Study on Ambrosia artemisiifolia L. roots colonized by arbuscular mycorrhizae in various herbaceous plant communities.
Ambrosia artemisiifolia L. is an invasive plant that has spread increasingly in Banat region, expanding their surface very fast, mainly the non-cultivated fields, abandoned pastures, roadsides, along the riversides, near construction sites and even waste areas. Recent research in the field assumed that arbuscular mycorrhizae (MA) are playing an important role in the spreading and development of this strong allergenic weed. Former research in this topic have been performed in France on 35 populations of Ambrosia. Therefore, it was noticed by the researchers that the spread of this invasive plant species could be facilitated by arbuscular mycorrhizae. The research aim of the work was to determinate the colonization rate of the Ambrosia artemisiifolia roots with arbuscular mycorrhizae in various herbaceous plant communities from Timisoara area and surroundings. Ambrosia artemisiifolia plants were collected from three locations, respectively the park inside the University of Agricultural Sciences and Veterinary Medicine "King Michael I of Romania" from Timisoara, one abandoned pasture belonging to locality Ghiroda located in the Giarmata Vii village area and a waste area located near the Timisoara International Airport. The mycorrhizal colonization rate of the roots by was determined using special techniques for cleaning and staining of the colonised roots for a good evidencing of the fungal structures. The method applied in this study for the quantification of the colonisation rate of the roots of the analysed root samples of Ambrosia artemisiifolia is on relatively common and is using trypan blue for mycorrhizae staining. Quantification of colonization rate of the roots was performed with the method of intersecting grid lines. The colonization rate of the roots of Ambrosia artemisiifolia ranged between 24 and 31%. The highest colonization rate was recorded in the roots of Ambrosia collected from park, respectively 31.02%. The greater colonization rate can be due in this site to the lack of the competition between plant species because it is well known that invasive plants are heavily mycotrophic, while grasses dominant in the park sward are less colonized. The lowest colonization rate was found in the Ambrosia roots collected from the abandoned pasture (24.70%). The fungal structures of the arbuscular mycorrhizae were observed to the microscope. There were observed fungal structures such as hyphae, which were prevalent, arbuscles, vesicles and even spores. Trypan blue staining has provided a good contrast and the mycorrhizal structures were well highlighted at the microscope.