دانلود رایگان مقاله ساختار جامعه قارچ میکوریز آربوسکولار در تپه شنی برزیل

Abstract

Arbuscular mycorrhizal fungi (AMF) are indispensable for the establishment of plant communities, which is essential for the stabilization of sediments in ecosystems, such as sand dunes. This study aimed at assessing the diversity and distribution of AMF in fluvial and maritime dunes, in order to verify if AMF community structure is influenced by physical and chemical soil characteristics. AMF species richness, diversity and community composition, spore density and mycorrhizal colonization were investigated in four natural dunes areas, i.e. two fluvial and two maritime dunes in Bahia State, northeastern Brazil. Soil samples were collected in September 2013 and March 2014. Spore density differed significantly among the dunes and sampling times, with the highest values recorded in the maritime dunes. Fifty-four AMF species were identified in the study areas, of which 51 were identified from field samples and three additional (Acaulospora longula,Acaulospora spinosa and Rhizoglomus natalense) after propagation in trap cultures. The most representative genera were Acaulospora (11), Glomus (10) and Gigaspora (8). Gigaspora margarita was the only species found in all areas at both sampling times. The AMF community composition significantly differed among the four dunes. There was a correlation between the AMF community composition and the soil characteristics. Highest species richness per sample was observed in the areas of maritime dunes. The fluvial and maritime dunes of Bahia showed high diversity of AMF and the soil is an important factor in the structure of the AMF community in sand dunes.

4. Discussion

The highest percentage of hyphae colonization in dune areas from this study is similar to the results observed by RodríguezEcheverría et al. (2008) in European sand dunes. According to Yang et al. (2008), hyphae comprise the main colonization structure of AMF and are widely distributed in plant roots. Arbuscules are ephemeral structures that are difficult to detect in field samples as they are lost within a short time (about 4–15 days), but their presence in field samples suggests that a transfer of nutrients occurs from the fungus to the host (Dennett et al., 2011), indicating that the symbiosis is active. The absence (almost total) of arbuscules in the roots of the fluvial dune areas may be due to degradation or could indicate a lower exchange of substances between plant and fungus. Besides, we can consider the bias related to the evaluation method and/or difficulty to see or finding arbuscules from field roots, especially as we sampled at the beginning and the end of wet and dry seasons, which corresponded to the beginning and end of the growing seasons. According to Rodríguez-Echeverría et al. (2008), low percentage of vesicles might possibly indicate lower acquisition of new resources and increased use of stored carbohydrates. The values observed in this study are within the range observed by these authors (3–18%)