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Sunflower is one of the most important bee-pasture crops and the leading oil crop plant in Hungary. There are very few studies concerning the nectar production of the plant, most of which consist only of partial data that show the apicultural value of sunflower under intensive cultivation conditions.The nectar production and nectar sugar concentration of six sunflower hybrids, Arena, Alexandra, Cledor, Coriste, Hysun 321 PR and Louidor, were examined in Mezőhegyes (south-east Hungary) from 2002 to 2004. The aim was to determine the nectar production and overall apicultural value of the hybrids. In the experiment the agroecological conditions were also examined and recorded. These agroecological conditions showed a distinctive effect on the consistency of the apicultural values of the hybrids.It can be determined from the results that the nectar production and its sugar content can be modified measurably by external factors. The nectar quantity was measurably increased by abundant precipitation during flowering, while an increase in the nectar sugar content was caused by excessively low air temperature. During these three years the average nectar production of the hybrids was 0.147 mg/floret, with a sugar content of 48.8%. Significant differences were found between the hybrids in nectar production and in the nectar sugar concentration.Averaged over three years Coriste displayed the best apicultural value. Its nectar production was stable and high (0.167 mg/floret). Its high sugar content (49.1%) also proved to be attractive to honey bees (sugar value 0.082). The lowest apicultural value was displayed by the hybrid Alexandra, with a sugar value of 0.059. This suggests that the honey production value of the individual hybrids should be taken into consideration during the selection of bee pastures.

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Plants have developed various mechanisms to protect themselves against oxidative stress. One of the most important non-enzymatic antioxidants is ascorbic acid. There is thus a need for a rapid, sensitive method for the analysis of the reduced and oxidised forms of ascorbic acid in crop plants. In this paper a simple, economic, selective, precise and stable HPLC method is presented for the detection of ascorbate in plant tissue. The sensitivity, the short retention time and the simple isocratic elution mean that the method is suitable for the routine quantification of ascorbate in a high daily sample number. The method has been found to be better than previously reported methods, because of the use of an economical, readily available mobile phase, UV detection and the lack of complicated extraction procedures. The method has been tested on Arabidopsis plants with different ascorbate levels and on wheat plants during Cd stress.

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The aim of the present study was to find the best way of measuring the viability of root and leaf samples from various plant species (pea, wheat and maize) exposed to different concentrations of the heavy metal Cd. A comparison was made of three viability tests, namely electrolyte leakage measurements, and TTC and NBT reduction. The results suggested that electrolyte leakage was the most useful method for measuring leaf viability, being simple, fast, reliable and reproducible. The TTC reduction measurement proved the most useful for maize roots, while NBT reduction was the best method for detecting the viability of pea and wheat roots.

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Summary

A reversed-phase ion-pairing liquid chromatographic (RP-IP-HPLC) method for simultaneous assay of theophylline (TH), phenobarbital (PB), codeine (CD), and ephedrine (EP) in an extemporaneous (magistral) suppository was developed and validated and used to investigate a reported serious adverse event. Samples were dissolved in dichloromethane and extracted by two-step liquid-liquid extraction with acetate buffer (pH 5.0) and, subsequently, 0.1 m NaOH solution. Separation was performed on an end-capped C18 silica column with stepwise gradient elution. Sample preparation and chromatographic conditions were optimized on the basis of the pK a values of the analytes. Freedom from interference from the excipients, linearity (r 2 > 0.999 for all the active ingredients), range (0.01–0.08 mg mL−1 for TH, CD, and EP; 0.0025–0.02 mg mL−1 for PB), intra-day and inter-day precision, and accuracy (recovery >95% for TH, CD, and EP and >90% for PB) of the method were demonstrated. Non-compliance of the examined product was confirmed.

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In the course of the Maize Consortium Project, investigations were made on the defence mechanisms employed by maize against various abiotic stress factors (low temperature, cadmium) and on the effects exerted by two compounds (S-methylmethionine, salicylic acid) capable of improving the stress resistance of plants to certain abiotic stresses. Salicylic acid (SA) was found to inhibit the uptake of cadmium (Cd), but caused damage to the roots, including a reduction in the activity of phytochelatin synthase (PCS), which meant that preliminary treatment with SA aggravated the damaging effect of Cd. It was also proved that as the result of 2-day treatment with Cd, there was a continuous rise in the Cd level in the plants, more Cd being accumulated in young leaves than in older ones. The PCS activity increased greatly after 24 hours, both in the leaves and in the roots, declining again after 2 days. The effect of SA was examined in both the hybrids and their parental lines, and the effect of this compound on the intensity of alternative respiration was also investigated. A comparison of chilling tolerance data and antioxidant enzyme activity indicated that these two parameters were not directly correlated to each other, i.e. antioxidant enzyme activity values could not be used to draw reliable conclusions on the chilling tolerance of maize lines and hybrids. With regard to the interaction between alternative respiration and salicylic acid, it was proved that exogenous hydrogen peroxide caused a similar increase in the ratio of alternative respiration to that observed after salicylic acid treatment. Abbreviations: SA, salicylic acid; Cd, cadmium; PCS, phytochelatin synthase; SMM, S-methylmethionine; PCs, phytochelatins; PAR, photosynthetically active radiation; TTC, triphenyl tetrazolium chloride; KCN, potassium cyanide; PSII, 2nd photochemical system; POD, guaiacol peroxidase; APX, ascorbate peroxidase; GR, glutathione reductase

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Water and pollution transport takes places in fissures, and fissures may also reduce the stability of the rock body. Therefore, fissures in rock are an important issue, especially in case of multi-directional fissure systems, where the situation is more complicated.The so-called azimuthal technique, by using the Schlumberger array is a routinely applied method in geoelectric fissure detections. As we demonstrate it by using analogue model measurements, this method has several shortages. In absence of a priori information, the fissure directions could be obtained only in 60% of the total cases with a precision of ±10%. We have also demonstrated that the effectivity of the method becomes even worse, when the covering sediment layer is thicker. At the same time, when we simply rejected the anisotropy paradox, it was found, that the effectivity of the method is increasing with increasing sediment thickness. The original azimuthal technique is based on the generally accepted hypothesis of the so-called geoelectric anisotropy paradox. The analogue modelling results have made clear that the critical point of the method is the application of the anisotropy paradox. The fissure directions can only be determined, if the conditions of the anisotropy paradox are clearly defined. However, having more than one fissure directions, statistically these fissure directions can be correctly determined.

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The effect of 10, 25 and 50 μM Cd(NO 3 ) 2 on the fatty acid composition was investigated in young maize seedlings ( Zea mays L., hybrid Norma). After 7 days’ exposure to cadmium slight changes were observed in the fatty acid composition, which were more pronounced in the roots than in the leaves. In the leaves cadmium did not affect the lipid composition of the monogalactosyldiacylglycerol (MGDG) or digalactosyldiacylglycerol (DGDG) fractions, while in the phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) fractions there was a decrease in the proportion of hexadecanoic acid (16:0) and an increase in the level of linoleic acid (18:2) and linolenic acid (18:3). The proportion of trans -Δ3-hexadecanoic acid in leaf PG also decreased. In the roots significant changes were observed in all the fractions examined after Cd stress. In the MGDG the level of stearic acid (18:0) and oleic acid (18:1) decreased, but that of 18:2 and 18:3 increased. In the case of PE the amount of 16:0 decreased, while that of 18:0, 18:1 and 18:3 increased. In the PG fraction the proportion of 16:0, 18:0 and 18:1 decreased, while that of 18:2 increased. The ratio of 16:0 also decreased in the DGDG fraction, while that of 18:0, 18:1 and 18:2 increased. The changes in the fatty acid composition were associated with an increase in the double-bond index and in the percentage of unsaturation in leaf PG, and in the MGDG, PG and DGDG fractions in the roots.

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Large numbers of wheat genotypes were grown under field conditions and screened for biotic stress tolerance and certain protective compounds. It was found that both the salicylic acid and polyamine contents of the investigated genotypes varied over a wide range, while the antioxidant enzyme activities showed a similar pattern in the different genotypes. In order to investigate stress-induced changes in salicylic acid and polyamine contents, samples were collected from plants artificially inoculated with leaf rust (Puccinia triticina), on which natural powdery mildew [Blumeria graminis (DC.) Speer f. sp. tritici Em. Marchal] infection also appeared. Biotic stress mostly resulted in elevated levels of total salicylic acid and polyamines in all the genotypes. The activities of various antioxidant enzymes showed similar changes after infection regardless of the genotype. The investigation was aimed at detecting a relationship between the level of stress tolerance and the contents of protective compounds, in particular salicylic acid and polyamines.

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The application of naturally occurring biologically active compounds could be an effective method to improve crop productivity under changing environmental conditions. In the present work the effects of priming maize seed with salicylic acid were tested on the grain yield under field conditions, and on the salicylic acid and polyamine metabolism under controlled environmental conditions. The field data suggested that the beneficial effects of pretreating maize seed with salicylic acid were mainly detectable in the yield in the case of early sowing dates. When young maize seedlings were exposed to low temperature stress, priming the seed with salicylic acid only modified the salicylic acid levels in the seed but not in the roots or leaves. The data suggested that salicylic acid was taken up by the seed and was then converted to bound forms. In contrast to salicylic acid, 5 days after sowing there was a substantial increase in the free form of ortho-hydroxy cinnamic acid in the seed, roots and leaves. Priming with salicylic acid also led to an increase in the putrescine content and a slight decrease in spermidine in the seed. The levels of putrescine, spermidine and spermine also increased in the roots of plants treated with salicylic acid under normal growth conditions. The results suggest that polyamines may also contribute to the stress tolerance of plants primed with salicylic acid.

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Acta Agronomica Hungarica
Authors: G. Kocsy, Magda Pál, A. Soltész, G. Szalai, Á. Boldizsár, V. Kovács, and T. Janda

Low temperature stress results in significant yield losses in cereals. Cereals of subtropical origin like maize and rice are severely damaged at temperatures below 10°C and are killed at subzero temperatures. This stress effect is called chilling. In contrast, cereals originating from the temperate zone (wheat, barley, rye and oat) may survive short periods even between −10 and −20°C, depending on the species and varieties, so they are freezing-tolerant to various extents. For the winter type of these cereals a gradual decrease in temperature up to −4°C results in cold acclimation, which increases their freezing tolerance. In addition, it fulfils their vernalization requirement, which is necessary for the correct timing of the vegetative to generative transition. During both chilling and freezing, oxidative stress is induced. Although the accumulation of high concentrations of reactive oxygen species may be lethal, a moderate increase in their level may activate various defence mechanisms. In this review the role of reactive oxygen species, antioxidants, carbohydrates, free amino acids, polyamines and hormones in the response to low temperature stress in cereals will be described. The effect of light and the use of the model plant Brachypodium distachyon L. to reveal the biochemical and molecular biological background of this response will also be discussed.

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