Fulltext search in archive

We conducted a pot experiment to evaluate the Cd and Zn accumulation in leaves and roots of Salix smithiana (BOKU-03DE-001) and S. caprea (BOKU-01AT-004) clones grown on a metal-contaminated soil as affected by native microbes extracted from the same experimental soil, and the fungus Cadophora finlandica. Plant biomass production of S. smithiana was decreased in all the treatments compared to the sterilized control. In contrast, S. caprea grew best on the non-sterilized soil. Similar effects were observed for plant Zn and Cd contents. Microbial treatments affected metal accumulation differently in the two Salix species. The effects of the microbial treatments on biomass and metal content of leaves were not related to the degree of mycorrhization. A comparison with literature data suggests that the plant response to microbial inoculation in terms of metal accumulation may depend on the plant-internal metal concentration. Our findings also illustrate a difficulty of successful rhizosphere management using metal-tolerant microbial isolates to further enhance the phytoextraction process.

Sequencing of cereal genomes is not a feasible task due to their large size and high content of repetitive DNA sequences. There are two basic approaches to simplify analysis of such genomes: reduced representation approaches, such as EST sequencing, methyl filtration and Cot-based cloning and sequencing; on the other side there is analysis of genomes in a step-wise manner, e.g. through creation of chromosome-specific genomic resources. Combination of both approaches - i.e. Cot-based cloning and sequencing of DNA obtained from a chromosome-arm-specific BAC library - was tested in this work.

To answer many questions of evolutionary developmental biology, it is necessary to identify genes which could be responsible for the studied traits. In this review, I have summarised the methods that are currently used to identify these genes. Mainly the PCR-based methods of gene cloning are discussed here, with the special attention given to the comparison of primer design strategies and PCR amplification strategies. In addition to the review of methods used by other authors, an overview of our experience with PCR-based gene cloning in dioecious model plant species Silene latifolia is included.

A pot greenhouse experiment was performed to determine the effect of contamination with nickel interacting with other heavy metals on the microbiological properties of soil. The study was conducted on samples of soils classified under natural conditions as typical Eutric Cambisol developed from heavy loamy sand and typical Eutric Cambisol developed from light silty loam. Soil material was contaminated with nickel in the amount of 50 and 200 mg Ni²⁺/kg. The treatments with 200 mg Ni²⁺/kg were additionally contaminated with other heavy metals (Zn²⁺, Cu²⁺, Pb²⁺, Cd²⁺, Cr⁶⁺), in the amount of 50 mg/kg soil. The following treatments, in which the soil was contaminated with heavy metals applied alone or in combinations, were compared in the study: Ni, Zn, Cu, Pb, Cd, Cr, NiZn, NiCu, NiPb, NiCd, NiCr, NiZnCu, NiZnPb, NiZnCd, NiZnCr, NiZnCuPb, NiZnCuCd, NiZnCuCr, NiZnCuPbCd, NiZnCuPbCr, NiZnCuPbCdCr. The experiment was carried out in four replications. A microbiological analysis was performed on days 28 and 56. The tested crop was oat. It was found that the impact of particular heavy metals on microbiological properties of soils depended on their type, interactions between nickel and zinc, copper, lead, cadmium and chromium (VI), date of analysis and soil species. Soil contamination with heavy metals reduced the population size of Azotobacter spp. The counts of other microbial groups, i.e. copiotrophic bacteria, spore-forming copiotrophic bacteria, oligotrophic bacteria, spore-forming oligotrophic bacteria, ammonifying bacteria, nitrogen immobilizing bacteria, cellulose-decomposing bacteria, Arthrobacter spp., Pseudomonas spp., actinomyces and fungi, showed varied susceptibility to heavy metals.

The aim of the present paper was to determine the impact of gypsum treatment of soils on initial growth and nutrient uptake by spring barley. Topsoil from 36 different farmed fields was used for the research. Two variants were established for each soil: control - without gypsum application, and response variant - with the application of 3.3 ppm CaSO₄.2 H₂O. Barley was grown on these soils for 21 days in a plant growth chamber under controlled conditions of cultivation. Concentrations of nutrients (N, NO₃^-, P, S, K, Mg, Ca, Na, Fe, Mn, Zn, Cu, B and Mo) were determined in the yield of barley shoot biomass. Paired t-test was used for the evaluation of results. After the gypsum treatment the yield of barley shoot biomass was significantly higher (by 15% on average) and nitrogen utilisation was better on all soils. The concentration of sulphur increased five times on average and Ca concentration increased by 22%. Significant increases were measured in Mg, Mn and Cu. Insignificant differences were recorded in K, Na, Fe and Zn. The uptake of anion nutrients (P, B and Mo) was influenced significantly. The concentration of P and Mo decreased on average by 28% and 31%, respectively. B concentration was higher by 10% on average.

This review is a short introduction to phylogenetic analysis. Phylogenetic analysis allows comprehensive understanding of the origin and evolution of species. Generally, it is possible to construct the phylogenetic trees according to different features and characters (e.g. morphological and anatomical characters, RAPD patterns, FISH patterns, sequences of DNA/RNA and amino acid sequences). The DNA sequences are preferable for phylogenetic analyses of closely related species. On the other hand, the amino acid sequences are used for phylogenetic analyses of more distant relationships. The sequences can be analysed using many computer programs. The methods most often used for phylogenetic analyses are neighbor-joining (NJ), maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference.

The use of plants to remove heavy metals from soil (phytoremediation) is expanding due to its cost-effectiveness as compared to conventional methods and it has revealed a great potential. Since contaminants such as Pb or Cd have a limited bioavailability in the soil, methods to facilitate their transport to the shoots and roots of plants are required for successful phytoremediation. The objective of this study was to investigate the effects of addition of different rates (0, 3, 6 and 12 mmol/kg) of ethylene diaminetetraacetate (EDTA) on heavy metal availability in soils contaminated with 50 mg/kg Cd (CdCl₂), 50 mg/kg Cu (CuSO₄), 50 mg/kg Pb [Pb(NO₃)₂] and 50 mg/kg Zn (ZnSO₄), and on the capacity of canola (Brassica napus L.) and Indian mustard (Brassica junceaL.) plants to uptake Cu, Cd, Pb and Zn in a growth chamber. Results indicated that EDTA application increased heavy metal availability and uptake by plants. Significant differences were obtained in both species and plant parts. As for plant species tested, canola was more effective in the uptake of Cu, Cd, Pb and Zn. Root heavy metal uptake of both species was higher than shoot heavy metal uptake.

Malt barley production requires a technology increasing nitrogen use efficiency, because of a high sensitivity of barley total grain yield and quality parameters to external growth factors. In the conducted study an effect of two P fertilizers on the background of N application on total and technological grain yields were studied. The highest total grain yield was harvested on plots fertilized with 60 kg N/ha, irrespective of the P fertilizer type. However, the technological grain yield showed a high year-to-year variability; the highest was recorded in 2001 on the plot fertilized with 60 kg N/ha and the P-PAPR fertilizer. The N and S concentrations and N:S ratios in immature grains at harvest were used to evaluate both yield types. Nitrogen concentration in the final total yield allowed making yields prognosis with the highest probability. The maximum yields of technological malt barley were attainable provided that total S concentration in immature grains at harvest was above 0.23% and the N:S ratio was narrower than 8.0.

A simple method for identification and characterization of telomere-binding proteins is described in this article. After Sodium Dodecyl Sulphate-Polyacrylamide gel electrophoresis (SDS-PAGE), proteins are eluted, renatured and used for retardation analysis with labelled oligonucleotides corresponding to human and plant of telomeric sequences. We show here that this method is efficient to recover sequence-specific DNA-binding abilities of putative telomere-binding proteins.

Ditylenchus dipsaci, the stem nematode, is a migratory endoparasite of over 500 species of angiosperms. The main method of D. dipsaci control is crop rotation, but the presence of morphologically indistinguishable host races with different host preferences makes rotation generally ineffective. Therefore, a sensitive, rapid, reliable, as well as cost effective technique is needed for identification of D. dipsaci in biological samples. This study describes the development of species-specific pairs of PCR oligonucleotides for detection and identification of the D. dipsaci stem nematode in various plant hosts. Designed DIT-2 primer pair specifically amplified a fragment of 325 bp, while DIT-5 primer pair always produced a fragment of 245 bp in all D. dipsaci isolates. Two developed SCAR primer pairs were further tested using template DNA extracted from a collection of twelve healthy plant hosts; no amplification was however observed. The developed PCR protocol has proved to be quite sensitive and able to specifically detect D. dipsaci in artificially infested plant tissues.

The effect of 24-epibrassinolide and 28-homobrassinolide on seed germination and seedling growth of radish (Raphanus sativus L.) was studied under cadmium toxicity. The impact of brassinosteroids (BRs) on free proline levels and the activity of antioxidant enzymes catalase (CAT; EC 1.11.1.6), peroxidase (POD; EC 1.11.1.7), superoxide dismutase (SOD; EC 1.15.1.1), ascorbic peroxidase (APOX; EC 1.11.1.11) and guaiacol peroxidase (GPX; EC 1.11.1.7) in radish seedlings under Cd toxicity was evaluated. The effect of BRs on the activity of ascorbic acid oxidase (AAO; EC 1.10.3.3) and lipid peroxidation in radish seedlings challenged with Cd stress was also investigated. BRs supplementation alleviated the toxic effect of the heavy metal and increased the percentage of seed germination and seedling growth. Out of the two substances, HBL was found to be more effective than EBL in stress alleviation. HBL (3µM) alleviated the toxic effect of the heavy metal and increased the percentage of seed germination by 57% over Cd and 20% over unstressed control. Similarly supplementation of HBL (3µM) caused an increase of 156%, 78% and 91% in length, fresh weight and dry weight of seedling, respectively, over Cd treatment alone. The amelioration of seedling growth by BRs under metal toxicity was associated with enhanced levels of free proline. The activities of antioxidant enzymes CAT, SOD, APOX and GPX were increased in the seedlings from treatments with Cd along with BRs. Brassinosteroid treatment reduced the activity of POD and AAO in heavy metal stressed seedlings. Lipid peroxidation induced by Cd was found reduced with the supplementation of BRs. The results obtained in the study clearly indicated the ameliorative influence of brassinosteroids on the inhibitory effect of Cd toxicity.

Rapidly increasing amount of biological data necessarily requires techniques that would enable to extract the information hidden in the data. Methods of molecular phylogenetics are commonly used tools as well as objects of continuous research within many fields, such as evolutionary biology, systematics, epidemiology, genomics, etc. The evolutionary process not only determines relationships among species, but also allows prediction of structural, physiological and biochemical properties of biomolecules. The article provides the reader with a brief overview of common methods that are currently employed in the field of molecular phylogenetics.

The lack of recombination in some genomic regions represents a serious obstacle in mapping studies. In this review, we describe methods that are currently used to overcome this problem. Main attention is given to the comparison of methods that are based on the principle of radiation hybrid mapping. We also discuss a strategy called HAPPY mapping (mapping based on the analysis of approximately HAPloid DNA samples using the PolYmerase chain reaction). In addition to reviewing the methods used by other authors, we also summarize our experience with deletion mapping of Y-chromosome in dioecious model plant species (Silene latifolia).

It has been demonstrated that endophyte-infected (EI) ryegrass performed better in response to N deficiency than its endophyte-free (EF) counterpart. When P is considered, there is a lack of related information. In this study, Lolium perenne L. infected with Neotyphodium lolii was employed to establish EI and EF populations. Soil-grown EI and EF ryegrass were tested for their responses to P deficiency. The results showed that the endophyte infection improved the adaptability of ryegrass to P deficiency. When P was limited, EI roots were significantly longer (EI, 398.8; EF, 323.4 m/pot) and heavier (EI, 30.58; EF, 23.20 g/pot) than EF roots; the root: shoot ratio of EI plants was greater than that of EF plants (P < 0.05). The content of total phenolics and organic acids was significantly greater for EI roots than for EF roots at low P supply; the concentration of both, however, was not improved by the endophyte infection. This suggested that it was the higher root dry weight (DW) that contributed to the higher content of total phenolics and organic acids for EI plants, and the endophyte infection might have negligible effects on chemical modification of perennial ryegrass. Endophyte infection did not increase P uptake rate but did significantly improve P use efficiency of ryegrass in response to P deficiency (EI, 0.734; EF, 0.622 g DW/mg P).

The effects of phosphate solubilizing bacterium (Bacillus FS-3) application on phosphorus contents of tomato (Lycopersicon esculentum L.) plant, growing performance and phosphorus forms in soil were evaluated under greenhouse condition. Five different phosphorus fertilizer treatments (normal superphosphate, triple superphosphate, di-ammonium phosphate, phosphoric acid, and rock phosphate) with and without bacterium (Bacillus FS-3) were applied in pots as 344 kg P/ha. Basal fertilizers were applied to all the pots as 180 kg N/ha (NH₄NO₃ 33% N), 100 kg K/ha (K₂SO₄ 50% K₂O). The results obtained showed that phosphorus availability from soil increased with phosphate solubilizing bacterium (PSB) application. The amount of plant available form of soil phosphorus fraction (resin-Pi + NaHCO₃-Pi + NaHCO₃-Po + NaOH-Pi + NaOH-Po) increased with PSB application. In all fertilizer types, bacteria application converted approximately 20% of less available phosphorus into labile forms. Statistically significant differences were obtained in shoot and root dry weight of tomato plants treated with PSB application. In all of the fertilizers, plant shoot and root weight and P uptake were greater with PSB applications than without PSB. The highest shoot-root dry weight and P uptake of plant were determined in triple superphosphate (TSP) with PSB application treatment. The data in the present study suggest that the application of PSB (FS-3) may increase the availability of soluble phosphate by dissolving the inorganic forms of phosphate and that bacterial strain tested in this study has a potential to be used as a bio-fertilizer in sustainable and organic agriculture.

In our work, we focus on the evolutionary studies of sex chromosomes. As model organisms we use several species of the plant genus Silene. An important part of our research is represented by genetic mapping based on the assays of DNA length or sequence polymorphisms. Apart from the other methods we also use the dCAPS method, which is very useful for detection of the sequence polymorphisms (SNPs). This method is unique as it is able to detect SNPs that are not situated in any restriction site; a fundamental principle of this method is usage of primer designed with one or two mismatches that bring into the target sequence the mutation in vicinity of SNP. Using this method, we found out some improvements that can make analyses more cost-effective.

The influence of N-S fertilizers on the copper content in the inter oilseed rape plants was studied in field experiments. The evaluation involved two treatments of a single rate for the first spring fertilizer application with 100 kg N/ha in the AN treatment (nitrochalk) and 100 kg N/ha + 50 kg S/ha in the ANS treatment (ammonium nitrate and ammonium sulphate). A positive influence of the ANS fertilizer on the copper contents in different parts of plants was determined. The highest Cu concentrations were determined in the leaves and inflorescences, the lowest ones occurred in the stem. The concentration of Cu ranged within the interval of 1.56-8.75 mg Cu/kg of dry matter depending on the growth period and the part of the plant. No differences in copper content were determined in the seeds of individual treatment. The highest uptake in the above-ground parts of the plants was recorded in the green pod period and amounted to 57.4 g Cu/ha for the ANS treatment.

Chlorophyll a fluorescence measurements were carried out on two barley (Hordeum vulgare L.) cultivars Arabi Abiad and Arabi Aswad at 8 and 14 days after emergence to identify their early tolerance mechanism for heavy metals (25 and 50μM of cadmium and lead). Transient fluorescence curves (OJIP curves) and energy flux models showed different specific reactions of photosystem II (PSII) of each cultivar to each type of stress. After 7 days of lead stress application plants of cv. A. Aswad showed weaker I and P peaks on the OJIP curve than control plants, and the appearance of a new K step; parameters of phenomenological energy fluxes for cv. A. Abiad were similar to those for control plants and only some silent reaction centers appeared. Generally, parameters of energy fluxes within PSII were directly shifted shortly (24 h) after the application of both heavy metals, especially in the case of plants grown under cadmium treatment. This suggests that these parameters could be good indicators for monitoring of these two pollutants in the environment at early stages of plant development.

Deoxynivalenol (DON) is the most prevalent Fusarium toxin in Czech wheat samples and therefore forecasting this mycotoxin is a potentially useful tool to prevent it from entering into food chain. The data about DON content in wheat grain, weather conditions during the growing season and cultivation practices from two field experiments conducted in 2002-2005 were used for the development of neural network model designed for DON content prediction. The winning neural network is based on five input variables: a categorial variable - preceding crop, and continuous variables - average April temperature, sum of April precipitation, average temperature 5 days prior to anthesis, sum of precipitation 5 days prior to anthesis. The most important input parameters are the preceding crop and sum of precipitation 5 days prior to anthesis. The weather conditions in April, which are important for inoculum formation on crop debris are also of important contribution to the model. The weather conditions during May and 5 days after anthesis play only an insignificant role for the DON content in grain. The effect of soil cultivation was found inferior for model function as well. The correlation between observed and predicted data using the neural network model reached the coefficient R² = 0.87.

Soil organic carbon (SOC) is the most often reported attribute and is chosen as the most important indicator of soil quality and agricultural sustainability. In this review, we summarized how cultivation, crop rotation, residue and tillage management, fertilization and monoculture affect soil quality, soil organic matter (SOM) and carbon transformation. The results confirm that SOM is not only a source of carbon but also a sink for carbon sequestration. Cultivation and tillage can reduce soil SOC content and lead to soil deterioration. Tillage practices have a major effect on distribution of C and N, and the rates of organic matter decomposition and N mineralization. Proper adoption of crop rotation can increase or maintain the quantity and quality of soil organic matter, and improve soil chemical and physical properties. Adequate application of fertilizers combined with farmyard manure could increase soil nutrients, and SOC content. Manure or crop residue alone may not be adequate to maintain SOC levels. Crop types influence SOC and soil function in continuous monoculture systems. SOC can be best preserved by rotation with reduced tillage frequency and with additions of chemical fertilizers and manure. Knowledge and assessment of changes (positive or negative) in SOC status with time is still needed to evaluate the impact of different management practices.

The influence of various ways of regulation in weed infestation of silage maize stands was studied in 1999-2001. Four variants of stands were compared: 1. without weed eradication (check), 2. mechanically weeded throughout the whole vegetation period, 3. mechanically weeded from the beginning of vegetation till the phase of 5^th leaf and later on without protection, 4. chemical weeding. The yield of dry mass and morphological characters (height of plants, stem diameter, number of ears per plant etc.) show the substantial negative effect of weed infestation upon the studied parameters. The yield from the check variant reached 8.09 t/ha, from the 2^nd variant 13.24 t/ha, from the 3^rd variant 11.46 t/ha and from the 4^th variant 12.34 t/ha. The decrease of mass in individual parts of plants were observed but their percentage portions were not affected by the level of weed infestation. A high dependence ( = 0.01) between the mass of the whole plant and the ear mass (r = 0.98) was proved. The total number of leaves was not affected by the level of treatment. The results show that the mechanical cultivation of stands at the beginning of vegetation cannot prevent the yield depression cost by weed infestation and the studied parameters cannot reach the level of fully weeded variants.

The autumn growth and development was studied in three types of winter oilseed rape varieties (line, hybrid and genetically modified hybrid) at three technologies (intensity, standard and low input). Technologies were different by soil preparation before sowing, sowing rate, chemical treatment levels, growth regulation and fertilisation. It is evident from the autumn period 1999-2002, that the yield of biomass and roots in the autumn period was influenced by the technology and year conditions (water soil condition). The occurrence of surface soil clods influenced negatively the creation of root and aboveground biomass irrespective of the soil cultivation (ploughing or cultivation without ploughing). Also the excessive soil moisture negatively influenced the root and aboveground biomass and increased the differences among variants. The low input variant was substantially worse than intensity and standard. The dry mass of aboveground and root biomass was statistically different (alfa = 0.05) in the intensive and standard variant in comparison with the variant without ploughing (low input). No statistically significant differences were found in the mass of aboveground and root biomass (alfa = 0.05). The percentage of dry mass in aboveground and root biomass was statistically significantly higher (alfa = 0.05) in intensity of growth regulator application tebuconazole (Horizon 250EW) + chlormequat-chloride (Retacel Extra R68) compared with standard and low input. The diameter of root neck, length of roots and number of leaves was statistically the highest (alfa = 0.05) in the intensive variant. Statistically the values differed from the standard and low input variants. Substantially lower differences were found in the varieties in the same characters. GM hybrid showed a lower heterosis effect and the studied characters did not reach the level of unmodified hybrid level.

Stability of breadmaking quality of four Croatian bread winter wheat cultivars was investigated using rheological traits from the farinogram (dough development time, stability, degree of softening, water absorption, Hankoczy quality number) and the extensogram (extensibility, maximum resistance, ratio of resistance to extensibility, energy) and the indirect traits (protein content, wet gluten content, Zeleny sedimentation volume, Hagberg falling number). Stability was evaluated for four cultivars grown in 12 environments in different parts of Croatia. Four stability parameters, covering a wide range of statistical approaches, were used to estimate cultivar stability. Variability for the stability of quality among cultivars was established. The cultivars Kuna and Banica showed high performance for most quality traits and were also identified as stable for the majority of them. The cultivar Žitarka was stable for four farinogram traits showing high level of performance only for dough development time, while Marija showed stability for only three traits but with unfavourable mean values for all of them. The largest contribution of genotype by environment effects in the total sum of variance components was found for the farinogram traits stability and dough development time, while the lowest, but similar to each other for protein content and wet gluten content.

This experiment was carried out for the study of differences in dynamics of formation and reduction of generative organs from the beginning of the flowering to the harvest, under different stand density of the winter rapeseed. The evaluation of the results of the study of stand density, confirms that from the technological point of view it is appropriate to choose a thinner population of rapeseed. Starting with the stand density of 60 plants/m² we do not observe significant differences in plants during the generative stage, neither in the number of branches nor in the number of created generative organs. At this density (60 plants/m²) a significant reduction of generative organs takes place, especially on the secondary branches. Differences in the number of fertile branches are visible in case of more dense populations only in the harvest. From the point of view of the yield it is more advantageous to support the creation of generative organs on primary racemes by agricultural interventions.

Numerous agricultural and associated ecological effects such as mineral nitrogen fertilising influence the yield of hop (Humulus lupulus L.) cones and its quality. Using a wide spacing of plants (in our case 2.6 × 0.8 m) we want to answer a hypothetical question about an appropriate number of test plants per plot vs. experimental plot area. The aim of this study was to compare the effect of different rates of mineral nitrogen, fertiliser combinations and their nitrogen split application on hop yield evaluated from different plot areas (micro trial: 30 plants per plot; macro trial: 320 plants per plot). Hop yield varied significantly between treatments, plot areas, years and interactions (year × treatment, plot area × treatment) (all at P £ 0.01). Cone yield in a micro trial was higher in all treatments in comparison with yield in a macro trial. In spite of common intensive fertilisation the appropriate fertilising combination and mineral N rate can influence the yield. Target nitrogen rate of160 kg mineral N/ha (at the level from 40.0 to62.5 kg nitrate N/ha in soil depth to0.3 m) and cheaper combination of calcium-ammonium nitrate (50 kg N/ha) at the beginning of vegetation plus urea (110 kg N/ha) for top dressing can be recommended. On plot areas of each size and each year all treatments showed similar trends of fertilising effect on yield. In spite of higher yield in the micro trial and lower coefficient of variation in comparison with the macro trial, the results proved that a risk of incorrect yield analysing in macro trials is very low for field experiments.

The mixtures of Bromus marginatus Nees ex Steud. + Coronilla varia L., Festuca pratensis L. + Lotus corniculatus L., Dactylis aschersoniana Graebn. + Trifolium repens L., Arrhenatherum elatius (L.) P. Beauv. ex J.S. et K.B. Presl + Medicago lupulina L. were sown in rows of 125 mm in the year 1997 in Prague (chernozem, altitude 281 m a.s.l., average precipitation is 472 mm per year, average year temperature 9.3°C). The stands were one or three times per year cut with the mass removing or one or two times mulched. Botanical composition (by weight method), number of present species and agrobotanical groups (grasses, legumes, other dicotyledonous) coverage were measured during 6 years of vegetation. The species number was highest on plots cut 3 times (6-17), it increased linearly. The sown species share in the dry mass yield was 75-99% and the share of grasses decreased linearly with time. The significantly highest dry mass yield was reached when mulched two times per year Bromus marginatus Nees ex Steud. with Coronilla varia L. (till 14 t/ha ). The stands coverage was 43-80%.

Non-symbiotic nitrogen fixation (potential nitrogenase activity - PNA) of soil samples originating from different plots of long-term field experiments (selected variants: Nil, NPK [mineral fertilisation: 64.6-100 kg N/ha/year], FYM [farmyard manure], and FYM + NPK from three blocks III, IV and B with different crop rotation) was determined in laboratory experiments. The symbiotic nitrogen fixation (total nitrogenase activity - TNA) of the same soil samples was evaluated in hydroponic experiments with pea (2001, 2002) and lucerne (2001) in which the soil samples were used as a natural inoculum. The high values of PNA were found in the variants fertilised with FYM in all three blocks and all experiments. Simultaneously, the variants fertilised with mineral NPK reached low values of PNA. The farmyard manuring enhanced the number of free-living bacteria Azotobacter spp. that were identified in all soil samples. In the hydroponic experiments with pea, the highest nonsignificant values of TNA were found in variants B 284 (FYM + NPK) and III 254 (FYM + NPK) in 2001, and B 214 (FYM) and III 214 (FYM) in 2002. Plants inoculated with soil from these variants formed also high amounts of nodules (significant differences in block IV in 2001) and plant biomass. In the experiments with lucerne, the nonsignificantly highest TNA values were found in variant III 154 (NPK). Variants from block III (214, 254) and IV (114 and 154) showed the nonsignificantly lowest TNA values. The rhizobia that effectuate symbiosis with pea were more active in the soil samples in 2001 than those forming nodules on lucerne.

Spring barley plants were exposed to water stress at different growth stages - from the period after emergence to the beginning of stem elongation, from emergence to the end of anthesis and from the beginning of stem elongation to the end of anthesis in pot experiments. In variants exposed to water deficit from emergence to the end of anthesis and from the beginning of stem elongation to the end of anthesis, effects of foliar fertilizers and Atonik preparation (applied before the growth stage DC 30 or at DC 33) to lower the stress impacts were tested. During the growing season, formation and reduction of tillers, florets per spike and the yield structure at full ripeness were investigated. The water deficit at stem elongation caused a withering out of the established tillers, drought during the formation of the florets reduced their number as well as their development into grains. In the variant where water stress was present to the beginning of stem elongation, the plants were able to compensate for stress implications by productive tillers that developed later (at stem elongation). The previous water deficit did not decrease 1000-grain weight, however protein content in grain increased due to low grain yield per pot. If foliar fertilizers and Atonik were applied before DC 30, a reduction of fertile florets decreased, which led to slight increase in a grain number per spike.

Effects of increasing doses of the herbicidal preparation Sencor 70 WP (metribuzin a.i.) on selected potato varieties were studied in a field and pot experiments using very rapid fluorescence induction (vrFI). Tuber yield, and in pot experiments a tuber number and characteristics of the aboveground biomass were assessed. The curve of rapid induction goes through the O-J-I-P phases. The parameters Fo, Fv/Fp and rFj were measured. Based on changes in the vrFI parameters in comparison with controls, varieties were ranked according to sensitivity to metribuzin in field experiments. Keřkovské rohlíčky and Ukama were the most sensitive varieties and Impala the least sensitive variety. In pot experiments in the growth chamber, significant decrease in tuber weight vs controls was found in sensitive varieties Keřkovské rohlíčky (in 1998, 0.75 kg.ha^-1 Sencor 70 WP decreased tuber weight by 28% and 1.5 kg.ha^-1 by 89%) and Ukama (in 1997, at 1.5 kg.ha^-1 by 35%). Under stable conditions in the growth chamber, there were lower differences in the rFj parameter in these varieties in comparison with controls than in resistant ones. Based on this finding it can be assumed that the sensitivity of varieties can be determined according to rFj changes under stable ambient conditions.

Weed mapping was conducted on 2 fields in Central Bohemia to characterize the spatial structure and temporal stability of weed populations over four years (1999-2002). A number of plants for each species and the total weed coverage were investigated on the grid points. To determine the weed infestation variability, and the Patchiness-Index was calculated. Use of Surfer-software, and weed maps were created. For single weed species occurrence the correlation between 1999 and 2000 was calculated. The results document heterogeneous occurrences of weeds, especially Cirsium arvense (PI = 9.09-15.86), Tripleurospermum maritimum (PI = 11.01-217.30) and Galium aparine (PI = 4.61-7.70), whereas Viola arvensis and Stellaria media were distributed more homogeneously. Weed grasses occurred in all years slightly. G. aparine is characterized by relatively high spatial stability.