盐条件下产胞外多糖植物促生细菌研究

Salt-tolerant plant growth-promoting rhizobacteria (PGPR) can play an important role in alleviating soil salinity stress during plant growth and bacterial exopolysaccharide (EPS) can also help to mitigate salinity stress by reducing the content of Na + available for plant uptake.In this study,native bacterial strains of wheat rhizosphere in soils of Varanasi,India,were screened to identify the EPS-producing salt-tolerant rhizobacteria with plant growth-promoting traits.The various rhizobacteria strains were isolated and identified using 16S rDNA sequencing.The plant growth-promoting effect of inoculation of seedlings with these bacterial strains was evaluated under soil salinity conditions in a pot experiment.Eleven bacterial strains which initially showed tolerance up to 80 g L -1 NaCl also exhibited an EPS-producing potential.The results suggested that the isolated bacterial strains demonstrated some of the plant growth-promoting traits such as phosphate solubilizing ability and production of auxin,proline,reducing sugars,and total soluble sugars.Furthermore,the inoculated wheat plants had an increased biomass compared to the un-inoculated plants.     

Bacterial inoculants for rice: effects on nutrient uptake and growth promotion

Beneficial soil bacteria are able to colonize plant root systems promoting plant growth and increasing crop yield and nutrient uptake through a variety of mechanisms. These bacteria can be an alternative to chemical fertilizers without productivity loss. The objectives of this study were to test bacterial inoculants for their ability to promote nutrient uptake and/or plant growth of rice plants subjected to different rates of chemical fertilizer, and to determine whether inoculants could be an alternative to nitrogen fertilizers. To test the interaction between putatively beneficial bacteria and rice plants, field experiments were conducted with two isolates: AC32 (Herbaspirillum sp.) and UR51 (Rhizobium sp.), and different nitrogen fertilization conditions (0%, 50%, and 100% of urea). Satisfactory results were obtained in relation to the nutrient uptake by plants inoculated with both isolates, principally when the recommended amount of nitrogen fertilizer was 50% reduced. These bacterial strains were unable to increase plant growth and grain yield when plants were subjected to the high level of fertilization. This study indicated that the tested inoculant formulations can provide essential nutrients to plants, especially when the levels of nitrogen fertilizers are reduced.     

Effect of plant growth-promoting bacteria and soil compaction on barley seedling growth, nutrient uptake, soil properties and rhizosphere microflora

Inoculants are of great importance in sustainable and/or organic agriculture. In the present study, plant growth of barley (Hordeum vulgare) has been studied in sterile soil inoculated with four plant growth-promoting bacteria and mineral fertilizers at three different soil bulk densities and in three harvests of plants. Three bacterial species were isolated from the rhizosphere of barley and wheat. These bacteria fixed N₂, dissolved P and significantly increased growth of barley seedlings. Available phosphate in soil was significantly increased by seed inoculation of Bacillus M-13 and Bacillus RC01. Total culturable bacteria, fungi and P-solubilizing bacteria count increased with time. Data suggest that seed inoculation of barley with Bacillus RC01, Bacillus RC02, Bacillus RC03 and Bacillus M-13 increased root weight by 16.7, 12.5, 8.9 and 12.5% as compared to the control (without bacteria inoculation and mineral fertilizers) and shoot weight by 34.7, 34.7, 28.6 and 32.7%, respectively. Bacterial inoculation gave increases of 20.3–25.7% over the control as compared with 18.9 and 35.1% total biomass weight increases by P and NP application. The concentration of N and P in soil was decreased by increasing soil compaction. In contrast to macronutrients, the concentration of Fe, Cu and Mn was lower in plants grown in the loosest soil. Soil compaction induced a limitation in root and shoot growth that was reflected by a decrease in the microbial population and activity. Our results show that bacterial population was stimulated by the decrease in soil bulk density. The results suggest that the N₂-fixing and P-solubilizing bacterial strains tested have a potential on plant growth activity of barley.     

Interactions of bacteria,protozoa and plants leading to mineralization of soil nitrogen

The capacity of bacteria and protozoa to mineralize soil nitrogen was studied in microcosms with sterilized soil with or without wheat plants. The effect of small additions of glucose or ammonium nitrate or both, twice a week was also tested. Plant dry weight and N-content, number of microorganisms and biomass plus inorganic N were determined after 6 weeks.The introduction of plants profoundly influenced the N transformations. In the presence of root-derived carbon, much more N was mineralized from the organic matter and immobilized mainly in plant biomass. “Total observable change in biomass N plus inorganic N” was negative in the unvegetated soils without additions, while a mineralization of 1.7 mg N microcosm^?1 was observed in microcosms with wheat plants grown with bacteria only. When protozoa were included, the N taken up by plants increased by 75%. Sugar additions resulted in an 18% increase of total N in the shoots when protozoa were present, but had no significant effect in the absence of grazers. Plants with the same root weight were more efficient in their uptake of inorganic N when protozoa were present. Plants grown with protozoa also had a lower R/S ratio, indicating a less stressed N availability situation. The lowest ratio was found with N additions in the presence of protozoa.The results indicate that, with energy supplied by plant roots or with external glucose additions, soil bacteria can mineralize N from the soil organic matter to support their own growth. Grazing of the bacteria is necessary to make bacterial biomass N available for plant uptake.     

Effect of manganese-reducing rhizosphere bacteria on the growth of Gaeumannomyces graminis var. tritici and on manganese uptake by wheat (Triticum aestivum L.)

Summary Five bacterial strains capable of Mn reduction were isolated from the rhizosphere of plants growing in different South Australian soils. They differed in their Mn-reducing capacity. The antagonism of these strains compared to the imported strain 2–79 (from the United States) against Gaeumannomyces graminis var. tritici was tested in agar and in a soil sandwich experiment at different Mn²⁺ concentrations in the soil. In addition, wheat seeds were coated with the different strains and with MnSO₄ or with MnSO₄ only in order to investigate their effect on plant growth and Mn uptake. With one exception, all strains inhibited the growth of G. graminis in agar, but to different degrees. In contrast, only two strains significantly inhibited the growth of the fungus in the soil. The hyphal density was decreased more than the hyphal length. The Mn²⁺ concentration in the soil also had a marked effect on fungal growth; low Mn concentrations slightly increased while high Mn concentrations strongly decreased the fungal growth. Seed treatment with MnSO₄ only (+Mn) increased Mn uptake above that of the control (no seed treatment). Only the weakest Mn reducer on agar significantly increased plant growth and Mn uptake from soil in comparison with the Mn treatment. One strain was tested as seed coating without adding MnSO₄; it increased the plant growth to an extent similar to the Mn treatment. Increasing the Mn uptake by plants may be one of the growth-promoting effects exerted by rhizosphere bacteria.     

Relationships between sulfur concentration in mulberry Leaves and the quality of silkworm cocoon

A 40-day gnotobiotic microcosm experiment was carried out to quantify the effect of bacterial-feeding nematode on plat growth and nutrient absorption.The results showed that inoculation of bacterial-feeding nematode Protorhabditis sp.stimulated the growth of wheat (Triticum aestivum) and the uptake of N.By the end of the 40-day incubation wheat biomass and N uptake in the treatment with nematode and bacteria (Pseudomonas sp.)increased by 6.5% and 5.9%,respectively,compared with bacteria alone treatment.The presence of nematode mainly accelerated the growth of aboveground of wheat,while it slightly inhibited the root development.There was little difference in plant tissue N concentration between treatments.P concentration and uptake of wheat,however,were generally reduced by nematode, It appears that the enhancement of plant growth and nitrogen uptake is attributed to the enhancement of nitrogen mineraliztion induced by nematode feeding on bacteria,and the reduction of phosphorous uptake is the result of ewak root status and comptetition by bacteria immobilzation.     

在受控条件下植物促生菌对扁豆的生长，结瘤和养分积累的效应

Application of plant growth-promoting rhizobacteria (PGPR) has been shown to increase legume growth and development under field and controlled environmental conditions. The present study was conducted to isolate plant growth-promoting rhizobacteria (PGPR) from the root nodules of lentil (Lens culinaris Medik.) grown in arid/semi-arid region of Punjab, Pakistan and examined their plant growth-promoting abilities. Five bacterial isolates were isolated, screened in vitro for plant growth-promoting (PGP) characteristics and their effects on the growth of lentil were assessed under in vitro, hydroponic and greenhouse (pot experiment) conditions. All the isolates were Gram negative, rod-shaped and circular in form and exhibited the plant growth-promoting attributes of phosphate solubilization and auxin (indole acetic acid, IAA) production. The IAA production capacity ranged in 0.5-11.0 μg mL-1 and P solubilization ranged in 3-16 mg L-1 . When tested for their effects on plant growth, the isolated strains had a stimulatory effect on growth, nodulation and nitrogen (N) and phosphorus (P) uptake in plants on nutrient-deficient soil. In the greenhouse pot experiment, application of PGPR significantly increased shoot length, fresh weight and dry weight by 65%, 43% and 63% and the increases in root length, fresh weight and dry weight were 74%, 54% and 92%, respectively, as compared with the uninoculated control. The relative increases in growth characteristics under in vitro and hydroponic conditions were even higher. PGPR also increased the number of pods per plant, 1 000-grain weight, dry matter yield and grain yield by 50%, 13%, 28% and 29%, respectively, over the control. The number of nodules and nodule dry mass increased by 170% and 136%, respectively. After inoculation with effective bacterial strains, the shoot, root and seed N and P contents increased, thereby increasing both N and P uptake in plants. The root elongation showed a positive correlation (R2 = 0.67) with the IAA production and seed yield exhibited a positive correlation (R2 = 0.82) with root nodulation. These indicated that the isolated PGPR rhizobial strains can be best utilized as potential agents or biofertilizers for stimulating the growth and nutrient accumulation of lentil.     

黄土和塿土中Fe, Mn, Cu和Zn向植物根部移动的机理

The pot experiments were conducted in the artificial climate laboratories to determine the relative importance of mass flow and diffusion in supplying Fe, Mn, Cu and Zn to wheat, soybean and maize plants growing in loessal soil and lou soil. It was found that the calculated relative contribution of mass flow of iron, manganese, copper and zinc to plant uptake varied from 5% to more than 100%, depending on the crop species and soil types as well as plant growth stage, soil moisture, atmosphere humidity, etc. The results also showed that the major transportation mechanisms of these micronutrients in soil-root system varied with the crop and its growth, climate and soil, significantly. In general, mass flow was more important for Cu and Zn and diffusion was more significant for Fe and Mn at the seedling stage.     

接种食细菌线虫对小麦生长和N、P吸收的影响

A 40-day gnotobiotic microcosm experiment was carried out to quantify the effect of bacterial-feeding nematode on plant growth and nutrient absorption. The results showed that inoculation of bacterial-feeding nematode Protorhabditis sp. stimulated the growth of wheat (Triticum aestivum) and the uptake of N. By the end of the 40-day incubation wheat biomass and N uptake in the treatment with nematode and bacteria (Pseudomonas sp.) increased by 6.5% and 5.9%, respectively, compared with bacteria alone treatment. The presence of nematode mainly accelerated the growth of aboveground of wheat, while it slightly inhibited the root development. There was little difference in plant tissue N concentration between treatments. P concentration and uptake of wheat, however, were generally reduced by nematode. It appears that the enhancement of plant growth and nitrogen uptake is attributed to the enhancement of nitrogen mineralization induced by nematode feeding on bacteria, and the reduction of phosphorous uptake is the result of weak root status and competition by bacteria immobilization.     

Mechanisms for the Movement of Fe,Mn,Cu and Zn to Plant Roots in Loessal Soil and Lou Soil

The pot experiments were conducted in the artificial climate laboratories to determine the relative importance of mass flow and diffusion in supplying ,Fe,Mn,Cu,and Zn to wheat,soybean and maize plants growing in loessal soil and lou soil.It was found that the calculated relative contribution of mass flow of iron,manganese,copper and zinc to plant uptake varied from 5% to more than 100%,depending on the crop species and soil types as well as plant growth stage,soil moisture,atmosphere humidity,etc.The results also showed that the major transportation mechanisms of these micronutrients in soil-root system varied with the crop and its growth,climate and soil,singnificantly,In general,mass flow was more important for Cu and Zn and diffusion was more significant for Fe and Mn at the seedling stage.     

Synergistic effect of inoculating plant growth-promoting Pseudomonas spp. and Rhizobium leguminosarum-FB1 on growth and nutrient uptake of rajmash (Phaseolus vulgaris L.)

Plant growth-promoting bacteria (PGPB) Pseudomonas lurida-NPRp15 and Pseudomonas putida-PGRs4 possessing multiple plant growth-promoting traits were isolated from rhizoplane of pea and rhizosphere of garlic, respectively. The effects of individuals and combinations of Pseudomonas spp. with effective root nodulating symbiotic nitrogen fixing Rhizobium leguminosarum-FB1 on plant growth, nutrient uptake and yield of the rajmash plant were studied under greenhouse conditions. Bacterial inoculation resulted in significantly higher values for plant dry biomass, N, P, K, Zn and Fe contents as compared to the uninoculated control. Furthermore, dual inoculation of P. lurida-NPRp15 with R. leguminosarum-FB1 significantly increased root and shoot dry weight, nodulation, nutrient uptake, pod yield, and nutrient content of pods of rajmash VL63 compared to controls, single and triple inoculation. The results of the study indicate the potential of harnessing the benefit of plant growth-promoting and nitrogen-fixing microorganisms to improve the growth and yield of rajmash.     

Influence of growth-promoting bacteria on the growth of wheat in different soils and temperatures

Plant-growth-promoting bacteria isolated from the rhizosphere, phyllosphere and soil of the root zone in different climatic regions of Germany and Uzbekistan were analysed for plant-growth-promoting effects and nutrient uptake on winter wheat on different soils and under different temperature regimes. The investigations were carried out in pot experiments using loamy sand and sandy loam soils from Müncheberg, Germany and Calcisol soil from Tashkent, Uzbekistan. The temperature and soil types were found to influence growth-promoting effects. Inoculation with bacterial strains Pseudomonas fluorescens PsIA12, Pantoea agglomerans 050309 and Mycobacterium sp. 44 isolated from Müncheberg (semi-continental climate) was found to significantly increase the root and shoot growth of winter wheat at 16 °C compared to 26 °C in loamy sand. Mycobacterium phlei MbP18 and Mycoplana bullata MpB46 isolated from Tashkent (semi-arid climate) were found to significantly increase the root and shoot growth of winter wheat in nutrient-poor Calcisol at 38 °C as well as in nutrient-rich loamy sand at 16 °C. Bacterial inoculation also resulted in significantly higher N, P, and K contents of plant components. The bacteria isolates were able to survive in the rhizosphere and in the soil of winter wheat after root and shoot inoculation.     

Biostimulant effects of Bacillus strains on wheat from in vitro towards field conditions are modulated by nitrogen supply

Bacillus velezensis strains, belonging to plant growth‐promoting rhizobacteria (PGPR), are increasingly used as microbial biostimulant. However, their field application to winter wheat under temperate climate remains poorly documented. Therefore, three B. velezensis strains IT45, FZB24 and FZB42 were tested for their efficacy under these conditions. Two biological interaction systems were firstly developed under gnotobiotic and greenhouse conditions combined with sterile or non‐sterile soil, respectively, and finally assayed in the field during two years coupled with different N fertilization rates. Under gnotobiotic conditions, all three strains significantly increased root growth of 14 d‐old spring and winter wheat seedlings. In the greenhouse using non‐sterile soil, only FZB24 significantly increased root biomass of spring wheat (+31%). The three strains were able to improve nutrient uptake of the spring wheat grown in the greenhouse, particularly for the micronutrients Fe, Mn, Zn, and Cu, but the observed increases in nutrient uptake were dependent on the organs and the elements. The root biomass increases in inoculated plants coincided with lowered nutrient concentrations of P and K. In 2014, under field conditions and absence of any N fertilizer supply, FZB24 significantly increased grain yields by 983 kg ha^?1, or 14.9%, in relation to non‐inoculated controls. The three strains in the 2015 field trial failed to confirm the previous positive results, likely due to the low temperatures occurring during and after inoculations. The Zeleny sedimentation value, indicative of flour quality, was unaffected by the inoculants. The results are discussed in the perspective of bacterial application to wheat under temperate agricultural practices.     

The impact of protozoa on the availability of bacterial nitrogen to plants

Summary Microbial N from ¹⁵N-labelled bacterial biomass was investigated in a microcosm experiment, in order to determine its availability to wheat plants. Sterilized soil was inoculated with either bacteria (Pseudomonas aeruginosa alone or with a suspension of a natural bacterial population from the soil) or bacteria and protozoa to examine the impact of protozoa. Plant biomass, plant N, soil inorganic N and bacterial and protozoan numbers were determined after 14 and 35 days of incubation. The protozoa reduced bacterial numbers in soil by a factor of 8, and higher contents of soil inorganic N were found in their presence. Plant uptake of N increased by 20010 in the presence of protozoa. Even though the total plant biomass production was not affected, the shoot: root ratios increased in the presence of protozoa, which is considered to indicate an improved plant nutrient supply. The presence of protozoa resulted in a 65010 increase in mineralization and uptake of bacterial ¹⁵N by plants. This effect was more pronounced than the protozoan effect on N derived from soil organic matter. It is concluded that grazing by protozoa strongly stimulates the mineralization and turnover of bacterial N. The mineralization of soil organic N was also shown to be promoted by protozoa.Communication No. 9 of the Dutch Programme on Soil Ecology of Arable Farming Systems     

The “soil microbial loop” is not always needed to explain protozoan stimulation of plants

Protozoa stimulate plant growth, but we do not completely understand the underlying mechanisms, and different hypotheses seek to explain this phenomenon. To test these hypotheses, we grew the grass Yorkshire fog (Holcus lanatus) in pots with soil, which contained either (1) no organisms but bacteria – or (2) bacteria and protozoa. Half of the pots received a glucose treatment so as to mimic an additional root exudation. We measured plant growth and plant nitrogen uptake, along with various microbial pools and processes that support plant growth. Protozoan presence significantly enhanced soil nitrogen mineralization, plant nitrogen uptake from organic nitrogen sources, plant nitrogen content, and plant growth. By contrast, we found no evidence that glucose addition, mimicking root exudation, increased soil nitrogen availability and plant nitrogen uptake. Moreover, although protozoan presence affected bacterial community structure, it did not affect the proportion of IAA-producing bacteria in the community or plant root morphology. These results refute the “soil microbial loop” hypotheses, which suggest that protozoan stimulation of plant growth results from complex interactions between plant roots, bacteria and protozoa. Our experiment thus favours the simple explanation that increased nitrogen availability is the key factor behind the positive protozoan effect on plant growth. To exploit natural resources in an efficient and environmentally friendly way, we need to understand in detail the functioning of ecosystems. This study stresses that to achieve this, it is still urgent, besides investigating intricate food-web and signal compound interactions, also to focus on the basic stoichiometric and energetic aspects of organisms.     

Changes in micronutrient availability and plant uptake under simulated climate change in winter wheat field

Purpose

Although micronutrients are essential to higher plants, it remains unclear whether the projected future climate change would affect their availability to plants. The objective of this study was to investigate the effect of carbon dioxide (CO₂) enrichment and warming on soil micronutrient availability and plant uptake.

Materials and methods

This study was conducted in an open field experiment with CO₂ enrichment and plant canopy warming. Four treatments were included: (1) free-air CO₂ enrichment up to 500 ppm (CE); (2) canopy warming by plus 2 °C (WA); (3) CO₂ enrichment combined with canopy warming (CW), and (4) ambient condition as control. Plant and soil samples were collected, respectively, at the jointing, heading, and ripening stage over the whole wheat growing season in 2014. The micronutrient concentrations both in soil and plant were both analyzed, and the accumulated uptake by wheat harvest was assessed.

Results and discussion

Both CO₂ enrichment and warming increased the availability of most soil micronutrients. The availability of Fe, Mn, Cu, and Zn under CO₂ enrichment increased by 47.7, 22.5, 59.8, and 114.1 %, respectively. Warming increased the availability of Fe, Cu, and Zn by 60.4, 23.8, and 15.3 %, respectively. The plant growth induced changes in soil pH and in soil microbial biomass carbon (MBC) accounted to the changes in soil micronutrient availability. The enrichment of CO₂ and warming had significant effects on micronutrient uptake by wheat. The enrichment of CO₂ decreased the concentration of Fe by 9.3 %, while it increased the concentrations of Mn and Zn by 18.9 and 8.1 % in plant shoot, respectively. Warming increased the concentration of Fe and Cu by 24.3 and 7.6 % in plant shoot, respectively. The increase in soil micronutrient availability did not always lead to the increase in micronutrient uptake. The element types and crop growth stage affected the uptake of micronutrients by wheat under CO₂ enrichment and warming. Additionally, CO₂ enrichment decreased the translocation of Fe and Zn by 25.3 and 10.0 %, respectively, while warming increased the translocation of Fe, Mn, Cu, and Zn across stages.

Conclusions

Our results demonstrated that CO₂ enrichment and warming would improve availability of some micronutrients and their uptake by wheat. However, it is still unclear whether a net removal of micronutrient through crop straw harvest would occur under CO₂ enrichment and warming.

     

Association of Azospirillum brasilense with pearl millet (Pennisetum americanum (L.) Leeke)

Summary Microscopic observations of the root system of pearl millet (Pennisetum americanum (L.) Leeke) var. BJ 104 after surface sterilization and incubation in phosphate malate triphenyl tetrazolium chloride (TTC) revealed extensive colonization by Azospirillum spp. when plants were grown in sterile, partially sterile and field conditions as evidenced by the TTC-reducing property of active cells of the bacterium. Quantitative studies showed the need to standardize the techniques further to ensure more precise monitoring of the bacteria in the rhizosphere, as large numbers of soil bacteria were found capable of growth on specific media, thus interfering with the plate counts. Seed inoculation with A. brasilense increased the mean grain yield of pearl millet under different agroclimatic conditions in India. The mean increase in grain yield due to inoculation over uninoculated controls was also noticed with graded levels of fertilizer nitrogen (urea). Inoculation alone contributed to increased nitrogen uptake of plants with varying levels of fertilizer nitrogen application under sandy loam soil conditions (pH 7.3). The effects of inoculation were more prominent under lower levels of nitrogen than at the higher levels. The root biomass under field conditions was increased with Azospirillum spp. inoculation at 10 and 20 kg N/ha than their corresponding uninoculated controls.     

Effect of Indigenous Plant Growth-Promoting Rhizobacteria on Wheat (Triticum Aestivum L.) Productivity and Soil Nutrients

The present study aimed at selection of efficient bacterial isolates with multiple plant growth-promoting (PGP) traits at variable doses of chemical fertilizers for enhanced wheat productivity and sustenance of soil health. Ten bacterial isolates from wheat (rhizosphere soil and root endosphere) were screened for PGP traits (indole acetic acid, phosphate solubilization, siderophore production, and ammonia production). Only three isolates (B2, SIR1, and BIS2) possessed all PGP traits. Net house evaluation of these isolates at graded doses of chemical fertilizers revealed that the potential of B2 isolate is significantly superior for enhancing wheat yield and soil properties. On the basis of 16S rDNA analysis, the potential isolate (B2) was identified as Serratia marcescens. Conjoint use of the B2 isolate at 80% recommended doses of fertilizers (RDF) significantly increased wheat growth and saved 18 kg nitrogen and 10 kg phosphorous on per hectare basis. The developed module not only increases profitability but also protects the environment and sustains soil health.     

硅对植物体中某些营养物质穿细胞及质外体吸收的影响

The positive effects of silicon（Si） on growth of plants have been well documented;however,the impact of Si on plant nutrient uptake remains unclear.The growth,nutrient content and uptake of wheat（Triticum aestivum L.）,canola（Brassica napus L.） and cotton（Gossypium hirsutum L.） plants were evaluated with or without application of 1.5 mmol L^-1 Si.Application of Si increased dry weights by 8%,30%and 30%and relative growth rate（RGR） by 10%,13%and 17%in the cotton,canola and wheat plants,respectively.The plant relative water content（RWC） was also increased,but the plant transpiration was decreased by Si application.The uptake and content of Ca²⁺ were 19%and 21%lower in the cotton and wheat plants with Si than those without Si,respectively;however,Si application increased both K⁺ and Fe uptake and contents in all plant species.Silicon application reduced B uptake and content only in cotton and increased P and Zn²⁺ contents in all three plant species.The decrease in Ca²⁺ uptake by Si application was sustained even in the presence of metabolic inhibitors 2,4-dinitrophenol and sodium cyanide.Uptake of Ca²⁺ by Si application was enhanced or did not change when plant shoots were saturated with water vapor or their roots were exposed to low temperature.Thus,Si application increased the uptake of transcellularly transported elements like K⁺,P,Zn²⁺ and Fe.In contrast,Ca2+ uptake which occurred via both apoplastic and transcellular pathways was decreased by Si application,possibly through reduction of apoplastic uptake.More efficient nutrient uptake might be another promoting effect of Si on plant growth.     

地表覆盖和施氮对冬小麦干物质和氮素积累与转移的影响

在黄土高原南部旱区,通过田间试验研究了地表覆盖在不同氮水平下对冬小麦生长和氮素累积及转移的影响。结果表明,覆膜显著增加冬小麦各生育期干物质的积累,提高干物质转移量或花后干物质累积量;覆草显著增加生长后期干物质累积量,随种植年限的增加,覆草能显著增加冬小麦生物产量和子粒产量,其增产作用与覆膜无显著差异。覆膜亦能显著增加冬小麦各生育期氮素的积累,提高氮素转移量;覆草显著增加了生长后期氮的累积,随种植年限的增加,覆草对地上部吸氮量和子粒吸氮量的影响与覆膜无显著差异。施用氮肥显著增加了各生育期干物质和氮素的累积,促进花后干物质的累积和花前累积氮的再转移,显著提高了冬小麦地上部和子粒吸氮量及生物产量和子粒产量。