László Lévai

Impact of moderate Fe excess under Cd stress on the photosynthetic performance of poplar (Populus jacquemontiana var. glauca cv. Kopeczkii)

Cadmium interference with Fe nutrition has a strong impact on the development and efficiency of the photosynthetic apparatus. To shed more light on the interaction between Fe and Cd, it was studied how iron given in moderate excess under Cd stress affects the development and functioning of chlorophyll-protein complexes. Poplar plants grown in hydroponics up to four-leaf stage were treated with 10 μM Cd(NO₃)₂ in the presence of 50 μM Fe([III])-citrate as iron supply (5xFe + Cad) for two weeks. Though leaf area growth was inhibited similarly to that of Cad (10 μM Cd(NO₃)₂ + 10 μM Fe([III])-citrate) plants, chlorophyll content, ¹⁴CO₂ fixation and quenching parameters calculated from PAM fluorescence induction measurements were control-like in 5xFe+Cad leaves. Increased chloroplast iron content (measured photometrically by the bathophenanthroline disulfonate method) without changes in the iron and cadmium content of leaves (determined by inductively coupled plasma mass spectrometry) pointed out that a key factor in the observed protection of photosynthesis is the iron-excess-induced redistribution of iron in the leaf. However, the chlorophyll a/b ratio and the chlorophyll-protein pattern obtained by Deriphat PAGE remained similar to that of Cad leaves. The decreased amount of PSII core and PSI in mature and developing leaves, respectively, refers to developmental stage-dependent remodelling of thylakoids in the presence of Cd. The results underline not only the beneficial effect of iron excess under Cd stress, but also refer to the importance of a proper Fe/Cd ratio and light environment to avoid its possible harmful effects.

Effects of Biofertilizers on Maize and Sunflower Seedlings under Cadmium Stress

Application of various alternative nutrient supplies can partly be substituted by chemical fertilizers, resulting in economical use with less environmental strains. Biofertilizers containing living microorganisms promote nutrition uptake, but still there are questions regarding their application under stress conditions. One of the main abiotic factors that can induce stress is contamination of soils with toxic elements. In the course of intensive plant-growth conditions, considerable quantities of basic cations are removed from the soil, resulting in acidification and thereby enhancing the uptake of heavy metals by plants. Cadmium (Cd) toxicity is a major problem affecting crop productivity worldwide. The presence of Cd in the rhizosphere can cause stress responses and alteration in many physiological processes, including nitrogen metabolism, photosynthesis, carbohydrate metabolism, sulfate assimilation, and plant–water interactions. Once in the plant, Cd can enter the food chain, causing public health problems. The aim of our work was to investigate the effects of biofertilizers on plant production and nutrient uptake in some Cd-contaminated soils. Our results revealed that Cd accumulated primarily in the roots and transport to the shoots was rather low; however, there were differences between the two plants species. Plant uptake by sunflower was greater than by maize, and sunflower appeared to be more stress tolerant of Cd than maize. With the use of the bacterium-containing biofertilizer, the toxic effect of Cd was moderated.

Effect of molybdenum treatment on molybdenum concentration and nitrate reduction in maize seedlings

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, sulfur 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 sulfur concentrations in the plant, even if these elements (Mo, S and Fe) play alike important roles in nitrogen metabolism. Furthermore, the physiological molybdenum level (1× 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.

Chelator-enhanced lead accumulation in agropyron elongatum cv. Szarvasi-1 in hydroponic culture

Hydroponic culture was applied to compare the efficiency of K2EDTA and citrate in mobilizing Pb for accumulation in Agropyron elongatum cv. Szarvasi-1 and their effects on some physiological characteristics of the plants. The plants were grown in nutrient solutions containing 0, 10, and 100 μM Pb(NO3)2 combined with chelating agents added to the nutrient solutions after 21 days of growth, in 3 concentrations (0, 100, and 500 μM). The effects were measured after eight days. The energy grass proved to be greatly resistant to the treatments, as was reflected in the slight inhibition of growth, the resistance of the photosynthetic electron transport chain and the chlorophyll composition and the lack of change in the malone-dialdehyde content. Fundamental differences can be identified between the effects of EDTA and citrate. Citrate had only a little effect on the physiological parameters, which may be due to the strongly increasing lead accumulation with increasing concentration of Pb in the nutrient solution. Additionally, citrate ensured a higher biomass yield with higher shoot Pb accumulation compared to EDTA in almost all treatments. Concerning biomass reduction, 10 μM Pb applied together with K2EDTA has the most deleterious effects on energy grass. The effects correlated with the concentration of EDTA.

Compensation effect of bacterium containing biofertilizer on the growth of Cucumis sativus L. under Al-stress conditions.

Biofertilizers are used to improve soil fertility and plant production in sustainable agriculture. However, their applicability depends on several environmental parameters. The aim of our study was to evaluate the effect of free-living bacteria containing fertilizer on the growth of cucumber (Cucumis sativus L. cvs. Delicates) under aluminium (Al) stress. Different responses to Al stress of cucumber growth parameters were examined in terms of root elongation and physiological traits, such as Spad index (relative chlorophyll value), biomass accumulation of root and shoot, Al uptake and selected element contents (Fe, Mn, Zn, Mg) of leaves and root. The applied bacteria containing biofertilizer contains Azotobacter chroococcum and Bacillus megaterium. The dry weights of cucumber shoots and roots decreased in line with the increasing Al concentration. Due to different Al treatments (10-3 M, 10-4 M) higher Al concentration was observed in the leaves, while the amounts of other elements (Fe, Mn, Zn, Mg) decreased. This high Al content of the leaves decreased below the control value when biofertilizer was applied. In the case of the roots the additional biofertilizer treatments compensated the effect of Al. The relative chlorophyll content was reduced during Al-stress in older plants and the biofertilizer moderated this effect. The root/shoot ratio was decreased in all the Al-treatments in comparison to the control. The living bacteria containing fertilizer also had a modifying effect. The root/shoot ratio increased at the 10-4 M Al2(SO4)2 + biofertilizer and 10-4 M Al(NO3)3 + biofertilizer treatments compared to the control and Al-treatments. According to our results the biofertilizer is an alternative nutrient supply for replacing chemical fertilizers because it enhances dry matter production. Biofertilizer usage is also offered under Al polluted environmental conditions. Although, the nutrient solution is a clean system where we can examine the main processes without other effects of natural soils. The soil can modify the results, e.g. the soil-born microorganisms affect nutrient availability, and also can modify the harmful effects of different heavy metals. The understanding of basic processes will help us to know more about the soil behaviour.

Time Course of the Appearance of Cd Effects on Photosynthetically Competent Poplar Leaves

Cd effects on photosynthetic performance of the third leaf of hydroponically cultured poplar (Populus glauca var. Kopeczkii) plants were followed during a 2-week treatment with 10 μM Cd(NO3)2. Growth and chlorophyll concentration were reduced by about 20%. Chlorophyll a/b ratio was strongly lowered due to the stronger reduction in the amount of photosystem I than that of lightharvesting complex II. A delayed and fast decrease in the transcript levels of lhca1 and lhca2–4 genes, respectively, and a transient increase in those of lhca5 and lil1 were detected by quantitative RTPCR. Actual quantum efficiency of photosystem II did not change in spite of an early (after second day) decrease in stomatal conductance and CO2 fixation probably due to the increased photorespiration rate (elevated glycolate oxidase activity). Decline in ascorbate peroxidase activity resulted in a moderately higher malondialdehyde level in leaves. In conclusion, decreased stomatal conductance/CO2 fixation and thylakoid reorganization were the first detectable symptoms of Cd treatment in photosynthetically competent leaves.

Növekvő molibdén-koncentráció hatása a különböző nitrogénformákra, valamint a molibdén nitrátasszimilációban betöltött szerepe@@@The effect of increasing molybdenum concentration on different nitrogen forms and the role of molybdenum in nitrate assimilation

Osszefoglalas A novenyek nitrogen asszimilacioja bonyolult biokemiai folyamatok osszessegen keresztul valosul meg. Novenyeink a nitrogent a talajbol tobb formaban vehetik fel. A felvett formatol fuggetlenul valamennyi forma ammoniumma alakul, hogy a noveny hasznositani tudja. Celkitűzesunk volt, hogy laboratoriumi korulmenyek kozott vizsgaljuk, hogyan hat a novekvő koncentracioju molibdenellatas a kulonboző nitrogen-formakra, valamint hogyan befolyasolja a nitratasszimilacio folyamatat. Kiserleti novenykent egy ketszikű (napraforgo, Helianthus annuus L. cv Arena PR) novenyt valasztottunk, melynel kulon vizsgaltuk a hajtas es a gyoker molibden koncentraciojat. Kiserletunkkel igazoltuk, hogy a nitratasszimilacio egyik lenyeges mozzanatanak, a nitratredukcionak a zavartalan lejatszodasahoz a molibden nelkulozhetetlen. A megfelelő molibdenellatas a nitrat-reduktaz enzim aktivitasat noveli, igy elkerulhetjuk, hogy a nitrat karos mennyisegben halmozodjon fel novenyeinkben. A molibdenellatas es a nitratredukcio ...

A molibdénellátás hatása kukorica csíranövényekre@@@The effect of molybdenum supply on maize seedlings

Osszefoglalas A molibden alapvető nyomelem a novenyi tapanyagellatasban. Novenyelettani jelentő seget 1940-ben bizonyitottak be. A noveny nitrogen anyagcserejeben van fontos szerepe, hianyaban nitrat felhalmozodas tapasztalhato. Kutatomunkank celja kettős volt: Kiserleteink soran egyreszt arra a kerdesre kerestuk a valaszt, hogyan valtozik a kukorica (Zea mays L. cv Norma SC) csiranoveny Mo, Fe es S koncentracioja novekvő kon centracioju Mo-kezelesek soran. Azert tartottuk fontosnak e harom elem koncentraciojanak nyomon koveteset, mert a nitratredukcioban, a nitrat-reduktaz műkodeseben ezek az elemek kiemelt szerepet toltenek be. Masreszt kiserleteinkkel laboratoriumi korulmenyek kozott kivantuk igazolni, hogy szoros osszefugges van a molibdenellatas es nitratredukcio kozott: a novenyek fiziologiai molibden szuksegletet biztositva, csokkenteni tudjuk nitrat tartalmukat. Kiserleteink az alabbi ket tipusba sorolhatok: rizoboxos- es tapoldatos kiserletek. Rizoboxos kiserleteinkben harom kulonboző koncentraci...

A közeg pH-jának szerepe a látens tápanyaghiány kialakulásában fiatal kukorica és uborka növényeknél

A növények tápanyagfelvétele a termés mennyiségét és a minőségét meghatározó egyik fő fiziológiai folyamat. A kedvezőtlen környezeti feltételek csökkentik a tápanyagfelvételt, a növény szervesanyag-felhalmozását, ezzel az elérhető termés mennyiséget is. A növénytermesztés eredményességét meghatározó, egyik legfontosabb abiotikus tényező a talaj pH-ja. Bár a talaj pH-jának hatása sokrétű, mégis az egyik leginkább kutatott terület a pH és a talajok felvehető tápanyagtartalmának összefüggése. Kísérleteinkben a tápoldat és az apoplazmatikus bikarbonát, valamint egy biotrágya (Phylazonit MC®) hatását vizsgáltuk laboratóriumi körülmények között, tápoldaton nevelt fiatal kukorica és uborka csíranövényekre. Meghatároztuk a növények relatív klorofill tartalmát, a hajtás és gyökér növekedését, szárazanyag-felhalmozását, elemtartalmát, különösen az egyik legfontosabb terméslimitáló elem, a vas felvételében. Megállapítottuk, hogy a környezet magas bikarbonát koncentrációja stresszként hat, a tápközeg pH-jának módosításán keresztül jelentősen befolyásolja a vizsgált folyamatokat. Megfigyelésünk alapján arra a következtetésre jutottunk, hogy a gyökér és a mezofillum sejtek tápanyagfelvétele azonos mechanizmus szerint történik. A tápoldatba és az apoplazmába juttatott bikarbonát hatása hasonló, ami mögött a tápanyagfelvétel hasonló membránfolyamatait valószínűsítjük. A pH mellett a mezofillum sejtközötti járatainak bikarbonát koncentrációja is okozhat tápanyag hiányt (látens tápanyaghiány) megfelelő tápanyagellátás esetén is. Eredményeink szerint a bikarbonát okozta stresszhatás mérsékelhető volt egy baktérium tartalmú biotrágya (Phylazonit MC®) kiegészítő használatával. Feltételezzük, hogy a kedvező hatás mögött a baktériumok és a magasabb rendű növények tápanyagfelvételi hasonlóságai vannak.