plant surface microbiology.pdf

However, at the moment, the mechanism as to how this was achieved by the
bacteria is not clear. One possibility might be a dissolution of the cutin polymer
by extracellular bacterial enzymes. Alternatively, one could also image a
pure physical basis. It was shown in the past that cuticular permeability for
water and many dissolved compounds can be increased by surfactants
(Riederer and Schönherr 1990). A similar mechanism might be used by
microorganisms, since for many of them it has been shown that they are able
to synthesise biosurfactants (Persson et al. 1988; Bunster et al. 1989; Karanth
et al. 1999). Moreover, it also may not be forgotten that in reality there are living
epidermal cells below the cuticle. They probably will significantly contribute
to inhibiting leaf surface microorganisms from penetrating the cuticle,
which is not the case in the artificial system using isolated cuticular
membranes. Future work will have to concentrate on this important question
of the interaction between epiphyllic microorganisms and the plant cuticle.
6 Conclusions
9 Interactions Between Epiphyllic Microorganisms and Leaf Cuticles 153
Fig. 5. Interaction
between Pseudomonas
fluorescens growing on
isolated cuticles of different
plant species and
cuticular water permeability.
The effect, which
was calculated from the
ratio of cuticular water
permeability after inoculation
divided by cuticular
transpiration before
inoculation, indicates the
relative increase in cuticular
water permeability
after inoculation with
bacteria
effect (P2/P1)
2.5
2.0
1.5
1.0
0.5
0.0
Pseudomonas fluorescens
control
Vinca
major
Hedera
helix can.
Prunus
laurocerasus
In conclusion, it must be stated that lipophilic surfaces of leaves form microhabitats
for many microorganisms, although living conditions in terms of
water and nutrient availability and climatic conditions in the phyllosphere are
far from optimal. Specific interactions between epiphyllic microorganisms
and the plant cuticle, leading to increased leaf surface wetting and elevated
rates of cuticular permeability, have been shown to occur. Nevertheless, there
is still a series of questions which deserves further attention in future
research. Using molecular biological tools, a more realistic description of the