Neotyphodium Coenophialum-Infected Tall Fescue and Its Potential Application in the Phytoremediation of Saline Soils

The growth response of endophyte-infected (EI) and endophyte-free (EF) tall fescue to salt stress was investigated under two growing systems (hydroponic and soil in pots). The hydroponic experiment showed that endophyte infection significantly increased tiller and leaf number, which led to an increase in the total biomass of the host grass. Endophyte infection enhanced Na accumulation in the host grass and improved Na transport from the roots to the shoots. With a 15 g l^?1 NaCl treatment, the phytoextraction efficiency of EI tall fescue was 2.34-fold higher than EF plants. When the plants were grown in saline soils, endophyte infection also significantly increased tiller number, shoot height and the total biomass of the host grass. Although EI tall fescue cannot accumulate Na to a level high enough for it to be termed a halophyte, the increased biomass production and stress tolerance suggested that endophyte / plant associations had the potential to be a model for endophyte-assisted phytoextraction in saline soils.     

Influence of phosphorus on the growth and ergot alkaloid content of Neotyphodium coenophialum-infected tall fescue (Festuca arundinacea Schreb.)

Tall fescue (Festuca arundinacea Schreb.) plants infected by the fungal endophyte Neotyphodium coenophialum (Morgan-Jones & Gams) (Glenn et al., 1996) often perform better than noninfected plants, especially in marginal resource environments. There is a lack of information about endophyte related effects on the rhizosphere of grasses. In a greenhouse experiment, four endophyte-infected (E+) tall fescue clones (DN2, DN4, DN7, DN11) and their endophyte-free (E–) forms were grown in limed (pH 6.3) Porter soil (low fertility, acidic, high aluminum and low phosphorus content, coarse-loamy mixed mesic Umbric Dystrochrept) at three soil P levels (17, 50, and 96 mg P kg^-1 soil) for five months. Excluding the genotype effect, endophyte infection significantly increased cumulative herbage DM yield by 8% at 17 mg P kg^-1 soil but reduced cumulative herbage DM yield by 12% at 96 mg P kg^-1 soil. With increased P availability in the soil, shoot and root DM, and root/shoot ratio in E+ plants were significantly less when compared to E– plants. Endophyte infection increased specific root length at 17 and 50 mg P kg^-1soil. At soil P level of 17 mg P kg^-1soil, E+ plants had significantly higher P concentrations both in roots and shoots. Similar relationships were found for Mg and Ca. E+ plants had significantly higher Zn, Fe, and Al concentration in roots, and lower Mn and Al concentration in shoots when compared to E– plants. Ergot alkaloid concentration and content in shoot of E+ plants increased with increasing P availability in the soil from 17 to 50 mg P kg^-1 but declined again at 96 mg P kg^-1 soil. Ergot alkaloid accumulation in roots increased linearly with P availability in the soil. Results suggest that endophyte infection affects uptake of phosphorus and other mineral nutrients and may benefit tall fescue grown on P-deficient soils. Phosphorus seems also to be involved in ergot alkaloid accumulation in endophyte-infected tall fescue.     

Competition between Lolium perenne and Digitaria sanguinalis: Ecological consequences for harbouring an endosymbiotic fungus

Abstract. This study examined the influence of the fungal endophyte Neotyphodium lolii on the competitive interactions between its perennial, cool season host, Lolium perenne (perennial ryegrass), and a warm season, annual grass, Digitaria sanguinalis (large crabgrass), in densely planted stands (>1000 plant.m^?2) in the glasshouse. Endophyte infection had little or no effect on L. perenne tiller production, above‐ or below‐ground biomass or root: shoot ratio in monoculture. However, endophyte infection significantly reduced L. perenne tiller production and above‐ground biomass in mixtures with D. sanguinalis. Conversely, D. sanguinalis had significantly higher above‐ground biomass and yielded more seed (g) when competing with endophyte infected L. perenne. An apparent trade‐off between allocation of resources to reproductive vs root tissues was observed in D. sanguinalis– root: shoot ratio was significantly lower when competing with endophyte infected L. perenne. Results indicate negative ecological consequences for harbouring the fungal endophyte when competing with the fast growing annual grass in newly established stands. These findings underscore the existence of a physiological cost of harbouring the fungal endophyte which is often overlooked.     

The effects of carbohydrate supply and host genetic background on Epichloë endophyte and alkaloid concentrations in perennial ryegrass

The ecological effects of novel grass–endophyte associations used in agriculture have not been widely studied. Previous studies of asexual Epichloë-infected Lolium perenne suggest that endophyte concentration is altered in high sugar grasses (HSGs) selectively bred to produce higher concentrations of water-soluble carbohydrates relative to conventional cultivars. We investigated whether differences are due to the effects of altered carbohydrates, or genetic background, by growing multiple cultivars in both high-sugar trait expression and non-expression conditions (using light/temperature treatments). Endophyte and alkaloid concentrations were measured in three HSG and three NSG (normal-sugar grass) cultivars infected with Lp19 or AR37 endophyte strains. Low molecular weight (LMW) carbohydrates had a small effect, explaining <6% of the variation in endophyte concentration. Endophyte concentrations were strongly dependent on plant genotype and fungal strain, with the highest concentrations seen in Lp19, suggesting that the interaction is highly dependent on genetic compatibility. Changes in endophyte concentration due to altered environmental variables and genetic compatibility may have consequences for persistence, toxicity, and invasive potential of endophyte-infected plants.     

Phosphate-assisted phytoremediation of arsenic by Brassica napus and Brassica juncea: Morphological and physiological response

In this study, we examined the potential role of phosphate (P; 0, 50, 100 mg kg^?1) on growth, gas exchange attributes, and photosynthetic pigments of Brassica napus and Brassica juncea under arsenic (As) stress (0, 25, 50, 75 mg kg^?1) in a pot experiment. Results revealed that phosphate supplementation (P100) to As-stressed plants significantly increased shoot As concentration, dry biomass yield, and As uptake, in addition to the improved morphological and gas exchange attributes and photosynthetic pigments over P0. However, phosphate-assisted increase in As uptake was substantially (up to two times) greater for B. napus, notably due to higher shoot As concentration and dry biomass yield, compared to B. juncea at the P100 level. While phosphate addition in soil (P100) led to enhanced shoot As concentration in B. juncea, it reduced shoot dry biomass, primarily after 50 and 75 mg kg^?1 As treatments. The translocation factor and bioconcentration factor values of B. napus were higher than B. juncea for all As levels in the presence of phosphate. This study demonstrates that phosphate supplementation has a potential to improve As phytoextraction efficiency, predominantly for B. napus, by minimizing As-induced damage to plant growth, as well as by improving the physiological and photosynthetic attributes.     

Zinc fertilizer placement affects zinc content in maize plant

Background and aims

Adequate zinc (Zn) in maize (Zea mays L.) is required for obtaining Zn-enriched grain and optimum yield. This study investigated the impact of varying Zn fertilizer placements on Zn accumulation in maize plant.

Methods

Two pot experiments with same design were conducted to investigate the effect of soil Zn heterogeneity by mixing ZnSO₄·7H₂O (10 mg Zn kg^?1 soil on an average) in 10–15, 0–15, 25–30, 0–30, 30–60 and 0–60 cm soil layers on maize root growth and shoot Zn content at flowering stage in experiment-1, and assessing effects on grain Zn accumulation at mature stage in experiment-2.

Results

In experiment-1, Zn placements created a large variation in soil DTPA-Zn concentration (0.3–29.0 mg kg^?1), which induced a systemic and positive response of root growth within soil layers of 0–30 cm; and shoot Zn content was increased by 102 %–305 % depending on Zn placements. Supply capacity of Zn in soil, defined as sum of product of soil DTPA-Zn concentration and root surface area at different soil layers, was most related to shoot Zn content (r?=?0.82, P?<?0.001) via direct and indirect effects according to path analysis. In experiment-2, Zn placements increased grain Zn concentration by up to 51 %, but significantly reduced the grain Zn harvest index from 50 % by control to about 30 % in average.

Conclusion

Matching the distribution of soil applied Zn with root by Zn placement was helpful to maximize shoot Zn content and grain Zn concentration in maize.     

Kinetics of zinc release from ground tire rubber and rubber ash in a calcareous soil as alternatives to Zn fertilizers

Ground rubber contains 15?C20 g Zn kg^?1 but very low levels of Cd and could serve as an inexpensive byproduct Zn fertilizer. The aim of this investigation was to test Zn release in a soil treated with ground tire rubber and rubber ash compared with commercial Zn fertilizer and a laboratory grade zinc sulfate. A Zn-deficient soil was chosen from wheat fields in Isfahan province, central Iran, and the ground rubber, rubber ash and fertilizer-Zn and laboratory ZnSO₄ were added at 0.5 and 2 mg Zn kg^?1; 0.5 kg ha^?1 would usually correct Zn deficiency in such pot tests. The soil DTPA-extractable Zn was then measured with time and the results were described examining first order, Elovich, power function and parabolic diffusion kinetics models. In the pot experiment, corn (Zea mays L.) plants were exposed to three rates of Zn (0, 20, 40 mg Zn kg^?1) from two different sources (ZnSO₄ and ground rubber). Ground rubber was applied as 2?C3 mm and <1 mm diameter particles. Zinc treatments were mixed with the soils before planting. At harvest, concentrations of Zn, Pb, and Cd in roots and shoots of corn were measured. Results showed that ground rubber and rubber ash significantly increased the concentration of DTPA-Zn in the soil and this increase was higher than achieved with the commercial Zn fertilizer. At the lower Zn application rate, Zn release followed parabolic diffusion, while at the higher rate the kinetics of release followed power function and Elovich models. There was an increase in Zn concentration of corn shoot and roots by adding of Zn regardless the source of applied Zn. With increase in the rate of rubber used, the shoot Zn uptake increased. The Pb concentration of shoot and Cd concentrations of shoot and roots were low (less than 0.02 mg kg^?1) in all treatments. The results showed that the soil DTPA Zn decreases over time if the soil is amended with a soluble form of Zn whereas the reverse was observed if the Zn is added as ground rubber which only gradually transforms. Thus ground rubber and rubber ash offer strong value as Zn fertilizer for Zn deficient soils.     

Accumulation of Hydrocarbons by Maize (Zea mays L.) in Remediation of Soils Contaminated with Crude Oil

This study has investigated the use of screened maize for remediation of soil contaminated with crude oil. Pots experiment was carried out for 60 days by transplanting maize seedlings into spiked soils. The results showed that certain amount of crude oil in soil (≤2 147 mg·kg^?1) could enhance the production of shoot biomass of maize. Higher concentration (6 373 mg·kg^?1) did not significantly inhibit the growth of plant maize (including shoot and root). Analysis of plant shoot by GC-MS showed that low molecular weight polycyclic aromatic hydrocarbons (PAHs) were detected in maize tissues, but PAHs concentration in the plant did not increase with higher concentration of crude oil in soil. The reduction of total petroleum hydrocarbon in planted soil was up to 52.21–72.84%, while that of the corresponding controls was only 25.85–34.22% in two months. In addition, data from physiological and biochemical indexes demonstrated a favorable adaptability of maize to crude oil pollution stress. This study suggested that the use of maize (Zea mays L.) was a good choice for remediation of soil contaminated with petroleum within a certain range of concentrations.     

3种土壤类型下红椿幼苗对铅胁迫的光合响应

采用盆栽试验,研究钙质紫色土、酸性紫色土和冲积土3种土壤类型上生长的红椿幼苗在不同浓度(0、200、450、2 000mg·kg-1)铅(Pb)胁迫下的光合生理响应,探讨红椿在不同土壤类型下Pb污染的生态适应性,为木本植物的重金属修复提供理论依据。结果表明:(1)3种土壤类型下,红椿幼苗叶片叶绿素a、叶绿素b及叶绿素总量随Pb胁迫浓度的增大呈总体降低的趋势,叶绿素含量在钙质紫色土上受Pb胁迫的影响不大,而在酸性紫色土和冲积土上降低明显。(2)不同土壤类型的红椿光合响应曲线变化趋势十分相似,红椿幼苗叶片的净光合速率均随Pb胁迫程度的加大呈先增加后降低的趋势且差异显著,并在Pb浓度为200和2 000mg·kg-1时光合速率分别达到最大值和最小值。(3)随着Pb胁迫浓度的增大,红椿的最大光合速率、表观量子利用效率、光补偿点等光合生理指标都发生了显著改变,说明Pb胁迫严重影响红椿幼苗的光合作用。研究表明,高浓度的铅抑制红椿幼苗叶片叶绿素的合成,从而抑制光合作用的强度,且铅胁迫的浓度越高,叶绿素含量越低,光合作用受到的抑制越强;较低浓度的Pb处理(200和450mg·kg-1)对酸性紫色土和冲积土上红椿的净光合速率影响很小,而对钙质紫色土上红椿的最大净光合速率的抑制最为明显。     

Leaf endophyte Neotyphodium coenophialum modifies mineral uptake in tall fescue

Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin, a fungal endophyte found primarily in shoots of tall fescue (Festuca arundinacea Shreb.), can modify rhizosphere activity in response to phosphorus (P) deficiency. In a controlled environment experiment, two cloned tall fescue genotypes (DN2 and DN4) free (E-) and infected (E+) with their naturally occurring endophyte strains were grown in nutrient solutions at low P (3.1 ppm) or high P (31 ppm) concentrations for 21 d. Endophyte infection increased root dry matter (DM) of DN4 by 21% but did not affect root DM of DN2. Under P deficiency, shoot and total DM were not affected by endophyte but relative growth rate was greater in E+ than E- plants. In high P nutrient solution, E+ plants produced 13% less (DN2) or 29% more (DN4) shoot DM than E- plants. Endophyte affected mineral concentrations in roots more than in shoots. Regardless of P concentration in nutrient solution, E+ DN2 accumulated more P, Ca, Zn and Cu but less K in roots than E- plants. When grown in high P nutrient solution, concentrations of Fe and B in roots of E+ DN2 plants were reduced compared with those of E- plants. Concentrations of P, Ca and Cu in roots of DN4 were less, but K was greater in E+ than E- plants. In shoots, E+ DN2 had greater concentrations of Fe and Cu than E- DN2, regardless of P concentration in nutrient solution. Genotype DN4 responded to endophyte infection by reducing B concentration in shoots. Nutrient uptake rates were affected by endophyte infection in plants grown in low P nutrient solution. A greater uptake rate of most nutrients and their transport to shoots was observed in DN2, but responses of DN4 were not consistent. Results suggest that endophyte may elicit different modes of tall fescue adaptation to P deficiency. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of endophytic fungi on some drought tolerance mechanisms of tall fescue in a hydroponics culture

Neotyphodium, a seed-transmissible nonpathogenic fungal endophyte (symbiont) is considered beneficial because endophyte-infected grasses are more drought-tolerant, produce more dry matter, utilize soil nitrogen more efficiently, and deter insects. In this study, the effects of endophytes on physiological mechanisms of drought tolerance in tall fescue (Festuca arundinacea Schreb.) were studied in a greenhouse. Two clonally propagated genotypes of tall fescue (F. arundinacea Schreb.), naturally containing endophyte (EI), and their endophyte-free ramets (EF) were tested at three water stress treatments exerted by PEG 6000 in a hydroponics system. Relative water content (RWC), cell membrane stability (CMS), proline and chlorophyll contents in plant leaves were measured during water stress treatments. After harvest, K⁺, Ca²⁺, and Mg²⁺ contents were measured in plant roots and shoots. After 20 days under stress conditions, plants were transferred to basal hydroponics medium, and their survival after stress relief was evaluated. The results showed that endophyte considerably contributes to host grass water stress tolerance. Both genotypes of EI and EF plants did not differ in RWC, but, regardless of the infection status, genotype 75 had the higher RWC than genotype 83. EI clones of both genotypes maintained slightly higher chlorophyll content and membrane stability than EF clones, although these differences were not significant. The EI plants of genotype 83 concentrated significantly more proline than EF plants, but in the genotype 75, differences between EI and EF clones were not significant. Plant mineral absorption was also influenced by the endophyte presence. EI clones had the higher concentrations of K⁺ in the shoots of both genotypes. The Mg²⁺ and Ca²⁺ contents in EF plants of both genotypes were higher than EI plants in the roots, but in the shoots there were no differences between EI and EF clones. EI clones survived longer after stress removal. These results strongly suggest that Neotyphodium endophytes exert their effects on tall fescue drought tolerance through alteration of various physiological mechanisms involved. Published in Russian in Fiziologiya Rastenii, 2009, Vol. 56, No. 4, pp. 563–570. This test was submitted by the authors in English.     

Biomass growth variation and phytoextraction potential of four Salix varieties grown in contaminated soil amended with lime and wood ash

Abstract

In a greenhouse experiment, plant growth and copper (Cu) and zinc (Zn) uptake by four Salix cultivars grown in Cu and Zn contaminated soils collected from a mining area in Finland were tested to assess their suitability for phytoextraction. The cultivars displayed tolerance to heavily contaminated soils throughout the experiment. After uptake, total mean Cu concentrations in the leaves, shoots and roots in all cultivars and treatments ranged from 163 to 474?mg kg^?1 and mean Zn concentrations ranged from 776 to 1823?mg kg^?1. Lime and wood ash addition increased dry biomass growth (25–43%), chlorophyll fluorescence (Fv/Fm) values (3–6%), the translocation factor (TF) (15–60% for Cu; 10–25% for Zn), the bio-concentration factor (BCF) (40–85% for Cu; 70–120% for Zn), and metal uptake (55–70% for Cu; 50–65% for Zn) compared to unamended treatment across all cultivars. The results revealed that Salix cultivars have the potential to take up and accumulate significant amounts of Cu and Zn. Cultivar Klara (Salix viminalis × S. schwerinii × S. dasyclados) was found to be the most effective cultivar for phytoextraction since it displayed greater dry biomass production, Fv/Fm, TF, BCF values and uptake percentage rates of Cu and Zn compared to the other three cultivars. This study indicates that further research is needed to clarify the wider phytoextraction capabilities of different Salix cultivars.     

Effect of Salinity on Zinc uptake by Brassica juncea

Salinity is a major worldwide problem that affects agricultural soils and limits the reclamation of contaminated sites. Despite the large number of research papers published about salt tolerance in Brassica juncea L., there are very few accounts concerning the influence of salinity on the uptake of trace metals. In this study, B. juncea plants divided through soil sets comprising 0, 900 and 1800 mg Zn kg^?1, were treated with solutions containing 0, 60 and 120 mmol L^?1 of NaCl, with the purpose of observing the effect of salt on Zn uptake, and some physiological responses throughout the 90 days experiment. Increasing concentrations of NaCl and Zn produced a decline in the ecophysiological and biochemical properties of the plants, with observable synergistic effects on parameters like shoot dry weight, leaf area, or photochemical efficiency. Nevertheless, plants treated with 60 mmol L^?1 of NaCl accumulated striking harvestable amounts of Zn per plant that largely exceed those reported for Thlaspi caerulescens. It was concluded that salinity could play an important role on the uptake of Zn by B. juncea. The potential mechanisms behind these results are discussed, as well as the implications for phytoremediation of Zn on saline and non-saline soils.     

Phytoextraction of Risk Elements by Willow and Poplar Trees

To characterize the phytoextraction efficiency of two clones of willow trees (Salix x smithiana Willd., Salix rubens) and two clones of poplar trees (Populus nigra x maximowiczii, Populus nigra Wolterson) were planted in contaminated soil (0.4–2.0 mg Cd.kg^?1, 78–313 mg Zn.kg^?1, 21.3–118 mg Cu.kg^?1). Field experiment was carried out in Czech Republic. The study investigated their ability to accumulate heavy metals (Cd, Zn, and Cu) in harvestable plant parts. The poplars produced higher amount of biomass than willows. Both Salix clones accumulated higher amount of Cd, Zn and Cu in their biomass (maximum 6.8 mg Cd.kg^?1, 909 mg Zn.kg^?1, and 17.7 mg Cu.kg^?1) compared to Populus clones (maximum 2.06 mg Cd.kg^?1, 463 mg Zn.kg^?1, and 11.8 mg Cu.kg^?1). There were no significant differences between clones of individual species. BCs for Cd and Zn were greater than 1 (the highest in willow leaves). BCs values of Cu were very low. These results indicate that Salix is more suitable plant for phytoextraction of Cd and Zn than Populus. The Cu phytoextraction potential of Salix and Populus trees was not confirmed in this experiment due to low soil availability of this element.     

Advances in introgression technologies for precision breeding within the Lolium - Festuca complex

The anticipated complexity of multifunctional grasslands with environment‐friendly and sustainable management practices demands better understanding of traits, their interactions, and their genetic control. Intergeneric hybrids between closely related Lolium and Festuca species are being used to broaden the gene pool and provide the plant breeder with options to combine complementary traits aimed at high quality but more robust grass varieties for the future. New techniques in introgression mapping provide opportunities for precision breeding whereby desirable gene combinations transferred from one species into another are selected preferentially, with the exclusion of deleterious alien genes. The close homology between genomes of Lolium and Festuca species allows high levels of chromosome pairing and recombination. Using genomic in situ hybridisation (GISH) on Lolium/Festuca hybrids and their derivatives, recombination between Lolium and Festuca chromosomes is observed at any point along the chromosome. The system provides unlimited access to any combination of Lolium and Festuca DNA sequence. Moreover, genes transferred between homoeologous chromosome sites are expected to function normally at their new locations. Alien chromosome segments may be reduced in size by further recombination events thereby reducing linkage drag. Molecular markers such as AFLPs, SSRs, SNPs, or RFLPs are being targeted to genes of interest to allow their selection through different generations in plant breeding programmes. Relatively simple PCR‐based marker systems are used for specific traits as breeders' toolkits in plant breeding programmes.     

Distribution and mobility of toxic metals in Thymus alsarensis Ronniger in the Allchar As–Sb–Tl mine,Republic of Macedonia

Abstract

The Allchar district is an abandoned antimony–arsenic–thallium deposit located in the north-western region of Ko?uf mountain in the Republic of Macedonia. The locality of Allchar has a complex and unique mineral composition. The current study sought to investigate the levels of uptake and distribution of different heavy metals, such as As, Sb and Tl, in the different organs of Thymus alsarensis Ronniger, an endemic plant species of the area. Root, stem, leaf and flower samples, as well as corresponding soils, were processed, digested and then analysed by inductively coupled plasma atomic emission spectrometry. Significant accumulation of As, Sb and Tl in this endemic species was observed. Total As content in the soil ranged from 34.7 to 5288 mg kg^–1, and the content of As in plants ranged from 0.25 to 140 mg kg^–1. The content of Sb in soil and plants ranged from 6.3 to 130 mg kg^–1 and 0.25 to 1.51 mg kg^–1, respectively. Lastly, the content of Tl in soil and plants ranged from 2.0 to 330 mg kg^–1 and 0.10 to 496 mg kg^–1, respectively. Similar results were obtained from extraction tests of soil samples using various solvents.     

Endophytes inconsistently affect plant communities across Schedonorus arundinaceus hosts

Fungal endophytes in cool-season grasses may affect communities at multiple trophic levels. However, it is unclear whether community-scale endophyte effects arise due to the endophyte itself or as a result of unique, endophyte–host interactions. We used a long-term field experiment to test whether common-toxic (CT) and non-ergot alkaloid-producing (novel) endophytes in Schedonorus arundinaceus (tall fescue) forage cultivars consistently affect communities across tall fescue hosts. Tilled plots (2 × 2 m; Guelph, ON) were seeded with Georgia 5 and Jesup cultivars containing either the CT or AR542 (novel) endophyte and allowed to be re-colonized by plant species from the local propagule pool. Non-seeded control plots were included to assess effects of seeding the non-native grass. We assessed plant, invertebrate, soil moisture, and soil nutrient responses to the endophyte–cultivar treatments after four growing seasons. Seeding tall fescue affected plant species abundances, but not richness, and did not consistently alter soil moisture and nutrient pools. Endophyte identity in the tall fescue cultivars affected the communities, but effects were not consistent between cultivars. Within Georgia 5, the AR542 endophyte reduced tall fescue abundance and altered the invertebrate community relative to CT plots. Within Jesup, the AR542 endophyte reduced species evenness and decreased soil moisture during dry periods relative to CT plots. Endophyte effects were not consistent between cultivars, and it is probable that the community-scale effects of endophyte infection in tall fescue cultivars arise due to unique interactions between cultivar and endophyte.     

Importance of seed Zn content for wheat growth on Zn-deficient soil

Seed nutrient reserves may be important for an early establishment of crops on low-fertility soils. This glasshouse pot study evaluated effects of seed Zn content on vegetative growth of two wheat (Triticum aestivum L.) genotypes differing in Zn efficiency. Low-Zn (around 250 ng Zn per seed) and high-Zn seed (around 700 ng Zn per seed on average) of Excalibur (Zn efficient) and Gatcher (Zn inefficient) wheats were sown in a Zn-deficient siliceous sand fertilised with 0, 0.05, 0.2, 0.8 or 3.2 mg Zn kg^-1 soil. After 3 weeks, plants derived from the high-Zn seed had better root and shoot growth; the cv. Excalibur accumulated more shoot dry matter than the cv. Gatcher. After 6 weeks, greater root and shoot growth of plants grown from the high-Zn seed compared to those from the low-Zn seed was obvious only at nil Zn fertilisation. A fertilisation rate of 0.2 mg Zn kg^-1 soil was required for achieving 90% of the maximum yield for plants grown from the high-Zn seed compared to 0.8 mg Zn kg^-1 soil for plants derived from the low Zn seed. The critical Zn level in youngest expanded leaves for 90% maximum yield was 16 mg Zn kg^-1 dry matter for both genotypes. Zn-efficient Excalibur had greater net Zn uptake rates compared to Zn-inefficient Gatcher after 3 weeks but they were not different at the 6-week harvest. Zinc-deficient plants had greater net uptake rates of Cu, Mn, B, P, and K but a reduced uptake rate of Fe. It is concluded that higher seed Zn content acted similar to a starter-fertiliser effect by improving vegetative growth and dissipating differences in Zn efficiency of wheat genotypes.     

内生真菌对氮添加羽茅根际土壤特性和微生物群落的影响

内生真菌不仅能改变与其共生植物的生理和生长指标,还可通过宿主植物间接对土壤的理化性质和微生物群落结构产生影响。以天然禾草——羽茅(Achnatherum sibiricum)为研究材料,探究在不同施氮水平下,内生真菌的种类对不同基因型的宿主植物根际土壤理化性质和微生物群落产生何种影响。结果表明,内生真菌侵染显著提高了羽茅根际土壤的pH值和微生物总量,但降低了土壤中真菌与细菌的比值。同时,土壤的pH值还受到了内生真菌种类的影响,其中感染Epichlo3 sibirica的羽茅根际土壤pH显著高于感染Epichlo3 gansuense-1的羽茅,而感染Epichlo3 gansuense-2的羽茅根际土壤pH与感染E.gansuensis-1、E.sibirica菌的羽茅相比没有显著差异。另外,内生真菌感染与否、内生真菌种类、施氮量以及宿主植物基因型对土壤总碳、总氮、微生物及碳矿化能力均无显著影响。