Mycorrhizal Status of Obligate and Facultative Epiphytic Ferns in a Valdivian Temperate Forest of Patagonia, Argentina

2010·6 MB·English

by  Natalia Fernández

Mycorrhizal and
Status of Obligate Facultative
Epiphytic Ferns in a Valdivian Temperate
Forest of
Patagonia, Argentina
Natalia FernAndez* and Sonia Fontenla
Dep.
Biologi'a General, Laboratorio de Microbiologi'a Aplicada de
Biotecnologi'a, Institute
y
Investigaciones en Biodiversidad Medioambiente (INIBIOMA), CONICET - UNComahue,
y
Quintral 1250, C. de Bariloche (R8400 FRF), Negro, Argentina
S.
Ri'o
Mari'a Ines Messuti
Dep.
Botanica, Institute de Investigaciones en Biodiversidad Medioambiente (INIBIOMA),
y
CONICET
- UNComahue,
Quintral 1250, S. C. de Bariloche (R8400 FRF), Rio Negro, Argentina
Autotrophic epiphytes grow upon which
are plants that other plants only
provide physical support and are not parasitized. Plants restricted to epiphytic
habitats are called "obligate epiphytes" and those that occur both epiphyti-
and known
cally
terrestrially are as "facultative epiphytes" (Benzing, 1990;
10%
Janos, 1993). Vascular epiphytes approximately
constitute of vascular
all
and
flora (Kress, 1986) play an important dynamics by
role in forest
contributing to species richness and by trapping and storing atmospheric
making them
nutrients, temporally unavailable
to terrestrial plants (Benzing,
1990).
* Corresponding Author: Tel.: [phone]/423374 (int.102), e-mail: natifern@yahoo.
FERNANDEZ
ET MYCORRHIZAL STATUS OF
AL.: EPIPHYTIC FERNS
Mycorrhizae
generally influence plant fitness by improving nutrient uptake
and
increasing plant resistance to drought and other environmental
stress
factors (Smith and Read, 1997; Read, 1999). Despite the importance and
abundance known
of epiphytes, about mycorrhizal
little is associations in these
(Bermudes and
plants Benzing, Allen
1989; etal., 1993; Janos, 1993; Michelsen,
Epiphytic
1993). habitats are usually considered extreme environments
for
plants because they
often are subjected to great variation in temperature and in
water and
nutrient availability (Benzing, 1990). Therefore, generally
is
it
may
expected that mycorrhizae be an important adaptation epiphytes
for
(Benzing, 1990; Lesica and Antibus, 1990; Janos, 1993; Rains
et al, 2003).
Nevertheless, has been observed
it that epiphytic species are usually non-
mycorrhizal (Allen (commonly
et al, 1993), facultative mycorrhizal mycorrhizal
when
grow
they and when
terrestrially inconsistently mycorrhizal they grow
epiphytically) (Maffia et al, 1993; Michelsen, 1993; Nadarajah and Nawawi,
and when AM,
1993), that they have colonization usually low (Bermudes and
is
Benzing, and Rowe
1989; Lesica Antibus, and
1990;
Pringle, 2005).
Studies concerning the occurrence of mycorrhizae in epiphytes are few and
only the Orchidaceae and Ericaceae have been
families relatively well studied
(Bermudes and
Benzing, and
1989; Lesica Antibus, 1990; Dearnaley,
2007).
Some
species included in the Bromeliaceae (Allen 1993; Rabatin
et al., et al,
Rowe
and
1993; Pringle, 2005) and other predominant famiHes
of vascular
epiphytes (such as the Araceae, Cyclanthaceae and Piperaceae) have been
also
analyzed (Bermudes and
Benzing, and
1989; Lesica Antibus,
1990; Janos, 1993;
Maffia et al., 1993; Michelsen, 1993). However, the mycorrhizal status of
epiphytic species included in families other than those mentioned here
remains an open much more
question. Therefore, information needed
before
is
generalizations about mycorrhizae in epiphytic environments can be made
(Bermudes and
Benzing, 1989; Allen
et al, 1993; Janos, 1993).
Abundant
among
epiphytes are present the vegetation of the Valdivian
temperate forests of South America. Within these forests, seedless vascular
mostly
plants, ferns (monilophytes, see Pryer 2004 and Smith
et al., et al., 2006),
one most
are of the important components The
of the epiphytic vascular
flora.
mycorrhizal group
status of this of plants poorly understood (Dhillion, 1993;
is
much
Zhao, and known
2000) about symbiosis
less is this in epiphytic species.
This research was conducted where
in Puerto Blest, previous studies have
AM
demonstrated
the presence
of in different plant species (Chaia
et 2006),
al.,
HBK
including Equisetum bogotense and Lycopodium paniculatum
Desv. ex
two
Poir., species of seedless vascular plants which were found be
to
facultative mycorrhizal (Fernandez The aim
et 2008). of the present study
al.,
AM
was
to analyze the occurrence of in sporophytes of different obligate and
facultative epiphytic
fern species.
Materials and Methods
Study area.—The
Valdivian temperate South America
forests of are included
in the Subantarctic Province (Subantarctic Domain, Antarctic Region). This
AMERICAN FERN VOLUME NUMBER
JOURNAL:
100
1 (2010)
/
\
(ieographical location
•ic. 1 of
tl
.
jointed out in a black rectangle,
L
ecoregion located in the Southern region of Argentina and Chile, from 35°
is to
48 S latitude between the Eastern slope of the Andes and the Pacific Ocean.
W)
Puerto Blest (4r 02' S, 71 49' part of the Valdivian temperate forest
is
region of Argentina and situated within the Nahuel Huapi National Park in
it is
Negro
Province, Patagonia Armesto
Ri'o (Cabrera, 1976; et aL, 1995) (Fig.
1). It
one
is of the rainiest places in the country, with an average annual rainfall of
mm
3000 and an annual average temperature 9^ The dominant
of C. tree
species hydrophilic Nothofagus dombeyi some
in this forest (Mirb.) Oerst. In
is
mixed IM
areas, this species forms forests with Fitzroya cupressoides (Molina)
Johnst., Saxegothaea conspicua Lindl., Dasyphyllum diacanthoides (Less.)
and Schodde
Cabrera, Laureliopsis philippiana (Looser) (Dimitri, 1972; Brion
et ai, 1988; Correa, 1998). Trunks and branches of these tree species are
usually covered by different epiphytes, including lichens, mosses and several
ferns. Epiphytic ferns present in Puerto Blest are small plants that range in size
from
20 cm.
2 to
—
Sampling. Five samplings were conducted Puerto between
in Blest spring
2004 and autumn
2006. Sporophytes of epiphytic ferns were sampled by
random
walk from trunks and branches of different tree species, such as N.
dombeyi, S. conspicua, D. diacanthoides and philippiana, which were
L.
m
away The
situated at least 5 from the footpath. epiph5^ic specimens were
m
collected from 0.5 to 2 height above the ground. Species that were found to
be also growing on the forest soil were considered as facultative epiphytes and
root samples were collected from epiphytic as well as from the conspecific
FERNANDEZ
ET MYCORRHIZAL STATUS OF
AL.: EPIPHYTIC FERNS
One
specimens. Hymenophyllum
terrestrial individual of dentatum,
a species
that is reported to be epiphytic (Rodriguez, 1995) but was found only on the
was
ground,
also sampled.
Sporophytes were removed
carefully from the substrate in order to preserve
most of the root system and were stored in labeled plastic bags and refrigerated
4°C
at until processed. Roots from samples were separated from
all the rest of
washed and
the plant, carefully cleaned under
a stereoscopic microscope
(Olympus SZ
remove
30) so as to all root pieces belonging to other plants.
Samples were 70%
fixed
in formalin-acetic acid-alcohol (FAA).
Analyses samples.—
of the All samples were stained using modified
a
Hayman
and method
Phillips Fernandez
(1970) (see et al, 2008). For each
individual three slides were made, each of them with ten stained root pieces of
cm
approximately mounted
1 length in glycerol. Root pieces were examined
with a light microscope (Olympus BX40) 20 X magnification. The
at criterion
AM
used in this study for the determination of was the presence of arbuscules
AM
one
in at least individual of each species. Structures corresponding
to or
other root fungi were documented as brightfield images, which were captured
with a camera (Sony ExwaveHAD) and
digital Image-Pro Plus
4.1.0.0. analysis
Windows.
software
for
Results
A
of 66 sporophytes belonging
total to ten species in three families were
Ten
sampled. specimens (15%) corresponded Asplenium
to dareoides, eight
(12%) to Grammitis magellanica and 48 (73%) to various species of the family
Hymenophyllaceae.
In Puerto Blest, A. dareoides and G. magellanica are the
only representatives of the Aspleniaceae and Polypodiaceae
families respec-
tively (Brion et al, 1988; de la Sota et al., 1998). At least five sporophytes were
found most
for of the species, except for H. cuneatum, H. falklandicum and H.
which
ferrugineum, were represented by only one two specimens
or (Table
1).
Most
of the samples (73%) were collected from epiphytic and we
habitats
observed that they frequently had attached
soil particles to the outside of the
probably consequence
roots, as a of their proximity to the ground. Terrestrial
sporophytes (27%) were from
collected loose organic with abundant
soils leaf
wood
and
them
litter, 2 (11%) of belonged to A. dareoides and 16 (89%)
to five
Hymenophyllum
species of (Table All the sporophytes examined presented
1).
mm
extensive, thin (less than 2 wide) and fibrous root systems with abundant
and
root hairs. Baylis (1975) John described system
St. (1980) this root
morphology
"graminoid".
as
AM
Most
of the sporophytes lacked structures, but in seven terrestrial
samples (11%
of the total specimens analyzed), corresponding H.
to
pectinatum and
H. seselifolium (Table scarce knobby hyphae and
1),
5%
structures similar to coils and vesicles were observed (less than of the
root length examined) (Fig. However, arbuscules were not detected in any
2).
of these specimens, so questionable these plants can be designated
it is if as
mycorrhizal.
AMERICAN FERN VOLUME NUMBER
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100
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Abundant and hyphae and
extra- intracellular of regularly septate generally
melanized
fungi frequently associated with microsclerotia and "cerebriform
were They
structures" present in root systems corresponded
all (Fig. to
3].
named
dematiaceous endophytes
root usually dark septate fungi (DSF).
Discussion
Of
examined
the ten species in the present study, G. magellanica and
S.
caespitosa were found to be obligate epiphytes (only growing as epiphytes),
while A. dareoides and five species of Hymenophyllum [H. cuneatum, H.
pectinatum, H. seselifolium, H. tortuosum and H. umbratile] were facultative
epiphytes (growing These
either epiphytically or terrestrially). observations
who
agree with de la Sota et (1998), described the same habits for these
al.
We
species. considered H. cuneatum as facultative epiphytic even though only
one terrestrial sporophyte was collected because described as epiphytic in
is
it
Hymenophyllum
the literature (Rodriguez, 1995). falklandicum and H.
ferrugineum could not be classified as obligate or facultative epiphytes
because only one or two individuals per species were found (Table
1).
Representatives of the Aspleniaceae, Polypodiaceae and most of the
AM
Hymenophyllaceae
families in Puerto Blest clearly lack colonization.
Chaia and Fernandez observed
et al. (2006) et al. (2008) that different plant
AM.
species growing in areas adjacent our study had Furthermore,
to site
AM
Chaia found
et al. (2006) out that in Puerto Blest the soil infective capacity
ranges from lU These
0.6 to 1.7 g/soil. findings indirectly demonstrate that
FERNANDEZ
ET AL.: MYCORRHIZAL STATUS OF EPIPHYTIC FERNS
Fungal colonization
Fig. 2. similar to arlniscular nivcoirhizas in //. pectinatum (a,b) and H.
seselitnhum and
(c,fl). a: Extra intracelhilar mycelia wliorc soine sopta can be observed,
b,c:
AM
inoculum where
there in the the samples were However,
is soil collected.
specimens
terrestrial of A. dareoides, H. cuneatum, H. tortuosum and
H.
AM
umhratile did not form despite the presence of inoculum in the which
soil,
supports the non-mycorrhizal behavior of these species. Even though we found
structures similar to vesicles and coils in roots of four out of
five terrestrial
sporophytes of H. pectinatum and in three out of seven sporophytes
terrestrial
of H. seselifolium (Fig. was not possible to record them as mycorrhizal
2), it
because arbuscules (the diagnostic feature of the symbiosis) were absent and
the colonization percentage was very low than
5%). Additionally,
(less
is
it
known
some
that other fungi are capable of forming structures similar those
to
AM
within some Rowe
of roots of epiphytic plants (Brundrett, 2002; and
These
Pringle, 2005]. structures can also stain dark blue (Fig. 2c,d) and in
AM
may
consequence they be mistaken The
for (Janos, 1993). presence of such
fungi could explain the presence of this type of structures in roots of H.
pectinatum and
H.
seselifolium.
The
absence of mycorrhizae in the epiphytic fern species examined
in
this
work
is concordant with previous studies that have analyzed this symbiosis
in
Gemma
other species belonging to the same families (Cooper, 1977;
et al,
Wang
1992; Zhao, 2000; and Qiu, but from some
2006), differs others have
that
AMERICAN VOLUME NUMBER
FERN [OURNAL:
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100
(2010)
1
Dark
Fk;. 3. soptato lungi in roots of opipinytic: t<iriis of Puerto Blest, a: Extraradical hypha and
intracelkilar microsclerotia in S. caespitosa, b: General view of extraradical DSF colonization in G.
^
a=50
Scale ^m; b,c=100
bars: d,e,f=20
\im;
urn.
AM
reported the occurrence same group
of in the of plants (Cooper, 1976; Iqbal
Gemma
Muthukumar
and
et al, 1981; et 1992; Udaiyan, 2000; Zhao, 2000;
al.,
Wang
and Our
Qiu, 2006). results are also consistent with Lesica and Antibus
who
and
Michelsen examined and
(1990) (1993), 13 eight species of epiphytic
ferns in Costa Rica and Ethiopia respectively (including five species of
Asplenium and one Hymenophyllum] and them
of described non-
as
,
Nawawi
mycorrhizal. Nadarajah and
(1993) studied the mycorrhizal status of
They
19 fern species in Malaysia. observed that these species were non-
all
AM
mycorrhizal in epiphytic habitats and that eight of them were able form
to
when
and/or were
vesicles coils they rooted in Nevertheless,
soil. as
it
occurred in this work, these authors did not detect arbuscules in any of the
AM
Although has been suggested by several authors that are generally
it
absent (Allen et al, 1993) or rare (Bermudes and Benzing, 1989; Lesica and
Antibus, 1990; Maffia et al, 1993, 2000; Michelsen, 1993; Nadarajah and
Nawawi,
1993) in epiphytes. Rains et (2003) found abundant mycorrhizal
al.
epiphytes in a Costa Rican cloud forest. This apparent discrepancy suggests
and
that the occurrence, possibly the role, of mycorrhizae in epiphytic habitats
may
is variable and be related to taxonomic affinities and diverse ecological
and
factors (Tester et 1987; Lesica Antibus, 1990; Michelsen, 1993).
al.,
AM
Different explanations have been suggested for the paucity of in
epiphytic For example, might be environments
habitats. that these are too
it
dry and exposed support fungus
to the or that the rate of photosynthesis
FERNANDEZ ET MYCORRHIZAL STATUS OF
AL.: EPIPHYTIC FERNS
(which low may
is relatively in epiphytes, see Benzing, 1986) be insufficient
to
maintain the symbiosis (Lesica and Antibus,
1990). Nutritional insufficiency,
and
consequently
the inability to sustain the energy cost of mycorrhizae, has
been
also suggested as a major factor determining mycorrhizal success
in
epiphytes (Benzing, Some
1990; Janos, 1993). substrate analyses have
demonstrated that trunks and canopy mats might be (Bermudes
nutrient rich
and
Benzing, 1989; Lesica and Antibus, and known
1990), high
that
it is
AM
suppresses
fertility of facultatively mycotrophic species
(Janos, 2007).
AM
Another widespread
explanation
is that epiphytic habitats are deficient in
inocula, so epiphytes usually do not have the opportunity of being colonized
by mycorrhizal and
fungi (Lesica Antibus,
1990; Janos, 1993; Michelsen,
1993).
This
suggestion contrasts with several authors (Mcllveen and
Cole, 1976;
Rabatin Mangan who
et ah, 1993; Janos et al, 1995; and Adler, 2000) have
AM
may
reported that spores and mycelia be dispersed
epiphytic
to
environments by
several vectors mainly and mammals).
birds, ants small
(e.g.,
AM
Moreover, other studies have established that many epiphytes lack despite
the presence of spores and external mycelia in the substrate (Lesica and
Antibus, 1990; Maffia et al, 1993; Rabatin et ah, 1993).
was
In study compare
this it possible to the mycorrhizal status of six
facultative epiphytic fern species. In the case oi A. dareoides, H. cuneatum, H.
tortuosum and AM,
H. umbratile specimens lacked and most
all in of the
terrestrial sporophytes of H. pectinatum (73%) and H.
seselifolium (73%)
AM
fungal structures similar to those of were completely absent. Therefore,
AM
deficiencies in inocula or in nutrient acquisition (which not
are limiting
when
factors plants are rooted in as has been demonstrated previous
soil, in
studies carried out Puerto would
in Blest) not explain the non-mycorrhizal
behavior observed
in these plants. Thus, is necessary to seek other
it
explanations phenomenon. Another
for this factor that might explain the
AM
absence
of in epiphytic ferns of Puerto Blest root system morphology.
is
Plants with long root length (Koide and 1991; Ryser and Lambers,
Li, 1995),
small root diameter (Reinhardt and Manjunath and
Miller, 1990; Habte, 1991;
Hetrick and abundant
et al., 1992) long root hairs (Baylis, 1975; John, 1980;
St.
Schweiger
et al, 1995), like those observed in this study ("graminoid roots"),
tend to be non-mycorrhizal
(Baylis, 1975; John, 1980; Hetrick, 1991;
St.
Michelsen, Zangaro
1993;
et 2005).
al.,
Dark
septate fungi (DSF) are conidial or sterile fungi that have been reported
in several plant species from (Jumpponen and
different habitats Trappe,
1998;
Jumpponen,
2001). Characteristic and hyphae and
inter- intracellular micro-
DSF
sclerotia corresponding to were observed in every specimen analyzed
in
work
this (Fig. 3). This is in accordance with previous studies that have
reported
the existence of this type of fungi within the roots of angiosperm
epiphytes (Bermudes and
Benzing, 1989; Allen
et 1993; Janos, 1993; Rains
al.,
and
et al., 1993) several fern species (Cooper, 1976; Dhillion, 1993; Fernandez
The
presence
et al., 2008). of "cerebriform microsclerotia" (Fig. has not
2f)
been
described
in the literature before, except in bogotense and
E.
L.
paniculatum, two
facultative mycorrhizal species also studied in Puerto
Blest
AMERICAN FERN
JOURNAL:
The DSF
(Fernandez et al, 2008). presence of within the roots of different fern
species demonstrates that these plants are capable of forming plant-fungal
associations with a diversity of fungal lineages (Winther and Friedman, 2007).
AM
According to Allen et al. (1993) and Rains et al. (2003), the lack of in most
DSF many
of the epiphytes in addition to the occurrence of in of them
is
and may DSF may
notable suggest that function as "mycorrhizal fungi", but
study needed
further hypothesis.
to test this
is
This study provides novel information about the occurrence of mycorrhizae
and work which
in epiphytic ferns the in the mycorrhizal status of
first
it
epiphytic species of Patagonia, Argentina recorded. More work on
a larger
is
needed
scale not only for understanding the behavior of epiphytic species of
is
Puerto Blest but also for developing patterns of mycorrhizal activity in
and
epiphytic habitats for determining ecological explanations for the paucity
AM
and
of in these plants (Lesica Antibus, 1990; Allen et 1993; Nadarajah
al.,
and Nawawi,
1993).
FERNANDEZ ET AL.: MYCORRHIZAL STATUS OF EPIPHYTIC FERNS