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1.
A greenhouse pot experiment with different phosphorus supply was conducted to study growth, photosynthesis and free polyamine
(PA) content in Plantago lanceolata L. plants in relation to arbuscular mycorrhizal (AM) colonization. Inoculum of Glomus fasciculatum (BEG 53) was used. Inoculated plants had high colonization intensities which were related to the P supply. Non-mycorrhizal
(NM) plants showed a typical yield response curve for P availability. Dry masses of mycorrhizal (M) plants were higher at
the lowest soil P content than those of NM plants, but the opposite was found at the highest P supply. P contents in M plants
were always higher. There were no differences in chlorophyll (Chl) concentrations (except the lowest soil P content) and ratios
of variable to maximum Chl fluorescence (Fv/Fm) values between M and NM plants, whereas M plants had higher ratios of leaf
area to fresh mass (A/f.m.) at low soil P contents and they had significantly higher CO 2 fixation capacities per unit leaf area. Free putrescine (Put), spermidine (Spd) and spermine (Spm) contents in NM plants
were usually highest at the lowest P supply. The ratios of Put/(Spd+Spm) were identical in M and NM leaves. They were significantly
higher, however, in NM roots at the two low P doses. It is concluded, that a P nutritional status might exist, below which
PA concentrations and ratio are increased drastically, possibly indicating P deficiency or a certain state of plant development
with a higher demand for AM symbiosis.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Comparative analyses of aspects of the carbon (C) physiology and the expression of C transporter genes in birch ( Betula pendula Roth.) colonized by the ectomycorrhizal fungus Paxillus involutus (Batsch) Fr. were performed using mycorrhizal (M) and non‐mycorrhizal (NM) plants of similar foliar nutrient status. After six months of growth, the biomass of M plants was significantly lower than that of NM plants. Diurnal C budgets of both sets of plants revealed that M plants exhibited higher rates of photosynthesis and root respiration expressed per unit dry weight. However, the diurnal net C gain of M and NM plants remained similar. Ectomycorrhizal roots contained higher soluble carbohydrate pools and increased activity of cell wall invertase, suggesting that additional C was allocated to these roots and their ectomycorrhizal fungi consistent with an increased sink demand for C due to the presence of the mycobiont. In M roots, the expression of two hexose and one sucrose transporter genes of birch were reduced to less than one‐third of the expression level observed in NM roots. Analysis using a probe against the birch ribosomal internal transcribed spacer region revealed that M roots contained 22% less plant RNA than NM roots. As the expression of birch hexose and sucrose transporter genes was reduced to a much greater extent, this suggests that these specific genes were down‐regulated in response to alterations in C metabolism within M roots. 相似文献
3.
5-Azacytidine (5-AzaC) causes hypomethylation of genomic DNA and induces phenotype variation in many plant species. Modulating the methylation status of cytosine by 5-AzaC to generate novel phenotypes in poplars have not been attempted. In this study, a population of 288 plants was regenerated from leaves of Populus nigra on medium supplemented with 100–1000 µM 5-AzaC. The differentiation of leaves was delayed and the differentiation rate decreased as the 5-AzaC concentration increased. Compared with plants regenerated on 5-AzaC-free medium (control), the plants regenerated on high-5-AzaC medium (600–1000 µM) had significantly higher DNA methylation levels and were shorter, whereas the plants regenerated on low-5-AzaC medium were unchanged; the plants regenerated on 100 µM 5-AzaC medium had significant more leaves; the plants regenerated on 400 µM 5-AzaC medium had significantly higher leaf chlorophyll b and total chlorophyll contents, while the plants on 800 and 1000 µM 5-AzaC medium had a significantly lower chlorophyll a content; most photosynthetic parameters of the plants regenerated on 5-AzaC-treated medium decreased, except for the net photosynthetic rate (Pn) and transpiration rate (Tr) of plants on 100, 200, and 400 µM medium, and the instant water utilization efficiency (WUEi) of plants on 1000 µM medium. The superoxide dismutase activity of plants on ≥ 400 µM 5-AzaC medium was significantly higher than in the control. Significant weak correlations were found between the methylation level of regenerants and plant height, chlorophyll a content, Pn, Tr, stomatal conductance, intercellular CO2 concentration, and WUEi, indicating these phenotypic changes were related to the methylation changes. Our results demonstrated the use of 5-AzaC at the regeneration stage induced epigenetic as well as phynotypic variations in poplar regenerants and generated plant materials for genetic breeding and epigenetic studies. 相似文献
4.
Plants of Helianthemum almeriense were micropropagated on MS medium and inoculated in vitro with Terfezia claveryi mycelium on MH medium and vermiculite. Mycorrhizal (M) and non-mycorrhizal (NM) plants were subjected to a drought stress
period of 3 weeks in greenhouse conditions with the soil matric potential maintained at –0.5 MPa. Drought stress did not affect
the amount of mycorrhizal colonization. The survival rate of M plants at the end of the drought stress period was higher than
that of NM plants. The water potential was higher in M plants than in NM plants by 14% in well-watered and 26% in drought-stressed
plants. Transpiration, stomatal conductance and net photosynthesis were higher in M plants than in NM plants. Transpiration
was 92% higher in M plants than in NM plants under drought-stress conditions and 40% when irrigated. Stomatal conductance
was 45% and 14% higher and net photosynthesis 88% and 54% higher, respectively, in M than in NM plants. Drought-stressed M
plants accumulated more N, P and K than drought-stressed NM plants. Reduced negative effects of drought stress on H. almeriense by the desert truffle T. claveryi could be ascribed to specific physiological and nutritional mechanisms, suggesting that this mycorrhizal symbiosis aids adaptation
to arid climates.
Accepted: 7 July 2000 相似文献
5.
The influence of arbuscular mycorrhizal fungi (AMF), Funneliformis mosseae and Rhizophagus intraradices, on plant growth, leaf water status, chlorophyll concentration, photosynthesis, nutrient concentration, and fractal dimension (FD) characteristics of black locust ( Robinia pseudoacacia L.) seedlings was studied in pot culture under well-watered, moderate drought stress, and severe drought stress treatments. Mycorrhizal seedlings had higher dry biomass, leaf relative water content (RWC), and water use efficiency (WUE) compared with non-mycorrhizal seedlings. Under all treatments, AMF colonization notably enhanced net photosynthetic rate, stomatal conductance, and transpiration rate, but decreased intercellular CO 2 concentration. Leaf chlorophyll a and total chlorophyll concentrations were higher in AM seedlings than those in non-AM seedlings although there was no significant difference between AMF species. AMF colonization improved leaf C, N, and P concentrations, but decreased C:N, C:P, and N:P ratios. Mycorrhizal seedlings had a larger FD value than non-mycorrhizal seedlings. The FD value was positively and significantly correlated to the plant growth parameters, photosynthesis, RWC, WUE, and nutrient concentration but negatively correlated to leaf/stem ratio, C:N and C:P ratios, and intercellular CO 2 concentration. We conclude that AMF lead to an improvement of growth performance of black locust seedlings under all growth conditions, including drought stress via improving leaf water status, chlorophyll concentration, photosynthesis, and nutrient uptake. Moreover, FD technology proved to be a powerful non-destructive method to characterize the effect of AMF on the physiology of host plants during drought stress. 相似文献
6.
Seedlings of the rootstocks Pineapple sweet orange (SwO), Carrizo citrange (CC), and sour orange (SO) were grown in low phosphorus
(P) sandy soil and either inoculated with the vesicular-arbuscular mycorrhizal (VAM) fungus, Glomus intraradices, or were non-mycorrhizal (NM) and fertilized with P. VAM and NM seedings of similar shoot size and adequate P-status were
selected for study of salinity and flooding stress. One-third of each of the VAM and NM plants were given 150 m M NaCl for a period of 24 days. One-third of the plants were placed into plastic bags and flooded for 21 days while the remaining
third were non-stressed controls. In general, neither stress treatment affected mycorrhizal colonization. Salinity stress
reduced the hydraulic conductivity of roots, leaf water potential, stomatal conductance and net assimilation of CO 2 (ACO 2) of mycorrhizal and non-mycorrhizal seedlings to a similar extent. VAM plants of CC and SO accumulated more Cl in leaves
than NM plants. Cl was higher in non-mycorrhizal roots of SwO and CC than in mycorrhizal roots. Flooding the root zone for
3 weeks did not produce visible symptoms in the shoot but did influence plant water relations and reduce ACO 2 of all 3 rootstocks. VAM and NM plants of each rootstock were affected similarly by flooding. Comparable reduction in nitrogen
and P content of both mycorrhizal and non-mycorrhizal plants suggested that flooding stress was primarily affecting root rather
than hyphal nutrient uptake.
Florida Agricultural Experimental Station Journal Series No. 7773. 相似文献
7.
Scots pine ( Pinus sylvestris L.) seedlings inoculated or not (NM) by a Zn-sensitive or a Zn-tolerant isolate of the ectomycorrhizal fungus Suillus bovinus (L. Fr.) Roussel were exposed to 0.1 or 150 μM Zn 2+ for 9 months. We hypothesized that inoculation with a Zn-tolerant S. bovinus isolate should result in added Zn resistance of the host plant. Plant and fungal growth as well as nutrient profiles and photosynthetic pigments in pine needles were quantified. In NM plants and in plants colonized by the Zn-sensitive isolate, plant growth, N, P, Mg and Fe assimilation were strongly inhibited under Zn stress and concurred with significantly reduced chlorophyll concentrations. In contrast, plants colonized by the Zn-tolerant isolate grew much better and remained physiologically healthier when exposed to elevated Zn. These results provide further evidence for the important role metal-adapted mycorrhizal fungi play as an effective biological barrier against metal toxicity in trees. 相似文献
8.
A pot-culture experiment was carried out to investigate the effect of arbuscular mycorrhizal (AM) fungus ( Glomus macrocarpum Tul. and Tul.) on plant growth and Cd 2+uptake by Apium graveolens L. in soil with different levels of Cd 2+. Mycorrhizal (M) and non-mycorrhizal (NM) plants were grown in soil with 0, 5, 10, 40 and 80 Cd 2+ mg kg −1soil. The infectivity of the fungus was not affected by the presence of Cd 2+ in the soil. M plants showed better growth and less Cd 2+ toxicity symptoms. Cd 2+ root : shoot ratio was higher in M plants than in NM plants. These differences were more evident at highest Cd 2+ level (80 mg kg −1 soil). Chlorophyll a and chlorophyll b concentrations were significantly higher in AM-inoculated celery leaves. The dilution effect due to increased biomass, immobilization
of Cd 2+ in root and enhanced P-uptake in M plants may be related to attenuation of Cd 2+toxicity in celery. 相似文献
9.
White spruce [ Picea glauca (Moench) Voss] seedlings were inoculated with Hebeloma crustuliniforme and treated with 25 mM NaCl to examine the effects of salinized soil and mycorrhizae on root hydraulic conductance and growth. Mycorrhizal seedlings had significantly greater shoot and root dry weights, number of lateral branches and chlorophyll content than non-mycorrhizal seedlings. Salt treatment reduced seedling growth in both non-mycorrhizal and mycorrhizal seedlings. However, needles of salt-treated mycorrhizal seedlings had several-fold higher needle chlorophyll content than that in non-mycorrhizal seedlings treated with salt. Mycorrhizae increased N and P concentrations in seedlings. Na levels in shoots and roots of salt-treated mycorrhizal seedlings were significantly lower and root hydraulic conductance was several-fold higher than in non-mycorrhizal seedlings. A reduction of about 50% in root hydraulic conductance of mycorrhizal seedlings was observed after removal of the fungal hyphal sheath. Transpiration and root respiration rates were reduced by salt treatments in both groups of seedlings compared with the controls, however, both transpiration and respiration rates of salt-treated mycorrhizal seedlings were as high as those in the non-mycorrhizal seedlings that had not been subjected to salt treatment. The reduction of shoot Na uptake while increasing N and P absorption and maintaining high transpiration rates and root hydraulic conductance may be important resistance mechanisms in ectomycorrhizal plants growing in salinized soil. 相似文献
10.
利用盆栽试验,在15 ℃和5 ℃低温胁迫下研究了丛枝菌根(AM)真菌对玉米生长、叶绿素含量、叶绿素荧光和光合作用的影响.结果表明:低温胁迫抑制了AM真菌的侵染;接种AM真菌的玉米地上部和地下部干物质量、相对叶绿素含量高于不接种植株.与非菌根玉米相比,菌根玉米具有较高的最大荧光(F m)、可变荧光(F v)、最大光化学效率(F v/F m)和潜在光化学效率(F v/F o)及较低的初始荧光(F o),并且在5 ℃处理中差异显著.接种AM真菌使玉米叶片的净光合速率(P n)和蒸腾速率(T r)显著增强;低温胁迫下,菌根植株的气孔导度(G s)显著高于非菌根植株;而胞间CO 2浓度(C i)显著低于非菌根植株.表明AM真菌可通过提高叶绿素含量及改善叶片叶绿素荧光和光合作用来减轻低温胁迫对玉米植株造成的伤害,提高玉米耐受低温的能力,进而提高玉米的生物量,促进玉米生长. 相似文献
11.
以采自甘肃民勤一年生的沙拐枣幼苗为试材,对不同NaCl浓度(0、50、100、200、300mmol·L~(-1))处理下沙拐枣光合生理特性进行分析,并对各生理指标与地上生物量进行灰色关联度分析,以探讨荒漠植物沙拐枣的抗盐机理,为沙拐枣的保护及其恢复荒漠生态系统稳定提供理论依据。结果显示:随着NaCl浓度的升高,沙拐枣同化枝内脯氨酸含量逐渐增大,而其可溶性糖含量逐渐减小;在低浓度NaCl(50mmol·L~(-1) NaCl)处理下,同化枝光合参数均增加,且净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)均达到最大值,比对照分别显著增加了33.3%、68.0%、60.8%;与50mmol·L~(-1) NaCl相比,处理浓度超过50mmol·L~(-1) NaCl时,Pn、Gs、Tr均降低;同化枝叶绿素b含量随着NaCl浓度的增加而降低,而叶绿素a和总叶绿素含量均呈先增加后降低的趋势。灰色关联度分析发现,同化枝的Tr、Gs、Ci以及叶绿素b与地上生物量的关联度较大。研究表明,低盐浓度NaCl激活了沙拐枣的某些生理机制,有利于植株的光合作用和生长,而植物在高盐浓度胁迫时能通过调节脯氨酸和可溶性糖的含量,减少叶绿素含量、Pn和Tr等维持自身的生长。 相似文献
12.
Predicted increases in atmospheric concentration of carbon dioxide (CO 2) coupled with increased temperatures and drought are expected to strongly influence the development of most of the plant species in the world, especially in areas with high risk of desertification like the Mediterranean basin. Helianthemum almeriense is an ecologically important Mediterranean shrub with an added interest because it serves as the host for the Terfezia claveryi mycorrhizal fungus, which is a desert truffle with increasingly commercial interest. Although both plant and fungi are known to be well adapted to dry conditions, it is still uncertain how the increase in atmospheric CO 2 will influence them. In this article we have addressed the physiological responses of H. almeriense × T. claveryi mycorrhizal plants to increases in atmospheric CO 2 coupled with drought and high vapor pressure deficit. This work reports one of the few estimations of mesophyll conductance in a drought deciduous Mediterranean shrub and evaluates its role in photosynthesis limitation. High atmospheric CO 2 concentrations help desert truffle mycorrhizal plants to cope with the adverse effects of progressive drought during Mediterranean springs by improving carbon net assimilation, intrinsic water use efficiency and dispersal of the species through increased flowering events. 相似文献
13.
Drought can limit the growth and reduce the yield of crops, but the safe
and effective bio-approach to improve the drought resistance of crops is very little. We conducted an experiment in which we monitored the effects of polysaccharide from the endophyte Bionectria sp. Fat6 on the growth of Tartary
buckwheat ( Fagopyrum tataricum (L.) Gaertn) seedlings under control and
drought-stressed conditions by determining gas exchange, photosynthesis parameters, photosynthetic pigment contents, and metabolite accumulation. Results
indicated that the polysaccharide from endophyte stimulated plant growth and
increased the aboveground biomass, root mass, and root/shoot ratio of Tartary
buckwheat. Application of the polysaccharide to drought-stressed plants resulted
in a significant increase in the net photosynthetic rate, stomatal conductance, and
transpiration rate of Tartary buckwheat and decreased the intercellular CO 2 concentration. The contents of chlorophyll a, chlorophyll b, chlorophyll a + b, and
carotenoids in leaves were higher in polysaccharide-treated seedlings than that
in control. Polysaccharide notably increased the soluble protein and proline content and decreased the malondialdehyde content in Tartary buckwheat leaves. The
endophytic polysaccharide may protect Tartary buckwheat against drought by
improving leaf gas exchange and photosynthetic capacity, and altering concentrations of protective metabolites. Together, these changes may compensate for the
negative impacts of drought stress on the growth of Tartary buckwheat. Thus,
the polysaccharide from the endophyte Bionectria sp. Fat6 may be an effective
biotic elicitor and a promising bio-approach to improve Tartary buckwheat production worldwide. 相似文献
14.
Crassulacean acid metabolism (CAM) and the capacity to store large quantities of water are thought to confer high water use
efficiency (WUE) and survival of succulent plants in warm desert environments. Yet the highly variable precipitation, temperature
and humidity conditions in these environments likely have unique impacts on underlying processes regulating photosynthetic
gas exchange and WUE, limiting our ability to predict growth and survival responses of desert CAM plants to climate change.
We monitored net CO 2 assimilation ( A
net), stomatal conductance ( g
s), and transpiration ( E) rates periodically over 2 years in a natural population of the giant columnar cactus Carnegiea gigantea (saguaro) near Tucson, Arizona USA to investigate environmental and physiological controls over carbon gain and water loss
in this ecologically important plant. We hypothesized that seasonal changes in daily integrated water use efficiency (WUE day) in this constitutive CAM species would be driven largely by stomatal regulation of nighttime transpiration and CO 2 uptake responding to shifts in nighttime air temperature and humidity. The lowest WUE day occurred during time periods with extreme high and low air vapor pressure deficit ( D
a). The diurnal with the highest D
a had low WUE day due to minimal net carbon gain across the 24 h period. Low WUE day was also observed under conditions of low D
a; however, it was due to significant transpiration losses. Gas exchange measurements on potted saguaro plants exposed to experimental
changes in D
a confirmed the relationship between D
a and g
s. Our results suggest that climatic changes involving shifts in air temperature and humidity will have large impacts on the
water and carbon economy of the giant saguaro and potentially other succulent CAM plants of warm desert environments. 相似文献
15.
Most mistletoe–host ecophysiological studies have paid attention to the influence of parasites on host performance. This paper explored the impact of varying hosts on the photosynthesis of a single mistletoe species. Here, we studied an obligate xylem‐tapping tropical mistletoe ( Dendrophthoe curvata (Blume) Miquel) parasitizing four different hosts ( Acacia auriculiformis A. Cunn. Ex Benth, Andira inermis (W. Wright) DC., Mangifera indica L. and Vitex pinnata L.) in a homo geneous tropical heath forest patch in Brunei Darussalam. We compared photosynthetic capacity and photosynthesis‐related characteristics of the mistletoe on four different hosts to evaluate the overall impact of hosts on the parasite. Results showed that the mistletoe–host patterns of CO 2 assimilation rates, transpiration rates and water use efficiency varied significantly based on the host. In the D. curvata–Vitex pinnata association, the mistletoe exhibited significantly lower CO 2 assimilation rates but showed no significant variations in transpiration rates and water use efficiency when compared to the host. In D. curvata–Andira inermis and D. curvata–Mangifera indica associations, the mistletoe showed significantly higher photosynthetic rates than the hosts, whereas in the D. curvata–Acacia auriculiformis association, there was no significant difference in photosynthetic rates between the counterparts. Host specificity also significantly influenced some mistletoe photosynthetic parameters such as light saturated photosynthesis, specific leaf area, leaf chlorophyll content, CO 2 assimilation rates, stomatal conductance, transpiration rates and water use efficiency. Different tree hosts intrinsically offer different resources to their obligate mistletoe parasites based on their physiology and environmental parameters. We argue that host‐specific responses have driven these intra‐specific variations in mistletoe physiology. This study provides background for future investigation on potential host‐regulated mechanisms that drive functional changes in host‐dependent mistletoes. 相似文献
16.
The purpose of this study was to investigate the effects of arbuscular mycorrhizal (AM) symbiosis on gas exchange, chlorophyll fluorescence, pigment concentration and water status of maize plants in pot culture under high temperature stress. Zea mays L. genotype Zhengdan 958 were cultivated in soil at 26/22°C for 6 weeks, and later subjected to 25, 35 and 40°C for 1 week. The plants inoculated with the AM fungus Glomus etunicatum were compared with the non-inoculated plants. The results showed that high temperature stress decreased the biomass of the maize plants. AM symbiosis markedly enhanced the net photosynthetic rate, stomatal conductance and transpiration rate in the maize leaves. Compared with the non-mycorrhizal plants, mycorrhizal plants had lower intercellular CO 2 concentration under 40°C stress. The maximal fluorescence, maximum quantum efficiency of PSII photochemistry and potential photochemical efficiency of mycorrhizal plants were significantly higher than corresponding non-mycorrhizal plants under high temperature stress. AM-inoculated plants had higher concentrations of chlorophyll a, chlorophyll b and carotenoid than non-inoculated plants. Furthermore, AM colonization increased water use efficiency, water holding capacity and relative water content. In conclusion, maize roots inoculated with AM fungus may protect the plants against high temperature stress by improving photosynthesis and water status. 相似文献
17.
Nicotiana tabacum L. plantlets were grown in glass vessels or in Magenta boxes with better CO 2 supply. To improve the ex vitro transfer we tested application of abscisic acid and elevated CO 2 concentration. In the first two weeks after transfer, net photosynthetic rate, chlorophyll a+ b content, and Chl a/ b ratio were higher, and content of xanthophyll cycle pigments lower in M-plants than in G-plants, but during further growth
the differences almost disappeared. ABA application alleviated the risk of wilting because it decreased stomatal conductance.
The effect of ABA was enhanced under CE (28 days after transfer). In situ, P N was always higher at CE than at CA, but when measured under CA, positive effect of CE was found 2 and 16 days after transfer
in M-plants and only 16 days after transfer in G-plants. Slightly increased Chl a content was found in all ABA-treated plants, and in M-plants grown under CE. The content of xanthophyll cycle pigments was
lower under CE compared to CA, and the lowest one was found in ABA-treated M-plants grown under CE. On the contrary, the degree
of their deepoxidation (DEPS) was slightly higher in plants grown under CE. No significant effects of ABA-treatment or growth
under CE on fluorescence kinetic parameters were found and inconsistent effects on photochemical activities. The photochemical
efficiency of PS2 (variable to maximum fluorescence ratio, F v/F m) after ex vitro transfer was similar to that in in vitro grown plants. This together with the values of DEPS indicated that no photodamage during ex vitro transfer occurred.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
In order to assess the actual role of ectomycorrhizae in ion uptake by the ectomycorrhizal root system, we used a microelectrode ion flux estimation methodology that provided access to local values of net fluxes. This made it possible to investigate the heterogeneity of ion fluxes along the different types of roots of Pinus pinaster associated or not with ectomycorrhizal species. We compared two fungi able to grow with nitrate in pure culture, Rhizopogon roseolus and Hebeloma cylindrosporum, the former having a positive effect on host tree shoot growth ( c. +30%) and the latter a negative effect ( c.? 30%). In non‐mycorrhizal plants (control), NO 3– was taken up at higher rates by the short roots than by the long ones, whereas K + uptake occurred mainly in growing apices of long roots. In mycorrhizal plants, H. cylindrosporum did not modify K + uptake and even decreased NO 3– uptake at the level of ectomycorrhizal short roots, whereas R. roseolus strongly increased K + and NO 3– fluxes at the level of ectomycorrhizal short roots without any modification of the fluxes measured along the fungus‐free long roots. The measurement of ion influxes at the surface of the ectomycorrhizal roots can provide a way to reveal actual effects of mycorrhizal association on ion transport in relation to mycorrhizal efficiency in natural conditions. 相似文献
19.
Medicago sativa L. (alfalfa) can exhibit photosynthetic down-regulation when grown in greenhouse conditions under elevated atmospheric CO 2. This forage legume can establish a double symbiosis with nitrogen fixing bacteria and arbuscular mycorrhizal fungi (AMF), which may increase the carbon sink effect of roots. Our aim was to assess whether the association of alfalfa with AMF can avoid, diminish or delay the photosynthetic acclimation observed in previous studies performed with nodulated plants. The results, however, showed that mycorrhizal (M) alfalfa at the end of their vegetative period had lower carbon (C) discrimination than non-mycorrhizal (NM) controls, indicating photosynthetic acclimation under ECO 2 in plants associated with AMF. Decreased C discrimination was due to the acclimation of conductance, since the amount of Rubisco and the expression of genes codifying both large and small subunits of Rubisco were similar or slightly higher in M than in NM plants. Moreover, M alfalfa accumulated a greater amount of soluble sugars in leaves than NM plants, thus favoring a down-regulation effect on photosynthetic rates. The enhanced contents of sugars in leaves coincided with a reduced percentage of arbuscules in roots, suggesting decreased sink of carbohydrates from shoots to roots in M plants. The shorter life cycle of alfalfa associated with AMF in comparison with the NM controls may also be related to the accelerated photosynthetic acclimation in M plants. Further research is needed to clarify to what extent this behavior could be extrapolated to alfalfa cultivated in the field and subjected to periodic cutting of shoots under climatic change scenarios. 相似文献
20.
The aim of this study is to investigate the effects of arbuscular mycorrhizal fungi (AMF) on garlic plants growth and the uptake of selenium (Se). Garlic plants were grown in the pots inoculated with Glomus fasciculatum and G. mosseae and maintained in a greenhouse. Three weeks after planting, the pots had received different concentrations of Se (5, 10, 15, 20, 25 mg kg ?1 of soil) in the form of selenium dioxide (SeO 2) at 3 weeks intervals up to 12 weeks. For physiological and biochemical analysis, the samples were randomly collected from five plants of each experiment. Maximum AM infection, spore population and plant biomass were observed in the roots of mycorrhizal-mediated plants without Se, and they were gradually declined in both mycorrhizal and non-mycorrhizal (NM) plants with increasing concentrations of Se. Among the two Glomus species tested, G. fasciculatum-mediated plants showed higher AM infection, spore population and plant biomass than G. mosseae. No differences were observed for the uptake of Se in mycorrhizal plants and NM plants. However, NM plants uptake more Se than mycorrhizal plants. Higher contents of total chlorophyll and sugars were observed in plants inoculated with G. fasciculatum without Se and they were decreased in the presence of Se. In contrast, increased amount of glutathione peroxidase was observed at increasing concentrations of Se up to 20 mg kg ?1. High-performance liquid chromatography data revealed that SeO 2 converted to organic form of Se as γ-glutamyl-Se-methylselenocysteine. These results are basis for further investigations on the role of AMF on plant growth and uptake of Se in crop plants. 相似文献
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