No abstract

There is a strong need for the creation of temporary water retention basins during high levels of river discharge. However, based on the data presented, it is concluded that such reconnection of former wetlands (currently serving as meadows) to the main river bed will strongly influence plant species composition and abundance.

No abstract

The adaptive reactions of Vicia faba major L. cv. Bartom to 13-27 days soil flooding and to 14 days of drainage following 13-days of soil flooding were studied. Under flooding, oxygen diffusion rate (ODR) in the root zone decreased from 2.28-3.44 to 0.09-0.28µmol O 2 m −2 s −1 ; the soil redox potential (Eh) decreased from 543 to 70 mV. Upon drainage of flooded soil the ODR and Eh values returned to the control levels. Oxidative damage and defense systems in leaves were assessed by the concentration of thiobarbituric acid reactive substances (TBARs) and by the activities of superoxide dismutase (SOD) and glutathione reductase (GR). Two stages of stress development are described. During the first stage (1-13 days) shoot dry mass did not decrease, the TBARs concentration and SOD activity increased, the GR activity decreased. The second stage (13-27 days) was characterized by a decrease in the TBARs concentration, SOD and GR activities, pigment concentrations and shoot dry mass. Drainage of flooded soil resulted in elevated concentrations of TBARs and also increased the activities of SOD and GR. Increased SOD activity in the first stage of hypoxic stress development and activations of SOD and GR at oxygen re-entry to soil are responsible for tolerance of Vicia faba to hypoxic and post hypoxic stress associated with soil flooding and subsequent drainage.

No abstract

A b s t r a c t. Stress responses of spring rape to soil hypoxia were investigated during 8-days flooding. Soil air-filled porosity decreased from 25-30% to 0%, oxygen diffusion rate -from 2.6-3.5 to 0.34 µmol O 2 m -2 s -1, and redox potential -from 460 to 150 mV within few hours. Alcohol dehydrogenase activity in roots increased up to 7-fold after one day of flooding and then decreased to 170% of control. Superoxide dismutase activity in roots increased by 27% during first 3 days and then dropped to 60% of control; in the leaves superoxide dismutase activity increased in average by 44%. Ascorbate peroxidase activity in leaves increased by 37% during first 3 days and then decreased to control value. Glutathione reductase activity increased by 45% in roots of flooded plants but did not change in leaves. Proline concentration in leaves increased up to 4-fold on the 3d day of flooding and then decreased to control value. Thus soil flooding induces increase of alcohol dehydrogenase activity and subsequent increase of superoxide dismutase and glutathione reductase activities in roots while the leaves display a few days increase of free proline concentration and ascorbate peroxidase activity, and a long-term increase of superoxide dismutase activity.K e y w o r d s: spring rape, flooding, oxygen diffusion rate, redox potential, enzyme activity INTRODUCTION Soil flooding changes subsurface plant gas exchange. The low diffusion rate of oxygen in water-filled pore space of the soil results in limitation of oxygen availability for plant roots and soil microorganisms and leads to a switch of aerobic metabolism of plant roots into less efficient anaerobic fermentation, causing a fast depletion of carbohydrate reserves. Hypoxic conditions in soil cause also a decrease of Eh (Balakhnina et al., 2009(Balakhnina et al., , 2010 Gliñski and Stêpniewski, 1985;Bailey-Serres and Voesenek, 2008). This, in turn, stimulates evolution of carbon dioxide, molecular hydrogen, hydrogen sulphide, ethylene, and methane and accumulation in the soil of reduced phytotoxins (Fe 2+ , Mn 2+ , sulfide and, at high concentrations, ammonium) which can have a negative impact on plants, causing, among others, growth retardation, reduction in leaf size, wilting of shoots and necrosis (Lucassen et al., 2002; Smith and Restal, 2006). Plant adaptation to soil hypoxia includes series of interconnected reactions directed to survival during the periods of hypoxic and anoxic conditions and to the homeostasis maintenance. Anatomical and morphological changes help to provide oxygen to the plant tissues (Colmer, 2003;Pederson et al., 2009;Vartapetian et al., 2003).In connection with the specificity of the effect of hypoxia on plants, of special interest are compensatory changes connected with transformations of respiration pathways. Under oxygen deficiency most plants exhibit intensification of glycolysis accompanied with accumulation of lactate and ethanol (Rocha et al., 2010). Under prolonged and deep hypoxic stress the formation of ethanol prevails. Pr...

No abstract

The aim of this study was examination possibility of Azolla caroliniana Willd. to aerate its medium enriched with Cd(II) and Hg(II) and comparison of DO and ODR methods in measurement aeration status of solutions. Azolla system has been chosen to verify the validity of the measuring ODR method in water solution. Water aeration measurements, one of important environmental tests, are performed most often by measurement of dissolved oxygen with oxygen sensors. Other similar method called oxygen diffusion rate is generally used in different porous materials such as soil. Our first objective was to check if these both methods are comparable and may be use exchangeable in water solution. The both types of measurements were performed in medium saturated at different oxygen concentrations. The linear relationship and high correlation (R = 0.89) were found between values of ODR and DO. The object of the second part of our studies was A. caroliniana Willd. (Azollaceae), a floating water fern living in symbiosis with cyanobacterium Anabaena azollae Strasb. (Nostoceae) that fixes atmospheric nitrogen. Azolla plants are used for centuries as a nitrogen biofertilizer. The second aim of our work was to find out, if the fern reduces or increases oxygen concentration in water. The ODR method was used to determine the aeration status of the nutrient solution. During 12 days of the experiment at laboratory conditions, an active role of A. caroliniana in aeration of the nutrient solution containing Cd(II) and Hg(II) was stated.