Effects of aluminum on organic acid,sugar and amino acid composition of the root system of sorghum (Sorghum bicolor L. Moench)

The effects of aluminum on the accumulation of sugars, amino acids and organic acids in two hybrid cultivars of sorghum were studied.

The concentration of these organic compounds increased in the roots of the Al‐treated plants, mainly in the tolerant cultivar. The composition of the organic acid fraction showed a significantly higher accumulation of trans‐aconitate and malate in the tolerant cultivar as compared with the sensitive one. The higher levels of these acids in the Al‐treated plants could be interpreted as being indicative of a chelating detoxifying mechanism of aluminum in these plants.     

Composition of amino acids,organic acids,and sugars in the peribacteroid space of soybean root nodules

In leguminous root nodules, bacteroids are differentiated from rhizobia and are surrounded by a peribacteroid membrane (PBM) forming an intracellular structure designated as symbiosome. Through the peribacteroid space (PBS) between the PBM and bacteroids, metabolic substances and signal compounds are exchanged between two symbionts. In this study, organic compounds with low molecular weight in the PBS were collected from isolated symbiosomes of soybean (Glycine max L.) root nodules, and their composition was analyzed and compared with that of the organic compounds in whole root nodules and bacteroids. Major differences were detected in the molar percentages of amino and organic acids, and sugars, to the total low molecular weight organic compounds among whole root nodules, PBS, and bacteroids. The PBS composition was characterized by abundant sugars and poor amino acids. Also the composition of the amino acids, organic acids, and sugars in the PBS was clearly different from that in whole root nodules and bacteroids. The PBS sugar composition was characterized by the predominance of inositols, especially myo-inositol at the 5th and 7th weeks of the host plant growth stages. Changes in the myo- and D-chiro- inositol balance at the host plant growth stages occurred and a syntony was observed between the PBS and bacteroids. The localization of myo-inositol in the PBS accounted for almost 70% of the total myo-inositol in root nodules. A small difference in the PBS composition between two soybean cultivars was recorded but it varied with the growth stages. It was tentatively concluded that the PBS sugar composition affected the bacteroidal sugar composition in soybean plants, and that inositol utilization in the bacteroids could be a factor controlling the bacteroidal function level which varied with the host plant growth stages.     

Biodegradation of humic substances by microscopic filamentous fungi: chromatographic and spectroscopic proxies

Purpose

The study of interactions between humic substances (HSs) and soil filamentous fungi is the key to understanding the sustainable soil functioning. The present work aims to examine the decomposition of HSs by filamentous dark-pigmented fungus Alternaria alternatа under the laboratory conditions and to determine the effect of easily assimilable organic carbon on this process. Analyzing such polydisperse substances like HSs by a complex integrated methodology makes it possible to explore the data on their decomposition by microorganisms.

Materials and methods

To achieve the aforementioned goals, we used chromatographic and spectroscopic approaches: low-pressure size-exclusion and hydrophobic interaction chromatography accompanied by absorption and fluorescence spectroscopy. To determine the effect cometabolism conditions produced on HS decomposition, two types of carbon substrates were added to the nutrient media: easily assimilable organic carbon (standard 0.3% or reduced 0.03% sucrose content) and hardly assimilable organic carbon (HSs), as well as their combinations. Five HS samples of different organic matter origin have been inspected: potassium humates (HPs) and humic acids (HAs) from coal, peat, and lignosulfonate. Correlation matrix and principal component analysis (PCA) were calculated for comprehensive data analysis.

Results and discussion

Transformations of the investigated HSs under fungal cultivation lead to the increase in the low molecular weight fraction, rise of hydrophilic fraction, enlargement of absorbance ratio A₂₅₀/A₃₆₅, shortening of the emission wavelength of the humic-type fluorescence, and growth in the fluorescence quantum yield measured with excitation at 355 nm. A positive correlation was observed between the accumulation of fungal biomass and the degree of HS decomposition. PCA analysis confirms that the difference in the results of HS decomposition largely depends on the sucrose content and the nature of HSs. We divided all the HS samples into four groups according to the degree of HS decomposition: original HS solutions, HPs altered using fungal cultivation at 0.03% sucrose, HAs after fungal cultivation at 0.03% sucrose, and finally, HSs (both HPs and HAs) after fungal cultivation at 0.3% sucrose.

Conclusions

In the laboratory experiments, we showed that (1) the isolated HAs were more effectively degraded than the parent HPs, and this process was more pronounced at a reduced sucrose content, and (2) the decomposition of stable organic compounds (HSs) was activated by the easily assimilable carbon sources (especially 0.3% sucrose) being present. We assume that it is the easily assimilable organic carbon that most likely triggers the HS degradation working as the priming effect in natural environments.

     

Influence of N fertilisation on the isolation of Acetobacter diazotrophicus and Herbaspirillum spp. from Indian sugarcane varieties

 Observations of newer diazotrophs like Acetobacter diazotrophicus and Herbaspirillum spp. in Indian sugarcane varieties is reported here for the first time. A. diazotrophicus was isolated from sugarcane plants where N fertilisation was nil, and numbers in the Indian cultivars were estimated to be up to 10⁶–10⁷ colony forming units g¹ fresh weight. N fertilisation was the limiting factor for the isolation of A. diazotrophicus, as evidenced by selective growth patterns in different concentrations of N sources, but Herbaspirillum spp. were found to occur both in N fertilised and unfertilised samples. The fact that N is not the limiting factor for Herbaspirillum spp. was evidenced in a similar study of its growth pattern in different N sources. Received: 14 May 1998     

The influence of early yield on the accumulation of major taste and health-related compounds in black and red currant cultivars (Ribes spp.)

The focus of our study was to investigate the effect of crop load on the accumulation and composition of primary metabolites (sugars and organic acids), selected groups of flavonoids (anthocyanins and flavonols), and total phenolics in two subsequent years in four black currant cultivars ('Titania', 'Triton', 'Tsema', and 'Cacanska crna') and three red currant cultivars ('Junifer', 'Rolan', and 'Stanza'). For the determination and quantification of compounds, high-performance liquid chromatography-photodiode array with a mass spectrometer was used. Significant differences among cultivars were detected in all analyzed compounds. Anthocyanins were the predominant phenolic group and were more abundant in black currant cultivars as compared to red ones. Similar amounts of sugars and organic acids were measured in both Ribes species; however, vitamin C was 3-fold higher in black currants. A larger crop load in the second year had a negative effect on the sugar content of berries and promoted a higher degree of acids, with the exception of vitamin C, which was higher in the year with a lower crop load. On the other hand, the content of anthocyanins and flavonols was higher in the year with a larger crop load, while there were no differences in total phenolic content.     

Composition of carbon fractions and potential denitrification in drained peat soils

The organic matter of five low-moor peat soils and one eutrophic raised-bog peat soil was chemically characterized by C fractionation and ion-exchange chromatography of amino acids and carbohydrates. C fractions were related to potential denitrification, D_pot, as a measure of microbial activity and C availability, determined by the acetylene inhibition technique. Chemical and physical properties vary distinctively between different kinds of peat, and show increasing C/N ratio and decreasing bulk density and ash content within the profile. Generally, the carbon composition reflects the geobotanical origin of the peat. In most samples more than 65% of organic C consists of non-hydrolysable C. Readily hydrolysable neutral sugar C represents up to about 12% of organic C, usually decreasing with depth. The recalcitrant fraction of neutral sugar C is much smaller (1 to 4.2% of organic C) and does not vary with depth. The content of readily hydrolysable glucose exhibits a strong profile differentiation that decreases with depth, whereas the higher contents of recalcitrant glucose carbon (12/0.5 M H₂SO₄) in the lower peat horizons reflect their cellulose character. Regression analysis between D_pot and single C components explains up to 51.5% of the variability. Combining fractions which point to C availability (readily hydrolysable glucose) and microbial metabolism (amino acids), it is possible to estimate D_pot with a certainty of more than 80%.     

不同抗性蚕豆品种根系分泌物对枯萎病菌的化感作用及根系分泌物组分分析

蚕豆枯萎病是土传病害,其发生与蚕豆根系分泌物有密切关系。本文以3个枯萎病不同抗性蚕豆品种——‘89-147’(高抗)、‘8363’(中抗)和‘云豆324’(感病)为材料,通过水培试验收集根系分泌物,测定根系分泌物对镰刀菌孢子萌发和菌丝生长的影响,分析对枯萎病表现出不同抗性的蚕豆品种根系分泌物中糖、氨基酸和有机酸的含量,分离鉴定了根系分泌物中氨基酸和有机酸的组分。结果表明,抗病品种的根系分泌物抑制了尖孢镰刀菌的孢子萌发和菌丝生长,在加入5 mL中抗品种根系分泌物时,显著促进尖孢镰刀菌孢子萌发,但对菌丝生长无显著影响;而在加入1 mL感病品种根系分泌物时,就能显著促进尖孢镰刀菌孢子萌发和菌丝生长。不同抗性蚕豆品种根系分泌物中氨基酸总量和总糖含量随抗性的降低而升高,有机酸分泌总量则随蚕豆品种对枯萎病的抗性增加而升高。感病品种和中抗品种中检出15种氨基酸,而高抗品种中检出14种,组氨酸只存在于中抗品种中,脯氨酸仅在感病品种中检出,3个蚕豆品种根系分泌物中均未检出精氨酸。蚕豆根系分泌物中天门冬氨酸、谷氨酸、苯丙氨酸、酪氨酸和亮氨酸含量高,可能会促进枯萎病的发生,而蛋氨酸、赖氨酸和丝氨酸含量高可能抑制枯萎病发生。酒石酸仅在抗病品种中存在,根系分泌物中有机酸种类丰富,有助于提高蚕豆对枯萎病的抗性。蚕豆对枯萎病的抗性不同,根分泌物对镰刀菌孢子萌发和菌丝生长的影响也不同,而这种抗病性差异与蚕豆根系分泌物中糖、氨基酸、有机酸的含量和组分密切相关。     

Recycling of Organic Wastes Amended with Trichoderma and Gluconacetobacter for Sustenance in Soil Health and Sugarcane Ratoon Yield in Udic Ustochrept

A field experiment was conducted with the objectives to relate the changes in the physical properties, soil organic carbon (SOC), nutrient availability, and uptake and output input ratios for sustaining sugarcane ratoon growth and yield in an Udic ustochrept. Eight combinations of trash and farmyard manure (FYM) with and without Trichoderma viride and Gluconacetobacter diazotrophicus were applied in two sugarcane ratoon (first and second ratoon in succession) crops. Application of Trichoderma-enriched trash showed the lowest bulk density (1.36 Mg m^?3) and the greatest infiltration rate (4.5 mm h^?1). Greater rate of increase in SOC was observed under inoculation of Trichoderma with FYM compared to trash mulch. The output/input ratios were greater in plots having trash-based treatments compared to FYM and inorganic fertilizers. Bioagent-inoculated FYM produced greater mean sugar yield (8.89 t ha^?1) compared to bioagent-inoculated trash (7.97 t ha^?1).     

花生主要碳代谢指标与根瘤固氮能力的关系

[目的]比较花生叶片碳代谢指标与根瘤固氮的关系,以寻找与根瘤固氮能力关系最为密切的叶片碳代谢指标,为花生育种提供可靠的判定方法.[方法]盆栽试验在山东省花生研究所莱西试验站进行,试验以19个花生品种(系)为材料,包括山东、河南、河北、四川等省份近年来审定或育成的品种(系),辅助利用15N示踪技术,测定了花生叶片叶绿素含...     

Quantitative analysis of exudates from soil-living basidiomycetes in pure culture as a response to lead, cadmium and arsenic stress

Six different ectomycorrhizal fungi (Hebeloma velutipes, Piloderma byssinum, Paxillus involutus, Rhizopogon roseolus, Suillus bovinus and Suillus variegatus) and two saprotrophic fungi (Hypholoma fasciculare and Hypholoma capnoides) were exposed to metal stress induced by Pb, Cd and As. After pre-growth in a nutrient solution in Petri dishes, metal exposure was performed either in a nutrient rich solution or in a nutrient poor solution for seven days. The fungi were exposed to two different metal concentrations, low and high (Pb: 10 + 100 μM; Cd: 1 + 10 μM; As: 1 + 10 μM). Exudation of low molecular weight organic compounds (low molecular weight organic acids (LMWOA), amino acids and dissolved monosaccharides), as well as dissolved organic carbon was quantified as a potential response to the metal stress. The main LMWOA identified was oxalate. Oxalate exudation increased significantly in response to both low and high Pb and Cd concentrations, as well as low As exposure, relative to nutrient controls. Exposure to As and mixtures of metals (Pb + Cd, Pb + As) did not result in any significant increase in oxalate production compared to controls. The presence of a carbon source (glucose) in this study is likely to have been important for exudation of organic compounds. For the nutrient rich (+1 mM glucose) metal treatments exposure to Pb and Cd mainly increased exudation of oxalate and total amino acids. Production of dissolved monosaccharides, as well as DOC, did not increase significantly in response to metal exposure, irrespective of nutrient conditions. This may be explained by re-absorption of the organic compounds by the mycelium or by the fact that metals had no effect on exudation of these compounds.     

Rhizodeposition and net release of soluble organic compounds by pine and beech seedlings inoculated with rhizobacteria and ectomycorrhizal fungi

Summary A lysimetric experiment was performed in a greenhouse to evalute root deposition and net release of soluble organic compounds after 1 and 2 years from pine and beech seedlings inoculated with an ectomycorrhizal fungus (Laccaria laccata) and/or rhizobacteria (Agrobacterium radiobacter for beech and Agrobacterium sp. for pine). Total C compounds released in the rhizosphere of both plants increased after inoculation with the bacteria or ectomycorrhizal fungus. The rhizobacteria increased root and plant growth and rhizodeposition, but the mycorrhizal fungi appeared to increase only root deposition. Soluble C compounds, collected after 2 years, represented only 0.1–0.3% of the total C compounds released into the rhizosphere, and were modified by inoculation with the microorganisms. After inoculation with the bacteria, levels of sugars and amino acids decreased in pine and beech rhizospheres, whereas organic acids increased, especially in the pine rhizosphere. In the rhizosphere of mycorrhizal beeches, sugar and amino acids increased, and organic acids differed from those released from non-mycorrhizal beeches. In the mycorrhizal pine rhizosphere, however, all compounds decreased. Following dual inoculations, mycorrhizal colonization increased, no effect on plant growth was observed, and virtually no organic acids were detected.     

Synergistic effects of vesicular-arbuscular mycorrhizal fungi and diazotrophic bacteria on nutrition and growth of sweet potato (Ipomoea batatas)

Summary Sweet potatoes were micropropagated and then transplanted from axnic conditions to fumigated soil in pots in the greenhouse. Spores of Glomus clarum were obtained from Brachiaria decumbens or from sweet potatoes grown in soil infected with this fungus and with an enrichment culture of Acetobacter diazotrophicus. Three experiments were carried out to measure the beneficial effects of vesicular-arbuscular mycorrhizal (VAM) fungi-diazotroph interactions on growth, nutrition, and infection of sweet potato by A. diazotrophicus and other diazotrophs obtained from sweet potato roots. In two of these experiments the soils had been mixed with ¹⁵N-containing organic matter. The greatest effects of mycorrhizal inoculation were observed with co-inoculation of A. diazotrophicus and/or mixed cultures of diazotrophs containing A. diazotrophicus and Klebsiella sp. The tuber production was dependent on mycorrhization, and total N and P accumulation were increased when diazotrophs and G. clarum were applied together with VAM fungal spores. A. diazotrophicus infected aerial plant parts only when inoculated together with VAM fungi or when present within G. clarum spores. More pronounced effects on root colonization and intraradical sporulation of G. clarum were observed when A. diazotrophicus was co-inoculated. In non-fumigated soil, dual inoculation effects, however, were of lower magnitude. ¹⁵N analysis of the aerial parts and roots and tubers at the early growth stage (70 days) showed no statistical differences between treatments except for the VAM+Klebsiella sp. treatment. This indicates that the effects of A. diazotrophicus and other diazotrophs on sweet potato growth were caused by enhanced mycorrhization and, consequently, a more efficient assimilation of nutrients from the soil than by N₂ fixation. The possible interactions between these effects are discussed.     

Dissolved components in precipitation water percolated through forest litter

Leaves lying on the forest floor are a major source of dissolved organic substances in soil and surface waters, and these substances have important effects in those environments. We used zero‐tension lysimeters to study the chemical characteristics of water percolating through litter from various species of forest trees. The leaching rates were greatest in the autumn and declined rapidly thereafter, especially for deciduous litter. During an annual cycle, 2.5–17% of the initial contents of the carbon in the litter was recovered as dissolved organic carbon in percolates. Humus‐like substances, hydrophilic acids and hydrophilic neutral compounds constituted the major fractions of dissolved C. Leachates from deciduous leaf litter were only partly biodegradable, and those from spruce needles were scarcely biodegradable. Low molecular weight organic acids constituted 0–12% of the dissolved organic carbon in the percolates of the first autumn sampling and decreased over time. Acetic and formic acids were present at the largest concentrations, up to 30 μmol l^?1 per g litter, and gluconic, pyruvic, fumaric, oxalic and citric acids were also frequent in significant concentrations. Among the aromatic acids, p‐hydroxybenzoic acid was identified in four out of five autumn samples. The organic components in litter leachates are important for the microbial activity in soil and surface waters. The organic acids enhance weathering and translocation of metals by their ability to form complexes. Litter is also a source of inorganic ions in soil solutions. The dominant cations in the percolates were K⁺, Ca²⁺ and Mg²⁺, and spruce litter also yielded large quantities of Al and Fe.     

混合施用微咸水和氮肥对甜高粱生物量和产糖量的影响

Soil salinization and non-point source pollution are among the most important and widespread environmental problems in European Mediterranean regions. Sweet sorghum (Sorghum bicolor (L.) Moench var. saccharatum) is a moderate to high salinity tolerant crop with low water and nutrient needs, seen as an alternative to grow in the water scarce regions. A three-year multifactorial study was conducted in southern Portugal to evaluate the combined effects of saline water and nitrogen application on the dry biomass (total, stems, and leaves), sugar content (total reducing sugars and sucrose contents), and sugar yield (here defined as the product of total reducing sugars and stems dry biomass) functions of sweet sorghum. Sorghum dry biomass and sugar yield showed diminishing returns for each incremental change of nitrogen. The use of saline irrigation waters also led to yield reduction. Exception was sucrose content which increased with increasing levels of sodium in the soil. Nitrogen need decreased as the amount of sodium applied increased. Stem dry biomass, sucrose content, and sugar yield progressively increased with progress in the experiment. The effect could be attributed to the increase of the amount of irrigation applied throughout the years, thus increasing the leaching fraction which promoted salt leaching from the root zone, reduced the salinity stress, increased plant transpiration, nitrogen uptake and biomass yield.     

The absorption and translocation of amino acids and amides in rice plant

It has been well known that the inorganic nitrogen compounds used as the common nitrogen source for the growth of higher plants can be replaced by some organic nitrogen compounds such as amino acids or amides. According to GHOSH and BURRIS (1), who investigated the effect of some amino acids as the nitrogen source, alanine, asparagine, glutamate and histidine were better nitrogen sources than ammonia for clover and tomato plants. For tobacco, however, nitrate and ammonia were superior to all organic nitrogen compounds used. RATNER et al. (2). made the same kind of study by using corn and sunflower plants and reported that the plants could grow with glycine, aspartate, glutamate and arginine, but all of them were inferior to inorganic nitrogen as the nitogen source.     

Fruit growth,carbon allocation,and related enzymes in tomato under different irrigation and potassium application regimes

Background

The increasing concentration of atmospheric CO₂ not only affects the growing environment of crops but also aggravates the global greenhouse effect and further aggravates the problem of water shortage. The combined effect of water deficit and potassium (K) application has not been widely studied.

Aims

A pot experiment was conducted to investigate the effect of deficit irrigation (DI) and K application at different growth stages on carbon allocation and enzyme activities related to sugar metabolism.

Methods

Tomatoes were transplanted and planted on April 26, 2017 and harvested on August 15, 2017. Four irrigation regimes were implemented with two water levels (full irrigation-W and DI-W/2) in different growth stages, and each water treatment was equally divided into two subgroups: with K (K1) and without K (K0). Fruits from the first to fourth trusses of the tomato plants were sampled. Tomato growth, carbon allocation, and related enzyme activities were measured.

Results

The fresh weight (FW), dry weight, and relative growth rate of dry mass were sensitive to irrigation amount under K fertilization, enhancing the promotion effect of irrigation on fruit. Meanwhile, carbon allocation was sensitive to irrigation amount under K regime. Sucrose synthase (SuSy), acid invertase (AI), and sucrose phosphate synthase (SPS) were also highly sensitive to irrigation amount under K application condition. Starch phosphorylase displayed a quadratic parabola for irrigation amount, and adenosine diphosphate glucose pyrophosphorylase (AGPase) was highly sensitive to irrigation amount without K fertilization. Carbon in the form of other carbohydrates, carbon in the form of soluble sugar (Csol), and fruit water content were the factors that had the greatest influence on the principal components. Classification by K-means algorithm and canonical correlation analysis showed that FW, fructose, sucrose, and starch could be used as significant indicators of the dry matter components of the fruit for the treatment without K. In the case of K regime, SuSy, AGPase, AI, and Csol could be used as a significant indicator of the correlation analysis of carbon metabolism activity.

Conclusions

The factors related to the improvement of fruit quality and carbon allocation by deficient irrigation and K application were explored. Water stress changed the distribution of photosynthetic carbon between starch and soluble sugar. K application further changed the balance between soluble sugars and other compounds. In particular, it significantly increased the carbon content of soluble sugars and decreased that of other compounds. AI and SuSy are key enzymes affecting carbon metabolism under water-deficient conditions.     

逐渐干旱胁迫下两种生物土壤结皮藓类的渗透调节作用响应

Biological soil crusts (biocrusts) widely occur in semiarid and arid regions throughout the world and play important roles in many desert ecosystems: protecting soil from wind erosion and detaining nutrient-rich dust and organic carbon. An experiment was conducted in the Shapotou revegetated area of the Tengger Desert, Ningxia Hui Autonomous Region of China to investigate the physiological responses of the dominant biocrust mosses, Bryum argenteum and Didymodon vinealis, to desiccant stress using different osmotic adjustments. B. argenteum and D. vinealis accumulated K⁺, total soluble sugar, sucrose, trehalose, proline, and glycine betaine during desiccation. The proline content of B. argenteum was about two times higher than that of D. vinealis. The K⁺ and glycine betaine contents in B. argenteum were slightly higher than those in D. vinealis. In contrast, the total soluble sugar, sucrose, and trehalose contents in D. vinealis were about 3 to 5 times higher than those in B. argenteum. With gradual desiccation stress, the Na⁺ content of B. argenteum was low and did not significantly change. On the contrary, the Na⁺ content of D. vinealis sharply increased and reached a very high level of about 10 to 18 times higher than that of B. argenteum, indicating that B. argenteum and D. vinealis gradually adapted to desiccation stress by osmotic substances accumulation to different degrees.     

不同品种小麦与蚕豆间作对蚕豆枯萎病发生、根系分泌物和根际微生物群落功能多样性的影响

通过田间小区试验和盆栽试验,研究了3个不同品种小麦［云麦42（YM42）,云麦47（YM47）和绵阳29（MY29）］与蚕豆间作对蚕豆枯萎病发生、 根系分泌物和根际微生物群落功能多样性的影响。结果表明,云麦42与蚕豆间作处理（YM42//B）和云麦47与蚕豆间作处理（YM47//B）使蚕豆枯萎病病情指数分别降低47.6%和33.3%,而绵阳29与蚕豆间作处理（MY29//B）对蚕豆枯萎病病情指数无显著影响。与蚕豆单作相比,YM42//B和YM47//B处理显著增加了根系分泌物中有机酸的含量,显著降低了根系分泌物中可溶性总糖和游离氨基酸含量; 显著提高了蚕豆根际微生物对碳源的利用强度,明显改变了蚕豆根际微生物群落结构,并且YM42//B处理的影响大于YM47//B; 而MY29//B处理对碳源利用强度、 根际微生物群落结构和根系分泌物中有机酸、 可溶性总糖和游离氨基酸含量均无显著影响。 YM42//B处理根际微生物利用碳源的种类比YM47//B处理多,同时YM42//B和YM47//B处理利用的糖类、 氨基酸类和羧酸类碳源种类完全不同。表明云麦42和云麦47与蚕豆间作通过增加有机酸含量,从而提高根际微生物活性和多样性,促进了根际微生物利用更多的碳源,同时云麦42和云麦47与蚕豆间作抑制了氨基酸和总糖的分泌,而最终控制了蚕豆枯萎病的发生。表明不同品种小麦与蚕豆间作系统根系分泌物-根际微生物的互作是影响蚕豆枯萎病抗性的重要原因。小麦与蚕豆间作控病效果受小麦品种的影响,以云麦42与蚕豆间作效果最好,其次为云麦47与蚕豆间作,而绵阳29与蚕豆间作无显著控病效果。     

Use of Humic Substances and Amino Acids to Enhance Iron Availability for Tomato Plants from Applications of the Chelate FeEDDHA

Two experiments in consecutive years were conducted in a commercial greenhouse located in the Southeast of Spain. The objective was to test if the addition of commercial organic compounds could improve the uptake of iron (Fe) by tomato plants (Lycopersicon esculentum mill.) cv Daniela. A commercial humic substance (HS) and a mix of amino acids (AA) were used as organic compounds in the first year of the experiment, and FeEDDHA (Q) as a source of iron. Both organic compounds improved iron uptake in comparison to a control without the addition of organic materials, especially the humic substance. A similar experiment was conducted the following year, but part of the chelate was progressively substituted by the humic compound. Results showed that the content of iron in the leaves increased with the substitution without any significant losses of yield or fruit quality. Plant nutrition was also improved because of an increase in the level of phosphorus in the leaves and a decrease in foliar sodium levels indicating a reduction in the effects of salinity.     

钾素对玉米茎腐病抗性反应中糖类物质代谢的影响

通过砂培试验比较人工接种禾谷镰刀菌（Fusarium graminearum）后,不同钾处理对玉米幼根中糖含量及糖代谢关键酶活性和基因表达的影响。结果表明,不施钾处理中,接菌比未接菌处理玉米幼根中蔗糖和葡萄糖含量显著降低,且蔗糖的下降速率高于葡萄糖的下降速率。随着病原菌入侵时间的延长,不施钾处理葡萄糖与蔗糖比值显著升高,接菌8 d后,缺钾幼根葡萄糖与蔗糖的比值是充足供钾幼根的近10倍。此外,钾素有利于病原菌入侵,幼根中蔗糖合成酶（SS）和蔗糖磷酸合成酶（SPS）活性提高,ss和sps基因表达量增加; 而缺钾处理中,ss基因的表达量几乎没有发生变化,sps基因的表达量在接菌后6 d才有所增加。说明在病原菌入侵后,钾素可以通过调节受侵染组织糖代谢相关酶的活性,协调受侵染部位糖代谢过程,增强抗病能力。