Assessment of the microbial pool of raised bog plants

Microbial communities of raised bogs were mainly examined in Sphagnum moss and peaty layers. Such choice is understandable and can be explained by the fact that Sphagnum moss plays an essential role in raised bogs' peat accumulating. Raised bogs are rich in unique prostrate shrubs and herbaceous plants that are more adapted to survival in oligotrophic conditions. These plant species have their own specificities and decomposition rate that differs from Sphagnum. The major aim of this work was to assess raised bogs' prostrate shrubs and herbaceous plants' microbial pool. In spring 2016, we took six samples of bog plants in a pine forest: two prostrate shrub species, namely Andromeda polifolia L., Ledum palustre L. and four herbaceous plants: Scheuchzeria palustris L., Eriophorum vaginatum L., Carex nigra (L.) Reichard and Drosera rotundifolia L. These plant samples (10 units of each plant) were taken at four sites spread at a distance from 50 to 100 meters. We analyzed vegetative organs, such as leaves, stems and roots. An average sample was prepared for each vegetative organ of all analyzed species. A weight sample of 10 grams was taken from the average sample and put into a 100-ml flask with sterile water. Samples were processed in ultrasonic disperser 'Bandelin Sonopuls HD 2017' (Germany) for 2 minutes at a 50% power and then diluted 10 times. The resultant suspension was put on a microscope slide by a micropipette (0.01 ml for accounting of bacterial cells; 0.02 ml for accounting of fungal mycelium length and the number of fungal spores and yeast-like cells) and was distributed evenly on the area of 4 m². 12 specimens were prepared for each sample. Specimens were then dried at room temperature and then fixed by light heating on a gas-burner flame. In order to conduct bacteria quantitative calculation, microscope slides were stained by acridine orange solution (1:10000; exposure time was 3 minutes). Calcofluor white was used to calculate fungal spores and mycelium (1:10000; exposure time was 10 minutes). Stained specimens were examined using 'LYUMAM-IZ' (Russia) luminescent microscope (optical filters ZHS-19, ZHS-18, x 90 L lens, x 4 or x 5 eyepieces). 20 microscope fields of view were analyzed in order to calculate the number of bacterial cells on each specimen, and 50 were analyzed to make an account of fungal spores and mycelia. Fungi, bacteria and yeast-like cells were detected in examined plants. We found both fungal spores and fungal mycelium. Plant species as well asits vegetative part determined microbial population density (See Table 1). The fungal mycelium length on examined plants' leaves and stems varied from 56 to 566 m/g, the number of spores and yeast-like cells varied from 3 to 24 million spores per gram, the bacterial number varied from 0.5 to 4 billion cells per gram (See Fig. 1-3). The fungal mycelium length and bacterial number on plant roots exceeded the same indicators on leaves and stems. On the contrary, fungal spores and the number of yeast-like cells on plant roots was lower than their number on leaves and stems. We established that Carex has the biggest quantity among the majority of microorganism groups and Drosera has the smallest one. Microbial biomass on vegetative parts of raised bog plants varied from 0.10 to 2 mg/g. Microbial biomass calculation on leaves and stems of the majority of examined plants gave close values. The biomass of the examined plant roots did not exceed a factor of two. This biomass calculation proved true for all plant species except for Carex. The microbial biomass of Carex roots was three to five times more than root biomass of other plant species (See Table 2). Bacteria, fungal spores and yeast-like cells proportion in the microbial biomass structure on leaves and stems was quite high (up to 96%), the fungal mycelium dominated in microbial biomass structure on plant roots (See Fig. 4). The paper contains 4 Figures, 2 Tables and 32 References.

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