Comparison of the morphology, flowering phenology, and life cycle type in plants of Grindelia lanceolata (Asteraceae) from cedar glades in middle Tennessee and northern Alabama: a common garden study

13 Pages·2003·6.8 MB·English

by  C A Adams

COMPARISON OF THE MORPHOLOGY, FLOWERING
AND
PHENOLOGY, CYCLE TYPE PLANTS OF
LIFE IN
GRINDELIA LANCEOLATA FROM CEDAR
(ASTERACEAE)
AND
GLADES MIDDLE TENNESSEE
IN
COMMON
NORTHERN ALABAMA: A GARDEN STUDY
Adams^
Christopher M.Baskin CBaskin
A. Jerry Carol
Department of Biology Department of Biology Deportment of Biology
Lexington, KY 40506, U.S.A. Lexington, KY 40506, U.S.A. Lexington, KY 40506, U.S.A.
KY
Lexington, 40546,
U.S.A.
ABSTRACT
The
life cycle type of Grindelia lanceolala Nutt. has been described as biennial, short-lived mono-
and
carpic perennial, (polycarpic) perennial in the taxonomic literature. Plants of this species in
middle Tennessee cedar glades clearly are monocarpic. However, observations suggested
field that
those from glades in northern Alabama are at least dicarpic, and further that they differ morpho-
logically and flower later than those in Tennessee glades. The purpose of this study was to deter-
mine
differences in morphology, flowering phenology and/or cycle type of Tennessee and Ala-
if life
bama plants are retained when grown from seeds "common garden" nonheated
in a - in a
i.e.,
greenhouse in Lexington, Kentucky Morphological differences (all statistically significant) between
nam
rosette and stem leaves; (2) ber of secondary basal stems; (3) height of primary stem; (4) number
number and
of capitula per plant; (5) of ray of disk flowers per capitulum; (6) diameter of capitulum;
and (7) length of ray flower corolla Tennessee plants began flowering about month eariier than
1
.
Alabama plants, and none of them produced basal rosettes after they flowered once (in their 2"''
year), confirming that they are strictly monocarpic. Alabama plants also flowered first in their 2"''
66% them
year; however, of have produced basal rosettes (which bolted and flowered) for five con-
secutive growing seasons, confirming that they are polycarpic. Also, individual Tennessee plants
many
potentially can produce twice as seeds as individual Alabama plants during a single flower-
ing/fruiting period. These results strongly suggest genetic differences exist in vegetative and floral
We
lanceolala. speculate that these differences could be associated with different ancestral geographic
origins: Tennessee plants from a monocarpic race in the Ozarks and Alabama plants from a peren-
campo
observaciones de sugieren que aquellas de zor
la
),
mas que morfologicamente que
icas; y alia, difieren y f loi
alcareos de Tennesssee. El proposito de este estudio fue d
fenologia floral y/o tipo de ciclo de vida de plantas de
T{
rmando
que
so
embargo,
sin
(
INTRODUCTION
an herbaceous grows
Grindelia lanceolata Nutt. (Asteraceae) species that in
is
open habitats on shallow soils underlain by limestone (Steyermark 1934, 1937;
Baskin and Baskin geographical range extends from the Ozarks of
1979).
Its
Missouri and southeastern Kansas, south through eastern Oklahoma and north-
ern and western Arkansas, and into northeastern and central Texas (Steyermark
GPFA Nesom
and Smith
Johnston
1934, 1999; Correll 1970; 1986; 1988; 1990).
Nesom (1990) also reports the species from the Monterrey area in Nuevo Leon,
Mexico. Disjunct populations occur in the Central Basin of Tennessee (Chester
1997) and in northern Alabama (Small 1933; Harper 1944), where they are
et
al.
&
associated closely with open cedar glades (Baskin Baskin 1979, 1996; Baskin
Grindelia lanceolata has been reported from Louisiana (Rydberg
et 1995).
al.
1932; Small 1933); however, Gandhi and Thomas (1989) do not list the species in
their recent treatment of the Asteraceae of Louisiana. The species also has been
reported from a single county in southeastern Ohio (Jones 1943; Fisher 1988),
where, apparently, has been introduced (Porter 1956).
it
Nesom
In his taxonomic treatment of Texas species of Grindelia, (1990)
recognized three varieties of G. lanceolata: lanceolata, texana (Scheele)Shinners,
known
and greenei (Steyermark) Nesom, the only from Mexico. However,
latter
Correll and Johnston (1970) did not recognize any separate taxonomic entities
and thus included only G. lanceolata in their treatment. Julian A. Steyermark
listed two forms of G. lanceolata in his Flora of Missouri (1999): lanceolata and
known
latijolia Steyerm., the latter from only one county in Missouri. Small
GPFA
Fernald Gleason Gleason and Cronquist
(1933), (1950), (1963), (1986),
and
(1991), Chester et (1997) do not recognize any intraspecific taxa in G.
al,
lanceolata.
With
regard to life cycle type, G. lanceolata has been reported to be bien-
&
(Rydberg monocarpic
nial 1932), short-lived perennial (Baskin Baskin 1979;
&
GPFA
1986; Gleason Cronquist and (presumably polycarpic) perennial
1991),
and Nesom
(Small 1933; Correll Johnston 1970; Enquist 1987; 1990). In their study
on and
the autecology population biology of G. lanceolata in the limestone ce-
Basm
dar glades of the Central of Tennessee, Baskin and Baskin (1979) found
that plants were short-lived monocarpic perennials plants lived for a few
(i.e.,
years before they bolted and flowered once, and then died). The youngest plants
to flower in the Baskins' study were in their third growing season (2+ years
old).
Other plants in the study flowered in their fourth or fifth year; plants died
all
flowering once monocarpic).
after
(i.e.,
However, during field studies in the limestone cedar glades in northern
Alabama, and Alabama
Baskin Baskin (pers. obs.) noticed that plants of G.
lanceolata differed in morphology, flowering time, and cycle type. In con-
life
trast to plants in Tennessee, rosettes were present on those with dead flowering
Alabama,
stalks in suggesting that this species at least dicarpic in the cedar
is
glades of northern Alabama. The purpose of this study was to determine there
if
are distinct measurable or observable differences in vegetative morphology, flo-
ral morphology, flowering phenology, and/or cycle type between G.
life
lanceolata plants from Tennessee and Alabama cedar To determine
glades.
if
morphology and environmen-
differences in cycle type are genetically-or
life
tally—based, both Tennessee and Alabama plants were grown from seed in a
common common
environment, garden experiment.
a
i.e.,
AND METHODS
MATERIALS
Growth
Conditions
All plants used in this study were grown from seeds in a nonheated greenhouse
m
autumn
in Lexington, KY. Seeds were collected 1996 from G. lanceolata popu-
growing and Alabama and sown
lations in cedar glades in Tennessee (sepa-
rately) on soil in metal flats. The greenhouse soil mix was a 3:1 (v/v) mixture of
and
limestone-derived topsoil river sand. Following germination, juveniles were
num-
transplanted to 15-cm-diameter plastic pots in spring 1997 and assigned a
ber Morphological and cycle features of 103 Alabama plants and of 88 Ten-
life
num-
nessee plants were monitored in this study; plants of both groups were
bered
consecutively.
Temperatures in the nonheated greenhouse were recorded continuously
with an thermograph
electric for the duration of the five-year study period.
From mean maximum minimum
and
these recordings, daily temperatures
for
±
January 6,95
±
February 10.95
±
March
14.48
±
21.92
April
±
May
28.6
±
30.62
±
July 32.13
±
August
31.68
±
September
28.18
± ±
October
20.05 12.6
±
3.03
month
each for each of the five years were determined. These temperatures then
maximum minimum
mean and monthly
were used to calculate (± SE) (±SE)
photon
teinperatures the study (Table Average daily photosynthetic
(°C) for
1).
LI-COR
nonheated measured with
irradiance at plant level in the greenhouse, a
model LI-1000 data logger and three LI-190-SA quantum sensors, ranged from
m
6 mol - d"l on overcast days to 25 mol m"^ d"^ on clear days during the grow-
ing season (March to October) (Snyder et 1994).
al.
and Morphology
Vegetative Floral
To determme morphology, various char-
there are differences in vegetative leaf
if
were compared between two groups Length, width, oven-
acters the of plants.
dry mass, and specific leaf area were determined for leaves collected from the
rosette and from the lower-, middle-, and upper (just below the terminal ca-
pitulum) portions of the main stem. One leaf each from these four regions of
the shoot was removed and measured/ weighed every plant in the study Leaf
for
mm
length and width were measured to the nearest using a standard metric
ruler The width measurement was taken the widest part of the Leaves
at leaf.
were dried in an oven at 70'C for 24 hours, and their dry mass determined with
an analytical balance. Average values for each leaf character were calculated
made
plants in the study Leaf prints were using Diazo-type paper for
lor all
am
monia and was determined by weight
developing, leaf area (one side of leaf)
was
of paper/area print relationships. Specific leaf area (SLA) calculated using
SLA
where
the following equation: = Aieaf/Wieal Aieaf is leaf area (one side only)
SLA
and leaf dry weight. was determined for one leaf from each of the
Wieai is
four shoot levels for each plant in the study, and then average values were cal-
number
each secondary stems
culated leaves of position. In addition, of basal
for
and
height each were determined and means
of plant averages calculated. All
were compared by
t-tests (P=0.05).
Number
of capitula the main stem and secondary stems were
for for all
m
counted and averages calculated for each plant the study. Floral measure-
ments were made on 15 Tennessee plants and on 15 Alabama plants selected
randomly random-numbers Number
using and
a table. of ray disk flowers,
length and width of ray flower corolla, and diameter were measured, to the near-
mm,
est for the terminal capitulum of the main stem of each of the 30 plants.
The
terminal capitulum is always the first to flower on a plant. Capitulum di-
ameter and corolla length and width were measured using a standard metric
ruler and means calculated. All means were compared by
t-tests (P=0.05).
Flowering Phenology
The terminal capitula of the main stems were monitored for flowering. The flow-
ering period in this study extended from the beginning of flowering (indicated
by the first anther of the first disk flower to shed pollen; ray flowers are pistil-
late) in the first plant and ended with the beginning of flowering in the last
plant. Beginning of pollen shed was determined by brushing a finger across the
anthers and observing clumps of the bright yellow pollen adhered
to
if
it.
Seed Production
Potential
number
To assess the reproductive effort of G. lanceolata, potential of seeds per
was number
individual plant calculated. Potential of seeds per individual for
Alabama and was number
for Tennessee plants calculated as follows: Potential
of seeds produced per plant = (Avg. no. capitula per main stem x Avg. no. ray
flowers per capitulum) + (Avg. no. capitula per main stem x Avg. no. disk flow-
ers per capitulum) + (Avg. no. capitula per secondary stem x Avg. no. secondary
stems X Avg. no. ray flowers per capitulum) + (Avg. no. capitula per secondary
stem X Avg. no. secondary stems x Avg. no. disk flowers per capitulum).
and Morphology
Vegetative Floral
SLA
Length, width, dry weight, and of leaves from the rosette, and from the
and upper main
lower-, middle-, portions of the stem, differed significantly
between Tennessee and Alabama plants of G. lanceolata (Table Only rosette
2).
dry weight and length of leaves on the lower portion of the stem were nonsig-
from Alabama had and
nificant. In general, plants longer, wider, heavier
leaves,
a higher SLA, and were than Tennessee However, Tennessee plants
taller plants.
produced significantly more secondary stems than Alabama plants (Table
2).
Tennessee plants produced significantly more capitula per plant on both
main stems and secondary, basal stems than did Alabama plants (Table Av-
3).
erage number of capitula per main stem and per secondary stem was signifi-
Alabama
cantly higher for Tennessee plants. plants produced larger capitula
SLA (cm7g)
±
0.057 0.004
Secondary Stems
No.
greater diameter) and more ray flowers per capitulum than did Tennessee
(i.e.,
Number
between
plants. of disk flowers, however, did not differ significantly
the two groups. Ray flowers from Alabama plants had longer petals than Ten-
m
was no width between two
nessee plants, but there difference petal the groups.
Flowering Phenology
All plants from both groups bolted and flowered in their second year Flower-
ing in Tennessee plants began on July 1998, and all terminal flowers of main
1
stems had flowered by August 1998 flowering Alabama
5 (Fig. In contrast, in
1).
plants began and ended on 26July and 7 September, respectively For both groups,
capitula elsewhere on the main stem and on secondary stems continued
to
from Tennessee and Alabama./
?olata plants
number produced by
of capitula plants.,
all
=
whereas
ficantly different test, P 0.05), N!
(t
Te^e..
Alabama
Character Signif. Level
Produced
Total No. Capitula
":
sf
Secondary Stems
Produced
No. Capitula
Main Stem
^
:::^;.3
Secondary Stems : Is :
No. Ray Flowers
m
± 34 NS 252 ±
71
Capitulum Diameter (cm) ± ±
4.4 0.2 5.7 0.5
main
flower 1-2 weeks following the beginning of anthesis of the last terminal
smgle
After completion of flowering, Tennessee plants (n=88) died; not a
all
many
one produced a new basal rosette. However, Alabama plants continued
new
to produce rosettes and to bolt and flower over the course of the five-year
One-hundred and Alabama and
study period three plants bolted
(Figs.
2).
1,
m m
flowered 1998, 78 1999, 74 in 2000, 73 in 2001, and 68 in 2002 (Fig. 2).
m m
Flowering period duration was 43 days in 1998, 48 1999, 43 2000, 39 in
m
and 44 2002 Length flowering period 1998 was 36 days
2001, in (Fig. of for
1).
and
Tennessee plants (Fig. Flowering (both terminal all other capitula) for
1).
both groups had been completed by mid-September.
Seed Production Potential
An
individual Tennessee plant had the potential to produce an average of 3,128
Alabama had produce only
seeds, while a single plant the potential to 1,568 seeds.
DISCUSSION
and Baskm Alabama appeared
Observations by Baskin that G. lanceolata plants
and from
to be distinct in morphology, flowering time, life cycle type those in
Alabama
Tennessee were supported by the results of this study. plants are taller
One more
and have larger leaves than Tennessee plants. of the striking differ-
number
ences between the two groups the of secondary basal stems. Tennes-
is
many
see plants produce more than two times as secondary basal stems as do
Alabama giving them suffrutescent-like appearance. Indeed, Tennessee
plants, a
IS
g i ^
b:
r^ £r 3
B
I
lllfl
IJ
Rosettes
Produced
No. Plants
Flower
in
Number
of seeds per plant produced during a single reproductive event
m
was monocarpic
considerably higher the perennial ("biennial") plants (Ten-
nessee) than in the polycarpic plants (Alabama). Salisbury (1942) reported that
many
biennials in Great Britain produced an average of more than four times as
Duffy monocarpic
seeds as did polycarpic perennials. (1999) predicted that
et
al.
species should maximize the number of meristems branches) devoted to
(i.e.,
many
which would
reproduction, allocate as reserves as possible to reproduc-
tive effort since there only one reproductive event. Conversely, they predicted
is
that polycarpic perennials should maximize the number of growth meristems
premium on and
(but not reproductive ones) since there a fitness longevity
is
many
competitive ability. Tennessee plants produced 2.2 times as secondary
which Alabama As
basal stems, all ot flowered, as did plants. a result, Tennes-
see plants produced, on average, significantly more capitula and had the po-
many
Alabama
tential to produce almost twice as seeds as did plants. Thus,
Tennessee plants obviously devoted more energy to reproductive meristems
than did Alabama which devoted more energy growth height and
plants, to in
Whereas ma-
perennation. all Tennessee plants died after flowering once, the
jority of Alabama plants continued to flower each year for several years. By pro-
new
Alabama
ducing fewer flowers, plants have reserve energy production of
for
rosettes perennation), which also should be considered growth meristems.
(i.e.,
number
Thus, there a tradeoff between of seeds produced per reproductive
is
and an
event lifespan of individual.
A
very interesting difference between Tennessee and Alabama plants
is life
cycle type. In the nonheated greenhouse, both Tennessee and Alabama plants
bolted and flowered in their second year However, whereas 88 Tennessee
all
Alabama
plants died after they reproduced once, only 13 of 103 plants did
so.
100% 13% Alabama
Thus, of the Tennessee plants, but only of the plants, be-
haved Another 12% Alabama were 12% were
as biennials. of the plants dicarpic,
and 1% dying and
tricarpic, tetracarpic, after their third, fourth, fifth years, re-
Alabama
spectively. Sixty-six percent of the original 103 plants have flowered
in their second, third, fourth, fifth, and sixth years, and it is expected that most
of them could survive and flower for the next several growing seasons.
Apparently, differences in morphology, flowering time, and cycle type
life
Alabama
between Tennessee and plants are genetically-based, since they were
m
common
grown
maintained plants from seeds environment. However,
in a
the advantage, any, for G. ianceolata behaving as a short-lived monocarpic
if
perennial in Tennessee glades, and of behaving as a polycarpic perennial in
it
m
the cedar glades northern Alabama, not known, Floristically and
is
Alabama
vegetationally, cedar glades of northern are very similar to those in
&
Baskm Baskm
central Tennessee (Baskin et al. 1995; 1999, in press). Further,