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Abstract

The aim of the performed experiments was to analyse relationships occurring between endophytic bacteria from the Herbaspirillum genus and Sinorhizobium meliloti Bp nodule bacteria and to examine the condition of plants subjected to coinoculation with the above-mentioned strains in in vitro conditions. In experiments examining the impact of Herbaspirillum frisingense on Sinorhizobium meliloti BP, the stimulation of growth of inoculated bacteria from the Sinorhizobium genus was recorded in all three combinations (48-hour culturing, sediment and supernatant). On the other hand, the examination of interactions between the Sinorhizobium meliloti strain and Herbaspirillum frisingense strain revealed that in the case of culture and supernatant, an antagonistic action was recorded. Besides, it was found that such coinoculation exerted a beneficial influence on the process of seed lucerne symbiosis and yielding as confirmed by increased numbers of root nodules, higher nitrogenase activity and greater plant mass.
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Abstract

In order to simulate the warming effects on Arctic wetlands, three passive open−top chambers (OTCs) and three control cage−like structures (CCSs) equipped with soil temperature and soil volumetric water content (VWC) probes for continuous micro− climatic measurements were installed in a wet hummock meadow, Petuniabukta, Billefjorden, central Spitsbergen, in 2009. The warming effects on primary productivity were investigated during summer seasons 2009 and 2010 in cyanobacterial colonies of Nostoc commune s.l., which plays an important role in the local carbon and nitrogen cycles. The microclimatic data indicated that the effect of OTCs was dependent on microtopography. During winter, two short−term snow−thaw episodes occurred, so that liquid water was available for the Nostoc communities. Because of the warming, the OTC hummock bases remained unfrozen three weeks longer in comparison to the CCSs and, in spring, the OTC hummock tops and bases exceeded 0 ° C several days earlier than CCS ones. Mean summer temperature differences were 1.6 ° C in OTC and CCS hummock tops, and 0.3 ° Cinthe OTC and CCS hummock bases. The hummock tops were drier than their bases; however the VWC difference between the OTCs and CCSs was small. Due to the only minor differences in the microclimate of OTC and CCS hummock bases, where the Nostoc colonies were located, no differences in ecophysiological characteristics of Nostoc colonies expressed as photochemistry parameters and nitrogenase activities were detected after two years exposition. Long−term monitoring of Nostoc ecophysiology in a manipulated environment is necessary for understanding their development under climate warming.
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