共查询到20条相似文献,搜索用时 31 毫秒
1.
The influence of below ground herbivory and plant competition on growth and biomass allocation of purple loosestrife 总被引:1,自引:0,他引:1
Experiments investigating plant-herbivore interactions have primarily focused on above-ground herbivory, with occasional
studies evaluating the effect of below-ground herbivores on plant performance. This study investigated the growth of the wetland
perennial Lythrum salicaria (purple loosestrife) under three levels of root herbivory by the weevil Hylobiustransversovittatus and three levels of plant competition by the grass Phleumpratense in a common garden. Plant growth, flowering phenology, and biomass allocation patterns of purple loosestrife were recorded
for two growing seasons. During the first year, root herbivory reduced plant height; plant competition delayed flowering;
and the interaction of root herbivory and plant competition resulted in reductions in plant height, shoot weight and total
dry biomass. Plant competition or larval feeding did not affect the biomass allocation pattern in the first year. These results
indicate the importance of interactions of plant competition and herbivory in reducing plant performance – at least during
the establishment period of purple loosestrife. In the second growing season, root herbivory reduced plant height, biomass
of all plant parts, delayed and shortened the flowering period, and changed the biomass allocation patterns. Plant competition
delayed flowering and reduced the dry weight of fine roots. The interaction of root herbivory and plant competition delayed
flowering. Root herbivory was more important than plant competition in reducing the performance of established purple loosestrife
plants. This was due, in part, to intense intraspecific competition among the grass individuals effectively preventing shoot
elongation of P. pratense and resulting in a carpet like growth.
Received: 3 April 1997 / Accepted: 27 July 1997 相似文献
2.
Invasive plant species can have strong direct negative effects on native plants. Depending on the nature of interactions among
competitors and consumers within a community, strong indirect interactions may either augment or offset direct effects. We
used path analysis to estimate the relative importance of direct and indirect effects of Euphorbia esula, an unpalatable invasive plant, on Balsamorhiza sagittata, a native forb, through “shared defense” and by suppression of native competitors. Our results indicate that E. esula had strong direct negative effects on B. sagittata, but also that its net effect was reduced by 75% because of indirect positive effects. This reduction was because in equal
parts of lessened competition from other native plants eliminated from E. esula stands and to lower levels of herbivory inside E. esula stands, apparently caused by indirect defense of B. sagittata by E. esula. To our knowledge, this is the first evidence that invaders may indirectly reduce herbivory on native plants, a phenomenon
that may commonly occur with unpalatable invaders. Furthermore, our results highlight the potential complexity of interactions
between native and invasive plants. 相似文献
3.
We tested the hypothesis that phytophagous insects would have a strong top-down effect on early successional plant communities
and would thus alter the course of succession. To test this hypothesis, we suppressed above-ground insects at regular intervals
with a broad-spectrum insecticide through the first 3 years of old-field succession at three widely scattered locations in
central New York State. Insect herbivory substantially reduced total plant biomass to a similar degree at all three sites
by reducing the abundance of meadow goldenrod, Solidago altissima. As a result, Euthamia graminifolia dominated control plots whereas S. altissima dominated insecticide-treated plots by the third year of succession. S. altissima is the dominant old-field herbaceous species in this region but typically requires at least 5 years to become dominant. Past
explanations for this delay have implicated colonization limitation whereas our data demonstrate that insect herbivory is
a likely alternative explanation. A widespread, highly polyphagous insect, the xylem-tapping spittlebug, Philaenus spumarius, appeared to be the herbivore responsible for the reduction in standing crop biomass at all three sites. Insect herbivory
typically caused little direct leaf tissue loss for the ten plant species we examined, including S. altissima. Consequently, the amount of leaf area removed was not a reliable indicator of the influence of insect herbivory on standing
crop biomass or on early succession. Overall, we found a strong top-down effect of insect herbivores on biomass at several
sites, so our results may be broadly applicable. These findings run counter to generalizations that top-down effects of herbivores,
particularly insects, are weak in terrestrial systems. These generalizations may not apply to insects, such as spittlebugs,
that can potentially mount an effective defense (i.e., spittle) against predators and subsequently reach relatively high abundance
on common plant species. Our results suggest that insect herbivory may play an important but often overlooked role during
early old-field succession.
Received: 26 December 1998 / Accepted: 3 April 1999 相似文献
4.
The effects of temperature on photosynthesis of a rosette plant growing at ground level, Acaena cylindrostachya R. et P., and an herb that grows 20–50 cm above ground level, Senecio formosus H.B.K., were studied along an altitudinal gradient in the Venezuelan Andes. These species were chosen in order to determine
– in the field and in the laboratory – how differences in leaf temperature, determined by plant form and microenvironmental
conditions, affect their photosynthetic capacity. CO2 assimilation rates (A) for both species decreased with increasing altitude. For Acaena leaves at 2900 m, A reached maximum values above 9 μmol m−2 s−1, nearly twice as high as maximum A found at 3550 m (5.2) or at 4200 m (3.9). For Senecio leaves, maximum rates of CO2 uptake were 7.5, 5.8 and 3.6 μmol m−2 s−1 for plants at 2900, 3550 and 4200 m, respectively. Net photosynthesis-leaf temperature relations showed differences in optimum
temperature for photosynthesis (A
o.t.) for both species along the altitudinal gradient. Acaena showed similar A
o.t. for the two lower altitudes, with 19.1°C at 2900 m and 19.6°C at 3550 m, while it increased to 21.7°C at 4200 m. Maximum
A for this species at each altitude was similar, between 5.5 and 6.0 μmol m−2 s−1. For the taller Senecio, A
o.t. was more closely related to air temperatures and decreased from 21.7°C at 2900 m, to 19.7°C at 3550 m and 15.5°C at 4200 m.
In this species, maximum A was lower with increasing altitude (from 6.0 at 2900 m to 3.5 μmol m−2 s−1 at 4200 m). High temperature compensation points for Acaena were similar at the three altitudes, c. 35°C, but varied in Senecio from 37°C at 2900 m, to 39°C at 3550 m and 28°C at 4200 m. Our results show how photosynthetic characteristics change along
the altitudinal gradient for two morphologically contrasting species influenced by soil or air temperatures.
Received: 5 July 1997 / Accepted: 25 October 1997 相似文献
5.
Two field experiments were conducted using three dominant perennial species of the Chihuahuan Desert: Hilaria mutica (a tussock grass), Larrea tridentata (a microphyllous shrub) and Opuntia rastrera (a flat-stemmed succulent cactus). Two hypotheses concerning competition in arid plant communities were tested. (1) Marked
resource partitioning with no interspecific competition could be expected since the three species belong to different life-forms,
and that plant growth in deserts is basically limited by harsh environmental conditions. (2) Alternatively, resource scarcity
(particularly water) will result in strong plant competition. In a 1-year removal experiment, water status and plant growth
of the three species were monitored in twelve 10 m × 10 m plots randomized in three blocks and assigned to the following treatments:
(a) removal of all species, except H. mutica; (b) removal of all species, except L. tridentata; (c) removal of all species, except O. rastrera, and (d) control without any manipulation. In a watering experiment, under two neighbourhood conditions (growing isolated
or in associations of plants of the three species in plots of 20 m2), the water status of the three species and the growth of H.mutica and L.tridentata were studied for 32 days after an irrigation equivalent to 30 mm of rain, similar to a strong storm event at the site. In
the removal experiment, where plants were free to capture water, no evidence of competition was observed. However, during
the watering experiment, in which water was forced into the soil, competitive effects were observed. Associated individuals
of L. tridentata had lower xylem water potentials and osmotic potentials (OPs) and produced shorter twigs and less leaves and nodes. Although
less pronounced, neighbours also had a negative effect on the OP in O. rastrera. According to these results, the intensity of the interspecific competition for water seems to depend on the level of resource
availability in the soil. Thus, the validity of the two hypotheses tested in this study also depends on the level of resources.
Competition could be absent or very low in years of low precipitation, as in the year of this study (173 mm against a 25-year
average of 264 mm). However, when soil water availability is high, e.g. following heavy rain, the negative interactions between
species could be more intense.
Received: 3 October 1997 / Accepted: 23 March 1998 相似文献
6.
John L. Maron 《Oecologia》1997,110(2):284-290
Seedlings suffer high mortality in most plant populations, with both competition and herbivory proposed as being important
mechanisms causing seedling death. The relative strength of these factors, however, is often unknown. Here I ask how interspecific
competition for light and insect herbivory jointly affect seedling survival of bush lupine (Lupinus arboreus), a native shrub common to coastal California. Bush lupine seedlings germinate in grasslands during winter, and throughout
spring potentially compete for light with surrounding fast-growing annual grasses. By early summer, after grasses have died,
seedlings can be defoliated by a locally abundant caterpillar, the western tussock moth (Orgyia vetusta). I examined the relative importance of competition and insect herbivory on seedling survival in two separate experiments.
First, I compared seedling mortality in plots either exposed to or protected from tussock moth larvae. Plants were protected
from herbivory by the judicious use of insecticide; control plants were sprayed with water. Tussock moth herbivory resulted
in significantly greater (31%) seedling mortality. To determine the effects of interspecific competition for light on seedling
survival, I manipulated the density of grass surrounding lupine seedlings. I removed all vegetation surrounding some individuals,
and left intact vegetation surrounding others. Reducing competition resulted in a 32% increase in seedling survival from February
to June, as well as changes in seedling growth. To determine whether there are interactive effects of competition and herbivory
on seedling survival, I enclosed tussock moth larvae on half of all surviving seedlings within each of the two prior competition
treatments, comparing growth and survival of defoliated and undefoliated seedlings. Defoliation in June led to an additional
50% mortality for individuals that had grown with competitors through spring, and a 53% additional mortality for seedlings
that grew without competitors through spring. Thus, although competition and herbivory both caused substantial seedling mortality,
there was no statistical interaction between these factors. Competition-free plants were not less vulnerable to herbivory
than plants that previously grew with competitors. Taken together, these experiments indicate that competition and herbivory
are both important sources of mortality for bush lupine seedlings.
Received: 4 April 1996 / Accepted: 5 November 1996 相似文献
7.
Some exotic plants are able to invade habitats and attain higher fitness than native species, even when the native species
are closely related. One explanation for successful plant invasion is that exotic invasive plant species receive less herbivory
or other enemy damage than native species, and this allows them to achieve rapid population growth. Despite many studies comparing
herbivory and fitness of native and invasive congeners, none have quantified population growth rates. Here, we examined the
contribution of herbivory to the population dynamics of the invasive species, Lespedeza cuneata, and its native congener, L. virginica, using an herbivory reduction experiment. We found that invasive L. cuneata experienced less herbivory than L. virginica. Further, in ambient conditions, the population growth rate of L. cuneata (λ = 20.4) was dramatically larger than L. virginica (λ = 1.7). Reducing herbivory significantly increased fitness of only the largest L. virginica plants, and this resulted in a small but significant increase in its population growth rate. Elasticity analysis showed that
the growth rate of these species is most sensitive to changes in the seed production of small plants, a vital rate that is
relatively unaffected by herbivory. In all, these species show dramatic differences in their population growth rates, and
only 2% of that difference can be explained by their differences in herbivory incidence. Our results demonstrate that to understand
the importance of consumers in explaining the relative success of invasive and native species, studies must determine how
consumer effects on fitness components translate into population-level consequences.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
Consumer-facilitated invasions have been proposed as an alternative mechanism to direct competitive exclusion to explain the
replacement of native plants by exotics. In a factorial field experiment manipulating competition from the exotic plant Alliaria petiolata and herbivory by exotic mollusks, we documented that mollusk herbivory significantly reduced the survival of two species
of native palatable plants, but found minimal direct herbivore effects on less palatable species, including the invasive A. petiolata. These effects were evident after one growing season on younger juvenile plants of Aster cordifolius, but only after two growing seasons on older transplants of the same species, suggesting a greater vulnerability of young
plants. In contrast to our expectations, A. petiolata competition alone had no effect on any of the six native species we tested. However, competition from A. petiolata did affect the survival of the most palatable native plant when mollusks were also present. While not significant for any
other single species, this same pattern was observed for three of the five remaining native species tested. The selective
grazing on palatable plants that we document provides novel evidence contributing to our understanding of observed shifts
in the forest herbaceous layer towards the dominance of exotic plants and unpalatable species. More broadly, our results highlight
the importance of the interactive effect of consumers and inter-specific competition in forest understories via its contribution
to differential survival among regenerating species. 相似文献
9.
African grasses, introduced into Neotropical savannas to improve forage quality, have spread successfully and displaced native
plants. To understand their competitive relationships, we compared biomass production and allocation, plant architecture and
phenology, net photosynthesis (Pn), water relations, and nutrient content under fire and simulated herbivory between two C4 grasses, the native Trachypogon plumosus and the introduced Hyparrhenia rufa from a seasonal savanna in Venezuela. All variables were strongly influenced by the rainfall regime. Hyparrhenia produced bigger plants (in mass and size) with a large proportion of mass (>75%) allocated to leaves and culms. Its biomass
production was more affected by fire than by defoliation. In contrast, Trachypogon was more affected by defoliation than by fire which promoted a flush of leaf growth even in the dry season. Fire caused up
to 85% mortality in Hyparrhenia but none in Trachypogon where it increased inflorescence production. However, fire promoted abundant seed germination and fast seedling growth in
Hyparrhenia, enabling it to colonize new areas. During the growing season Trachypogon had higher Pn and lower leaf water potential (Ψ) than Hyparrhenia but differences among treatments were not significant for either grass. Pn of Trachypogon ceased at a lower Ψ (−3.0 MPa) than in Hyparrhenia (−2.0 MPa), indicating its higher tolerance to water stress. During the dry season, Trachypogon leaves remained alive and retained low Pn. Leaf nutrient content was higher during the rainy season in both species. Differences
in Pn could not explain the higher seasonal biomass production of Hyparrhenia. However, its water stress evasion strategy, larger biomass allocated to leaves, abundant germination and fast seedling growth
appeared to be responsible for the success of Hyparrhenia as an invader of Neotropical savannas.
Received: 17 August 1998 / Accepted: 3 March 1999 相似文献
10.
Efficient production of recombinant barley α-amylase has been achieved in Aspergillus niger. The cDNA encoding α-amylase isozyme 1 (AMY1) and its signal peptide was placed under the control of the Aspergillus nidulans glyceraldehyde-3-phosphate dehydrogenase (gpd) promoter and the A. nidulans trpC gene terminator. Secretion yields up to 60 mg/l were obtained in media optimised for α-amylase activity and low protease
activity. The recombinant AMY1 (reAMY1) was purified to homogeneity and found to be identical to native barley AMY1 with respect
to size, pI, and immunoreactivity. N-terminal sequence analysis of the recombinant protein indicated that the endogenous plant signal
peptide is correctly processed in A. niger. Electrospray ionisation/mass spectrometry gave a molecular mass for the dominant form of 44 960 Da, in accordance with the
loss of the LQRS C-terminal residues; glycosylation apparently did not occur. The activities of recombinant and native barley
α-amylases are very similar towards insoluble and soluble starch as well as 2-chloro-4-nitrophenol β-d-maltoheptaoside and amylose (degree of polymerisation = 17). Barley α-amylase is the first plant protein efficiently secreted
and correctly processed by A. niger using its own signal sequence.
Received: 22 August 1997 / Received revision: 21 November 1997 / Accepted: 29 November 1997 相似文献
11.
Both competition and herbivory have been shown to reduce plant survival, growth, and reproduction. Much less is known about whether competition and herbivory interact in determining plant performance, especially for introduced, weedy plant species in the invaded habitat. We simultaneously evaluated both the main and interactive effects of plant neighbors and insect herbivory on rosette growth and seed reproduction in the year of flowering for Cirsium vulgare (bull thistle, spear thistle), an introduced Eurasian species, in tallgrass prairie in 2 years. Effects of insect herbivory were strong and consistent in both years, causing reduced plant growth and seed production, whereas the effects of competition with established vegetation were weak. The amount of herbivore damage inflicted on rosettes did not depend on the presence of neighbor plants. We also found no interaction between competition and herbivory on key parameters of plant growth and fitness. The results of this study contradict the hypothesis that competitive context interacts with insect herbivory in limiting the invasiveness of this introduced thistle. Further, the results provide additional, experimental evidence that high levels of herbivory on established rosettes by native insects exert significant biotic resistance to the invasiveness of C. vulgare in western tallgrass prairie. 相似文献
12.
H. Okada T. Sekiya K. Yokoyama H. Tohda H. Kumagai Y. Morikawa 《Applied microbiology and biotechnology》1998,49(3):301-308
A cbh2 cDNA encoding Trichoderma reesei QM9414 cellobiohydrolase II, located on the expression vector whose copy number is controlled by the level of gentamicin,
was successfully expressed under the control of a human cytomegalovirus promoter in the fission yeast, Schizosaccharomyces pombe. The 24-amino-acid leader peptide of the cbh2 gene was recognized by the yeast, enabling the efficient secretion of the heterologous cellobiohydrolase. The transformed
S. pombe strain produced over 115 μg cellobiohydrolase proteins/ml rich medium supplemented with malt extract and 100 μg/ml gentamicin.
The molecular masses of the recombinant cellobiohydrolases, secreted as two molecular species, were estimated to be 70 kDa
and 72 kDa by sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE). Deglycosylation treatments revealed that
the recombinant enzymes were overglycosylated and scarcely susceptible to α-mannosidase. The recombinant enzymes showed no
carboxymethylcellulase activity, but showed similar characteristics to those of a native enzyme purified from T. reesei in their optimum pH and temperature, pH and temperature stabilities, and V
max values toward phosphoric-acid-swollen cellulose as substrate, except that their K
m values were about fourfold higher than that of the native enzyme.
Received: 4 August 1997 / Received revision: 13 October 1997 / Accepted: 31 October 1997 相似文献
13.
There is a semidian (≈12 h) rhythm in the flowering response of the short-day plant Pharbitis nil Choisy following 90 min exposure to either far-red light/darkness or a temperature drop (27 °C to 12 °C) given at various
times in constant conditions before an inductive dark period. This semidian rhythmic response to the temperature-drop pretreatments
in the light is also evident through the inductive dark period without change of phase. Furthermore, those pretreatments which
increase flowering also advance the time of maximum sensitivity to red light (R) interruptions of the dark period by up to
1.5 h and shorten the critical night length. Conversely, pretreatments which reduce flowering delay the time of maximum R
inhibition by up to 1.5 h and increase the critical night length by the same amount. However the phase of a circadian rhythm
of flowering response had no effect on either the time of maximum R inhibition or the critical night length. Thus, the semidian
rhythm determines both the time of maximum R inhibition and the critical night length in Pharbitis.
Received: 8 November 1997 / Accepted: 7 January 1998 相似文献
14.
The novel associations between invasive plants and their natural enemies in the introduced range have recently received increasing attention; however, the effects of novel enemies on exotic plant performance and competition with native species remain poorly explored. Here, we tested the impact of herbivory by a native beetle, Cassida piperata, on the performance of the exotic species Alternanthera philoxeroides and competition with a native congener, Alternanthera sessilis, using common garden experiments in central China. We found A. philoxeroides was able to fully compensate for intense herbivory by C. piperata. Herbivory by C. piperata that released at the average density in this region had no impact on competition between the native and exotic plant species. Our results indicate that herbivory by novel enemies may not reduce exotic plant performance due to plant compensation. However, high tolerance to herbivory may not confer a competitive advantage for exotic species compared to less tolerant native competitors if the herbivore damage is below a certain threshold. Thus, it is necessary to assess the impact of novel enemies on exotic plant performance and competition with native plants along gradients of insect densities. This may lead to a better understanding of how best to exploit the role of native herbivores in facilitating or slowing plant invasions. 相似文献
15.
A. J. Sillman C. J. O'Leary C. D. Tarantino E. R. Loew 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1999,184(1):37-47
Scanning electron microscopy, microspectrophotometry, and spectrophotometry of digitonin extracts were employed to characterize
the photoreceptors and visual pigments of two freshwater Acipenseriformes. The retinas of the shovelnose sturgeon, Scaphirhynchus platorynchus (Acipenseridae), and the paddlefish, Polyodon spathula (Polyodontidae) are dominated by large rods with long, broad outer segments. A second rod, rare and much narrower than the
dominant rod, is present in Scaphirhynchus but not seen in Polyodon. The absorbance maximum of the visual pigment in the rods of Polyodon is near 540 nm; that of Scaphirhynchus near 534 nm. The retinas of both species contain substantial numbers of large, single cones, about 33% of the photoreceptors
in Scaphirhynchus; 37% in Polyodon. Scaphirhynchus cone pigments have absorbance maxima near 610 nm, 521 nm and 470 nm, respectively. Polyodon cone pigments absorb maximally near 607 nm and 535 nm, respectively. All visual pigments are based on vitamin A2. The data are compared to those from other Acipenseriformes and are discussed in terms of lifestyle and behavior.
Accepted: 7 October 1998 相似文献
16.
Natural selection on flowering phenology has been studied primarily in terms of plant–pollinator interactions and effects
of abiotic conditions. Little is known, however, about geographic variation in other biotic factors such as herbivores and
its consequence for differential selection on flowering phenology among populations. Here, we examine selection by floral
herbivores on the flowering phenology of Arabidopsis halleri subsp. gemmifera using two adjacent populations with contrasting herbivory regimes. Intensive floral herbivory by the leaf beetle Phaedon brassicae occurs in one population, while the beetle is absent in another population. We tested the hypothesis that the two populations
experience differential selection on flowering time that is attributable to the presence or absence of floral herbivory. A
two-year field study showed that early flowering was favoured in the population under intensive floral herbivory, whereas
selection for early flowering was not found in one year in the population where floral herbivory was absent. Selection for
early flowering disappeared when the abundance of floral herbivores was artificially decreased in a field experiment. Thus,
the heterogeneous distribution of P. brassicae was a major agent for differential selection on flowering time. However, flowering time did not differ between the two populations
when plants were grown in the laboratory. The lack of genetic differentiation in flowering time may be explained by ongoing
gene flow or recent invasion of P. brassicae. This study illustrates that the role of floral herbivory in shaping geographic variation in selection on flowering phenology
may be more important than previously thought. 相似文献
17.
We studied the effects of a change in flowering date on the reproductive output of a short-day annual plant, Xanthium canadense. The flowering date was changed by photoperiodic manipulation to 1 month earlier or later than the natural flowering date.
Plants with the natural flowering date attained the highest reproductive output. For those flowering 1 month earlier or later,
the reproductive output was decreased by 42% or 23%, respectively. The reproductive output was analyzed as the product of
the biomass production during the reproductive period and its allocation to the reproductive organs. Although delay in flowering
increased biomass production, it decreased its fractional allocation to the reproductive organs. The highest reproductive
output in the natural flowering plants resulted from a compromise between these two effects of flowering. Plants flowering
earlier had higher translocation rates to the reproductive organs and accelerated plant senescence. Later flowering caused
a reduction in biomass translocation to the reproductive organs and thus extended the reproductive period. These experimental
results are discussed in relation to the cost of reproduction and the optimal time for flowering that maximizes the final
reproductive output. It is suggested that the natural flowering time maximized the reproductive output while minimizing the
cost of reproduction.
Received: 11 September 1997 / Accepted: 12 December 1997 相似文献
18.
Invasive plants may be attacked both above ground and below ground. Few studies have, however, investigated the simultaneous effects of above‐ground and below‐ground herbivory. In the present study, we report the effects of beetle herbivory and nematode infection on alligator weed, Alternanthera philoxeroides, an invasive plant in China. We found that the root‐knot nematode Meloidogyne incognita widely occurred on the plant in south China. To examine its effect on the plant in conjunction with above‐ground herbivory, we conducted a field common garden experiment with a local insect defoliator, Cassida piperata. We also included the native congener Alternanthera sessilis in our experiments for a comparison of the response of invasive and native species. We found no significant effects on plant biomass of the nematode infection in conjunction with the above‐ground herbivory. Further chemical analysis, however, showed that the water‐soluble carbohydrate content in roots of A. philoxeroides was significantly increased in plants attacked by both the nematode and the herbivore compared with the water‐soluble carbohydrate content in plants attacked by only the nematode or herbivore alone. We found no such change in the native congener A. sessilis. Together these results may suggest that A. philoxeroides tolerates joint above‐ground and below‐ground damage by allocating more resources to below‐ground material. 相似文献
19.
Trichoderma asperellum strain T34 has been reported to control the disease caused by Fusarium oxysporum f.sp. lycopersici (Fol) on tomato plants. To study the importance of iron concentration in the growth media for the activity and competitiveness
of T34 and the pathogen, we tested four iron concentrations in the nutrient solution [1, 10, 100, and 1000 μM provided as
EDTA/Fe(III)] in a biological control experiment with T34 and Fol in tomato plants. The reduction of the Fusarium-infected
shoot by T34 was only significant at 10 μM Fe. We hypothesized that Fe competition is one of the key factors in the biocontrol
activity exerted by T34 against Fol, as an increase in Fe concentration over 10 μM would lead to the suppression of T34 siderophore
synthesis and thus inhibition of Fe competition with Fol. T34 significantly reduced the populations of Fol at all the doses
of Fe assayed. In contrast, Fol enhanced the populations of T34 at 1 and 10 μM Fe. Nevertheless, several plant physiological
parameters like net CO2 assimilation (A), stomatal conductance (g
s), relative quantum efficiency of PSII (Φ
PSII), and efficiency of excitation energy capture by open PSII reactive centers (Fv′/Fm′) demonstrated the protection against
Fol damage by treatment with T34 at 100 μM Fe. The first physiological parameter affected by the disease progression was g
s. Plant dry weight was decreased by Fe toxicity at 100 and 1,000 μM. T34-treated plants had significantly greater heights
and dry weights than control plants at 1,000 μM Fe, even though T34 did not reduce the Fe content in leaves or stems. Furthermore,
T34 enhanced plant height even at the optimal Fe concentration (10 μM) compared to control plants. In conclusion, T. asperellum strain T34 protected tomato plants from both biotic (Fusarium wilt disease) and abiotic stress [Fe(III) toxic effects]. 相似文献
20.
The influence of herbivory and weather on the vital rates of two closely related cactus species
下载免费PDF全文
![点击此处可从《Ecology and evolution》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kristen E. Sauby John Kilmer Mary C. Christman Robert D. Holt Travis D. Marsico 《Ecology and evolution》2017,7(17):6996-7009
Herbivory has long been recognized as a significant driver of plant population dynamics, yet its effects along environmental gradients are unclear. Understanding how weather modulates plant–insect interactions can be particularly important for predicting the consequences of exotic insect invasions, and an explicit consideration of weather may help explain why the impact can vary greatly across space and time. We surveyed two native prickly pear cactus species (genus Opuntia) in the Florida panhandle, USA, and their specialist insect herbivores (the invasive South American cactus moth, Cactoblastis cactorum, and three native insect species) for five years across six sites. We used generalized linear mixed models to assess the impact of herbivory and weather on plant relative growth rate (RGR) and sexual reproduction, and we used Fisher's exact test to estimate the impact of herbivory on survival. Weather variables (precipitation and temperature) were consistently significant predictors of vital rate variation for both cactus species, in contrast to the limited and varied impacts of insect herbivory. Weather only significantly influenced the impact of herbivory on Opuntia humifusa fruit production. The relationships of RGR and fruit production with precipitation suggest that precipitation serves as a cue in determining the trade‐off in the allocation of resources to growth or fruit production. The presence of the native bug explained vital rate variation for both cactus species, whereas the invasive moth explained variation only for O. stricta. Despite the inconsistent effect of herbivory across vital rates and cactus species, almost half of O. stricta plants declined in size, and the invasive insect negatively affected RGR and fruit production. Given that fruit production was strongly size‐dependent, this suggests that O. stricta populations at the locations surveyed are transitioning to a size distribution of predominantly smaller sizes and with reduced sexual reproduction potential. 相似文献