Since 1940 molybdenum has been known as an essential trace element in plant nutrition and physiology. It has a central role in nitrogen metabolism, and its deficiency leads to nitrate accumulation in plants. In this study, we cultivated maize seedlings (Zea mays L. cv. Norma SC) in nutrient solution and soil (rhizoboxes) to investigate the effect of molybdenum treatment on the absorption of molybdenum, sulphur and iron. These elements have been previously shown to play important roles in nitrate reduction, because they are necessary for the function of the nitrate reductase enzyme. We also investigated the relationship between molybdenum treatments and different nitrogen forms in maize. Molybdenum treatments were 0, 0.96, 9.6 and 96 μg kg-1 in the nutrition solution experiments, and 0, 30, 90, 270 mg kg-1 in the rhizobox experiments. On the basis of our results, the increased Mo level produced higher plant available Mo concentration in nutrient solution and in soil, which resulted increased concentration of Mo in shoots and roots of maize seedlings. In addition it was observed that maize seedlings accumulated more molybdenum in their roots than in their shoots at all treatments. In contrast, molybdenum treatments did not affect significantly either iron or sulphur concentrations in the plant, even if these elements (Mo, S and Fe) play alike important roles in nitrogen metabolism. Furthermore, the physiological molybdenum level (1x Mo = 0.01 µM) reduced NO3-N and enhanced the NH4-N concentrations in seedlings, suggesting that nitrate reduction was more intense under a well-balanced molybdenum supply.

Mineral content of propolis tinctures in relation to the extraction time and the ethanol content of the extraction solvent Áron SOÓS* a -Éva BÓDI a -Szilvia VÁRALLYAY a -Szabolcs MOLNÁR b -Béla KOVÁCS a

Arsenic is one of the most toxic elements that can be found in the environment. Excessive uptake of arsenic may cause physiological changes in plants. The aim of the study was to investigate the effect of different arsenic treatments on relative chlorophyll content and dry weight of shoot and root of maize and sunflower in the early phases of plant development. Seedlings were grown in climatic room in nutrient solution under strictly regulated environmental conditions. The plants were exposed to 3, 10 and 30 mg kg-1arsenic, whereas there was no arsenic treatment on the control plants. We applied arsenic in the form of arsenite (NaAsO2) and arsenate (KH2AsO4), respectively. After 14 days of arsenic treatments, changes in relative chlorophyll content and dry weight of maize shoots and roots were recorded. In the case of sunflower these physiological parameters were measured after 21 day. The applied arsenic decreased the relative chlorophyll content of maize and sunflower leaves, especially at concentration of30 mg kg-1. The increasing amount of As treatment were resulted the lower weight of the experimental plants, which was more considerable in the case of the roots. The results indicate that the sunflower plants is more sensitive to arsenic toxicity than maize plants and all data demonstrate that the As(III) is more toxic to these crop plants than the As(V).

No abstract

Selenium (Se) is an example of an essential element becoming more and more insufficient in food crops as a result of intensive plant production in many countries. Se is an essential biological micronutrient in diet of animals and humans, and plant foods are important sources of dietary Se. It is an essential constituent of several enzymes in which it is present in the form of the unusual amino acid selenocysteine (SeCys). Then, engineering food crops to accumulate higher levels of Se would provide adequate Se to target population. In this study, two species of soluble inorganic selenium forms, selenite (Se IV ) and selenate (Se VI ) at different concentrations were investigated on sunflower plants that were growing in nutrient solutions during 3 weeks and at the end of the experiment, amounts of SLA for first and second leaves of sunflower were measured. In accordance with the results that we observed, our regarded Se concentrations in Se IV form have not been had positive effect on sunflower plants. Whereas samples that had been treated with 0.3 mg.L -1 Se VI , had the high SLA amount and for second leaves, this increase was significantly. Although high level of 0.9 mg.L -1 and 3 mg.L -1 Se VI had negative affect on growth of the samples that had been treated by them.