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Abstract

Girdling was applied to 5-year-old potted beech individuals of early, intermediate and late phenological forms to block assimilate export from leaves. Phloem severance caused accumulation of soluble carbohydrates and starch in leaves and increased the C/N ratio. While the hexose content increased continuously until the end of the experiment, the sucrose and starch contents peaked earlier, depending on the plant's phenological features. Different rates of chlorophyll degradation and H2O2 and TBARS (thiobarbituric acid-reactive substances) production in different phenological forms implied that phloem girdling was the source of oxidative stress and, depending on the phenological form, accelerated leaf senescence to different degrees. The variable rate of the increase in soluble carbohydrate and starch content, characteristic of the different phenological forms, had different modifying effects on the antioxidant activity in leaves. Compared with the early phenological form, the late form was characterized by a smaller increase in H2O2 and TBARS content and delayed and slowed chlorophyll and carotenoid degradation. In conjunction with the larger increase in the activity of antioxidant enzymes (catalase, ascorbate peroxidase and superoxide clismutase) induced by carbohydrate accumulation and slower carotenoid degradation, these changes led to the late form having greater resistance to oxidative stress and slower senescence.

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W Kraj
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Abstract

Studies undertaken in 2002–2004 on ‘Golden Delicious’ apple fruits showed the presence of amino acids on the surface of their skin. Amount of total free amino acids ranged from 2.5 to 3.0 mg/L. In in vitro bioassays it was found that amino acids as a basic source of nitrogen did not activate germination of conidia of Peltaster fructicola (Johnson). However amino acids stimulated elongation of germ tubes and early hyphal growth. It was confirmed that fruit washings also contained sugars that stimulated both conidial germination and germ tube elongation. We proved also that different carbon to nitrogen proportions significantly affected P. fructicola growth. Proportions of C:N were evaluated according to newly introduced amino acid sugar index (ASI)

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Beata Wrona
Mark Gleason
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Abstract

This study investigated the potential of three microalgae taxonomic groups of Chlorophyta, Cyanoprokaryota and Bacillariophyceae for biogas production. Biogas potential was assessed in mesophilic anaerobic digestion batch tests over a period of 20 days. The cumulative biogas yield (CBY) of Chlorophyta and Cyanoprocaryota was respectively 396.21 mL/g Volatile Solids (VS) and 382.45 mL/g VS. Bacillariophyceae digestion showed lower biogas production of 357.07 mL/g VS. The highest cumulative methane yield (CMY) of 241.25 mL CH 4/g VS was recorded for Cyanoprocaryota biomass, which was signifi cantly higher (p<0.05) than the other two types of microalgae. The highest methane content in biogas of 63.08% was observed with Cyanoprokaryota. Chemical composition of biomass as well as biogas productivity are infl uenced by algal taxonomy.
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Authors and Affiliations

Marta Kisielewska
1
Marcin Dębowski
1
Marcin Zieliński
1

  1. Uniwersytet Warmińsko-Mazurski w Olsztynie, Department of Environmental Engineering

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