共查询到20条相似文献,搜索用时 31 毫秒
1.
The dwarf seagrass Zostera noltii is an important primary producer in Atlantic coastal ecosystems from Mauritania to southern Norway and the Mediterranean
Sea. Sessile intertidal organisms existing at the interface between marine and terrestrial environments may be particularly
vulnerable to environmental change. In this study, we asked how near to thermal tolerance limits natural populations of Z. noltii are in the Ria Formosa coastal lagoon system in southern Portugal. We recorded the maximum temperatures in the Ria Formosa
during the 2007 summer, and conducted experiments to determine the sub-lethal temperature of Z. noltii shoots sampled at two sites located at different tidal heights. Mortality rates and photosynthetic performance were recorded
within a range of heat shock temperatures between 35 and 41°C. Survival was recorded ≤37°C, while higher temperatures led
to a sudden drop in photosynthetic capacity followed by mortality (shoot loss) that occurred more rapidly with increasing
temperatures. At 39°C and above, the rate of shoot mortality in both sites was close to 100%, occurring between 5 and 13 days
after the heat shock. Survival was ca. 95 and 90% at 35 and 37°C, respectively. From these results for Z. noltii populations in the Ria Formosa we estimated sub-lethal temperature to be approximately 38°C for Z. noltii, close to the maximum of 36°C recorded in the summer 2007. Considering predicted trajectories in the coming decades, these
results raise concern as to the future viability of intertidal Z. noltii populations near the southernmost edge of their distribution.
Handling editor: S. M. Thomaz 相似文献
2.
The density, biomass and shoot morphology of two populations of Zostera noltii were monitored from January 1998 to July 1999 at two shallow Mediterranean lagoons of Biguglia and Urbino, which differ in hydro-morphological conditions and nutrient loading. Monitoring included the principal biological and foliar parameters (shoot density, aboveground and belowground biomass, length, width and number of leaves, LAI and coefficient A: percentage of leaves having lost their apex), the organic matter contents of the sediment and the environmental conditions (salinity, turbidity, temperature, nutrient concentrations and dissolved oxygen levels). The two populations of Z. noltii displayed seasonal changes in density (1600–19600 m2), aboveground biomass (11–153 g. DW. m−2), leaf length (33–255 mm), and leaf width (0.9–1.8 mm). Temperature and turbidity were significant environmental factors influencing the temporal changes observed in the Z. noltii meadows studied. Conversely, the belowground biomass, the number of leaves per shoot and the LAI did not undergo any seasonal changes. In the Biguglia lagoon, the functioning dynamics of the Z. noltii seagrass beds are determined by the catchment area and the inputs of nutrients derived from it, whereas in the Urbino lagoon the dynamics of the Z. noltiibeds depend on low levels of water turbidity. 相似文献
3.
Hanna Ciecierska 《Hydrobiologia》2006,570(1):141-146
Urban lakes belong to various groups, for example from “young” to “old” with regard to development, and from “natural” to
“anthropogenic” with respect to transformations due to human activity. The majority of these lakes are eutrophic and polytrophic,
but special attention should be paid to mesotrophic ones, with relatively unchanged vegetation, with species of the class
Charetea, e.g. Lake Redykajny (43.3% of the phytolittoral) or Lake Tyrsko (44.0% of the phytolittoral). 相似文献
4.
Theoretically, complete rejuvenation of mature trees should occur through somatic embryogenesis, however, this has not been
extensively studied. The main objective of the present study was to increase the efficiency of in vitro clonal propagation
for mature Quercus robur (100–300 years old), by induction of somatic embryogenesis as rejuvenation step prior to establishment of shoot culture through
micropropagation of somatic embryo-derived plantlets. Shoot culture lines of “mature” origin were established from epicormic
shoots of two centenarian oak genotypes (Sainza and CR-0) and maintained by axillary shoot proliferation. Embryogenic lines
were also initiated from epicormic leaf explants of the same genotypes and maintained by secondary somatic embryogenesis.
Although the frequency of somatic embryo conversion into plantlets was low in pedunculate oak, shoot culture lines could be
established and maintained by axillary branching from several germinated somatic embryos. For each genotype and shoot culture
line of the two origins (mature tree and somatic plantlets), shoot multiplication rate and elongation as well as rooting ability
parameters were compared. Compared with “mature-origin” shoot cultures and after more than one year propagation in vitro,
shoot lines established from somatic plantlets produced a significantly higher proportion of elongated, rootable shoots (from
26.0–31.6 to 36.8–40.5%) with increased rooting ability (from 3.3–45.6% to 23.2–89.8%). In the case of 300-year-old Sainza
genotype such a high organogenic capacity was similar to shoot cultures initiated from basal sprouts. Basal sprouts are considered
as “mature” material that retains juvenile characteristics compared with epicormic shoots forced from crown branches. Somatic
embryogenesis only slightly improved plant regeneration of shoot cultures from basal sprouts, thus validating their use as
“juvenile control”. The present results provide evidence that some rejuvenation occurred during the process of somatic embryogenesis
and resulted in improved shoot growth and rooting of somatic embryo-derived culture compared with “mature” shoot culture.
The results reported in this study might be useful in embryogenic systems with low plant conversion rates. The proposed experimental
model might also be useful in finding molecular markers of plant ontogeny. 相似文献
5.
Tsutom Hiura 《Trees - Structure and Function》1998,12(5):274-280
Relationships between leaf or shoot size, number, and arrangement in response to light were investigated to test the hypothesis
that these characteristics are linked. In order to test this hypothesis, the divergence in allometry and shoot dynamics in
saplings of Japanese beech (Fagus crenata) obtained from four populations and having different leaf sizes were examined in a nursery under both full sun and shade
conditions. Trees with different leaf sizes also showed large differences in canopy structure, particularly when shade-grown
saplings were compared. The final leaf mass distributions of the large-leaf populations were conical or “bottom - heavy”,
while those of the small-leaf populations were planar or “top - heavy”. The slope of the allometric relations between leaf
mass and shoot and branch mass in small-leaved populations were steeper than those in large-leaf populations. The four populations
were classified into two growth types: populations producing a few large leaf and shoot modules corresponded to “stem growth
type”, and those producing many small leaf and shoot modules corresponded to “leaf growth type”. These kinds of intra-specific
variation in architecture and growth of F. crenata trees may influence the structure and dynamics of forests in accordance with differences in competitive ability or sensitivity
to disturbances such as windstorm.
Received: 18 March 1997 / Accepted: 21 October 1997 相似文献
6.
Alicia L. Carriquiry William P. Ireland Wolfgang Kliemann Etsuro Uemura 《Bulletin of mathematical biology》1991,53(4):579-589
A mathematical model (Kliemann, W. 1987.Bull. math. Biol.
49, 135–152.) that predicts the quantitative branching pattern of dendritic tree was evaluated using the apical and basal dendrites
of rat hippocampal neurons. The Wald statistics for χ2-test was developed for the branching pattern of dendritic trees and for the distribution of the maximal order of the tree.
Using this statistic, we obtained a reasonable, but not excellent, fit of the mathematical model for the dendritic data. The
model's predictability of branching patterns was greatly enhanced by replacing one of the assumptions used for the original
model “splitting of branches for all dendritic orders is stochastically independent”, with a new assumption “branches are
more likely to split in areas where there is already a high density of branches”. The modified model delivered an excellent
fit for basal dendrites and for the apical dendrites of hippocampal neurons from young rats (30–34 days postpartum). This
indicates that for these cells the development of dendritic patterns is the result of a purely random and a systematic component,
where the latter one depends on the density of dendritic branches in the brain area considered. For apical dendrites there
is a trend towards decreasing pattern predictability with increasing age. This appears to reflect the late arrival of afferents
and subsequent synaptogenesis proximal on the apical dendritic tree of hippocampal neurons. 相似文献
7.
A comparison of phenotypic plasticity between two species occupying different positions in a successional sequence 总被引:1,自引:0,他引:1
Yingxin Huang Xueyong Zhao Hongxuan Zhang Gang Huang Yayong Luo Wisdom Japhet 《Ecological Research》2009,24(6):1335-1344
We compared the phenotypic plasticity of two greenhouse-grown species (Corispermum macrocarpum and Salsola collina) occupying different positions in a successional sequence in Horqin Sandy Land, by treating with different population density
and the availability of soil nutrients and water. The same species can exhibit different patterns of plasticity in response
to different environmental factors. In the soil nutrient treatments, the plasticity pattern of S. collina could be described as “master-of-some”. However, in the soil-water and population-density treatments, it showed no significant
difference from C. macrocarpum in the reaction norm for plasticity. It was similar to a “jack-of-all-trades” plasticity pattern. Contrary to the previous
conclusion that late successional species had higher reproductive allocation than early successional species, in this successional
sequence, the late species had lower reproductive allocation in all treatments. Reproductive allocation of both species increased
with the increase in water availability and also increased with a decrease in nutrient levels. However, density had no effect
on reproductive allocation. Although the root:shoot ratio increased with decreasing water availability, there were no differences
in the plasticity pattern for this trait in both species. Root:shoot ratio was, however, not significantly affected by nutrient
availability and density. In a word, the plasticity patterns of invaders are adapted to the analyses of succession. 相似文献
8.
Field surveys have shown a limited distribution ofL. branchialis in Baltic waters due to heterogenic salinity. The parasite is not suited as “natural” tagging of the cod population in these
waters. 相似文献
9.
Gross primary production (GPP) and respiration (R) in an intertidal Zostera noltii (Hornemann, 1832) community were estimated each month from in situ CO2 flux measurements during the emersion period in the Bay of Morlaix (France). Simultaneously, the Chlorophyll a biomass of Z. noltii leaves, associated epiphytes and sediment within the benthic chambers were also monitored. The significant positive exponential
relationship established between R and the maximum daily temperature emphasized that temperature was a good predictor of seasonal
variation in the community R in Z. noltii bed. In contrast, the amplitude of the fitted curve on GPP was low and represented <25% of the annual mean value (90.9 ± 15.2 mgC m−2 h−1). The Chlorophyll a biomass of sediment was high (133.70 ± 22.96 mg m−2) but it was likely constituted by detritus which did not contribute much to the community GPP. The Chlorophyll a biomass of associated epiphytes was higher in winter and varied over the year inversely with Z. noltii. Therefore, the asynchronous dynamic of primary producers could support a constant rate of production at community scale
over the year. 相似文献
10.
N. Rashevsky 《Bulletin of mathematical biology》1969,31(4):789-795
The author's theory of the adoption of certain types of behavior patterns (Rashevsky, N., 1957, “Contributions to the Theory
Initiative Behavior”.Bull. Maths. Biophysics,19, 91–119; 1968,Looking at History through Mathematics, Cambridge, Massachusetts: M.I.T. Press) consisting of elementary behaviors for each of which there is an opposite one and
the two are mutually exclusive, is applied to describe the changes in the general type of behavior of a society. The elementary
acts of which the whole problem consists may be either overt activities or beliefs or opinions. The general behavior patternsadopted by the society are considered as the “proper” or “just” ones. Any deviation from it in either one or more of the component
elementary behaviors is considered as “unjust” and is subject to some punitive action. The total number of possible mutually
exclusive behavior patterns is very large but finite. Within this very large range of possible patterns, we find that this
notion of justice is relative, because changes from any behavior pattern to any other may occur. It is further shown that
the amount of punishment for the deviation from the accepted pattern in order to be effective as well as efficient must be
applied in different ways to different individuals even for the same transgression. 相似文献
11.
Saïd Achamlale Bernadette Rezzonico Micheline Grignon-Dubois 《Journal of applied phycology》2009,21(3):347-352
Detritus of the seagrasses Zostera noltii and Z. marina collected on the beaches of Arcachon Lagoon (France) over a 3-year period was screened as a new source of zosteric acid (ZA).
This natural sulphated phenolic acid is a high value-added product capable of preventing settlement of marine organisms and
protecting crops from fungal diseases. The seasonal variation of the ZA content was quantified in methanolic and aqueous crude
extracts using high-performance liquid chromatography. The concentration found ranged from 65 to 456 μg g−1 dry wt for Z. noltii and 51–692 μg g−1 dry wt for Z. marina, respectively. This is the first report of ZA in Zostera noltii. Detrital leaves of Zostera have never before been screened for their bioactive substances. These results show that this low cost, very abundant and
renewable, but heretofore unused, marine resource has potential as a source of a rare and naturally occurring bioactive product. 相似文献
12.
Fernando G. Brun Elleke van Zetten Eva Cacabelos Tjeerd J. Bouma 《Helgoland Marine Research》2009,63(1):19-25
Seagrasses are well known ecosystem engineers that can significantly influence local hydrodynamics and the abundance and biodiversity
of macrobenthic organisms. This study focuses on the potential role of the seagrass canopy structure in altering the abundance
of filter-feeding organisms by modifying the hydrodynamic driven food supply. We quantified the effect of two ecosystem engineers
with contrasting canopy properties (i.e. Zostera noltii and Cymodocea nodosa) on the food intake rate of a suspension-feeding bivalve Cerastoderma edule living in these seagrass meadows. Field experiments were carried out in two seagrass beds (Z. noltii and C. nodosa) and bare sediment, located on sandflat characterised by a relatively high hydrodynamic energy from waves and currents. Results
demonstrated that the filter-feeding rate was almost twofold increased when C. edule was inhabiting Z. noltii meadows (1.10 ± 0.24 μg Chl g Fresh Weight−1) when compared to cockles living on the bare sediment (0.65 ± 0.14 μg Chl g FW−1). Intermediate values were found within C. nodosa canopy (0.97 ± 0.24 μg Chl g FW−1), but filter feeding rate showed no significant differences with values for Z. noltii meadows. There were no apparent correlations between canopy properties and filter-feeding rates. Our results imply that food
refreshment within the seagrass canopies was enough to avoid food depletion. We therefore expect that the ameliorated environmental
conditions within vegetated areas (i.e. lower hydrodynamic conditions, higher sediment stability, lower predation pressure…)
in combination with sufficient food supply to prevent depletion within both canopies are the main factors underlying our observations. 相似文献
13.
François Mankessi Aubin R. Saya Frédéric Boudon Yann Guédon Fabienne Montes Marc Lartaud Jean-Luc Verdeil Olivier Monteuuis 《Trees - Structure and Function》2010,24(4):743-752
Shoot apical meristem (SAM) domes derived from five different outdoor and in vitro sources of juvenile and mature Eucalyptus urophylla × Eucalyptus grandis akin genotypes were compared. Overall measurements of SAM dome height H and diameter D ranged from 2 to 35 μm and 20 to 80 μm, with significant differences according to the various physiological origins of plant
material investigated. SAM domes from the mature trees “Mat” were taller than those from the rejuvenated ministock plants
“Rej”; from the in vitro microcuttings “IVM” of the same clone and also from the in vitro juvenile seedlings “IVJ”, whereas
outdoor seedlings “Juv” exhibited intermediate SAM dome height. SAM domes from the rejuvenated material “Rej”, from the in
vitro mature “IVM” and juvenile “IVJ” origins were also narrower than those from the outdoor seedlings “Juv” and to lesser
extent than those from the mature trees “Mat”. Overall, the mature source “Mat” displayed bigger and somehow sharper hemispherical
domes than those from “Rej” and “Juv”, physiologically more juvenile, or those from the in vitro origins “IVM” and “IVJ” which
looked flatter and smaller. SAM dome height, diameter D and H/D values varied also significantly according to the plastochron. More specifically, H, D, and H/D SAM differences between the five origins were not significant during the early plastochron phase corresponding to leaf initiation,
to become more salient as leaf structures started to elongate and to differentiate. This was particularly obvious for mature
tree “Mat” SAM dome shapes which showed at this stage much higher H/D values than the other SAM sources. A shape index S used for characterizing more accurately dome shape confirmed these trends. These observations provide additional arguments
to the view that juvenility in trees becomes more and more time- and shoot-tip restricted as ageing increases in the course
of time during the ontogenetical process and could be ultimately confined to the most organogenic phase of SAM, from which
shoot characteristics derive. 相似文献
14.
Showe-Mei Lin 《Journal of applied phycology》2006,18(3-5):671-678
Four flattened Gracilaria species have been reported from Taiwan: G. spinulosa, G. vieillardii, G. textorii and G. punctata, identified based on branching pattern, the presence or absence of spines, and characters that often vary seasonally. Gracilaria spinulosa was originally described from the type locality, Tainan. Species with toothed margins are usually referred to G. “vieillardii”; those with smooth margins to G. “textorii”, and those with smooth margins and dark spots scattered over the blade to G. “punctata”. Molecular analyses show that specimens with marginal teeth cluster in three different groups: a G. “vieillardii” clade, a G. spinulosa clade, and a clade sister to G. spinulosa. An undescribed species comprises the third clade, which is distinguished by its relatively large gonimoblast cells and weakly developed tubular nutritive cells. The three clades can be separated by the character of the tubular nutritive cells, the size of gonimoblast cells and certain vegetative features. Plants with entire margins form a single clade characterized by cystocarps with basal tubular nutritive cells and their absence in the cystocarp cavity. They are nested in the Hydropuntia complex and are referred to as Gracilaria “punctata” here. The records of G. textorii and G. punctata from Taiwan require reinvestigation in comparison with the Japanese species. 相似文献
15.
K. Suhasini A. P. Sagare K. V. Krishnamurthy 《In vitro cellular & developmental biology. Plant》1996,32(1):6-10
Summary Somatic embryos which originated from mature embryo axes of the chickpea (Cicer arietinum L.) showed varied morphologies. Embryos were classified based on shape of the embryo and number of cotyledons. “Normal” (zygotic-like)
embryos were bipolar structures with two cotyledons and a well-developed shoot and root apical meristem, whereas “aberrant”
embryos were horn-shaped, had single and multiple cotyledons, and were fasciated. Histological examination revealed the absence
of a shoot apical meristem in horn-shaped embryos. Fasciated embryos showed diaxial fusion of two embryos. Secondary embryogenesis
was also observed, in which the embryos emerged from the hypocotyl and cotyledonary region of the primary somatic embryo.
This report documents the absence of an apical meristem as a vital factor in the lack of conversion of aberrant somatic embryos. 相似文献
16.
Many woody plants show hierarchical shoot growth: annual shoot length decreased with increasing branching order. We hypothesize
that plants showing hierarchical shoot growth improve the efficiency in terms of space acquisition and use per invested shoot
length. This hypothesis was tested by using a simple geometric simulation model of branch development. In this study, the
effective shoot length (EL), the shoot length produced within a growth season without any overlap from other shoots, was used
as the index of space availability. We compared EL among shoots on different branching orders of a “simulated” branch system.
The EL decreased with an increasing branching order. The results suggested that space availability decreased with increasing
branching orders. The results also showed that simulated plants with the hierarchical shoot growth showed higher efficiency
in terms of space acquisition per investment than those with the non-hierarchical shoot growth. We concluded that the difference
in space availability between the branching orders could be an important ultimate factor causing hierarchical shoot growth. 相似文献
17.
Nina Rosa F. Castillo Nahla V. Bassil Sugae Wada Barbara M. Reed 《In vitro cellular & developmental biology. Plant》2010,46(3):246-256
Questions often arise concerning the genetic stability of plant materials stored in liquid nitrogen for long time periods.
This study examined the genetic stability of cryopreserved shoot tips of Rubus germplasm that were stored in liquid nitrogen for more than 12 yr, then rewarmed and regrown. We analyzed the genetic stability
of Rubus grabowskii, two blackberry cultivars (“Hillemeyer” and ‘Silvan’), and one raspberry cultivar (“Mandarin”) as in vitro shoots and as field-grown plants. No morphological differences were observed in greenhouse-grown cryopreserved plants when
compared to the control mother plants. In the field, cryopreserved plants appeared similar but were more vigorous than mother
plants, with larger leaves, fruit, and seeds. Single sequence repeats (SSR) and amplified fragment length polymorphism (AFLP)
analyses were performed on shoots immediately after recovery from cryopreservation and on shoots subcultured for 7 mo before
analysis. Ten SSR primers developed from “Marion” and “Meeker” microsatellite-enriched libraries amplified one to 15 alleles
per locus, with an average of seven alleles and a total of 70 alleles in the four genotypes tested. No SSR polymorphisms were
observed between cryopreserved shoots and the corresponding mother plants regardless of subculture. Although no polymorphisms
were detected in shoots analyzed immediately after recovery from cryopreservation, AFLP polymorphisms were detected in three
of the four Rubus genotypes after they were subcultured for 7 mo. Field-grown plants from the polymorphic shoot tips of R. grabowskii and ‘Silvan’ displayed the same AFLP fingerprints as their corresponding mother plants. Only long-cultured in vitro shoot tips displayed polymorphisms in vitro, and they were no longer detected when the plants were grown ex vitro. The transitory nature of these polymorphisms should be carefully considered when monitoring for genetic stability. 相似文献
18.
The spikemoss is marked by the unique root-producing pleurogeous rhizophore as well as the lycophytic microphyll. Imaichi
and Kato (Bot Mag Tokyo 102:369–380, 1989; Am J Bot 78:1694–1703, 1991) revealed that the exogenous developmental process in the rhizophore is clearly distinguishable from the developmental process
in the endogenous root, argued that the axial organ could be coordinate with other fundamental organs including the root and
stem, and demonstrated the “rhizophore concept.” In this paper, we report on the expression pattern of the spikemoss Selaginella class 1 KNOX gene, SuKNOX1, in the rhizophore. We show that the SuKNOX1 mRNA is specifically accumulated at the tip of the rhizophore as well as the shoot apical apex, but not in the root tip.
This result supports the “rhizophore concept” at the molecular level. 相似文献
19.
The effects (and interaction) of two solution concentrations of Mg (50, 500, μM) and two of K (250, 4250 μM) on the growth of micropropagated plants of “F. 12/1” and “Colt” were investigated using a flowing solution culture system.
Magnesium inflow and growth of “Colt” and “F. 12/1” were inhibited to a similar extent by an increased concentration of K
in the nutrient solution. However, the consequences of this inhibition were different. Reduced inflow of Mg in “F. 12/1” caused
Mg deficiency symptoms at high and low concentrations of K, whereas this only occurred with a combination of high K concentration
and low Mg concentration in “Colt”. The distribution of dry matter within the plant was significant in determining susceptibility
to Mg deficiency. Since “F. 12/1” has a smaller root:shoot ratio than Colt it is unable to sustain the same concentration
of Mg in leaves as “Colt” irrespective of external K concentration. The molar ratio of K:Mg in soil solutions should remain
<8.5:1 in order to ensure maximum growth of “F. 12/1” and “Colt”.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
20.
Timing of induced volatile emissions in maize seedlings 总被引:23,自引:0,他引:23
Maize (Zea mays L.) releases specific volatiles in response to herbivory by caterpillars. These volatiles are known to serve as cues for
parasitic wasps to locate the herbivores. In the present study the exact time of volatile emission after simulated herbivory
(mechanical damage and treatment with caterpillar regurgitant) was measured for seedlings of the cultivars “Ioana Sweet Corn”
and “LG11”. Odours were collected every 0.5 h for a total of 12 h. Typical “green leaf odours”, (Z)-3-hexenal, (E )-2-hexenal, (Z)-hexen-1-o1, and (Z)-3-hexen-1-yl acetate, were emitted immediately upon damage and their amounts dropped
rapidly after the first collections. Several of the induced compounds were released within 2 h after treatment, while others
(mainly sesquiterpenoids) started to be released after 4 h. The LG11 seedlings emitted several compounds (e.g. β-myrcene,
(Z)-β-ocimene, benzyl acetate, β-caryophyllene, (E,E )-α-farnesene) that were not detected for Ioana. (E,E )-α-farnesene was continuously emitted by LG11 seedlings, even by undamaged plants. Timing of the release of volatile compounds
that the two varieties had in common did not differ significantly, with the exception of indole for which the peak production
was considerably earlier for LG11. These findings are discussed in the context of biosynthetic pathways and mechanisms involved
in induced emissions of plant volatiles and the exploitation of the resulting odour by parasitoids and predators of herbivores.
Received: 23 October 1997 / Accepted: 9 June 1998 相似文献