Root tip demography of a 43 year old Sitka spruce stand was determined over a two year period. A total of 35,300 root tips were examined. A total of 14 mycorrhizal and 4 non-mycorrhizal root tip types were recognised. One mycorrhizal type, formed by Tylospora fibrillosa, made up 67% of the root tips examined, the rest each made up less than 5% of the population. The level of infection was high, with c. 94% of the root tips infected with mycorrhizal fungi. There were marked short term fluctuations in the numbers and relative abundance of some of the types, as well as longer term, unidirectional increases in the dominant type and decreases in the numbers and relative abundance of non-mycorrhizal root tips. The effect of the addition of carbon and nitrogen was examined. Carbon addition had very little effect on the mycorrhizal population as a whole. Nitrogen, on the other hand, had a very marked effect on several of the root tip types. The relative abundance and the numbers of Tylospora fibrillosa mycorrhizas were both reduced by the addition of nitrogen, whereas the relative abundance and numbers of non-mycorrhizal tips increased. A large gradient of weight of organic matter and moisture existed on the site and this was shown to strongly influence the spatial distribution of the root tip types. Russula ochroleuca mycorrhizas were shown to have a positive association with organic matter and moisture. The occurrence of E-type mycorrhizas was negatively correlated with the accumulation of organic matter, which supports the idea that these mycorrhizas are primarily associated with mineral soil. Finally, the population structure of T.fibrillosa was examined using somatic incompatibility (SI) to determine the clone size of the fungus on the site. No SI was found between any of the isolates, even when collected 20m apart. This could mean that either T.fibrillosa does not exhibit SI or that the clone from which the isolates were collected was larger than 20m across.

Aluminium toxicity is the main limiting factor in crop production on acid soils. The main symptom of aluminium toxicity is a rapid inhibition of root growth, but the mechanism of root growth cessation remains unclear. In this diploma thesis we deal with the question of whether phospholipases PLDα1 and PLDδ may play a role in the mechanism of aluminium toxicity. We compared the responses of plants lacking PLDα and PLDδ with WT plants. Growth analysis of roots was performed in hydroponic conditions. The most sensitive part of roots was transient zone in which cells were dying earlier. It was further found that pldα1 plants were less sensitive on aluminium toxicity because their roots showed less growth inhibition than WT. Pldδ plants did not differ from WT plants in their response to aluminum. During further analysis of the pldα1 reactions, it was found that the root cells were capable of cell expansion during aluminum toxicity, and the cellular malformations were formed on the roots. This phenomenon was associated with faster reorientation and even depolymerization of cortical microtubules in response to toxic aluminium in pldα plants compared to WT plants. The results indicated that PLDα1 molecule affects the stability of cortical microtubules. Microtubules were less stable and they depolymerized...

Ectomycorrhizal colonisation potential of Pinus radiata seedlings inoculated with the commercially available Trichoderma species bio-inoculant, Arbor-Guard™, was investigated in a commercial containerised nursery setting and in a separate glasshouse experiment, which included the co-inoculation of specific ectomycorrhizal fungi. Application of Arbor-Guard™ to Pinus radiata seedlings in a containerised commercial nursery had no significant effect on the ability of the naturally occurring ectomycorrhizal (ECM) fungi to colonise the seedlings. Thelephora terrestris was the dominant ectomycorrhizal species colonising the P. radiata root tips and has been described as a species able to rapidly outcompete other ECM species colonisation, particularly in high organic matter media like that used at the containerised commercial nursery investigated. In a similar experiment run to augment the commercial experiment, specific ECM fungi identified as Rhizopogon roseolus, Suillus luteus, and Rhizopogon villosulus were co-inoculated with Arbor-Guard™ to investigate the effect on the colonisation potential of the respective ECM species in combination with Trichoderma. The treatment effect of the addition of Arbor-Guard™ did not negatively impinge on the ECM species found, or the abundance of ECM root tips colonising the P. radiata seedlings. Ectomycorrhizal species in the Thelephoraceae family were the dominant species found colonising the P. radiata root tips. Of the inoculated ECM, S. luteus was the only detected species colonising the P. radiata root tips but was only found in low abundance. Non-conducive abiotic factors for optimum ECM colonisation were considered the most likely reason for the low colonisation of the inoculated ECM species. Any effect of the unintentional co-inoculation of the wood decaying fungi Hypholoma fasciculare and Lentinula edodes, due to misidentification, with the inoculated ECM species was unable to be resolved in this study. However, it was speculated that H. fasciculare may have had a negative effect on the inoculated ECM species colonisation. In vitro dual culture assays were initiated to investigate the specific interactions between each of the candidate ECM fungi inoculated in the glasshouse experiment when challenged with each of the six Trichoderma isolates in Arbor-Guard™. Both competition for nutrients and/ or space were concluded to be the main antagonistic mechanisms potentially used by five of the Trichoderma isolates against all co-inoculated ECM species and L. edodes. Hypholoma fasciculare was not inhibited by the five Trichoderma isolates, however, one Trichoderma isolate (LU 663) competitively antagonised all inoculated ectomycorrhizal/ saprophytic species before the mycelial fronts converged. Agar diffusible secondary metabolites were speculated to be potential mechanism of antagonism expressed by LU 663 over volatile antibiotics such as 6-pentyl-α-pyrone. No direct correlation could be dervived from the in vitro dual culture assays and what was observed in the containerised in planta results. Overall the results indicated no negative impact of the Trichoderma bio-inoculant Arbor-Guard™ on ectomycorrhizal colonisation of Pinus radiata seedlings in a containerised nursery system.