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1.
2.
Tissue-specific expression of the ORF13 promoter from Agrobacterium rhizogenes 8196 was assessed throughout the development of transgenic tobacco plants using a GUS reporter gene. ORF13 exhibited high
activity in roots but with different patterns of expression. The activity of the ORF13 promoter in vascular tissues increased
from the base to the tip of the stem. The ORF13 promoter is wound inducible in a limited area adjacent to the wound site.
The time course of wound induction of ORF13 in transgenic tobacco containing an ORF13 promoter-GUS translational fusion was
similar to that previously described for genes involved in plant defense responses. A series of 5′ deletions of the ORF13
promoter fused to the β-glucuronidase gene was examined for expression in roots and leaves of transgenic plants. Cis-acting
elements that modulate quantitative expression of the transgene after wounding were detected.
Received: 11 July 1996 / Accepted: 19 November 1996 相似文献
3.
Effects of changes in atmospheric carbon dioxide on the location of hosts by the moth, Cactoblastis cactorum 总被引:3,自引:0,他引:3
Gert Stange 《Oecologia》1997,110(4):539-545
Sensory organs that detect CO2 are common in herbivorous moths and butterflies, but their function has been unclear until now. As the CO2 gradients in the vicinity of a host plant depend on its physiological condition, CO2 could provide a sensory cue for the suitability of the plant as a larval food source. This study investigated whether changing
the atmospheric CO2 concentration affected oviposition by Cactoblastis cactorum on its host, the cactus Opuntia stricta. On host plants exposed to rapid fluctuations in CO2 concentration, the frequency of oviposition was reduced by a factor of 3.2 compared to the control. As the fluctuations mask
the much smaller CO2 signals generated by the plants, this suggests that those signals constitute an important component of the host identification
process. On host plants exposed to a constant background of doubled CO2, oviposition was also reduced, by a factor of 1.8. An increased background reduces host signal detectability, partially as
a consequence of a general principle of sensory physiology (Weber-Fechner's law), and partially due to other factors specific
to CO2-receptor neurons.
Received: 4 October 1996 / Accepted: 16 January 1997 相似文献
4.
The heat increment of feeding in house wren chicks: magnitude, duration, and substitution for thermostatic costs 总被引:3,自引:3,他引:0
Mark. A. Chappell Gwendolyn C. Bachman Kimberly A. Hammond 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):313-318
The heat increment of feeding (HIF), a transient postprandial increase in metabolic rate, is the energy cost of processing
a meal. We measured HIF in house wren chicks (Troglodytes aedon) ranging in mass from 1.6 to 10.3 g. This mass range (age 2–10 days) spanned a transition from blind, naked, ectothermic
chicks through alert, endothermic birds with nearly complete feathering. We fed chicks crickets (2.7–10% of chick body mass)
and determined HIF from continuous measurements of oxygen consumption rate (O2) before and after meals. At warm ambient temperatures (T
a) of 33–36 °C, the magnitude of HIF (in ml O2 or joules) was linearly related to meal mass and was not affected by chick mass. HIF accounted for 6.3% of ingested energy,
which is within the range of results for other carnivorous vertebrates. The duration of HIF was inversely related to chick
mass; 10-g chicks processed a standard meal approximately twice as fast as 2-g chicks. HIF duration increased with increasing
meal mass. The peak O2 during HIF, expressed as the factorial increase above resting metabolism, was independent of body mass and meal mass. In
large, endothermic chicks ( > 8 g), HIF substituted for thermoregulatory heat production at low T
a.
Accepted: 11 December 1996 相似文献
5.
Large floral displays should theoretically provide advantages to plants through increased pollinator visitation and resulting
fruit and seed set. However empirical tests of the response of pollinators to floral display size have been limited by a lack
of direct experimentation, and the results of such studies have been equivocal. In addition, other selective agents such as
pre-dispersal seed predators might modulate effects of floral display on pollination. By artificially altering flower number,
we examined the direct effects of floral display in the monocarpic herb, Ipomopsis aggregata (Polemoniaceae), on visitation rates by broad-tailed and rufous hummingbird pollinators, as well destruction of fruits by
a pre-dispersal seed predator (Hylemya: Anthomyiidae). In addition, we quantified the ultimate effects of flower number on female reproductive success. Plants with
larger floral displays were most likely to be visited first in any given foraging bout (P < 0.01). As expected, plants with more flowers received more total flower visits. However, we found no gain in the proportion
of flowers visited for many- versus few-flowered plants, or the total number of approaches/hour. In fact, a significantly
greater percentage of flowers were visited on few-flowered plants. Plants did not compensate for our reduction in flowers
by increasing investment in the number or proportion of flowers that set fruit, the number of seeds/fruit, or seed weight.
Pre-dispersal seed predation was greater for many- than for few-flowered plants (P < 0.001), but this did not offset the potential fitness gains of producing large displays. Our data support the hypothesis
that large floral displays function primarily in long-distance attraction of pollinators, and enhance maternal success.
Received: 21 March 1996 / Accepted: 24 October 1996 相似文献
6.
7.
We studied the effects of host plant hybridization on the survival and mortality of the leaf-mining moth Phyllonorycter salicifoliella on hybrid and parental willow plants in the field and in a common garden experiment. P. salicifoliella survival differed significantly among three willow taxa in the field in 1994 but not in the field in 1995 or in the common
garden. Parasitism by eulophid wasps differed significantly among taxa in 1994 and appeared to account for the variation in
their survival. In the field in 1995, host feeding predation varied significant among taxa. The theory of tritrophic interactions
predicts that plant genotype can affect natural enemy impact, and this study supports this prediction. Significant variation
in survival and eulophid parasitism was also found among genotypes within taxa in the field in both years and in the common
garden experiment. The common garden results show that genetic differences in plants affect the herbivore-parasitoid interaction.
Variation among years in the patterns of survival and causes of mortality among field plants suggest that genotype by environment
interactions may be important.
Received: 1 March 1996 / Accepted: 4 November 1996 相似文献
8.
9.
Odour-mediated responses of phytophagous mites to conspecific and heterospecific competitors 总被引:8,自引:0,他引:8
Plants under herbivore attack produce volatiles, thus attracting natural enemies of the herbivores. However, in doing so,
the plant becomes more conspicuous to other herbivores. Herbivores may use the odours as a cue to refrain from visiting plants
that are already infested, thereby avoiding competition for food, or, alternatively, to visit plants with defences weakened
by earlier attacks. We investigated the response of one species of herbivore (the spider mite Tetranychus urticae) to odours emanating from cucumber plants infested by conspecific or heterospecific (the western flower thrips, Frankliniella occidentalis) herbivores. Olfactometer experiments in the laboratory showed that spider mites have a slight, but significant, preference
for plants infested with conspecifics, but strongly avoid plants with thrips. These results were substantiated with greenhouse
experiments. We released spider mites on the soil in the centre of a circle of six plants, half of which were infested with
either conspecifics or heterospecifics (thrips), whereas the other half were uninfested. It was found that 60–70% of the mites
were recaptured on the plants within 5 h after release. Results of these experiments were in agreement with results of the
olfactometer experiments: (1) significantly fewer spider mites were found on plants infested with thrips than on uninfested
plants and (2) more mites were found on plants with conspecifics than on clean plants (although this difference was not significant).
From a functional point of view it makes sense that spider mites prefer clean plants over thrips-infested plants, since thrips
are not only competitors, but are also known as intraguild predators of spider mites. Possible reasons for the slight attraction
of spider mites to plants infested with conspecifics are discussed.
Received: 22 June 1996 / Accepted: 29 September 1996 相似文献
10.
Water relations dynamics during simulated sunflecks at high (36°C) and medium (27°C) temperatures and high and low vapour
pressure deficits beween leaf and air (VPD) were studied on shade-grown Piper auritum H.B. & K. plants, a pioneer tree, common in gaps and clearings of tropical rain forests. The leaves of P. auritum wilt rapidly when exposed to high light. Exposure to high VPD and high light caused substantial and rapid dehydration of
leaves. Dehydration could be prevented under high humidity irrespective of temperature. Water stored in leaf cells served
as initial source for transpiration upon high light exposure. This effect increased with increasing VPD and temperature. The
pronounced decrease in leaf water content over time in high light caused a rapid decrease in leaf water potential (Ψl) and a concomitant increase in water potential gradient (ΔΨ/Δx) between trunk and leaf, yet the high leaf elasticity (small bulk elastic modulus, ε) allowed turgor maintenance under most
conditions. Under high VPD and high temperature, stomata remained open and ΔΨ/Δx frequently exceeded 0.95 MPa · m−1, the cavitation-inducing threshold (ΔΨ/Δx
cav) causing high rates of acoustic emissions from stems and leaf petioles and leading to concomitant losses in hydraulic conductance
per leaf area (k
l). At medium temperature (high VPD), stomatal closure contained xylem embolism by keeping ΔΨ/Δx at or below this threshold. We argue that wilting substantially contributes to creating a sufficient driving force for water
uptake from the soil, and reducing the VPD (through a decrease in radiation load and thus leaf temperature) to avoid excessive
dehydration.
Received: 3 March 1996 / Accepted: 10 November 1996 相似文献
11.
12.
Light response characteristics of a morphologically diverse group of southern hemisphere conifers as measured by chlorophyll fluorescence 总被引:5,自引:0,他引:5
Unlike northern hemisphere conifer families, the southern family, Podocarpaceae, produces a great variety of foliage forms
ranging from functionally broad-, to needle-leaved. The production of broad photosynthetic surfaces in podocarps has been
linked qualitatively to low-light-environments, and we undertook to assess the validity of this assumption by measuring the
light response of a morphologically diverse group of podocarps. The light response, as apparent photochemical electron transport
rate (ETR), was measured by modulated fluorescence in ten species of this family and six associated species (including five
Cupressaceae and one functionally needle-leaved angiosperm) all grown under identical glasshouse conditions. In all species,
ETR was found to increase as light intensity increased, reaching a peak value (ETRmax) at saturating quantum flux (PPFDsat), and decreasing thereafter. ETRmax ranged from 217 μmol electrons · m−2 · s−1 at a PPFDsat of 1725 μmol photons · m−2 · s−1 in Actinostrobus acuminatus to an ETR of 60 μmol electrons · m−2 · s−1 at a PPFDsat of 745 μmol electrons · m−2 · s−1 in Podocarpus dispermis. Good correlations were observed between ETRmax and both PPFDsat and maximum assimilation rate measured by gas-exchange analysis. The effective quantum yield at light saturation remained
constant in all species with an average value of 0.278 ± 0.0035 determined for all 16 species. Differences in the shapes of
light response curves were related to differences in the response of non-photochemical quenching (q
n), with q
n saturating faster in species with low PPFDsat. Amongst the species of Podocarpaceae, the log of average shoot width was well correlated with PPFDsat, wider leaves saturating at lower light intensities. This suggests that broadly flattened shoots in the Podocarpaceae are
an adaptation to low light intensity.
Received: 15 April 1996 / Accepted: 30 September 1996 相似文献
13.
14.
Michael J. Webster Timothy P. Scheett Matthew R. Doyle Matthew Branz 《European journal of applied physiology and occupational physiology》1997,75(6):520-524
The purpose of this study was to investigate the effect of a thiamin derivative, thiamin tetrahydrofurfuryl disulfide (TTFD),
on oxygen uptake (˙VO2), lactate accumulation and cycling performance during exercise to exhaustion. Using a randomized, double-blind, cross-over
design with a 10-day washout between trials, 14 subjects ingested either 1 g · day−1 of TTFD or a placebo (PL) for 4 days. On day 3, subjects performed a progressive exercise test to exhaustion on a cycle ergometer
for the determination of ˙VO2submax, ˙VO2peak, lactate concentration ([La− ]), lactate threshold (ThLa) and heart rate ( f
c). On day 4, subjects performed a maximal 2000-m time trial on a cycle ergometer. A one-way analysis of variance (ANOVA) with
repeated measures was used to determine significant differences between trials. There were no significant differences detected
between trials for serial measures of ˙VO2submax, [La−] or f
c. Likewise, ˙VO2peak [PL 4.06 (0.19) TTFD 4.12 (0.19) l · min−1, P = 0.83], ThLa [PL 2.47 (0.17), TTFD 2.43 (0.16) l · min−1, P = 0.86] and 2000-m performance time [PL 204.5 (5.5), TTFD 200.9 (4.3) s, P = 0.61] were not significantly different between trials. The results of this study suggest that thiamin derivative supplementation
does not influence high-intensity exercise performance.
Accepted: 19 December 1996 相似文献
15.
V. Cavaliere S. Spanò D. Andrenacci L. Cortesi G. Gargiulo 《Molecular & general genetics : MGG》1997,254(3):231-237
The Drosophila vitelline membrane protein gene VM32E is expressed according to a precise temporal and spatial program in the follicle cells. Results from germ line transformation
experiments using different fragments of the −465/−39 VM32E region fused to the hsp/lacZ reporter gene revealed that the region −348/−39 is sufficient to confer the wild-type expression pattern. Within this segment,
distinct cis-regulatory elements control VM32E expression in ventral and dorsal follicle cells. The region between −135/−113 is essential for expression of the VM32E gene in the ventral columnar follicle cells. Expression in the dorsal domain requires the two regions −348/−254 and −118/−39.
Furthermore, the region −253/−119 appears to contain a negative element that represses gene activity in anterior centripetal
cells. We suggest that the expression of the VM32E gene throughout the follicular epithelium is controlled by specific cis-regulatory elements acting in distinct spatial domains and following a precise developmental program.
Received: 22 October 1996 / Accepted: 14 November 1996 相似文献
16.
A survey of root pressures in vines of a tropical lowland forest 总被引:6,自引:0,他引:6
Pre-dawn xylem pressures were measured with bubble manometers attached near the stem bases of 32 species of vines on Barro
Colorado Island, Panama, to determine if pressures were sufficient to allow for possible refilling of embolized vessels. Of
29 dicotyledonous species 26 exhibited only negative xylem pressures, even pre-dawn during the wet season. In contrast, three
members of the Dilleniaceae exhibited positive pre-dawn xylem pressures, with a maximum of 64 kPa in Doliocarpusmajor. A pressure of 64 kPa is sufficient to push water to a height of 6.4 m against gravity, but the specimens reached heights
of 18 m. Thus, in all 29 dicotyledons examined, the xylem pressures were not sufficient to refill embolized vessels in the
upper stems. In contrast, two of the smaller, non-dicotyledonous vines, the climbing fern Lygodiumvenustrum and the viny bamboo Rhipidocladumracemiflorum, had xylem pressures sufficient to push water to the apex of the plants. Therefore, a root pressure mechanism to reverse
embolisms in stem xylem could apply to some but not to most of the climbing plants that were studied.
Received: 18 March 1996 / Accepted: 24 October 1996 相似文献
17.
In order to test whether an increased export of carbohydrates by leaves and starch mobilization are critical for floral transition
in Arabidopsis thaliana, the Columbia ecotype as well as its starchless mutant pgm and starch-in-excess mutant sex1 were investigated. Induction of flowering was achieved by exposure of plants to either one long day (LD) or one displaced
short day (DSD). The following conclusions were drawn: (i) Both the pgm and sex1 mutants have a late-flowering phenotype in days shorter than 16 h. (ii) When inductive treatments cause a large percentage
of induced plants, there is always a large, early and transient increase in carbohydrate export from leaves. By contrast,
when an inductive treatment results in only a low percentage of induced plants (pgm plants exposed to one DSD), the export of carbohydrates from leaves is not increased, supporting the idea that phloem carbohydrates
have a critical function in floral transition. (iii) Starch mobilization is not required to obtain an increased carbohydrate
export when induction is by one LD (extended period of photosynthesis), but is absolutely essential when induction is by one
DSD (period of photosynthesis unaffected). (iv) Floral induction apparently increases the capability of the leaf phloem-loading
system.
Received: 27 August 1997 / Accepted: 6 March 1998 相似文献
18.
Y. K. Ip G. Q. Tan S. S. L. Kuah S. F. Chew 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(3):213-220
The capability of Phascolosoma arcuatum to detoxify sulfide in anaerobic conditions was examined. Sulfane sulfur, which underwent cold cyanolysis, was the major
excretory end product of sulfide detoxification during anoxia. Thiosulfate was not excreted into the external medium. Instead,
it was absorbed by P. arcuatum and its absorption was stimulated by the presence of sodium sulfide (Na2S) in the incubation medium. The effective formation and excretion of sulfane sulfur by P.␣arcuatum required the presence of both Na2S and sodium thiosulfate (Na2S2O3). Results obtained indicate that rhodanese might be involved in sulfide detoxification in this sipunculid. Rhodanese could
act as a catalyst in the transfer of sulfur atoms from thiosulfate to HS−. The body wall and the introvert were the main sites of sulfide detoxification. However, it is unlikely that epibiotic bacteria
associated with the outside surface of the worm were involved in the detoxification process. A time-course study on the contents
of thiosulfate and sulfane sulfur in the body wall of P. arcuatum incubated anaerobically in the presence of Na2S + Na2S2O3 verified that thiosulfate absorbed was utilized to detoxify sulfide to sulfane sulfur.
Accepted: 24 October 1996 相似文献
19.
M. E. Kubiske Kurt S. Pregitzer Carl J. Mikan Donald R. Zak Jennifer L. Maziasz A. Teeri 《Oecologia》1997,110(3):328-336
We tested the hypothesis that elevated CO2 would stimulate proportionally higher photosynthesis in the lower crown of Populus trees due to less N retranslocation, compared to tree crowns in ambient CO2. Such a response could increase belowground C allocation, particularly in trees with an indeterminate growth pattern such
as Populus tremuloides. Rooted cuttings of P. tremuloides were grown in ambient and twice ambient (elevated) CO2 and in low and high soil N availability (89 ± 7 and 333 ± 16 ng N g−1 day−1 net mineralization, respectively) for 95 days using open-top chambers and open-bottom root boxes. Elevated CO2 resulted in significantly higher maximum leaf photosynthesis (A
max) at both soil N levels. A
max was higher at high N than at low N soil in elevated, but not ambient CO2. Photosynthetic N use efficiency was higher at elevated than ambient CO2 in both soil types. Elevated CO2 resulted in proportionally higher whole leaf A in the lower three-quarters to one-half of the crown for both soil types. At elevated CO2 and high N availability, lower crown leaves had significantly lower ratios of carboxylation capacity to electron transport
capacity (V
cmax/J
max) than at ambient CO2 and/or low N availability. From the top to the bottom of the tree crowns, V
cmax/J
max increased in ambient CO2, but it decreased in elevated CO2 indicating a greater relative investment of N into light harvesting for the lower crown. Only the mid-crown leaves at both
N levels exhibited photosynthetic down regulation to elevated CO2. Stem biomass segments (consisting of three nodes and internodes) were compared to the total A
leaf for each segment. This analysis indicated that increased A
leaf at elevated CO2 did not result in a proportional increase in local stem segment mass, suggesting that C allocation to sinks other than the
local stem segment increased disproportionally. Since C allocated to roots in young Populus trees is primarily assimilated by leaves in the lower crown, the results of this study suggest a mechanism by which C allocation
to roots in young trees may increase in elevated CO2.
Received: 12 August 1996 / Accepted: 12 November 1996 相似文献