPa) elevated DM in all teparies except one resistant line. Both leaf- and root-derived calli of sensitive teparies exhibited osmotic adjustment (OA) but reduced RGR that remained after rehydration in one line. We concluded that preexisting force of low cellular ψs rather than induced OA plays an important role in buffering adverse effects of dehydration and conditioning drought resistance of tepary beans. This information may aid Phaseolus breeders in screening for drought resistance among large number of accessions. 相似文献
11.
Blaikie FH Brown SE Samuelsson LM Brand MD Smith RA Murphy MP 《Bioscience reports》2006,26(3):231-243
The protonmotive force (Δp) across the mitochondrial inner membrane drives ATP synthesis. In addition, the energy stored in Δp can be dissipated by proton leak through the inner membrane, contributing to basal metabolic rate and thermogenesis. Increasing mitochondrial proton leak pharmacologically should decrease the efficiency of oxidative phosphorylation and counteract obesity by enabling fatty acids to be oxidised with decreased ATP production. While protonophores such as 2,4-dinitrophenol (DNP) increase mitochondrial proton leak and have been used to treat obesity, a slight increase in DNP concentration above the therapeutically effective dose disrupts mitochondrial function and leads to toxicity. Therefore we set out to develop a less toxic protonophore that would increase proton leak significantly at high Δp but not at low Δp. Our design concept for a potential self-limiting protonophore was to couple the DNP moiety to the lipophilic triphenylphosphonium (TPP) cation and this was achieved by the preparation of 3-(3,5-dinitro-4-hydroxyphenyl)propyltriphenylphosphonium methanesulfonate (MitoDNP). TPP cations accumulate within mitochondria driven by the membrane potential (Δψ), the predominant component of Δp. Our hypothesis was that MitoDNP would accumulate in mitochondria at high Δψ where it would act as a protonophore, but that at lower Δψ the accumulation and uncoupling would be far less. We found that MitoDNP was extensively taken into mitochondria driven by Δψ. However MitoDNP did not uncouple mitochondria as judged by its inability to either increase respiration rate or decrease Δψ. Therefore MitoDNP did not act as a protonophore, probably because the efflux of deprotonated MitoDNP was inhibited. 相似文献
12.
Retroprocessed pseudogenes, calmodulin II (ψ1, ψ2, and ψ3 CALMII), ψα-tubulin, π-glutathione S-transferase (ψπ-GST) from rat, lactic acid dehydrogenase (ψ LDH) from mouse, and heat shock protein 60 chaperonin (ψ HSP60)
from Chinese hamster, were examined for their presence in these species by polymerase chain reaction (PCR). Pseudogenes of
these murine rodents were detected by PCR only in those species in which the genes were originally identified, suggesting
that the selected pseudogene of one species arose too recently to be detected in the genomes of the other rodent species.
The calculated ages of the rodent pseudogenes ranged from 1.7 Myr (ψα-tubulin) to 7.5 Myr (ψ3 CALMII) when employing a homologous functional gene of the taxon as a reference in the relative rate test with the mouse
or rat as the outgroup. Given the high rate of divergence of the genes of rodents relative to other species, selection of
an outgroup with similar mutation rates seems warranted. To justify further the conclusion that the selected pseudogenes were
indeed retroprocessed after these three taxa diverged, the presence of the pseudogenes in the genome of different rat species
was examined. The existence of ψ3 CALMII and ψα-tubulin pseudogenes of Rattus norvegicus among species belonging to Rattus sensu stricto is evidence for the common ancestry of this group.
Received: 23 May 2001 / Accepted: 31 May 2001 相似文献
13.
Functional lox-like sequences have been identified within the yeast and mammalian genome. These hetero-specific lox sites also allow Cre recombinase to specifically target efficient integration of exogenous DNA into the endogenous pseudo-lox (ψlox) sequences that occur naturally in the host genome using a Cre/loxP integrative recombination system. We investigated whether the Cre/ψlox system is useful for site-specific integration of transgenes and for improving the production efficiency of transgenic animals.
This is the first report on Cre-mediated integrative recombination targeting an endogenous lox-like sequence termed pseudo-loxm5 (ψloxm5) in early mouse embryos. We characterized the Cre/ψloxm5 system in embryonic environment. Cre-expressing plasmid and a transgene (CMV/LacZ gene) flanked by ψloxm5 and ψloxcorem5 sites were co-microinjected into the pronucleus of fertilized mouse oocytes. The injected eggs were transferred into foster
mothers, and the recombination products were investigated. The results show that the ψloxm5 site is an active substrate for Cre-mediated recombination in the mouse embryonic environment. The transgenesis efficiency
was up to 27% (6/22). The site-specific integration of the transgene into the endogenous ψloxm5 site was found in 50 % of the transgenic pups. Our findings demonstrated that the Cre/ψloxm5 integrative recombination system is an efficient and simple strategy for targeting an endogenous lox-like site in mammalian embryos. 相似文献
14.
Water status and gas exchange of beech (Fagus sylvatica L.) and sessile oak [Quercus petraea (Mattuschka) Liebl.] were studied in a mixed stand in the Montejo de la Sierra forest (central Iberian Peninsula), one of
the southernmost locations of both species in Europe. Gas exchange and water potential were measured in leaves at different
canopy levels over several days in two growing seasons. The daily variation pattern was established with the measurements
of three selected dates per year, representative of the soil moisture content situations in early, mid- and late summer. A
similar daily time course of leaf water potential was found for the two species. Nevertheless, beech showed a most noticeable
decrease of water potential at midmorning and maintained lower leaf water potential than oak in the early afternoon. In 1994
the sessile oak saplings showed higher values of predawn water potential (Ψpd) than beech at the end of summer, when soil moisture content was lowest (20 cm depth). Beech showed a significantly lower
net assimilation rate (A) than sessile oak for leaves under the same PPFD. Maximum net photosynthesis values (A
max) for beech and sessile oak on sunny leaves were 10.1±0.4 μmol m–2 s–1 and 17.8±1.7 μmol m–2 s–1 respectively, and those for water vapour stomatal conductance (g
wv) were 265±31 mmol m–2 s–1 and 438±74 mmol m–2 s–1. Differences in A and g
wv between the two species were maintained throughout the day on all measurement dates. No clear relationship was found between
water status of saplings and stomata performance; there was only a negative correlation between Ψpd and g
wvmid in beech. Nevertheless, a significant response to the air vapour pressure gradient between leaf and air was translated into
stomata closure on an hourly basis, more intensively in beech.
Received: 4 March 1999 / Accepted: 21 December 1999 相似文献
15.
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
16.
The technique of isopiestic thermocouple psychrometry was used for the analysis of bud transition from dormancy to growth
and back in 8-18-day-old pea (Pisum sativum L.) seedlings. We monitored changes in the water (ψw) and osmotic (ψs + m) potentials and also turgor pressure (ψp) in dormant buds and threshold turgor (Y) in growing buds, the latter being one of the cell-wall rheological characteristics. Seedling decapitation resulted in a
decrease of Y in the bud, which coincided with the start of its outgrowth. The replacement of terminal shoot with exogenous auxin (IAA
or NAA) retarded bud outgrowth and maintained the high level of Y, which argues for the auxin control of this parameter. When growth of the first axillary bud was inhibited by the second
one, positioned higher and remained on the plant, the beginning of Y increase preceded visible correlative growth suppression; this makes this rheological index an early marker of bud transition
from growth to dormancy. The effects of the terminal shoot part and auxin application on the bud osmotic status differed substantially.
In fact, bud transition to dormancy in the presence of the terminal shoot, the main or developing from the second axillary
bud, was accompanied by the rise in ψs + m, whereas, in the case of the replacement of the second bud with exogenous auxin, the first bud growth suppression occurred
with the decrease in ψs + m. The low value of the bud ψs + m is a factor for creating a considerable gradient of the water potential between the stem and bud supporting water transport
to the bud, which was much more active than in plants with a terminal shoot. It seems likely that this is the reason for the
absence of complete growth suppression observed by us and other researchers even after application of high auxin concentrations.
Immediately after seedling decapitation, ψs + m in the buds reduced; however, this was not the result of trophic metabolite redistribution due to the loss of their active
sink because ψs + m reduced also in experiments with complete isolation of the bud releasing from dormancy in the chamber at 100% humidity. Auxin
application to the cut surface of decapitated seedlings did not affect the ψs + m decrease. Like decapitation, cotyledon removal resulted in the increase in the bud turgor pressure. However, in this case,
water stress did not change the bud osmotic status. Thus, the induction of osmotica accumulation in the bud after the removal
of the terminal shoot is evidently related to neither trophic, nor auxin, nor hydraulic signal. The data obtained allowed
us to conclude that both components of the bud water potential—ψs + m and Y—play an important role in the control of bud growth at apical dominance. Auxin produced in the shoot apex is involved in
the control of Y, whereas the nature of the signal controlling the ψs + m level is unclear. 相似文献
17.
K. Hayakawa Y. Ueno S. Kawamura T. Kato R. Hayashi 《Applied microbiology and biotechnology》1998,50(4):415-418
In order to test the possibility of utilizing high pressure in bioscience and biotechnology, a simple method for high-pressure
generation and its use for microbial inactivation have been studied. When a pressure vessel was filled with water, sealed
tightly and cooled to sub-zero temperatures, high pressure was generated in the vessel. The pressure generation was 60 MPa
at −5 °C, 103 MPa at −10 °C, and 140 MPa at −15 °C, −20 °C, and −22 °C. The high pressure generated inactivated microorganisms
effectively: yeasts (Saccharomyces cerevisiae and Zygosaccharomyces rouxii), bacteria (Lactobacillus brevis and Eschericia coli), and fungi (Aspergillus niger and Aspergillus oryzae) were completely inactivated when stored in sealed vessels −20 °C for 24 h. However, Staphylococcus aureus was only partly inactivated under the same conditions. This method opens up a new application of high pressure for storing,
transporting, and sterilizing of foods and biological materials.
Received: 28 July 1997 / Received last revision: 12 June 1998 / Accepted: 19 June 1998 相似文献
18.
This article reports on quantified soil water gains and their possible effects on summer water relationships in a semiarid
Stipa tenacissima L. grasslands located in SE Spain. We believe that the net soil water gains detected using minilysimeters could be from soil
water vapour adsorption (WVA). Our study of high water-stress showed stomatal conductance (21.8–43.1 mmol H2O m−2 s−1) in S. tenacissima leaves unusual for the summer season, and the evapotranspiration from S. tenacissima grassland, estimated by a multi-source sparse evapotranspiration model, closely corresponding to total WVA. This highlights
the importance of summer soil WVA to stomatal conductance and vital transpiration in S. tenacissima. This study measured pre-dawn leaf water potential (ψ) response to sporadic light rainfall, finding that a light summer rainfall
(1.59 mm day−1) was sufficient to vary ψ in S. tenacissima from −3.8 (close to the turgour loss point) to −2.7 MPa. We hypothesize that soil WVA can supply vegetation with water vital
to its survival in seasons with a severe water deficit, giving rise to a close relationship between soil water dynamics and
plant water response. 相似文献
19.
The xylem pressure potential (Ψxylem) of the leaves ofQuercus cerris, Acer campestre andCarpinus betulus was measured under anticyclonic weather types. The autocorrelation analysis revealed the daily course of the Ψxylem values approaching the stationary random process. A close statistical relation was found between the results obtained in three successive measurements of the Ψxylem (interval 2 h). A close statistical relation also between the value of the base potential (Ψb) measured at dawn and the actual values of the Ψxylem allowed the prediction of the Ψxylem values on the base of the known Ψb-values by means of a simple linear regression model. 相似文献
20.
M. V. B. Figueiredo H. A. Burity C. R. Martínez C. P. Chanway 《World journal of microbiology & biotechnology》2007,23(2):187-193
A greenhouse experiment was carried out aiming to evaluate the response to drought stress of cowpea nodule enzymatic activities
during different plant developmental stages leading to biological N2 fixation. Stress was applied by controlling soil’s water-potential through a porous cup. Cowpea plants cv IPA 205 were grown
in pots with yellow latosol soil under three different matric potential (ψm) treatments. Even with high evaporative demand and limited soil water availability, cowpea could not induce an extremely
low leaf water potential (ψw). Sap ureides concentration in cowpea declined during the drought stress period. There was a decline in enzyme activity in
the metabolic pathways concerned with N2 fixation: NADH-dependent glutamate synthase (EC 1.4.1.14), glutamine synthetase (EC 6.3.1.2) and phosphoenolpyruvate carboxylase
(EC 4.1.1.31). In contrast, an increase in glutamate dehydrogenase (EC 1.4.1.4) was observed as the ψm declined. Metabolism associated with N2 assimilation was impaired every time that the ψw was reduced below −0.73 MPa as had happened in the stressed treatments. The stress applied by the porous cup was gradual
and the plant recovered its turgor, avoiding permanent deleterious alterations in the cellular metabolism, even from a limited
cowpea-growth ψm. 相似文献