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r9961 FISHER
ET AL.: STEM STRUCTURE
OF GASTROCOCOS t25
Principes, 40(3), I996, pp. 125-128
Stem Structure of the Cuban
Belly Palm
(Gastrococos
crispa)
Jecx B. FrsHER,r
Jeuns
N. Buncu, eno Lenny R. Nosrtcr2
tFairchild Tropical Garden, 11935 Old Cutler Road, Miami, Florida 33156; and. Department of Biological,
S ciences, Flnrid.a Inter national Uniaer sity, Miam.i, Florid.a 33 I 99
ABSTRACT
Tissue samples were taken from the periphery and center
of a single trunk with a pronounced swelling (three times the
basal stem diameter) halfway up the trunk. In the hard periph-
eral region, fresh density increased and percent water content
decreased from the upper to the lower levels of the trunk. In
the trunk center, fresh densities
of upper and lower levels
were
similar and twice that of the swollen middle level. The dry
density of the trunk center was greatest at the base, which
was l0 times that of the swollen middle level. Percent water
content of the trunk center at the middle level was about twice
that of the lower and one+hird more than the upper level. The
observations
on density and anatomy support the view that the
peripheral ring of lignified tissue is the main mechanical tissue
in the trunk. The swollen region had little or no starch and is
the main water-storing region of the trunk.
The localized trunl< swellings in some palms
have long attracted the interest of botanists and
palm enthusiasts.
The Cuban belly palm, Gastro-
cocos
crispa(Kunth) H. E. Moore (formerly Acro-
cotnia. crispa (Kunth) Baker ex Becc.) with its
pronounced trunk swelling is a fine example. The
spongy tissue that makes up the bulk of the swell-
ing is assumed to be an adaptation for water stor-
age in this endemic from seasonally dry areas of
Cuba. However, we found no published informa-
tion on the structure or density of the tnrnk of
this species. There are no documented observa-
tions as to how the swelling develops: whether it
is a result of primary growth within the leaf crown
or whether it develops by later thickening when
the region is older and some distance below the
leaf crown (Tomlinson
1990: p. l?l).
On 24 August 1992 a mature specimen of
Gastrococos
growing on the grotrnds of The Mont-
gomery Foundation in Miami, Florida was blown
down
during Hurricane Andrew. This presented
a
I Correspondence
to the Fairchild Tropical Garden address.
' Present address: Montgomery Foundation, I l90l Old Cut.
ler Road, Miami, Florida 33156.
unique research opportunity to collect and exam-
ine trunk material of a precious horticultural spec-
imen that would not otherwise be sacrificed for
study. The effects of Hurricane Andrew have
already been described (Klein 1992) and illus-
trated on the cover of the October 1992 issue of
Principes.
Materials and Methods
A tree of Gastrococos
crispa (FTG 9t-4264)
estimated
at over 40 years old was collected at
The Montgomery Foundation, Miami, Florida on
19 September
1992, more than 3 wk after it was
blown down. The leaf crown was still green and
had l7 expanded leaves and three spear leaves.
The trunk was cut with a chain saw (Fig. l). Six
small samples were collected from the periphery
and center of each of three disks cut from lower.
middle (swollen), and upper levels of the tmnk.
The lower level was I80 cm long and cylindrical
with a diameter of. 25 cm. The middle, swollen
level was 460 cm long with a maximum diameter
of 70 cm. The upper level was 260 cm (to the
l. Collecting trunk samples of. Gastrococos. Entire lower
region (held by J. Burch on left), half of the swollen middle
region (held by L. Noblick on right).
r26 PRINCIPES [Vor. 40
2 5. Cross sections of trunk tissue. 2. Peripheral vascular bundle of upper trunk; note region of very thick-walled fibers
and starch
grains inside cells
ofthe ground tissue. 3. Peripheral ground tissue
ofmiddle trunk; starch grains absent. 4. Central
vascular bundle of lower trunk. 5. Central vascular bundles and ground tissue of upper trunk, stained with IrKI that stains
starch
grains
black.
F, fibers; G, ground
tissue; V, vascular bundle.
Bars: 50 p'm(2,3, 4); I00 pm (5).
base of the leaf crown) and cylindrical with a
diameter
of 2l cm.
The tissue samples were weighed fresh and their
volume
calculated by water displacement
(adjusted
for water absorption into the spongy tissue by
reweighing after volume measurements). The sam-
ples were dried in a 75"C oven for 4 wk and
weighed.
Adjacent tissue samples were preserved
in FAA
(formalin-alcohol-acetic
acid) and stored in 70%
ethanol. Sections
were later cut with a razor by
hand and stained with aqueous
toluidine blue for
ree6l FISHER ET AL.: STEM STRUCTURE
OF GASTROCOCOS t27
6,7. Central ground tissue oftrunk in cross section. 6. Lower trunk; note thick cell walls. 7. Swollen, middle trunk;
note larger cells with thinner walls that collapsed
during preparation, Bar: 50 pm (6, 7).
general anatomy, with I,KI solution for starch,
and with phloroglucinol-HCl for lignin. Some blocks
of tissue were air-dried, sputter coated with gold-
palladium, and observed
with a scanning electron
microscope
(I.S.I. Model Super IIIA).
Results
Anatomy. The peripheral region of the trunk
was dense and extremely hard throughout its
length. Vascular bundles were arranged close
together, and each had a wide zone of thick-walled
fibers (Fig. 2). The cells of the ground tissue
between the vascular bundles were thick-walled
and lignified (fig. 3). The hardest
tissues with the
thickest-walled fibers and ground
parenchyma cells
were at the lower level of the trunk. The cell
Iumen was barely visible in each fiber (Fig. 2).
The trunk center had more diffuse vascular
bundles, each with a wide fiber zone (Fig. ).
Bundle density was similar in the upper and lower
levels and was least in the swollen middle level.
The cells of the central ground tissue
(Fig. 4) were
more radialy elongated than in the periphery. The
cell walls were thickest and most lignified at the
lowest
level (Fig. 6). Walls are thinnest and unlig-
nified at the middle level (Fig. 7). Intercellular
spaces, which impart the spongy consistency to
the tissue, were most numerous at the middle level
and related to the elongated shape of these cells.
It was difficult to cut the central part of the middle
region without crushing because the tough fiber
bundles were imbedded within the soft spongy
ground tissue.
Chemical tests for starch
(IrKI solution) showed
that large amounts of starch occurred
in the upper
level of the trunk in the ground cells of the periph-
eral and central regions
(Figs.
2,5). No starch was
present within the vascular bundles. We found
from little to essentially no starch in the lower and
middle levels of the trunk (fig. 3). The spongy
central tissue in the swollen middle level lacked
starch but had small cytoplasmic structures that
were possibly plastids or lipid droplets.
Tissue Density. Fresh and dry tissue densities
were directly correlated to the relative wall thick-
ness and lignification in the fibers and ground
tissue (Table l). The most dense tissue was the
peripheral region of the lower level. The least
dense tissue occurred in the central region of the
middle level. The maximum difference in periph-
eral dry density was 7:I0 (middle
to lower). The
maximum difference in central drv densitv was
approximately l:10 (middle to lower). Percent
water content was greatest in the central middle
region, twice that of the central lower and one-
third more than that of the central upper region
(Table I).
128 PRINCIPES lVoL. 40
Fresh
Level in Density
Trunk (g/cm3)
D.y Water
Densitya Content
(g/cm3) (percent)
Table l. Comparisons
of trunk tissues in the
trunk of Gastrococus
crispa. Auerages of six tis-
sue sanples are giuen
for each location.
Prolonged expansion
and cell division within the
ground tissue of the central region of the trunk
of.
Archonto phoenix were demonstrated
convinc-
ingly by Waterhouse
and
Quinn
(I978). However,
the timing of such ground cell expansion,
whether
within or below the crown, is undocumented
for
Gastrococos.
The suggestion
that the swollen region acts as
a o'bottle" to store water is supported
by the high
percentage
of water contained
in the spongy
cen-
tral tissues.
Acknowledgments
This research was supported by grants from
the National Science Foundation (grant DEB-
9224126) and The John D. and Catherine T.
MacArthur Foundation. Larry Noblick was sup-
ported by a Montgomery Foundation
postdoctoral
fellowship. We thank Birgith Phillips for technical
assistance
and George Taylor for help with the
SEM.
LrrnRerunr Ctruo
Krrm, W. M., JR. 1992. Fairchild Tropical Garden
hit by
Hurricane
Andrew.
Principes 36: 225-227.
RIcu, Peul M. 1986. Mechanical
architecture of arbores-
cent
rain forest palms.
Principes 30: I l7-131.
I987a. Developmental anatomy of the stem of
Welfia georgii, Iriartea gigantea, and other arborescent
palms:
implications
for mechanical
support. Amer. J. Bot.
74: 792-802.
1987b. Mechanical structure of the stem of arbo-
rescent palms.
Bot. G..az. 148: 42-5O.
ScHourE,
J. C. I9I2. Uber das Dickenwachstum
der Pal-
men. Ann. Jard. Bot. Buitenzorg, 56r. 2. ll: I-209.
ToMLINSoN,
P. B. 1990. The structural biology of palms.
Clarenden
Press,
Oxford.
WArERHousE,
J. T., AND C. J. QuInn. 1978. Growth pat-
terns in the stem of the palm Archontophoenix cun'
ninshanLiana.
Bot. J. Linn. Soc.77:73-93.
Lower 1.264a
Middle I.l7 2b
Upper \.l44b
Periphery of trunk
Center o{ trunk
1.0lla 20.0a
0.692b 4r.1b
0.693b 38.9b
Lower
Middle
Upper
0.893a
0.4r8b 0.483a
0.048b 46.0a
88.5b
62.2c
0.807c 0.305c
Within each column, values followed by the same letter are
not significantly different (using an F test with P : 0.00I).
Periphery and center regions are compared separately.
u Presented
as dry mass per original fresh mass.
Discussion
The dense,
lignified peripheral tissues form a
cylinder of supporting tissue in the trunk. The
density of older tissues
increases
at the base of
the trunk, as
in other palms
(Rich 1986, I987a,
b). The cell walls of fibers and parenchyma cells
(ground tissue),
which appear to remain alive for
the life of the palm, increase in thickness and
degree of lignification as they age' Thus, the
mechanical
strength
of the trunl<
increases
at lower
Ievels
as the trunk grows taller.
In Gastrococos.
the swollen middle level is a
result
of ground
tissue cells
becoming
radially elon-
gated
with these
thin-walled,
unlignified
cells
radi-
ating around each of the vascular bundles
in the
cential region, similar to other palms vrith soft,
spongy trunk centerse
€.g., Socra'tea'
(Tomlinson
I 990) and Roystonea
(Oredodoxa),
Caryota, and
Ptychos
p
erma (Actino
phloeus)
(Schoute
I 9
t 2).
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