A Revision of Panicum Subgenus Phanopyrum Section Laxa (Poaceae: Panicoideae: Paniceae)

49 Pages·1992·34.5 MB·

by  Fernando O Zuloaga

772 Annals
of the
Garden
Missouri Botanical
I
spikelets are paired on second-order branches, will Tliree-flowered spikelets were occasionally ob-
i
grumosum,
these branches unilaterally disposed in relation to served in specimens of P. e.g., Quarin
2745
the first-order ones; the second-order branches are et al, and Milldn 568, with anthecium
I
appressed or divergent from the axis of first-order neuter, while anthecium II and upper anthecium
lemma
branches, and there variation in the length of were bisexual, the two latter with the and
is
the second-order branches, which gives the palea indurate.
inflo-
more
rescence a or lax appearance.
less
UPPER ANTHECIUM TEXTURE AND
ORNAMENTATION
SPIKELET
(fIG. 1)
The spikelet in section Laxa has the typical The epidermis of the lemma and palea has rect-
structure angular long arranged in longitudinal rows,
cells
two anthecia, the lower one with a lemma and with with longitudinal and transverse anticlinal walls
or without a palea, the flower present or absent, strongly undulated. Stomata, simple papillae, prick-
being male when present; the upper anthecium and bodies are present in species of
le hairs, silica
is
lemm
section
this
among
Internodes of the rachilla are inconspicuous be- The presence of stomata variable the
it. is
when
tween glumes, lower and upper present, to-
flower. different species, being located,
The lemma
spikelets are biconvex, the lower glume ward the apex of the and palea.
reaching Vz to ?4 the length of the spikelet, 1-3- Simple papillae are regularly distributed in Ion-
nerved; the upper glume and lower lemma are gitudinal rows. They are associated with the pericli-
and
subequal, or the upper glume slightly shorter nal, external wall of the long cells, eccentric,
is
and
not covering the apex of the upper anthecium, near the anticlinal transversal distal wall.
may apex ot
5(-7)-nerved; the lower palea be conspicuous Prickle hairs are frequent toward the
and either the same length as the lower lemma, or the lemma and palea, being retrorse in P. breso-
antrorse
reduced to completely absent; the lower flower P. polygonatum^ and P. pilosum,
linii,
is
laxum, and P.
occasionally present, with two lodicules and three in P. stagnatile, P. longum, P.
r-
stamens, but usually absent; the upper anthecium hylaeicum Mez, with both dispositions in
is or
leptachne.
encloses a perfect flower, with two cuneiform, con- grumosuniy P. stevensianum, and P.
more cross-
duplicate which embrace or less
lodicules, the lower bor- SUica bodies are exfoliate,
ders of the palea; the caryopsis has a punctiform shaped nodular.
to
membranous
to oblong hilum, with the embryo reaching The upper anthecium varies from
V^ to
P
r
grumosum,
V2 the length of the caryopsis. at maturity, in such species as P.
& Was
The lemma
lower commonly membranous Smith
but
is
condensa-
occasionally indurate at maturity in specimens of hausen, P. leptachne, P. longum, P.
& more
polygonatum,
P. e.g., Idroho Cuatrecasas turn, P. stevensianum, and P. stagnatile, to
&
2665, and laxum, laxum, r.
P. e.g., Cuatrecasas Llanos or less indurate in P. polygonatum, P.
24054,
Bisexual flowers occur in the lower anthe- hylaeicum, and pilosum.
P.
the
cium of specimens of P, stevensianum, relation to
with two Anthecial ornamentation varies in
papillae,
lod simple
texture of the anthecium, with
cium, with two styles and a plumose stigma; bod
in this
spe
case there is no variation in the consistency of the with membranous anthecia. In the rest of the
lemma,
lower it being similar to the upper glume; cies with indurate upper anthecia, such as P-^P^
no ana r-
caryopsis found in these bisexual lower lygonatum, P. pilosum, P. hylaeicum,
The na
flowers. presence of bisexual flowers in the laxum, stomata, simple papillae, and prickle
lower anthecium Panicum bodies
of was
previously
re-
ported by Palacios (1968), Pohl (1980), and Zu- are ocJasionally present at the tip of the lemma,
m
&
loaga Sendulsky found
(1988). ones
Verrucose simUar the
papUlae, to
Figure ""* longum,
1. electron photomicrographs -A. Panicum
of female Panicum.
florets of species of
XIOO
(from type specimen).- Panicum grumosum, x500 & auritum.
B. Panicum
{Smith
Klein 15723). C. D.
x50.-D.
Upper
C. portion, Tip of the lemma. x250 Dorsal ^.^c
(Merrill Panicum grande.-Y.-
101). E. F.
xino.
s.dc
^250
Dorsal
(Black
— u I^PJ'^^f'"^'"" VU^'Jr"""«' 15352). G, H. Panicum scabridum.-G.
,nn
X 100. H. Veiilral side, x 100 (Wurduck &
Adderley
42986).
Number
4
Volume Zuloaga
79, et 773
al.
Revision of Panicum subg. Phanopyrum
1
Laxa
sect.
774
Annals
of the
Missouri Botanical Garden
Figure
Panicum
2. Distribution of
bresoUnii, longum,
P. and
P. pilosum
species of subgenus
Steinchisma, & Panicum
are sometimes (Mehra
Chaudhary, 1976, 1981).
present specimens
in uf P. laxum. = Panicum
grumosum:
2n 40 1952).
(NiiSez,
=
/'a""
hylaeicum: 2n 40 (Bouton 1981).
CHKOMost)ME Numbers at al.,
& 1972b,
20 Pohl,
laxu. (Davidse
There
are few
karyological studies on taxa be- r974,T978);"2« - » S^o^de-r Strom
ou
vv.uu.u
longmg
to section Laxa, with data = &
of the cytology Davidse^
967; Tateoka, 2n 40 (Pohl
1 962);
1
of only
species being
vjuuiu Soderstrom ^
* ^ X OL .juutri UIll, L :7\J *
number • , toll k f.
10
characterizes = & 19^^'
the 1972a,
sec- losum:
n 10
(Davidse Pohl,
Panicum
tion. auritum: n
15 (Mehra, = undej
&
1982); 1978); 2n 20 1971,
(Pohl Davidse,
2n & *
30
(Christopher
Abraham,
1976; Mehra 2n
P. Panicum pernanihucense:
millejlorum).
&
Chaudhary,
1981; Mehra,
1982); 2n 36 Pa"'
40
(Bouton rivulare).
et 1981. under P.
al..
-c y--^
Number
Volume 4 Zuloaga 775
79, et
al.
Panicum Phanopyrum
1992 Revision of subg.
Laxa
sect.
n
ficuRE polygonatum.
3. Distribution of P. grumosum, P. hylaeicum, and P,
^^m =
& become apparent once additional
polygonatum: them wiU only
2n 40
(Pohl Davidse,
1971, under & Dav- species of section Laxa are collected and fixed in
P. boliviense Hackel; Pohl
>dse, The anatomical description of the section
1971).
the
field.
be based
pilo-
Leaf
Anatomy
6-17)
(Figs.
Uplachne,
longum, P,
P,
sum, P. bresolinii, P.
stevensianum, P. auritum, P. con-
stagnatlle, P.
constituted here, exhibits
polygonatum. These species
and
J^anable leaf blade anatomy, and two densatum, P.
slightly dif-
^rent
species groupings These two constitute
are evident.
groups uniform
intergrade anatomy, and the
in their leaf
•^xonornic
between trated
significance of the differences
776
Annals
of the
Missouri Botanical Garden
Figure
4. Distribution of p. laxum and
P. leptachne
be
one
metrical on either side of the median vb, with
anatomy
grumosum
of P.
and
P. pernambucense
half being more asj-m-
slightly wider, with vbs; this
wOl be
treated
separately,
as anatomy
their
differs metry I'vd
not pronounced due an extra
being to
somewhat
from
that of the Laxa
group
(Figs. with an I'vbs
7, additional 3'vb between successive
This
be
1 2). will iiiformaUy called Grumosum
the maximum
one
in
half of lamina; can a
result in
this
species group.
52
an
of 20 of
extra vbs in one half out of a total
(up 99
to some
in specimens
LEAF BLADE
IN TRANSVERSE the
SECTION entire section, fhic mid-lamina
d adaxial ribs
""^/"f^u'r"r^ows: rounded
Outline: expanded, """^
either
flat or ver^v bbrrooaaddilvy
.1
always size
present over aU
v
V-shaned- armc
the nf
'.»^,'«
1 i
lTi:.Jul^"^! ^! "!'"^ ^'^her straight specimens
ar.d shape;
'f size of ribs di between
bowed
th
ribs
Number
4
Volume Zuloaga
79, 111
at
al.
Revision of Panicum subg. Phanopyrum
1
Laxa
sect,
UGURE
5. Distribution of P. pernambucense, P. stagnaiile, P. stevensianum, and P. condensatum.
vanes
from groups; type of keel differs
very shallow medium furrows on by bulliform cell this
to
^ Grumosum
difff>r*.r,f specm• iens -. ,. . considerably from that present in the
—
where the keel intergrades
group of section,
vary this
"/ "*^«-"iguisiiauiC5 ui«-
iruiri aiigiii
J
uulations
associated with the vbs the same with the lamin
to ribs
size as the adaxial ribs, resulting in a ± moniliform (8 )9-13(-18) 1 'vbs in entire blade, usuaBy with
outline. Keel: always and amount an additional I'vb in one half of lamina; 3, 4, 5,
present, but
size
33w.iated
parenchyma vanes
colorless
variable;
no 2Vbs.
by one each half of the lamina;
in
differs
adaxial
colorless parenchyma vbs centrally located in the blade thickness.
-developed
to well All
shaped
displaced
be sliehtly ahaxially
including 3
yr»S the vbs Vascular bundle description: S'vbs angular with
' all ahaxially located; no lacunae;
»n»s
structure abruptly separated from the lamina xylem and phloem distinguishable, I'vbs circular
778
Annals
of the
Missouri Botanical Garden
—
Figure
Leaf anatomy
6. blade of P. condensatum.
k. Transverse section of poorly reconstituted herbarium
specimen; fusoid and
cells pallisadelike adaxial chlorenchyma are present.— B. Abaxial epidermis with narrow costal
zones dumbbell
witli silica bodies and the intercostal zones clearly divided into lateral stomatal bands, and central files
without stomata
but with microhairs; epidermal (x250,
cells nucleate based on Davidse al 11494).
et
to slightly elliptical in outline; phloem up
adjoins the to V2 leaf thickness. Epidermal cells small, reg-
ibs; lysigenous cavities and protoxylem
present; ular in size, with a distinct continuous cuticle; no
metaxylem
circular
vessels narrower than
the obs macrohairs, Abaxial
prickles, or papillae. epider-
cells as seen in section. Vascular bundle mal
sheaths: no no
cells: bulliform thickened cuticle,
cells;
obs
of 3'vbs conspicuous,
entire, round, without epidermal
projections.
extensions, although an
additional adaxial
cell
is
sometimes
evident,
consisting of 5 or 6
inflated,
ABAXIAL EPIDERMIS SURFACE VIEW
rounded IN
but up 8 some
cells, to in specimens
of
F. hylaeicum,
P. auritum, P. stevensianum, x
P. Intercostal long elongated, up to 3 lon-
cells:
stagnatile, and
P. bresoUnii,
especially toward the ger than wide; parallel side walls; vertical or angled
midnerve;
adaxial tend be
cells to largest; chlo- „ „„, undulating
._._ __
, ^
roplast presence and
type
variable: either absent, waUs; conspicuous. CeU shape
ticlinal this sinuosity
or
rarely,
relatively
small,
centripetal specialized consistent across zones except that in-
intercostal
chloroplasts occur
with few, small plastids; ibs ab- terstomatal long are shorter, long ceDs in a
cells
Obs
sent. of I'vbs round
or by
slightly elliptical, with either adjoin one another or are separated
file
slight abaxial
interruption, without narrow or
extensions, short cells— and cell
.in either a single
tall
comprised 8-1
of
cells; cells smaller than usuaUy
those Conspicuous nuclei
1 cork-silica
cell pairs.
Stomata:
simila present in intercostal long and short cells.
shape, but extreme
abaxial ceUs tend to be smallest, low dome-shaped may tend to low
or ovoid but
Chloroplasts
as in obs of 3'vbs. Ibs present, com- conspicuous nu-
triangular; subsidiary ceUs with
plete, of small ceUs
with uniformly
thickened evagination at
walls, cleus often contained within a slight
Sclerenchyma:
minute,
inconspicuous per
adaxial 6- stomata
^ ^^ of
^. ^„„..„„ w,i„t,h„
files
1
and
abaxial
girders associated
with 3-6 long
ybs; central
all fibers interc*ostal zone, with the
"only
—
kening
more elon-
;le- cell files without stomata these cells
renchyma
cap
in margin. Mesophyll:
chlorenchy- may less
gate than and stain
the interstomatals
ma
not radiate but adaxial
cells tend to a of cells,
pallisade-
intensely. Stomatal rows in adjoining files
type of arrangement;
these ceUs
tabular whereas successive
usually one between
interstomatal
cell
the abaxially located chlorenchyma
are very variable.
cells stomata arrangement
in a but
this
file
irregular shape; more
in than 8
chlorenchyma
by
Stomata A
cells separated from the costal files
files
between
consecutivR vbs- thp ooJlc r^o^»:„..i„_i-. xl
short
2
Intercostal
— intercostal without stomata.
files
definit narrow
- and
ce/Zs; either absent, on solitary and tall
„ ...
resemblmg arm ,
walls,
cells very and taO
closely. Fusoid
or paired with both cork and ceUs
silica
m
ceUs present mesophyU:
elongate, com-
narrow, and most
and
narrow. but
Distribution irregular,
mon
FapH^^^-
in central of intercostal zones.
files
each Very
vb.
Uttle reduction
evident
except near
themargm
where
the
lateral may
fusoid ceUs except
be
„;„ {Chase 6616) absent
Prickle hairs:
ateent^o
colorless Adaxial
cells. epidermal oi P-
specimen
cells: for small hooks on one
intercostal
^7T ''^'"'' ^""""^ *"^"^^" prickled
"' /^'^-"'" <^«--^- SmaD angular
21866).
llsTnr!^
an
-^
^:t:r ^Ucr.
•-^^' ^^^n margin.
•r:^^!r!!^^^T^"^ ^ barbs present on the leaf
-a^
fan-shaped,
inflated
central ccU
or
ceUs; occupy
fingerl
I
Number 4
Volume Zuloaga
79, 779
et
al.
1992 Revision of Panicum subg. Phanopyrum
Laxa
sect.
A
I
—
Figure
7. Leaf blade anatomy Panicum grumosum. A~F, transectional anatomy. A. Gently
of
—
.
Wade
margin; acute margin with small
note near margin. B. Slightly
rather irregular occurrence of fusoid cells
scJerenchyma
cap; most bundles and presence irregular, with other bundles
fusoid not associated with three lateral
*||^^*^d near margin.— many bundles (more than with adaxial bundle
the C. Keel consisting of vascular 12). all
sheath
extensions and gradually intergrading into the lamina; fusoid cavities in this region of the leaf resemble lacunae,
—
as only Specimen which
a single cavity present in the mesophyll between successive bundles. D. in keel is less
is
developed
but incorporates seven bundles; note lacunae intergrading laterally into typical fusoid cavities. -
at least
much
Detail of and shorter bundle sheath extensions
mesophyll occurrence of fusoids
^j-- at mid-lamina; note regular
—
than
nearer and extension of the outer bundle sheaths
the center of the blade, F. Irregular occurrence of fusoid cells
«f
the third-order epidermal structure.— G. Nucleate intercu.stal long
vascular bundles in particular. G, H. Abaxial
and
short cells and narrow costal zones with irregularly dumbliell-shaped silica bodies; central files in intercostal zones
—
^nout
based on Zuloaga
slomala. H, Detail of nucleate intercostal long, short, and triangular subsidiary cells (A, E,
H
•^^87; B. D. A-D x50; E-G xl25; x200).
F, H, Zuloaga Zuloaga 3073;
s.n.; C, G,
cells of equal and only overlying the 3'vbs). Alternate
length; deciduous with very rarely
distal cell
" walls; common m regularly with similar shaped or shorter coital short
the center of the intercostal
only 3 (rarely
^^- ^^cro-hairs: absent except new cush- cells along central costal file; 5) files
for
.
Each zone
'on-based hairs on single specimen of P. pilosum of cells per costal zone. costal therefore
{Davidse
bo<l
21866).
Silica bodies: vertically clon-
ed Pa
bounded
dumbbell-
or cross-shaped, or equidimen-
sjonal on analomy
dumbbell-shaped (more This
eloneated nodular S( I
to
(
780
Annals
of the
Missouri Botanical Garden
A
B
'5. • ir...
,
H
3'-ii-t--jpr3-frfr?
^ -«-^
t - ^
J^F
t
-
Figure
8. Leaf blade anatomy of Panicum hylaeicum. A-F, transectional anatomy.— aA.. iL^aatieerraali pp^air.t "of lamina
showing tapermg margin with small cap of sclerenchyma; note regular presence of fusold cells associaatteedd wwiitthh aalUl
vascular bundles except
for penultimate and comprising
ultimate lateral bundles in the margin.— B. Restricted keel
three vascular bundles; adaxial parenchyma developed bundle and
in association with median vascular
first-order
these
with
ted
"
-^"^ -.«.—
"iiiiuui uiuuiupia&is, lusoias narrow and inclinea towara ine auaAiai
adaxial chlorenchyma
with pallisade arrangement. -D. those
arm
Detail of chlorenchyma ceUs, particularly
cell-like
located abaxially and adjacent — of
— to the fusoid cells; note the fusoid cavities appear to be bounded by the thin walls
the lusoid cells. E. Reeular occnrrftncp nf a fiicr>;^ ^„ii „ .*! ;j. r F Specimen with
i Kundles
zones
bundl
Narrow costal
G.
(3-5 and
fUes wide) wide intercostal zones (16-19 wide).-H. Low intercosttaall
throughout
files triangular stomata
m in files
zones,
horizontal and
all cell files, but tend to be less concentrated in the central of the zones; subsidiary
files
intercostal long with
cells characteristic
persistent alternating
nuclei; note irregular dumbbeU-shaped bodies
costal silica
with sumlar shaped
cork
along H.
cells G,
costal cells files (A, B, E, F, Zuloaga 2293; Zuloaga 2218; D,
C,
et al. a
Zuloaga 3197; A, B x G x80; H
50; C-F, xl25). .
.
oitheLaxaspecies
group,
P. hylaeicum,?. _
laxum, maximum
R
/)/7o5um and
P. polygonatum,
weU
as
as P. groupTaUhough urto'99 cin occur in P. M«^'-
leptachne, longum,
P.
P. condensatum, 57
vbs);
P. an- cum); asymmetry marked versus
(48
less
ntum
P. stagnatde, '""''
P. stevensianum, keel
and
P. thickness mid-lamina generaUy greater;
at
bresohnu. The Grumosum m
group, grumosum (1-5
P. 7-12
vbs
well developed,
incorporating
and
P. pernarnhurense
differs
in several
respects: Laxa group), wide and expanded and intergradtng
lam.nn
u.dth
generally
wider,
although group):
P. hy- Laxa
into the lamina (not abrupt as in
P
P^stagnauU
laeicum,
and
leptachne o
some- parenchyma
lacunae
present
in the colorless
have
tinu-s blades as wide
as those of P. grumosum, vessel
metaxylem
the
keel (absent Laxa group);
in
r
Number 4
Volume Zuloaga
79, et 781
al.
1992 Revision of Panicum subg. Phanopyrum
Laxa
sect.
Figure 9. Transectional anatomy of the leaf blade outline of Panicum laxum.—k. Gently tapering margin with
only the most laterally situated vascular bundles without associated fusoid cells.— B. Mid-lamina region showing four
third-order vascular bundles located between successive first-order bundles; note fusoid cavities on either side of all
bundles. C-E. Variation in the structure of the keel.— C. Insignificant keel incorporating only the median vascular
—
common
bundle; this first-order bundle with small amount of adaxial colorless cell tissue. D. Most intermediate keel
—
type incorporating 3 vascular bundles and adaxial colorless tissue. E. Unusual elaborate V-shaped keel with 5
vascular bundles and extensive parenchyma; note abrupt delimitation from lamina by bulliform cell groups
colorless
(A, based on Zuloaga 3290; Stevens 25354; Zuloaga 2337; D, Davidse 30703; E, Zuloaga et at. 4330;
B, C,
A-E
X50).
diameters bundle sheath extensions always present (variable,
greater than Laxa group wider
in (often
than obs 8-10 from 1-4 deep); adaxial; uniseriate to biser-
ceUs); outer bundle sheath with cells
cells around 3Vbs (5-6(-8) Laxa 16- longest extensions closer to keel; chlorenchy-
group); iate;
in
20 ma and more compact, adaxial
I cells in obs of I'vbs (8-11 Laxa group); cells smaller cells
in
i'-^Kc
D
E
F
-A. lamina where
Figure Thinner part of
Panicum laxum. lateral
1- 0^.. Detail of transectional leaf anatomy of
anatomy
fusoid Specimen w.th typical of
chloroplasts.-B.
occurrence without
less regular; outer sheath cells
is
theU
chloroplasts.-L. lypical Laxa-
-xa without
group: and parenchyma sheath cells
regular presence
fusoid
cell
Fused
vpe ptlo$um^-p. and
anatomy, those of P.
but and furrows, very similar to
note well-developed adaxial ribs
bundle above the fusoid cavities,
particularly
sheath -E. palisadeUke,
cell structure. Adaxial chlorenchyma tissue -
Specimen
*'hereas wall invaginations. F.
the with discernible cell
abaxial chlorenchyma are equidimensional
cells
which
*nth anatr.r»„, .^„j- //- „ f^w .-»„trinpiallv located chloroplasts, differ
tending t. o t.1he in.termed.i.at. e Ci^3/C, .type .w.i.:t.hu a few, ceriti
>m nf thp nresence of fusoid
thnc<> tVio /-V.lr.i-/>n/-Kirma- nntf>
Zuloaga
Zuloaga 4330; D.
f. laxum Zuloaga 3290; C. et al.
25275;
'^] specimens based on ^Stevens B,
(A.
AD
x2
ft
«'
4367; E, Zuloaga 2337; Brou^n xl25; E, F 200).
F, 19;