Péter Kanalas

Short-term chromium(VI) stress induces different photosynthetic responses in two duckweed species, Lemna gibba L. and Lemna minor L.

Physiological responses of two duckweed species, Lemna gibba and Lemna minor, to hexavalent chromium [Cr(VI)] were studied in axenic cultures using short-term (48 h) treatments by K2Cr2O7 (0–200 μM). Chlorophyll (Chl) fluorescence parameters and photosynthetic pigment composition of plants were screened to determine the effects of Cr(VI) exposures. The two duckweed species exhibited different sensitivity in the applied Cr(VI) concentration range. Chl fluorescence parameters of dark-adapted and light-adapted plants and electron transport inducibility were more sensitive to Cr(VI) in L. minor than in L. gibba. We also found fundamental differences in quantum yield of regulated, Y(NPQ), and nonregulated, Y(NO), non-photochemical quenching between the two species. As Cr(VI) concentration increased in the growth medium, L. minor responded with considerable increase of Y(NPQ) with a parallel significant increase of Y(NO). By contrast, in L. gibba only 200 μM Cr(VI) in the growth medium resulted in elevation of Y(NPQ) while Y(NO) remained more or less constant within the regarding Cr(VI) concentration range during 48 h. Photosynthetic pigment content did not change considerably during the short-term Cr(VI) treatment but decrease of Chl a/b and increase of Car/Chl ratios were observed in good accordance with the changes in Chl fluorescence parameters. The data suggest that various duckweed species respond with different sensitivity to the same ambient concentrations of Cr(VI) in the growth medium, and presumably to other environmental stresses too, which may have an influence on their competitive relations when heavy metal pollution occurs in aquatic ecosystem.

Osmotic stress responses of individual white oak (Quercus section, Quercus subgenus) genotypes cultured in vitro

White oaks (Quercus section, Quercus subgenus) are widely distributed in Europe. Quercus petraea (sessile oak), an economically important species is predicted to be affected by climate change. Q. pubescens (pubescent oak) and Q. virgiliana (Italian pubescent oak) are economically less important, drought tolerant species. Frequent hybridization of white oaks was observed and currently the introgression of Q. pubescens and Q. virgiliana in non-mediterranean regions of Europe has been reported. Our goal was to use tissue cultures established from individual trees of the above taxa and their putative hybrids, all present in the forest stand of Síkfőkút LTER Research Area (NE Hungary) as simple experimental model systems for studying drought/osmotic stress tolerance. Tissue cultures are more suitable models for such studies, than seedlings, because they are genetically identical to the parent plants. Polyethylene glycol (PEG6000) treatments were used for this purpose. The identification of taxa was based on leaf morphological traits and microsatellite analysis and showed that Q. petraea is genetically distinct to all other taxa examined. We established six callus lines of Quercus. As expected, in Q. petraea cultures PEG6000 induced severe loss of fresh weight and the ability to recover after removal of the osmoticum, which was not characteristic for Q. pubescens and Q. virgiliana. Putative hybrids exhibited an intermediate response to osmotic stress. Activity gels showed the increase of single-strand preferring (SSP) nuclease and no significant change of guaiacol-peroxidase activities in drought-sensitive genotypes/cultures and no significant increase of SSP nuclease activities accompanied with increases of guaiacol-peroxidase activities in drought-tolerant ones. This indicates that drought/osmotic stress tolerance is associated to increased capacity of scavenging reactive oxygen species and hence less susceptibility to DNA damage. Our results confirm that tissue cultures of oak are suitable model systems for studying drought/osmotic stress responses.

Seasonal and diurnal variability in sap flow intensity of mature sessile oak (Quercus petraea (Matt.) Liebl.) trees in relation to microclimatic conditions.

In this study sap flow dynamics of mature sessile oak trees (Quercus petraea) in a marginal sessile oak-turkey oak forest was investigated in 2009. That year spring was dry without significant rain in April and May and the driest month was August. Due to the extreme weather conditions the volumetric soil water content (SWC) of upper 30 cm was low on experimental days in May (0.13-0.14 cm3 cm-3) but it reached the lowest value in August (0.08 cm3 cm-3). Sap flow was measured in a dominant and a co-dominant tree by heat dissipation method from 26 March till 30 October. In the present paper several three-day long periods of the continuous seasonal recordings were chosen to represent the effects of typical weather conditions and different stages of canopy development on sap flow dynamics. The daily maximum sap flow density values of dominant and co-dominant trees were similar (0.30-0.32 cm3 cm-2 min-1) in moist period (July). Rains and transient increase of SWC after proceeding drought resulted in change of diurnal course of sap flow in experimental days of July. In this period dominant trees also showed considerable sap flow (0.19 cm3 cm-2 min-1) during night hours and short sap flow peaks in early morning (6:00 to 8:00 a.m.) indicating the refilling of desiccated tissues. After the progressive drought in August the daily maximum sap flow density decreased to 0.07 cm3 cm-2 min-1 in dominant tree and to 0.12 cm3 cm-2 min-1 in the co-dominant. Both trees exhibited gradual stomatal closure from morning hours.

Anthocyanins: possible antioxidants against Cr (VI) induced oxidative stress in Spirodela polyrrhiza.

Rural economy in Croatia with your small sized sector of peasant enterprises still stays in the shadow of restructuring of large industrial sector. The slow leading process of privatization, the wandering in the claim the best solution in agricultural development, absence of consensus about key development priorities, as well as common indicators of backwardness, are only part of gray scale of problems which dented the continue pauperization of wide rural area in Croatia. The Croatian government administration late with implementation of new rural policy measures, which are recommended by Council Regulation (EC) No 1257/1999. This act emphasis the balanced development of the countryside alongside the market support measures in the lights of the social and territorial cohesion. It is based on the following principles: recognising the multifunctional role of agriculture, improving competitiveness, ensuring that environmental issues are taken into account, diversifying economic activity, and conserving rural heritage. In the past time new rural policy in Croatia is considered below local and regional development programs, where the LEADER approach take important role. This is result of pre-accession process to EU and new possibilities of using considerable financial support in IPA subsidy program 2007- 2113.

Springtime Leaf Development of Mature Sessile Oak Trees as Based on Multi-Seasonal Monitoring Data

Abstract - Based on a four year leaf growth data-set we modelled the thermal time-dependent leaf ontogeny in upper and lower canopy layers of mature sessile oak trees, in a Quercetum petraeae-cerris forest stand (NE Hungary). Our regression models revealed no considerable differences between the timing of leaf unfolding and leaf expansion of different canopy layers. On the other hand seasonal course in leaf mass-to-area ratio (LMA) indicated that sun leaves needed considerably longer thermal time to fully develop their anatomical structures compared to shade leaves. LMA of sun leaves was higher during the whole leaf maturation process suggesting that ‘sun’ and ‘shade’ characteristics develop in very early stage of leaf ontogeny. Functioning of photosynthetic apparatus (Fv/Fo) in shade leaves have built up faster and performed better in all developmental stages which could be attributed to two main factors: 1) very early determination of leaf traits as a function of light environment and 2) evolving shading effect of upper canopy layer eliminates photoinhibition in lower leaves. Kivonat - Levélnövekedés és a fotokémiai hatékonyság tavaszi felépülése kocsánytalan tölgyfák lombkoronájában, többéves monitoring adatok alapján. Jelen munkánk során több levéljellemző változása alapján modelleztük a levélfejlődés folyamatait a hőösszeg függvényében, egy mérsékelt övi cseres-tölgyes erdőállomány idős kocsánytalan tölgyfáinak alsó és felső lombkorona-rétegében. Az eredményeink alapján a levélterület kialakulása a lombkorona alsó és felső részében egyszerre kezdődik és fejeződik be. A fénylevelek esetében a levéltömeg/terület arány (LMA) később érte el a nyári értékét, és a levélfejlődés minden szakaszában nagyobb vastagságot és/vagy nagyobb sűrűséget jelzett, ami a fény- és árnyéklevél-tulajdonságok igen korai kialakulását jelzi. A levelekben a PSII kvantumhozam (Fv/Fo) szezonális fejlődését szintén befolyásolja a lombkorona-helyzet. Az árnyéklevelek a teljes fejlődési folyamat alatt magasabb Fv/Fo értékekkel rendelkeztek, és gyorsabban elérték a szezonális maximumukat, mint a fénylevelek, Az utóbbi eredmények szintén a fény- és árnyékjelleg korai determinációjára utalnak, továbbá jelzik azt is, hogy a levélterület-növekedéssel párhuzamosan kialakuló önárnyékolás sietteti a PSII kvantumhozam felépülését.

Effects of drought on some ecophysiological traits of sessile oak (Quercus petraea L.)

Our objectives were to assess and rank 3 soil condition variants - root zone improving (RI), mulch leaving (NIL) and minimum disturbing (MD) - suitability to soil quality improvement and demonstrate the plant responses to different soil state and rind a possible relation between soil condition and plant growth under extreme climate. To rank the soil-plant interrelations twelve soil and plant factors were assessed; quality and depth of loosening state, surface protection by plants and stubble residues, soil aggregation, earthworm number, water supply in the root zone, tillage-induced C-flux, rooting depth of plants, yield, dry biomass and biomass recycling. Finally, seven fundamental requirements were selected to mitigate climate-stress and to improve plant resistance to the heat damage. A climate damage mitigation soil tillage strategy can establish a harmony between soil conservation and the demands of crop production.The results of a small-pot experiment of cadmium-loading (5 mgkg) with the addition of zinc (5 mgkg) carried out are introduced in this paper. For this, soil samples were taken from 4 sites of plough-land, grassland and forest land-use types. Accumulation characteristics of the two metals as well as their interaction with the soil properties were analysed. The results show that land-use has significant effect on zinc uptake. There is close correlation between the zinc and cadmium uptake of plants as well as that cadmium concentration of soils plays an important role in it. Zinc shows positive correlation while cadmium shows negative correlation with organic matter. Beside organic colloids, inorganic colloids i.e. clay fraction also showed close correlation.The effects of soil and climatic properties was studied on the winter wheat (Triticum aestivum L.) concerning on the heavy metal content of the plants. During this study the distribution of cobalt, copper, iron, manganese, nickel, and zinc was studied within a plant. Sampling was carried out in the same period of subsequent three years between 1995 and 1997. Our hypothesis was that the individuals of the same species has similar physiological answer for the same environmental properties. In this study we found no significant differences among the different plant’s parts and years. Our results can reveal that the ecological indication of plants could be major driver of agro-environmental studies to recognize unusual patterns of soil attributes.

Ecophysiological traits of beech regenerating in contrasting environmental conditions

Our objectives were to assess and rank 3 soil condition variants - root zone improving (RI), mulch leaving (NIL) and minimum disturbing (MD) - suitability to soil quality improvement and demonstrate the plant responses to different soil state and rind a possible relation between soil condition and plant growth under extreme climate. To rank the soil-plant interrelations twelve soil and plant factors were assessed; quality and depth of loosening state, surface protection by plants and stubble residues, soil aggregation, earthworm number, water supply in the root zone, tillage-induced C-flux, rooting depth of plants, yield, dry biomass and biomass recycling. Finally, seven fundamental requirements were selected to mitigate climate-stress and to improve plant resistance to the heat damage. A climate damage mitigation soil tillage strategy can establish a harmony between soil conservation and the demands of crop production.The results of a small-pot experiment of cadmium-loading (5 mgkg) with the addition of zinc (5 mgkg) carried out are introduced in this paper. For this, soil samples were taken from 4 sites of plough-land, grassland and forest land-use types. Accumulation characteristics of the two metals as well as their interaction with the soil properties were analysed. The results show that land-use has significant effect on zinc uptake. There is close correlation between the zinc and cadmium uptake of plants as well as that cadmium concentration of soils plays an important role in it. Zinc shows positive correlation while cadmium shows negative correlation with organic matter. Beside organic colloids, inorganic colloids i.e. clay fraction also showed close correlation.The effects of soil and climatic properties was studied on the winter wheat (Triticum aestivum L.) concerning on the heavy metal content of the plants. During this study the distribution of cobalt, copper, iron, manganese, nickel, and zinc was studied within a plant. Sampling was carried out in the same period of subsequent three years between 1995 and 1997. Our hypothesis was that the individuals of the same species has similar physiological answer for the same environmental properties. In this study we found no significant differences among the different plant’s parts and years. Our results can reveal that the ecological indication of plants could be major driver of agro-environmental studies to recognize unusual patterns of soil attributes.