Abstract
Although microbes are generally found as endophytes in many plant tissues,
the plant shoot meristems have been considered virtually sterile. Plant tissue
culture, which utilizes mostly the meristems, has nevertheless given numerous
references to microbial existence in these tissues. Since the bud-derived tissue
cultures of Scots pine (Pinus sylvestris L.) also become
easily occupied by microbes, microbial presence was considered to be one
potential cause of the low regeneration capacity of tissues from mature trees.
The origin of the microbes occurring in tissue cultures of buds of Scots pine was
established in this study. One of the microbes, classified as Hormonema
dematioides (Ascomycota), was localized in the
scale tissues of a bud. Several other microbes were detected, and were associated
especially with the meristematic tissues of Scots pine buds. This group was
comprised of the yeast Rhodotorula minuta, and bacteria
belonging to Methylobacterium spp., the
Pseudomonas fluorescens subgroup, and a
Mycobacterium sp. These endophytes were located particularly
in the outermost cells of meristems, in the epithelial cells of resin ducts, and
in the cells of the developing stem, in the vicinity of the meristems. These
endophytes were less frequently found in the vascular tissue or in the
intercellular spaces of cells, which are typical locations for the previously
known endophytic bacteria.
The meristem-associated endophytes were discovered to affect growth of pine
tissues, and some of them produced substances that are suitable as precursors for
phytohormone synthesis. Additionally, pure cultures of both bacterial and fungal
endophytes showed antagonism in vitro against pathogens.
When the correlation between the presence endophytes and the degeneration of
bud-derived tissue cultures of Scots pine was studied, it was discovered that the
endophytes grew uncontrollably once a tissue culture was initiated from the bud.
A high level of chitinase production was also detected in these tissue cultures,
which was considered to be indicative of a defense reaction. However, the
endophytes were not found to colonize excessively in every tissue, but all
bud-derived tissue cultures of Scots pine eventually degenerate. Therefore, it
was concluded that the endophytes may not exclusively be considered responsible
for the degeneration of the cultures.
| Identifer | oai:union.ndltd.org:oulo.fi/oai:oulu.fi:isbn951-42-6444-4 |
| Date | 27 June 2001 |
| Creators | Mattila née Pirttilä, A. M. (Anna Maria) |
| Publisher | University of Oulu |
| Source Sets | University of Oulu |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis, info:eu-repo/semantics/publishedVersion |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess, © University of Oulu, 2001 |
| Relation | info:eu-repo/semantics/altIdentifier/pissn/0355-3191, info:eu-repo/semantics/altIdentifier/eissn/1796-220X |
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