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1.
Aluminium (Al) tolerance of fourteen white clover (Trifolium repens L.) cultivars from eleven countries was compared in the greenhouse in the Wainui silt loam (Typic Dystrochrept) to which
Al had been added at nine levels (0, 2.5, 5, 20, 50, 150, 250, 500 and 750 mg kg−1 of soil) as Al2 (SO4)3 and incubated for 30 days. None of the white clover cultivars, including those either referred to as Al-tolerant, Dusi and
Pathfinder, or from countries that have large areas of acid soils, El Lucero M.A.G., Bayucua, Bage and Zapican, showed greater
Al-tolerance than ‘Grasslands Huia’ white clover. Subsequent screening for Al-tolerance can therefore be restricted to germplasm
with wide agronomic adaptation. 相似文献
2.
Quan-fu Wang Yan-hua Hou Jin-lai Miao Guang-you Li 《Acta Physiologiae Plantarum》2009,31(6):1097-1102
The effect of ultraviolet-B (UV-B) radiation on Antarctic phytoplankton has become an attractive ecological issue as a result
of annual springtime ozone depletion. The effects of UV-B radiation on the growth and antioxidant enzymes were investigated
using Antarctic sea ice microalgae Chlamydomonas sp. ICE-L as the material in this study. The results demonstrated that UV-B radiation could notably inhibit the growth, especially
at high UV-B radiation intensity (70 μW cm−2). Malondialdehyde and O2
·− content in ICE-L increased rapidly in early days (1–3 days) exposed to UV-B radiation enhancement, then decreased rapidly.
In the stress of UV-B radiation enhancement, the superoxide dismutase, peroxidase and Catalase activities of 1–4 days in ICE-L
were obviously higher than those in the control, and their activities became higher at high UV-B radiation intensity (70 μW cm−2). These enzymes activity of 7 days would kept stable at low UV-B radiation intensity (35 μW cm−2), but kept high level at high UV-B radiation intensity (70 μW cm−2). However, the ascorbate peroxidase activity in ICE-L kept stable under the stress of UV-B radiation enhancement. The above
experimental results indicated that the antioxidant enzyme system played an important role in the adaptation of Antarctic
ice microalgae under the UV-B radiation change of Antarctic ecosystems. 相似文献
3.
The combined effects of UV-B irradiation and foliar treatment with selenium on two buckwheat species, common (Fagopyrum esculentum Moench) and tartary [Fagopyrum tataricum (L.) Gaertn.] buckwheat, that underwent different intensity of breeding, were examined. Plants grown outdoors under three
levels of UV-B radiation were studied for 9 weeks, from sowing to ripening. At week 7 they were sprayed with solution containing
1 g(Se) m−3 that presumably mitigates UV-B stress. Morphological, physiological, and biochemical parameters of the plants were monitored.
Elevated UV-B radiation, corresponding to a 17 % reduction of the ozone layer, induced synthesis of UV absorbing compounds.
In both buckwheat species it also caused a reduction in amounts of chlorophyll a during the time of intensive growth, an effect, which was increased in tartary buckwheat in the presence of selenium. The
respiratory potential, measured as terminal electron transport system activity, was lower in plants subjected to enhanced
UV-B radiation during the time of intensive growth. The effective quantum yield of photosystem 2 was also reduced due to UV-B
radiation in both buckwheat species and was mitigated by the addition of Se. Se treatment also mitigated the stunting effect
of UV-B radiation and the lowering of biomass in common buckwheat. 相似文献
4.
Due to anthropogenic influences, solar UV-B irradiance at the earth’s surface is increasing. To determine the effects of enhanced
UV-B radiation on photosynthetic characteristics of Prunus dulcis, two-year-old seedlings of the species were submitted to four levels of UV-B stress, namely 0 (UV-Bc), 4.42 (UV-B1), 7.32 (UV-B2) and 9.36 (UV-B3) kJ m−2 d−1. Effects of UV-B stress on a range of chlorophyll (Chl) fluorescence parameters (FPs), Chl contents and photosynthetic gas-exchange
parameters were investigated. UV-B stress promoted an increase in minimal fluorescence of dark-adapted state (F0) and F0/Fm, and a decrease in variable fluorescence (Fv, Fv/Fm, Fv/F0 and F0/Fm) due to its adverse effects on photosystem II (PSII) activity. No significant change was observed for maximal fluorescence
of dark-adapted state (Fm). Enhanced UV-B radiation caused a significant inhibition of net photosynthetic rate (P
N) at UV-B2 and UV-B3 levels and this was accompanied by a reduction in stomatal conductance (g
s) and transpiration rate (E). The contents of Chl a, b, and total Chl content (a+b) were also significantly reduced at increased UV-B stress. In general, adverse UV-B effects became significant at the highest
tested radiation dose 9.36 kJ m−2 d−1. The most sensitive indicators for UV-B stress were Fv/F0, Chl a content and P
N. Significant P<0.05 alteration in these parameters was found indicating the drastic effect of UV-B radiation on P. dulcis. 相似文献
5.
Ulla Anttila Riitta Julkunen-Tiitto Matti Rousi Shiyong Yang Markus J. Rantala Teija Ruuhola 《Oecologia》2010,164(1):163-175
Enhanced ultraviolet-B (UV-B) radiation may have multiple effects on both plants and animals and affect plant–herbivore interactions
directly and indirectly by inducing changes in host plant quality. In this study, we examined combined effects of UV-B and
herbivory on the defence of the mountain birch (Betula pubescens ssp. czerepanovii) and also the effects of enhanced UV-B radiation on a geometrid with an outbreak cycle: the autumnal moth (Epirrita autumnata). We established an experiment mimicking ozone depletion of 30% (a relevant level when simulating ozone depletion above Northern
Lapland). Both arctic species responded only slightly to the enhanced level of UV-B radiation, which may indicate that these
species are already adapted to a broader range of UV-B radiation. UV-B exposure slightly induced the accumulation of myricetin
glycosides but had no significant effect on the contents of quercetin or kaempferol derivatives. Mountain birch seedlings
responded more efficiently to herbivory wounding than to enhanced UV-B exposure. Herbivory induced the activities of foliar
oxidases that had earlier been shown to impair both feeding and growth of moth larvae. In contrast, the contents of foliar
phenolics did not show the same response in different clones, except for a decrease in the contents of tannin precursors.
The induction of foliar phenoloxidase activities is a specific defence response of mountain birches against insect herbivory.
To conclude, our results do not support the hypothesis that the outbreak cycle of the autumnal moth can be explained by the
cycles of solar activity and UV-B. 相似文献
6.
Several studies have found the photosynthetic integration in clonal plants to response to resource heterogeneity, while little
is known how it responses to heterogeneity of UV-B radiation. In this study, the effects of heterogeneous UV-B radiation (280–315
nm) on gas exchange and chlorophyll fluorescence of a clonal plant Trifolium repens were evaluated. Pairs of connected and severed ramets of the stoloniferous herb T. repens were grown under the homogeneity (both of ramets received only natural background radiation, ca. 0.6 kJ m−2 d−1) and heterogeneity of UV-B radiation (one of the ramet received only natural background radiation and the other was exposed
to supplemental UV-B radiation, 2.54 kJ m−2 d−1) for seven days. Stomatal conductance (g
s), intercellular CO2 concentration (C
i) and transpiration rate (E) showed no significant differences in connected and severed ramets under homogenous and heterogeneous UV-B radiation, however,
net photosynthetic rate (P
N) and maximum photosynthetic rate (P
max) of ramets suffered from supplemental increased UV-B radiation and that of its connected sister ramet decreased significantly.
Moreover, additive UV-B radiation resulted in a notable decrease of the minimal fluorescence of dark-adapted state (Fo), the electron transport rate (ETR) and photochemical quenching coefficient (qP) and an increase of nonphotochemical quenching (NPQ) under supplemental UV-B radiation, while physiological connection reverse
the results. In all, UV-B stressed ramets could benefit from unstressed ramets by physiological integration in photosynthetic
efficiency, and clonal plants are able to optimize the efficiency to maintain their presence in less favourable sites. 相似文献
7.
Near-isogenic lines of maize varying in their genes for flavonoid biosynthesis were utilized to examine the effects of foliar
flavonoids and nutrient deficiency on maximum net photosynthetic rate (P
N) and chlorophyll (Chl) fluorescence (Fv/Fm) in response to ultraviolet-B (UV-B) radiation. Plants with deficient (30 to 70 % lower N, K, Mn, Fe, and Zn) and sufficient
nutrients were exposed to four irradiation regimes: (1) no UV-B with solar photosynthetically active radiation (PAR), (2) two day shift to ambient artificial UV-B, 8.2–9.5 kJ m−2 d−1 (21–25 mmol m−2 d−1); (3) continuous ambient artificial UV-B; (4) continuous solar UV-B in Hawaii 12–18 kJ m−2 d−1 (32–47 mmol m−2 d−1). The natural ratio of UVB: PAR (0.25–0.40) was maintained in the UV-B treatments. In the adequately fertilized plants, lines
b and lc had higher contents of flavonoids and anthocyanins than did lines hi27 and dta. UV-B induced the accumulation of
foliar flavonoids in lines hi27 and b, but not in the low flavonoid line dta or in the high flavonoid line lc. In plants grown
on deficient relative to adequate nutrients, flavonoid and anthocyanin contents decreased by 30–40 and 40–50 %, respectively,
and Chl a and Chl b contents decreased by 30 and 70 %, respectively. The UV-B treatments did not significantly affect P
N and Fv/Fm in plants grown on sufficient nutrients, except in the low flavonoid lines dta and hi27 in which P
N and Fv/Fm decreased by ∼15 %. P
N, Fv/Fm, and stomatal conductance decreased markedly (20–30 %) in all lines exposed to UV-B when grown on low nutrients. The decrease
in Fv/Fm was 10 % less in higher flavonoid lines b and lc. The photosynthetic apparatus of maize readily tolerated ambient UV-B in
the tropics when plants were adequately fertilized. In contrast, ambient UV-B combined with nutrient deficiency significantly
reduced photosynthesis in this C4 plant. Nutrient deficiency increased the susceptibility of maize to UV-B-induced photoinhibition in part by decreasing the
contents of photoprotective compounds. 相似文献
8.
We report the effect of UV-B radiation (0.8 ± 0.1 mW cm−2) and UV-B radiation supplemented with low-intensity PAR (∼80 μmol photons m−2 s−1) on the photosynthesis, photosynthetic pigments, phosphoglycolipids, oxidative damage, enzymatic antioxidants, and UV-absorbing
compounds in Phormidium tenue, a marine cyanobacterium. UV-B radiation resulted in a decline in photosynthesis and photosynthetic pigments leading to lower
biomass. P. tenue synthesized UV-absorbing compounds like mycosporine-like amino acids (MAAs) and scytonemin in response to UV-B radiation.
Quantity of MAAs and scytonemin was higher when UV-B was supplemented with low-level PAR. UV-B treatment also resulted in
quantitative changes in phosphoglycolipids of the membrane. The UV-B treatment resulted in a slight increase in the level
of peroxidation of cell membrane and very little increase in the activity of superoxide dismutase (SOD). Results indicate
that UV-B affected photosynthesis and that the main protective system was the synthesis of MAAs and scytonemin-like compounds
rather than antioxidant enzymes such as SOD. 相似文献
9.
Li Fangmin Wang Jun Chen Yuping Zou Zhirong Wang Xunling Yue Ming 《Frontiers of Biology in China》2007,2(4):414-418
Five different doses of ultraviolet-B (UV-B) radiation were supplied to tomato (Lycopersicon esculeutum. Mill) with the doubled CO2 concentration (700 μmol · mol−1) in the winter plastic greenhouse. The influences on the seedling growth, fruit quality and yield of tomato were investigated.
Results showed that the seedling growth, and the contents of UV absorbing compounds, soluble sugar, organic acid, vitamin
C and lycopene of tomato fruits, and yield of tomato increased under doubled CO2 concentration. Under the doubled CO2 concentration the effects of lost doses of UV-B radiation could further promote the effects of doubled CO2 concentration. However, there is no significant increase in yield of tomato. The best dose of UV-B radiation is about 1.163
kJ·m−2. When the dose of UV-B radiation is more than it, the effects of UV-B will be reduced.
__________
Translated from Journal of Wuhan Botanical Research, 2006, 24(1): 49–53 [译自: 武汉植物学研究] 相似文献
10.
Microcoleus chthonoplastes constitutes one of the dominant microorganisms in intertidal microbial mat communities. In the laboratory, the effects of
repeated daily exposure to ultraviolet radiation (16:8 light:dark cycle) was investigated in unicyanobacterial cultures isolated
from three different localities (Baltic Sea = WW6; North Sea = STO and Brittany = BRE). Photosynthesis and growth were measured
in time series (12–15 days) while UV-absorbing mycosporine-like amino acids (MAAs) and cellular integrity were determined
after 12 and 3 days exposure to three radiation treatments [PAR (22 μmol photon m−2 s−1) = P; PAR + UV-A (8 W m−2) = PA; PAR + UV-A + UV-B (0.4 W m−2) = PAB]. Isolate-specific responses to UVR were observed. The proximate response to radiation stress after 1-day treatment
showed that isolate WW6 was the most sensitive to UVR. However, repeated exposure to radiation stress indicated that photosynthetic
efficiency (F
v/F
m) of WW6 acclimated to UVR. Conversely, although photosynthesis in STO exhibited lower reduction in F
v/F
m during the first day, the values declined over time. The BRE isolate was the most tolerant to radiation stress with the lowest
reduction in F
v/F
m sustained over time. While photosynthetic efficiencies of different isolates were able to acclimate to UVR, growth did not.
The discrepancy seems to be due to the higher cell density used for photosynthesis compared to the growth measurement. Apparently,
the cell density used for photosynthesis was not high enough to offer self-shading protection because cellular damage was
also observed in those filaments under UVR. Most likely, the UVR acclimation of photosynthesis reflects predominantly the
performance of the surviving cells within the filaments. Different strategies were observed in MAAs synthesis. Total MAAs
content in WW6 was not significantly different between all the radiation treatments. In contrast, the additional fluence of
UV-A and UV-B significantly increased MAAs synthesis and accumulation in STO while only UV-B fluence significantly increased
MAAs content in BRE. Regardless of the dynamic photosynthetic recovery process and potential UV-protective functions of MAAs,
cellular investigation showed that UV-B significantly contributed to an increased cell mortality in single filaments. In their
natural mat habitat, M. chthonoplastes benefits from closely associated cyanobacteria which are highly UVR-tolerant due to the production of the extracellular UV-sunscreen
scytonemin. 相似文献
11.
Hofmann Rainer W.; Swinny Ewald E.; Bloor Stephen J.; Markham Kenneth R.; Ryan Ken G.; Campbell Bruce D.; Jordan Brian R.; Fountain David W. 《Annals of botany》2000,86(3):527-537
This study aimed to quantify and identify flavonoids involvedin the response of nine populations of white clover (Trifoliumrepens L.) to ultraviolet-B radiation (UV-B). Plants were grownfor 12 weeks in controlled environment rooms with or withoutsupplemental UV-B radiation of 13.3 kJ m-2d-1. Methanolwaterextractable flavonoids were quantified using high performanceliquid chromatography (HPLC). Two major peaks showed significantenhancement in the HPLC chromatogram in response to supplementalUV-B. The structures of the compounds responsible were identifiedby1H and13C nuclear magnetic resonance (NMR) spectroscopy tobe the flavonols quercetin-3-O-ß- D -xylopyranosyl-(1 2)-ß- D -galactopyranoside and kaempferol-3-O-ß-D -xylopyranosyl-(1 2)-ß- D -galactopyranoside. Withsupplemental UV-B, quercetin glycoside levels increased on averageby 200% while the kaempferol glycoside response was much smaller.Significant differences in flavonol accumulation were foundamong T. repens populations, both constitutively and in responseto UV-B. Stress-adapted populations displayed particularly highflavonol levels under UV-B. There was an inverse correlationbetween plant productivity and quercetin accumulation. Furthermore,higher quercetin accumulation under UV-B was correlated withtolerance against UV-B-induced growth reduction. In conclusion,within-species comparisons in T. repens lend support to a distinctrole for ortho -dihydroxylated flavonoids in the adaptationto UV-B stress and suggest particular advantages in this UV-B-inducedbiochemical adaptation for populations characterized by lowhabitat and plant productivity. Copyright 2000 Annals of BotanyCompany Ultraviolet-B, Trifolium repens, white clover, HPLC, NMR, flavonoids, flavonols, quercetin, kaempferol, biomass, genetic variation, intraspecific 相似文献
12.
13.
Solar ultraviolet-B radiation (UV-B) can have large impacts on the interactions between plants and herbivorous insects. Several studies have documented effects of UV-B-induced changes in plant tissue quality on the feeding performance of insect larvae. In contrast, the effects of UV-B-induced plant responses on the behavior of adult insects have received little attention. We carried out a series of field and glasshouse experiments using the model plant Arabidopsis thaliana L. and the crucifer-specialist insect Plutella xylostella L. (diamondback moth) to investigate the effects of UV-B on natural herbivory and plant–insect interactions. Natural herbivory under field conditions was less severe on plants exposed to ambient UV-B than on plants grown under filters that attenuated the UV-B component of solar radiation. This reduced herbivory could not be accounted for by effects of UV-B on larval feeding preference and performance, as P. xylostella caterpillars did not respond to changes in plant quality induced by UV-B. In contrast, at the adult stage, the insects presented clear behavioral responses: P. xylostella moths deposited significantly more eggs on plants grown under attenuated UV-B levels than on plants exposed to ambient UV-B. The deterring effect of UV-B exposure on insect oviposition was absent in jar1-1, a mutant with impaired jasmonic acid (JA) sensitivity, but it was conserved in mutants with altered ethylene signaling. The jar1-1 mutant also presented reduced levels of UV-absorbing phenolic compounds than the other genotypes that we tested. Our results suggest that variations in UV-B exposure under natural conditions can have significant effects on insect herbivory by altering plant traits that female adults use as sources of information during the process of host selection for oviposition. These effects of natural UV-B on plant quality appear to be mediated by activation of signaling circuits in which the defense-related hormone JA plays a functional role. 相似文献
14.
The combined effects of soil water deficit and above and below ground interspecific plant competition on the growth, water-use
efficiency (WUE), and measured carbon isotopic composition (δ13C) values of white clover and ryegrass were studied. White clover and ryegrass were grown in specially designed crates 1)
individually; 2) in shoot competition; or 3) in shoot + root competition and either well-watered or at a moderate or severe
soil water deficit. The effects of shoot + root competition on shoot dry matter growth were substantial and benefited both
white clover and ryegrass when well-watered or at a moderate soil water deficit, while severely reducing white clover shoot
dry matter growth at severe soil water deficit. Plant competition did not affect the WUE of white clover or ryegrass. As soil
water deficit increased, the WUE of white clover did not change whereas the WUE of ryegrass increased and was greater than
that of white clover. This was attributed to the lower leaf water conductance of ryegrass which conserved water and maintained
growth longer compared to white clover. A stronger correlation existed between soil water deficit and measured δ13C values for ryegrass at each plant competition level (P<0.001) than existed for white clover (individual: P<0.01; shoot + root: P<0.001; shoot: P<0.10). Unlike white clover, the relationship between measured δ13C values and shoot dry matter growth indicated that C assimilation for ryegrass was dependent on type of plant competition.
That WUE remained constant for white clover while measured δ13C values increased as soil water deficit increased, suggests that the role below ground respiration rate played in determining
δ13C values increased. The WUE of white clover appears to be independent of the nature of the competition between plants and
the soil water deficit level at which it is grown, whereas for ryegrass, the addition of root competition to shoot competition
should lead to increases in its WUE.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
Juha Heijari Minna Kivimäenpää Helinä Hartikainen Riitta Julkunen-Tiitto Anu Wulff 《Plant and Soil》2006,282(1-2):27-39
In greenhouse experiments, selenium (Se) has been shown to defend plants against detrimental effects of heavy UV-B radiation
stress. The aim of this study was to investigate whether this positive effect can be found in open-field conditions with enhancement
of UV-B radiation. In the experiment, conducted with strawberry (Fragaria×ananassa, cultivars “Jonsok” and “Polka”) over two growing seasons, plants were exposed to UV-B radiation (including UV-A) and cultivated
without Se or supplied with Se added at two levels (0.1 and 1.0 mg kg−1). The plants were monitored for growth, flavonoids, chlorophyll fluorescence, net photosynthesis as well as tissue and cell
structure. Photosystem II was observed to be sensitive to UV-B stress under field conditions. In the leaves, a decrease in
Fv/Fm was seen at the end of the growing season, implying a cumulative effect of UV-B stress. Several parameters, especially cell
and tissue structures, were affected by UV-B and UV-A treatments, which proves the need for UV-A control in outdoor UV-B supplementation
studies. Addition of Se did not ameliorate the harmful effects of UV-B but the lower Se-increment level increased leaf growth.
The effects of UV-B and Se differed during the two experimental years, indicating the need to repeat experiments during several
growing seasons. 相似文献
16.
Ultraviolet-B (UV-B, 280–320 nm) radiation may have severe negative effects on plants including damage to their genetic information.
UV protection and DNA-repair mechanisms have evolved to either avoid or repair such damage. Since autotrophic plants are dependent
on sunlight for their energy supply, an increase in the amount of UV-B reaching the earth’s surface may affect the integrity
of their genetic information if DNA damage is not repaired efficiently and rapidly. Here we show that overexpression of cyclobutane
pyrimidine dimer (CPD) photolyase (EC 4.1.99.3) in Arabidopsis thaliana (L.), which catalyses the reversion of the major UV-B photoproduct in DNA (CPDs), strongly enhances the repair of CPDs and
results in a moderate increase of biomass production under elevated UV-B. 相似文献
17.
The photosynthetic performance of Microcystis aeruginosa FACHB 854 during the process of UV-B exposure and its subsequent recovery under photosynthetic active radiation (PAR) was
investigated in the present study. Eight hours UV-B radiation (3.15 W m−2) stimulated the increase of photosynthetic pigments content at the early stage of UV-B exposure followed by a significant
decline. It suggested that UV-B damage was not an immediate process, and there existed a dynamic balance between damage and
adaptation in the exposed cells. Short-term UV-B exposure severely inhibited the photosynthetic capability, but it could restore
quickly after being transferred to PAR. Further investigations revealed that the PS II of M. aeruginosa FACHB 854 was more sensitive to UV-B exposure than PS I, and the oxygen-evolving complex of PS II was an important damage
target of UV-B. The inhibition of photosynthetic performance caused by UV-B could be recovered to 90.9% of pretreated samples
after 20 h exposure at low PAR, but it could not be recovered in the dark as well as under low PAR in the presence of Chloromycetin.
It can be concluded that PAR and de novo protein synthesis were essential for the recovery of UV-B-damaged photosynthetic
apparatus. 相似文献
18.
The responses of the early development of Laminaria japonica collected from Kiaochow Bay in China to enhanced ultraviolet-B radiation (UV-B, 280–320 nm) were studied in the laboratory.
The low UV-B radiations (11.7–23.4 J·m−2·d−1) had no significant effects on zoospores attachment, but when the UV-B dose > 35.1 J·m−2·d−1 the attachment decreased significantly compared with the control. Germination of embryospores was >93% under the low (11.7–35.1
J·m−2·d−1) doses, and in the range of 78.5%–88.5% under the high (46.8–70.2 J·m−2·d−1) UV-B doses, indicating a significant radiation effect. Under the higher UV-B exposure (35.1–70.2 J·m−2·d−1), all of the few gametophytes formed from embryospores died 120 h post-release. After exposure to the low UV-B radiation
(11.7–23.4 J·m−2·d−1), the formation of sporophytes decreased and the female gametophyte clones increased compared with the control. However,
the sex ratio and the relative growth of female gametophytes/sporophytes had not significantly changed. According to the results,
enhanced UV-B radiation has a significant effect on the early development of L. japonica under laboratory conditions, suggesting that the UV-B radiation could not be overlooked as one of the important environmental
factors influencing the ontogeny of macroalgae living in marine ecosystems.
Supported by the Program for New Century Excellent Talents in University (Grant No. NCET-05-0597) and National Natural Science
Foundation of China (Grant No. 30270258) 相似文献
19.
Spatial patterns of foliar stable carbon isotope compositions of C<Subscript>3</Subscript> plant species in the Loess Plateau of China 总被引:1,自引:0,他引:1
The spatial pattern of foliar stable carbon isotope compositions (δ13C) of dominant species and their relationships with environmental factors in seven sites, Yangling, Yongshou, Tongchuan, Fuxian,
Ansai, Mizhi and Shenmu, standing from south to north in the Loess Plateau of China, was studied. The results showed that
in the 121 C3 plant samples collected from the Loess Plateau, the foliar δ13C value ranged from −22.66‰ to −30.70‰, averaging −27.04‰. The foliar δ13C value varied significantly (P<0.01) among the seven sites, and the average δ13C value increased by about 1.69‰ from Yangling in the south to Shenmu in the north as climatic drought increased. There was
a significant difference in foliar δ13C value among three life-forms categorized from all the plant samples in the Loess Plateau (P<0.001). The trees (−26.74‰) and shrubs (−26.68‰) had similar mean δ13C values, both significantly (P<0.05) higher than the mean δ13C value of herbages (−27.69‰). It was shown that the trees and shrubs had higher WUEs and employed more conservative water-use
patterns to survive drier habitats in the Loess Plateau. Of all the C3 species in the Loess Plateau, the foliar δ13C values were significantly and negatively correlated with the mean annual rainfall (P<0.001) and mean annual temperature (P<0.05), while being significantly and positively correlated with the latitude (P<0.001) and the annual solar radiation (P<0.01). In general, the foliar δ13C values increased as the latitude and solar radiation increased and the rainfall and temperature decreased. The annual rainfall
as the main influencing factor could explain 13.3% of the spatial variations in foliar δ13C value. A 100 mm increment in annual rainfall would result in a decrease by 0.88‰ in foliar δ13C values. 相似文献
20.
The tolerances of 20 Beauveria bassiana isolates derived from host insects worldwide to UV-B irradiation were assessed quantitatively in multi-dose bioassays. Conidial
suspensions of the isolates smeared on glass slides were exposed to the gradient UV-B doses of 0.1–1.6 J cm−2 (D), which generated from 0.75 to 10.17 min irradiation of weighted 312-nm wavelength at 2.0–2.61 mW cm−2. Irradiated conidia were then incubated for 24 h at 25°C under saturated humidity. The ratio of germination at each dose
over that in the blank control was defined as survival index (I
s). For all isolates, the I
s − D observations fit well with the survival model I
s = 1/[1 + exp(a + bD)] (0.94 ≤ r
2 ≤ 0.99) generated widely spanned lethal doses of 0.154–0.928, 0.240–1.139, and 0.383–1.493 J cm−2 for their losses of 50%, 75%, and 95% viabilities, respectively. These were far below the solar UV-B dose of 2.439 J cm−2 measured in a sunny day during the summer. The large variation of UV-B tolerance among the isolates indicates a necessity
to select UV-tolerant candidates for formulations applied to insect control during summer. The highly efficient bioassay method
was developed to measure accurately the UV-B tolerances of fungal biocontrol agents as lethal doses. 相似文献