California State
Un::i.voTs.L't~y_,
Northridge
,
FLOfu\:L EORPHOl.OC Y OF
CHi~rfO?ODTUt;
EURAL E L.
A thesis subrxi.tted in partia~L satisfaction
of the reqt1irments for the degree of
}ir.lste.r os· ;::c5 e:tce 1n
B:i.Ol.C>JY
by
Thoms.~
Randc·J.ph Gordon
/
June., 1976
The Thesis of Thomas Handolph Gordon is approved:
__ _.,__,._,~~A-•
~-
Dona~Ld.
John
D
- ... -~--..~.. ~~---
J.l.tt
~-~-~~--~~··•_.,.-
E. BianchiL
--··
~----------·--••••••--
- · ----
---~--
&"VarlSOYl
California State UnivenJity, Northridge
jj_
{J
ACl\NO~·i.LKrFl·IFl'JTS
I am gratefu.1 to all thof:e •.'Tho have assisted me in the
completion of this project.
I am indebted to Dr .. Ke:rmeth A. \'>f:ilson
for his encouragement at the outset of this sb.idy, and for his advice
an.d as::listance throu.ghout.
I am also thankful. to Dr. John
R~
Svvanson
for countless timely consultations, to Dr .. Donald E. Bianchi for his
careful reading and thoughtfuJ. criticism of this manuscript, and to
Greg Poseley for hiD help in the prep2ration of the plates contained
herein.
iii
TABLE OF CONTF:i'JTS
Page
Acknowledgements •••••
Table of Contents ••
•••••••o••·••••••••••••"•o•••ltoeo~••••v
TabJ~es
List of
Fig·u!~es .. f. ••••••••••
Abstrct.ct,-~~
• ••••
Chapter I.
Cha.pter
II.
Chapter
III.
••••
~
••
o ...... c •••
iJ
c ••
c
~.
iv
lj:
••
vi
.,
e
4
.................
e- • o • " • • •
viii
<~>e$eeo••o•••••••eeo
1
.Iv1ethodst~~~"G•&•.,••••.,oo•<9"'liCOo
2
CI••••••••"$••-•'!J•••e••••••••o•ott•••
5
Introduction ............ G•••
r.lateriflls and
Hesults ••
iii
v
List of
e
~.e
······~········8~·.a••··4·········(1··
General Pat tern of Grmvth •••
The Stem •.
4 a • • • • .o • • • • • .., • o •
. ....... .
•
• • ·o •
•
•
•
e • •
• •
a •
..
~
The Stem Apex •••••••••
The Root •• *••
The Leaf •••••
•••••Geoeooct•••·••$o•e9
The Inflorescence •..
The Flov·Ter ••••••••••••••••••• •••
Vascularization of the
~
...
.......... .. .
~
,..ill.~t••••••
inflorescence .......
c ......... "
...............
Distribution of Perfect a..11d Pistillate
Flov-.iers • .....................................
Chapter
rr.
Discussion~. •••••••••••••o•••a•G•••••••••-o••
27
'
l
j
Literature Ci ~ed4 o
... ., . . . . . o . . . . . . . a • • • •
\t
..
e ••••
o
~ ............. .
30
I!
I
i
I
1
I
I
i
j
!
I
i'
......,_' ""' ·.l
iv
LIST OF T.A.BLES
Pa.ge
Table I
An ern1meration of the perfect flowers in the six
uppermost dichasia of fifteen plantD..............
26
I
1
j
l..,,., -.;r
• ,._..,..., ..-.<
,•,~•.._.,.._,_..,~-' •-"<~-~' ' "' "·'•="·'-" "-~-.- ;..-,-·.,...=•~·'•c->< ...,.,-~,.~_,.-,,..~J-"'•--~--r•-·•'-'_.,..,, ""·-·--~~~~~·~·.-c-- •-•~'-->-'-•..,.,,_,_.~..,_~~ :·~~~-><-·-~" ~.-., ._._.~,,·~~- .,--,~-'>.•'•""~''"•"'"..,.,_.r "<-~''-"-'·'""''"'"<- '"'~·'' -~·-·•.-,.·.~
•N
v
•
,,
I
''"•'-' ,
j
LIST OF FIGUP.ES
Page
Plate I
Figare 1
A cross section through a mature stem.......
18
Figure 2
A median longitudinal section through the
s-tern a.pe.-..:<.c_#oo.O••••••••••!Iil• ...,. ••••••• tii:O•••••fl'•
18
Figure 3
A cross section through a young stem.*
18
Figure 4
A cross section through a young stem •• .....
'i
01
....
.,
o o
18
Plate II
Figure 1
A cross section through a young root ••••••
C)4
20
Figure 2
A cross section through a mature rootea•e•G•
20
Fi.gure 3
A cross section through the midrib of a
Ina ·tllre
Figure h
]_ eaf • ..•. " ....... "' •••.. -a . . . . .
<II
<0 •
o" •
~
•
$
•
•
20
•
The outline of a leaf borne on the main stem
Figure 5
20
The outline of a leaf borne on a lateral
branch••••••••••••••••e•••~~•••oaoQoo••o••••e
20
Plate III
Figure 1
Vessel
~Jlem •••••••••
22
Figure 2
Vessel element of the primary xjlem •••••••• o
22
Figure 3
Vessel element of the primary xylem.........
22
Figure h
Vessel ele.mei1t of the secondary xylem •••••• "
22
Figure 5
Vessel element· of the secondary
~Jlem .••••••
22
Figure 6
Vessel
of the secondary xylem.......
22
Figure 7
A fiber, present in the secondary xylem.....
22
Figure 1
Diagram of young dichasium..................
24
Figur!C; 2
Diagram of a dichasium at an ]..ntermedia.te
stage of development.........................
24
Plate
I
el~nent
of the primary
rl
Figure 3
!
ela~ent
Diagram of a dichasiu.m at a later stage of
developrne.nt
~ ~ .z. • • • " • • o " ., .. ~ ~ . . . . o • •
f.•. .,._..,.....,_,""".,'"~'~~~<-··......... «~~-·-.-·~· r...-.,,,..,~ •• .....-.-~..._..,__~
f't_
.......
•
n--....-.-," ·-~·-.....-·•~-ti,~1~--~-. -~-=~•"-<»"'"'""--~"'·' __. =·-""""''-._. ... ..,.,..,,--,.-o<•.-.h·-'-'·'~---.-.•-J->-' --·«·'""•-·~- _..,,.,,._.. --~-···--~ .-...,.,._
vi
Q
•
..,
o
--~ .._...,.¥_ "-~---
•.-
I
.-.-·-------·=---'- ~-....,...J
Figure 4
Diagram of a yo1mg inflorescence............
24
Figure 5
Diagram of an open perfect
flo~1er...........
24
I
L ....................-~ ..........-...-..... --------- ...... ··-- ....... ,
vii
ABSTHt\CT
THE VEGETATIVE
F:t..ORAL l'IOBPHOtOGY OF
A!~ATONY
AND
.QliEN_Q!~QDIUH
f.'ITJP.A:LE L.
by
Thomas Ranc.olph Gordon
1-'Iaster of Science in Biology
June, 1976
The anatomy and morphology of
~opod:i,~ !e:!-_:r_~.§.
L. was
exmn:Lned by usint_: stcmdard paraffin and clearing tech11iques.
inflorescence vJas studied by marking it and rnaldng periodic
The
ob~
serve>.tions of living plants and. also by examining serial paraffin
~>ections
and cleared specimens.
The anoma.lous secondary thickening in the stem and root,
characteristic of the Chenopodiaceae and related farnilies, is
described in detail.
Secondary grov.rth in the stem is comparable to
that -vrhich occurs in _g_. a1.bur!:!_ L., differing in the process by rr;bich
secondary phloem is formed.
correlated
~"Ji.th
The onset of secondary thickening is
the cessation of stem elongation.
Secondary grGvth
in the root of C. !:_mrale does not differ significantly from that
which has been described for _g_. ElblJln anci
The inflorescence,
\~dely
·Bet~ yulgar;L_~
L.
regarded as indeterminate and referred
to as panicuJ..ate, is best described as numerous compound dichasia
disposed on a short, deterrninate axis.
The dichasia shoH an
asyrnmetrical pattern of development, in .,;ihich one side of each
dichotomy elongates more extensively and flmvers mature more rapidJ.y
than on the opposite side.
'I'vm types of flowers are present:
viii.
and pisU.llate.
occur on the more
Perfect f1mvers i'l.re comparatively rare and
~trongly
deveJ.oped side of the dichasiw--n.
Plants are autog<.>Jnous and abunda.nt seed is produced by plants gro\.vn
:i.x
CHAPTER I
INTRODUCTION
Cheny_Eodi~ ~le
L. is a stout, tap-rooted annual, which rarely
'-
!exceeds
40 em. in height.
i
It is a native of Europe and occurs as a
iweed of orchards and garoens throughout North America.
I
The .genus
l
_Chenop_~iun_1
!North American species.
.,
l
!L.,
i
according to WalLl (l95Lt), includes Lt8
C. nmrale is ascribed, along
to subsection Undata of section Chenopodia.
.
with~·
urbicym
The treatment of the
j genus by Aellen and Just (1943) differs from that of 1-'Iahl by including
j
!a third member
I
in subsection Undata,
f.
~olyspe~
L.
j
1\-JO characteristics of C. ~rale are particularly notev1orthy.
I
.
lFirst is the anomalous secondary growth exhibited by both stem and
Iroot,
1
a phenomenon ;..;hich is common in the Chenopocliaceae and related
!
l~ r~~~~.
C:Ud..LL). 8 S •
The second feature is the inflorescence, a congested
I
!assemblage of :minute flowers, both pistillate and perfect, which has
l'
!never been accurately described morphologically.
Il
This study describes the anatomy of
I
f·
rnurale, including the
.
!process of secondary growth in the stem and root, and delirruts the
1
essential features of inflorescence development.
I
.
Also, the pattern in
.
l
Iwhich perfect and pistillate
I
f1owers occur
!
described.
i
I
l
l
I
1
jn
the inflorescence is
CHAPTEH I I
MA.TERIALS AND
T'IT~THODS
The plants used in this study were either collected at various
sites in close prozjmity to the California State University Northridge
campus, or were grovm from the seed obtained from these plants.
Seeds
v-fere sovm in straight vermiculite, maiJ1tained under greenhouse
conditions and periodically given an inorganic fertilizer.
100
% germination
Nearly
vias realized 1.mder these conditions, and plants
gre;.>J to maturity quickly.
Stem apices and roots Here fixed in Ro.ndolph 1 s modified navashin
fluid (Johai1sen, 1940).
Aceta-Alcohol (FAA).
All other material was- fixed in Formalin-
I·Tature stems lirere sectioned, while fresh, on a
sliding microtome, and stained in safranin a.nd fast green (Johansen,
1940).
All other sections were obtained by standard tech.Diq_ues of
dehydration and embedding in paraffin.
For staining, both JohaDsen 1 s
Quadruple (Johansen, 1940) and safranin and fast green gave good
results.
Safranin a11d analine blue (Johansen, 1940) gave results
inferior to both the above procedures.
-To study vascularization of the stem and inflorescence, serial
sections were used in conjunction vrith cleared specimens.
-were obtained by soaking in 5
% sodium
The latter
hydroxide for two to three days
(Foster, 1942), and stainLng in safranin.
Jeffrey's maceration
technique (Johansen, 1940) was used in examining elements of the :xylem.
Observation of living plants was employed in the study of the
inflorescence, in addition to the standard techniques described above.
Yovng flowers -...·;ere marked -w-ith acrylic paint, and their position
2
vd.thjn the inflorescence
\'laS
noted at regrCLa.r interv.<Lls.
The pattern
of development of indiYidua1 flowers was also studied on living plants.
This 1..-Jas done by marking a flower vJhen very young, and making daily
observations until the seed was mature.
The distrj_bution of perfect and pistillate flo(!\Jers vms deterrrined.
Fifteen plants v-:ere exc.i.rni.ned on a daily basis, flowers were marked red
if anthers \.vere evident (uerfect flowers) and marked black if a.<'J.thers
were not present (pistillate flowe~s).
Because flowers are deciduous
in age, an additional mark was made at the point of attachment.
!VI,_1.rking 1"ras continued for forty-five days, until the sex of
nearly eight hundred floiNers was noted for each of the fifteen plants.
At this point the inflorescence vias removed and the position of each
perfect flower vms catalogued.
..
To verify the pattern thus detenrJ.ned,
ten additional plants v:ere examined; they were collected in the field
at an advanced stage of development.
The analyses of these
inflorescences were based on an exam:ination of the remaining flowers.
·The distribution pattern verified that ·which was noted for the fifteen
greenhouse grovrn plants.
In order to assess the degree to Hhich plants were self--fertile,
a clay pot vms seeded and placed in an insect proof enclosure.
The ·
soil was kept moist by spraying v-.rj.th a wash bottle through the screen
which covered one side of the container.
This enclosure was kept in
the laboratory, where no other plants we:ce grmv-l1'1g.
When we.ll
developed seedlings were present, all but one was removed.
Photoperiod investigations ~tJere initially· made in the short and
long day greenhouses.
Day lengths as short as ten and as long as
nineteen hours were available.
To exatiline the effect of a shorter
L,.
photoperiod, a growth chamber was used.
1\·Ienty four plants :,.·,rere grchv11
from seed under a daylength of eight hours.
regime until fl01tJering was evident.
They were kept under this
CHAPTER III
HESULTS
General Pattern of Growth
Germination is profuse in the fall and vdnter months but seedlings
are feN du_rj_ng the vrarner parts of the year.
Under greenhouse
conditions seeds germinate between four and six days after sovving.
The cotyledons are oblong and entire, up to 2.0 em. long; true leaves
are rhombic ovate and toothed, 2.0 to 6.0 em. long.
Leaves are formed
in apparently decussate fashion, but only the first pair is truly
opposite.
The sub-opposite nature of later formed leaf pairs is
belied by the separation of pair members as the stem elongates.
A total of twelve stem leaves are formed before floweri.'1g ensu.es •
,
.
Plants grov.m under day-lengths as short as eight hours and as long as
twenty bega..n. flov.;ering, vdthout exception, after twelve stem leaves
were formed.
The time required to reach this twelve leaf stage was
essentially the same for all plants, regardless of photoperiod.
Accordingly,
C.
mure>~e
must be regarded as a day- neutral plant, unlike
C. album which is a short-day plant (Gifford and Tepper, 1961).
Soon after the initiation of the floral apex, shoots in the axils
of stem leaves develop more or less extensively.
The conditions
under which the plant is grovrlng vrill determine hmv substantial the
lateral branches arej in dry situations they are quite small.
These
branches bear leaves which are smaller than those on the main stem.
Also, they are oblanceolate to spatulate 1N"ith an entire margin, while
stem leaves are rhombic ovate v-rith a toothed rriargin (figures 4 and 5,
plate II).
5
'
D
The Stem
-·-The stem is glabrous, green, somev,rhat reddish in age, shor.-.rLng an
irregular out.l:tne in cross section, vdth alternate ridges and furror..,rs.
The plant is usuaTLy erect, often Vlith well developed side shoots, at
times becoming prostrate.
The epidermis consists primarily of cells which are uniformly
thickened.
Some, however, shov.r greater thickenings on their
tangentiaJ. walls, notably those which occur on the ridges.
The cortex
(figure 4, plate I), which underlies the epiderrrd.. s, is divisible into
two regions.
Innermost is a layer, two to four cells thick, of large,
thin walled parenchyma.
These cells are not photosynthetic, except in
very young stems; crysta11ine deposits are common, often occupying
nearly the entire lumen of the cell.
The outer portion of the cortex
consists of b:o cell types: small photosynthetic cel1s, internal to
the furrows, and collenchyma, internal to the ridges.
collench)~a
Although the
differentiates early, it does not hamper stem elongation;
as noted by Esau (1965), t'he ·plastic nature of these cells aJ.lov-rs them
to stretch considerably without damage.
In a young stem, numerous collateral vascular bundles fonn a
ring arou.'1d the central pith.
At a given internode as L'1any as
eighteen bundles are present.
Nodes are unilacunar which, as noted
by Bisalputra (1962), is typical for the family.
The present study
revealed that each leaf is supplied by three traces and each axillary
bud by tv--ro.
Bundl~s
adjacent to those destined to depart as leaf
traces branch, keeping the number of stein bundles relatively constant.
The spaces beb>reen vascular buncUes is occupied by parenchyma, within
which the interfascicular cambium develops.
t"''~__..,._.__.._,~......,_~c·~, ~L >-<=.o .' o..;.>;.;>.;->'->'""-~-~·•''-""""''·~""""'· •<-'~~ ">~>-"
_ .-c•.;...oo·~· --~-"''~~·.·~·-' -"'"-"''""''"'
~=-"-"""'"'"""-"""<="<V.-o-,o..,._, ,,.,.~u, ,~-....~,_, =-~~-" _._._....,_~- ,._,~."'""~ ·~'-~o,-..l. "'~"'-"' h
_.,.-<<"'""''
The primary phloem (figure 3, plate III} forms a small roundish
1ma.ss in the outer portion of each vascular bundle, consisting of
Isieve tubes,
companion cells, :parench;yBa
2tDd
fibers.
The latter are
I
!not common, being entirely absent from the smaller bu.Ddles.
Elements
!
j of the primary xylem (figures l-3, plate Ill). include vessels and
i
l
jparench;yma. Vessel elements shard both armular and helical secondary
! .
!walls. In the secondary xylem (figures 4-7,· plate III) vessel
I
j elements are shorter, being exclusively of the pitted variety, and a."Ll
Ijhave
simple perforations on their end walls.
Elements on the order of
i
1.1_5-.17 mm .. in length, w.i_th a short tail are the most common
!
I! (figure 4,
!scattered,
plate III).
Unlike the primary xylem, in which vessels are
the secondary xylem regularly contains vesseJ.s arra..'lged in
I
jradial rows.
Fibers (figure
7,
plate III), by far the most abw1dant
l
!cell
type
jn
the secondary ti.ssue, are fusiform, with vestigal
j
!pitting.
I
The large-celled parenchyma, which constitutes the pith,
jgradually deteriorates so that mature stems are frequently hollow.
l
l by
l
The anomalous secondary thickening in C. muraJ.e has been studied
Balfour (1965), and the observations included herein support those
of the earlier \'mrk.
Hovrever, Balfour indicates that secondary
1
j thickening begins at the twelfth internode (cou...'1ting the uppermost as
number one and continuing basipetally), ~~th no reference to the age
1
lof the plant. It should be mentioned that only twelve vegetative
!l l.nternodes are formed on the main stem.
l
l secondary
lj reference
I
For
v.fhile it is true that
growth is first seen at the twelfth internode, a t.enrporal
is actually more meaningful tha..11 a dista11ce from the apex.
ex~.i1lple,
at the inception of flov.rering there is no indication of
L----·--·-""· ..-----·------.--·~·····"···~···-·-·~····....- .....---··~--·········-,......... _......~...........-···~~-...-.........-......- ...._, .... ,._._.................................... ~-- ....·-·-··)
8
,secondary thickening at the lowest level of the stem (the tr,,relfth
!
hnternode); hvo months later there is conspicuous cambial activity
!
ieven at the last formed vegetative internode.
Since vegetative grov-rth
j
ihas a fixed duration it is not surprising that secondary grov.rth,
j
}
!starting at the base of the stem and moving upv-mrd, is eventually
l
i
!fqund in the highest internodes.
Hovrever, secondary thickening does
!
!not appear irnmediately after the inception of flcrwering; it begins
I
.j
jonly after stem elongation is completed.
At the lowest internode this
l
l
lis two to three vreeks after flowering begins.
·I
V·Then the primordial inflorescence is first visible, after twelve
iI
.lstem leaves are formed, the second formed leaf pair appears opposite;
I
.
I
jthose above it are more perceptibly displaced but can still be
I
I
lrer-arded as sub-opposite.
0
.
Also, longitudinal stem sections thrm1gh
--
i the third internode reveal vessel elements tATith only spiral or annular
!thickenings.
ljdevelops
For the next several weeks, as the inflorescence
extensively, the stern continues to elongate.
Tangential stem
l
l sections taken in the latter part of this period shall severely
I
I
·1
.
!stretched and torn xylem vessels.
At this point all stem leaves,
!save the first two, are clearly alternate.
The separation of the
'apparently sub-opposite leaves is due simply to the elongation of the
!!few cells which separate them.
Only after this elongation is complete
I
i
1.·
1
!
!
jdoes secondary growth begin.
l
I
The cambial region which separates xylem and phloem in each
lvascuiar bundle is evident in young stems (figure 3, plate I) pdor
I
I to flowering.
I
However, its contribution to secondary thickening is
jnegligible, adding o~~y a few cells to the .xylem and phloem.
As the
!
!-elongation of the stem nears completion, the interfascicular cambium
!..~.·"'"'"--~-~---··-"··-·-~--~~-~·~···--·-··<>--------··-··-···~----~··--··-"-~···-·····-~····-----·-····"·'··-·········-~"~'-"'"''·'•"••<>··~ ...................-•...J
9
r····--·-----....."... -..........-.•-~-..,"..-····-"·-~----~~---"'~"--~·-~---...-....._...~·-··-····--···~·-------~----···---~---·~---"······""
/becomes evident.
Eventually, a continuous CP.Jllbium is present which
i
!links all the vascular bundles.
l
Concomitant v-Jith this is the
!differentiation of cortical cells into fibers.
These form a dis-
!
!continuous ring, one cell thick, just outside the vascu..lar tissue.
I
.
!Artschvvager (1920) notes that such fibers may abut directly on the
i
lphloem in C. album, but he doesn1 t direct his reference to the primary
I
-
.
!or secondary phloem.
In
Q. murale, the prirnary phloem never abuts on
I
l
lthe fibers; secondary phlo6n is occasionally found so positioned.
Ij
Internal derivatives of the interfascicular can1bium differentiate
l
/into fibers; this activity pushes the cambial layer outward until it
ij.
· !ls level
~<·rith
the outer edge of the primary phloem in the adjacent
i
I
i
lvascular bu.11dles. By this time the cambial cells vrithin each vascular
1
!bundle have differentiated into fibers. At this point the inter-
!
j
J
l
/fascicular cambium, which has produced no external derivatives,
j
I
.
1becomes active external to the original ring of vascuJ.ar bundles,
!producing fibers and vessels internally.
This activity eventually
!engulfs the primary phloem (figure 1, plate I).
Isolated patches of
1
l
1
I
I
I
!secondary ph~oem are formed internally by this extrafascicular
I
Icambium;
these also become embedded in the lignified tissue which
Icontinues to form.
This process does not occur uniformly throughout
the stem, so discontinuous rings of vascular tissue are present.
l Esau
(1965), referring to _anomalous secondary grO'i.rth ·in the
jchenopodiaceae, interprets the secondary tissue as xylem vrithin which
1
!groups of phloem are
l
l
that description.
scatter~d;
.·
.
secondary growth in C. murale fits
----
All of this meristematic activity takes place
1
!interior
1
·l
to the ring of fibers in the cortex.
_
c::=-~0:_~~~~-th~-::~::s r~_::_:~:~~--
A cork cambium is
j
'
------------ ---·. --_
_j
10
The stem apex (figure 2, plate I) has a tunica-.corpus arrangement.
The tunica, characterized by anticlinal divisions, is two layers th.ick,
except at the sites of leaf formation where it is represented by
single layer.
c:.
Gifford and Tepper (1961) note that cells in the outer-
most layer of the tunica are rectangular and larger in periclinal
than anticlinal dimension.
In _g_.
mu.~ale,
cells of this layer are
nearly isodiametric, being generally somewhat larger in periclinal
dimension.
planes.
Beneath the h.mica is the corpus v.lhich divides in various
An orderly rib meristern, showing distinct vertical ranks of
cells, is not present in the stem apex proper.
It is, hm-.rever, ev::i_dent
at a lower level in the stem, just beneath the stem apex.
The Root
Young roots are diarch, having tt·,JO protoxylem points (figure 1,
plate II).
The endodermis_, fairly distinct at this stage, becomes
increasingly difficult to discern as the root matures.
Several small
groups of primary phloem are formed, separated from the xylem by a
vascular cambium.
The activity of this cambium pushes out the phloe..Yfi
as it forms a solid central core of
Soon, this meristematic
~flem.
activity ceases, to be continued by a
n~vly
formed C@nbial layer
(figure 2, plate II) external to the phloem which forms xylem
internally and phloe..'1l externally.
Eventually, a complete ring forms,
and then, the process repeats itself.
Accordingly, mature roots
shov.l concentric rings of vascttiar tissue.
Unlike the stem, the root
sloughs off its epidermis as a resLtit of secondary thickening.
The
process of secondary gro0th described above is comparable to that
observed by Korsmo (1954) in
G.
alburn.
11
The J.eaf
Figure 3, plate- II, shovm a cross section through the midrib of
a mature leaf e
On the adaxial side, just beneath the epidermis are
two cell layers of
p3~isade
parenchymao
the abaxial side is the spongy
Underlying the epidernus on
parench:~a,
cellular spaces beneath the midrib.
with conspicuous inter-
There is a single vasclJlar bundle
in the midrib, being the largest of the three which entered the
leaf~
Stomata, present on both sides of the leaf, are on a level with the
epidermis.
Hechanical tissue is apparently absent in the leaf; however,
epidermal cells covering the midrib do have conspicuously thickened
outer walls.
Epidermal hairs are present, being -particularly abundant
· on young leaves.
They have a stalk, of two to three cells placed
end to end, which terminates in a spherical, fluid-filled, bladderlike cell.
1
The Inflorescence
Ulbrich (1934) describes members of the Chenopodiaceae as
having an inflorescence which is basically a dichasium.
His
description is based, in part, on an examination of Chenopodiw"!!
apparently no other, gives a
d~tailed
account of the develcpment of
the inflorescence in any member of the genus Chenonodium.
The
tendency to merely examine the mature structure is evidenced by the
fact that the inflorescerice of C. murale is often refered to as
paniculate; a description which fails to point out its primarily
1 Terndnology is based on Rickett (1944)
12
r'-A·~·-.r.,.,___.-,.,_..,..,_""-_·'"""""'"- ---~ ~"""u
~·-'"-" """"··~--,,.....,._.,.__.=...,._"'='-··~~-._.......,. ·--·~
:u ~ ..-_,._...,._..,_~~ k'--.<•=--
.,_.,..._......,_,~_•
.,_.o .• •·'""·" .,_._...._O>.'"~""'~·~.....~ _.-. -=_...--< •.-_._~..,~.·-• •.,., ._ ->-··"'"'""', x. ·. -=~"-'"~ ...,_,... '"'~- -:.~~-~-·· .......,~
-,·.~
-·• ,. ""•'"''
i
1determinate mode of development. There is every reason to believe
'
jthat other members of the genus also suffer from a lack of careful
!
!scrutiny and have been sinli1arly misinterpreted.
Ijthe
.
An examination of
development of the inflorescence is essential to an u.nderstanding
!of the structure ultimately formed.
The jnitial formation of the inflorescence represents the only
j
-
1stage in -,._,Jhich indeterminate growth occurs.
l)apex from
Upon transition of the
vegetative to floral, primordial dichasia are formed
l
lacropetally, each dichasiUi11 is subtended by a bract.
Anywhere from
l
l! six
to tvJelve such dichasia are laid doy..rn before the shoot terminates
1
lin a single flower (figure
!
4, plate IV).
The bracts are arranged in
ithe same phyllotactic pattern as the leaves on the stem.
l
As vlith the
l
jstem leaves, bracts initially appear to be opposite, but after the
I
!axis elongates they are clearly alternate.
This elongation results
IJfrom residual meristematic activity and cell elongation.
I
In each dichasium, the continued deVelopment of subtCnding
!flowers forms an extensive compound dichasium (figures l-3, plate IV).
I
jThis structure is not s;yrrnnetrical, but undergoes greater elongation
I
land shows more rapid maturation of flowers on one side of the
those borne on the false axis, to drop off after the seed has matured.
!Accordingly, in its mature condition each compound dichasium appears
Jas a group of &llill.l flower clusters disposed on an jndeterminate
!rachis.
l
l
l
~.
Hence, the entire inflorescence could be incorrectly
l
interpreted as a terminal, spike-like panicle.
t...-•. .,-........-~~"''-'·~'~'""-·-_...
·-:'""'~~,...,,.,
....,.,-..,~ ...,.., ..,.~ .... .., .......... ~ ... ~ ...,,,,.._ •._. .._ ..........,_~~-·~"----,....,._~~,..._-·-·,...,_,..,_,__.......,
-----~,.-,...,~
:r.rJuch the
... --..-....... ......-.-,.._,_ ......... ...__ • ......--~-
~~
same
,
""--'"·«'-"'-•"""·· ~,.,.,., .........., ".-.................,..... ,."-""""<>"'"~-·-....-·><""'-·~~·
1.3
jin some cases the compleY.i ty of the inflorescence is augmented by the
I
igrowth of floral buds in the axils of bracts subtending each dichasium.
lEach of these bude. forms a secondary flovvering shoot, nearly identical
lto the one on ~vhich it is borne.
Hov.rever, these secondary shoots
i
jremain mnall, extensive development has never been observed.,
'
j
Two modifications of the pattern outlined above occur vrith some
!t
•J..
ireguJ.arlt.JY.
One i.s the occasional failure of one side of a dichotomy
I
jto develop.
This is found most often on the less strongly developed
!side of the initial dichotomy.
l
SeconciJ.y, there is the formation of a
!third subtendjng flower, forming a three-membered pJ.eiochasium.
This
I
!has only been observed on the more strongJ.y developed side of the
l
l
!initial dichotomy.
All things considered, the Lnflorescence of
l
~
!
lc.
~-
rrruraJ.e is best described simply as numerous compound dichasia
---
jdisposed on a short, determ:inate axis, vv-ith the occasional development
--------------j
'
j of secondary shoots subtending each dichasium.
I
I
I
The forgoing discussion has deaJ.t exe1.usively w;ith the
I
jinflorescence which terminates the main shoot; axillary floral
branches develop in much the same way.
!terminal
~hey consist merely of a
j
fl0111er with several compound dichasia beneath, each subtended
Iby a bract.
I
Often
1
However, plants grown in rich, v-Tell-v-latered soil
I
!
generally have vegetative axillary branches •ihich form seVeral leaf
Ipachc:::f;:~:r tenninal
'
l
I
inflorescence develops.
j
:F'lov.rers consist of a five-parted uniseriate perianth, a
!
.l unilocu.lar ovary bearing two or three styles, and, in perfect flowers,
1
i
I
! five stamens (rarely four or six).
l'"~~-~·-·-•---~-----.-~~<"----·~----~------~-••·•· '·•••--•~--·--··"-"·''"'"""
I
FloHers are of 'tt,vo types, perfect
'" "''"'
""~" ~--"''""~"M "'""''""'"-"''"--"----~"'>-•
.... ,,,•,w•••---·---·---"·"
.•
J
and pistillate.
Organogenesis occurs acropeta1ly; first formed is the perianth,
fol~owed
by the androecium, and finally the gynoecium.
The androecium
is initiated in all floviers1; in pistillate flowers its development is
soon arrested.
anthers.
This results in the formation of five minute, sessile
Of course, these are not fertile, and they can only be seen
by removing the ovary which covers them.
gynoeci~un,
In. perfect flO'\r<ers the
although last to be initiated, matures before the
st~~ens.
It develops in such a way that the styles are always external to the
calyx which encloses the ovary and the immature stamens.
The anthers
are exposed by the elongation of the filmnents which force back the
calyx lobes.
An open flower is shovm in figure· 5, plate IV.
The
anthers dehisce and the filaments ·wither in a matter of tvm or three
days, at which tline the calyx lobes close to again envelop the ovary.
When the seed is mature the calyx may again open, allm<'ing the seed to
· fall.
Often though the entire flower will fall, seed included.
Vascularization of the Inflorescence
After the departure of the last leaf traces, the remaining stem
bundles branch repeatedly; twenty or more enter the inflorescence.
Each compound dichasium on the primary axis is supplied by three
traces.
The number of traces supplying the bracts is variable, those
.lowest in the inflore~cence (first formed) having as manyas nine
traces.
Bracts near the apex of the prirr~ry axis (see figure
4,
plate
IV) have fewer traces, the uppermost sho•Hing only vestigial
vascularization.
This is corr'elated with the size of the bract; the
_lowest are comparable in size to the stem leaves, while the highest
are mere enations.
In the axil of each bract is a bud which is
J..>
regularly supplied by tvro traces.
The flower which termi.J.'1ates the primary a.us is suppJ_ied by three
traces, all other flmvers have two.
lrfithin the flower the vascular
bundles branch extensively, the first to depart are five traces to
supply the sepals.
From each of these there is a vestigal trace to
the stamen opposite that sepal.
even in pistillate fl01r.rers.
the ovary.
These vestigal traces are present
The remaining vascular tissue supplies
In serial sections discrete bundles are difficult to
discern at this point.
However, in cleared whole mounts it appears
that there are two traces per ovary.
· Distribution of Perfect and PistHlate Flowers
Ex.s.mination of excised inflorescences revealed that, contrary to
prior accounts (Hunz,
1959), pistillate flowers are not rare, and, in
·fact, far outnumber the perfect flcrv.rers.
"'
However, this approach did
not lend itself to the determination of the pattern in which the floral
types occured.
This was primarily due to the tendency of mature
floHers to drop off.
To elucidate this pattern it was necessary to
mark flowers.
The flov1er which terminates the primary .:uds is ·always perfect.
\vi thin each dichasimn perfect flOir.Jers_ generally appear· on the· more
strongly developed side of a given dichotomy.
The original central
flower in each dichasium is nearly always perfect.
Table I shows the
results of an examination of nearly eight hundred flOirJers on each of
fifteen plants.
In that table, sides B and C correspond to those
sides, in figures 1-3, plate IV, v-,rhich contain flmvers B and C
respectively.
Note that the vast majority of perfect flowers are
found on side B, the more strongly developed member of the initial
16
?"~ =,._,.,~-"""'
...~'""'--~~- ;...·~.• -'"-"--"""""_,.:·=··"·"·~...~,. .....~-·-=··"~-""'-~·...._~,.~~~·- ,. _
I dj_chotomy.
l! more
........
=~=--
~-'""
.. ""''-''
~~-~~-.,.,..._,_=
......... ,..,,..~.....~"""" --......-'"'"""'-"""'"'""...............,_... ...,~.....,_, ..,...- .... ,.....--.=_·...,··~-<~-..-=-o;.·.,-~,-,"".' ~~-,.,..-~....-... ~,__.__,_, """"'-~.,.........-,.,,,.__
~1ithin side B, most perfect flowers are on side B-2, the
strongly developed member of the dichotomy subtending flov:er B.
!
l
; The same pattern holds for side C and further subdivisions of both B
!
land C.
l
A plant was grovm in isolation to assess the efficacy with which
i
I it
j
cocld produce seed.
Abundant seed was produced and a repeat of
I
l this
I
I
!
j
I
I
l
I
ex;:oeriment gave similar results.
17
1
I
l
!
I
I
I
I
PLATE I
FIGURE 1
A cross section through a mature stem, shov.ring
secondary xylem (B) which has nearly surrounded
the primary phloem (A) •
I
FIGURE 2 A median longitudinal section through the stem
apex,
sho~ring
the tunica-corpus arrangement.
FIGURE 3 A cross section
throL~h a young stem
collateral vascular bundle.
show~r.g
a
A cross section through a you..."'1g stem. The
location of collenchyma is shown by light
stippling, the heavier stippling represents
the vasclL1ar buncHes. The ljne connecting
these bundles represents the Lnterfascicular
cambium.
I
l
l
1"
~··-·'-)
t'igure 1
Figure 2
E
E
Figure 4
Figure 3
3
3
.16 mm
lC
-/
PLATE II
FIGURE l
A cross section through a young root, showing
two protoxylem poles.
FIGUF..E 2 A cross section through a mature root, showing
secondary growth. The letter A indicates the
outer edge of the central core of xylem; the
letter B illdicates secondary xylem which vdll
eventually be part of a complete ring.
FIGUfili 3 A cross section through the midrib of a mature
leaf.
FIGURE 4
The outline of a leaf borne on the main stem.
FIGURE 5 The outline of a leaf borne on a lateral branch.
20
Figure 2
Figure I
.25 mm
.15 mm
Figure 3
Figure 4
Figure 5
.17 mm
21
r"_ _,_ .
------~
-----~.,~~--"'·:------~-.-~-
·- -·- - - - - - . . . . -,.- - - ·- . - - _ _ _ _"_ _ _ _ _ _
-~-
·----·~--------
- -· _,_ _ _ _ _ _. _ _ _ - -----------------l
-~---
j
I
l
l
l
I
I
l
I
i
!
j
l
I
PLATE III
FIGURES 1-3 Vessel elements of the pr:iJnary xylem.
I'
I
l
FIGURES 4-6 Vessel elements of the secondary xylem.
FIGURE 7 A fiber, present in the secondary xylem•
.
!
II
j
l
t. . ~·~-m-..:~"'~'"''' ......""''~""'""''"""'-.....=t.<fi~·,....,.._~ .....,•..,.=.~,.........".,."'"'"""'"·'*"~"'"·~-.~···"'-......... """-"·~·»""""'-~d~..-----n-n<..~ .....-=~"'". . . .,._, . . ,_.,......"""""="'-..,'.,',...."<'""-"'''''"''~''''--...-~-;,op-e~.'t<>~~....,,........"'u.-..................,...,._~..-,,...,..._,.......J
22
Figure 2
Figure 3
Figure 1
s
13
~
s
e
s
s
<Xl
cq
C'l
~
Figure 7
'Figure 6
Figure 5
Figure 4
s
s
1./:)
.....
-------:..------------...
--_-----_ __--:.:-=
---
s
s
s
s
.
r:-
.....
.
-~-
23
I
I
.I
PLATE IV
I
I
FIGURES l-3 A diagr~uatic representation of the development
of a single compound dichasium; individual flowers
are labeled to provide continuity.
l
i
FIGURE 4
A diagramatic representation of the inflorescence
which terminates the main stem. The primary axis,
bearing six dichasia with subtending bracts,
terminates in a single flower.
FIGURE 5
A diagram of an open perfect flower.
.
.
l
L«>~-·=·-•~~=••·~~~=.,=·•m.~·-~~·----~~--·~--~~~~;•-~••'"--~·~--~.. -~-~-,---- '"~-•·"---·-.~·~~--~···~·~•·-~·~.,.,~-~-·-1
21,.
Figure 2
Figure 1
Figure 3
Figure 4
Figure 5
-~
25
TABLE I
An enumeration of the perfect flowers in the six
uppermost dichasia of fifteen plants. Side B
represents the more strongly developed side of the
initial dichotomy and Side C the less strongly
developed side.
I
II
I
I
l
I
I
r--w. . . ----..
( PLANT
NU:HBER
'!.
-----------.. .
~
DICHASIUM
NUl'~"J.BER
SIDE
B
SIDE
c
..
-·-~------- ---------------~---·-·-.._....
PLANT
DICHASIUH
NUl·IDER
NmJBER
SIDE
SIDE
B
c
__.. . .__
~-~~"--·-·-------~~-·------~~~
PLANT
DICHASIU}f
NUMBER
NUMBER
SIDE
B
SIDE
c
I
1:
!
l'
Ii
I
!
•a
I
1
I'
)
1
2 .
3
4
5
6
.
Ii
2
1
2
3
4
4
5
5
4
4
5
7
4
4
5
0
1
2
-o
i
4
5
i
6
'
l
8
2
3
4
4
0
2
II
I
I
1
3.
1
I
~~
4
5
3
5
6
1
1
0
1
1
0
2
1
1
1
2
2
0
1
r
6
5
~
l
!
2
3
4
I
i
I'
i
4
i
!:
4
5
6
I
l
''
2
3
i
~ .
5
'I
4
5
i
6
;
l
6
5
4
4
5
5
5
4
4
4
4
6
1
1
1
2
0
0
2
2
0
i'
j
1
e
f.
)
... ,
!_____ __.._" -·-·---~. . . . . . . -w....., .............--..~-~---------·-'-'·.._........--
7
B
1
2
3
4
4
4
4
5
3
6
1
2
3
2
1
5
4
4
4
4
2
5
6
4
3
4·
r-
1
2
3
::;
6
4
4
5
8
2
3
5
6
4
5
10
5
7
5
3
7
5
3
3
5
4
5
6
1
9
2
2
0
2
0
0
0
0
2 .
0
1
0
0
2
2
1
1
2
2
2
0
3
2
1
0
3
2
2
1
6
1
2
3
4
5
6
~
........__...,_.. ____...._,. ______ ~...-...·--. . ~·~~. . --....--····'·
-----------"---~·-~·---
11
1
2
3
/+
5
12
6
1
2
3
4
5
13
14
15
6
1
2
3
5
3
5
5
4
1
2
0
2
2
2
3
2
2
3
6
7
5
4
5
4-
6
1
2
3
4
9
5
5
4
L~
5
3
6
1
2
3
5
6
2
0
1
2
1
2
2
6
4
4
·-·*'-"-'-~----.,..._-
5
5
4
4
4
4
2
7
3
4
4
3
3
........-~ ...-.._b_~·-·--·...-~'-"'-- . '"-·•-•""'~- . . . . . . . . . .-.~ ....-.. ---·-· . __
0
2
1
2
2
1
1
2
2
2
1
2
2
~
I
I
~
~
l
I
i
I
I
!
)
!
l
l
il
l
1
l
!
I'
i
;
~
I
'
~
l
;
.1
i
l
l
~
i
l
j
l
t
~
•
~
;
/\)
()'-,
CHAPTER IV
I
DISCUSSION
j·
Numerous species in the genus Chenopodiu:rr', have been shoi.\rrl by
j Cumming
to be eithf~J::' long day or short day plants.
(1969)
The
I
lregularity with Hhich C. nrura.le flowers, regardless of photoperiod,
j
-·---·
~·
; is apparently quite exceptional.
Perhaps there are conditions under
i
hrJhich C. !mJ.r~e VJ01Jld be sensitive to photoperiod; further study
!would be required to settle this
l,l
is~J.e.
Only a few- representatives of this genus have been exami11ed
,1
II' ane..tomica.lly,
1
scrutinized.
and of these C. album has been the most closely
-
---
Anatomical features in C.
mura:]:_~
!exceptions, quite similar to those reported for
are, vlith some
f·
album.
!
jf.
albu.lTl are described as triarch (Korsmo 1
19.54),
while in
Roots., J.n
f·
murale
i
l
!roots are diarch.
I
Esau
(1965)
poL~ts out that the number of prot~Jlem
)
!poles may vary even vrithin a given plant, so this discrepancy is
l
jprobably not significant.
I
j root of
f·
The anomalous secondary thickening in the
murale follows the same pattern as both
I
)1954)
and Beta vulgaris (Artschwager,
f.
album (Korsmo,
1926).
Regarding the stem, the origin of the secondary phloem in
C. murale is somev;hat different than· in C. albu.rn.
In the former it
forms from internal derivatives of the vasclliar cambium, meristematic
cells are used uu in this region.
.
~
-
A new cambium then forms in the
.
I
!l
parenchyma adjacent to the outer face of the phloem group (Artscln-vager, 1
1920).
.
.
I
The result is the same in both cases, phloem groups
are scattered within the secondary xylem.
No prior study noted the
correlation betv.reen the cessation of stem elongation and the onset of
27
j
l
28
secondary thickening, shor.vn herein for
f· nn.1rale.
The initial development of the infioresc.ence, culnLinating in the
formation of a terminal flower, is the same in f· album (Gifford and
Tepper, 1961) as in
f.
rrrurale.
However, Gifford and Tepper were
concerned primarily \vith aspects of the transition of
~he
apex from
the vegetatj_ve to the floral. condition_; they did not describe the
development of the inflorescence beyond its primordial condition.
A
closer examination would be illuminating as the mature structure is
quite different from the inflorescence in
f.
mura1~.
In fact, most
members of the genus would profit from a critical ex8Jl1ination of their
inflorescence morphology.
Prior to this study, the distribution of perfect and pistillate
flowers in the inflorescence had not been determined for any species
·of Chenopodium.
Although a pattern is evident in
incompletely understoodo
s:_.
murale, it is
For example, the original central flower
in a compound dichasium is occasionally pistillate; the appearance
of pistillate flowers at this position is apparently random.
It is
not correlated with the position of the dichasium on the primary axis.
There are other loci in the inflorescence where a perfect flower is the
rUle and a pistillate flmver is occasionally found.
These
irregularities notwithstanding, the tendency for perfect flowers to
appear on the more strongly developed side of a given dichotomy is
marked.
No speculation
produces this pattern.
is
made v..r;ith regard to the mechanism which
Additional information would certainly be ·
gleaned from an examination of related species.
The growth of plants in isolation indicates that C. murale is
autogamous, and that abundant seed production is possible in spite of
29
-,·--..
r"-~--,-~c
.
I
l
I
.
~-~-·-c -·-··c·«---·----·~~~-·~~~··--··~·"·~·· =·,----·~· c·---~"--·---~-~.····
i the paucity of fertile antherse
Thus there is an effective breeding
system, 11-r.i.th what would appear to be a nunirrrwn of pollen.
Of course,
this is based on results obtained from only tvJO plants, and again, it
j
would be instru.ctive to examine related species.
!
I
.I
!
f
Ij
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LITERATURE CITED
'
l Aellen, P. and Just, T.
1943. Key and synopsis of the American
species of the genus Chenopodium L. knero }lidl. Nat. 30: 47-76.
I
I Artschwager,
E.F. 1920. On the anatomy of Chenopodium
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j
1
I
lI
albu~
L.
1926. Anatomy of the vegetative organs of the
_{ .. Agric. Res. 33: 143-176
sugar beet.
Balfour, E. 1965. Anomalous secondary thickening in Chenopodiaceae,
Nyctaginaceae and Amaranthaceae. Phytomorphology ~5: lll-122
Bisalputra, T. 1962. Anatomical and morphological studies in the
Chenopodiaceae III. Aust. ;I_. Bot. 10: 13-24.
Il
I CUmming,
B.G. 1969. Circadian rhythms of flower induction and their
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l_
l
.1
324·.
II Esau,
K. 1965.
New York.
Plant !\natomy.
2nd ed.
John v.filey & Sons,
A.S. 1949. Practical Plant Anatomy.
! Foster,Nostrand,
New York.
2nd ed.
D. Van
l Gifford,
I
i
l
E.N. and Tepper, H.B. 1961. Ontogeny of the inflorescence
in Chenopodium album. Amer. ;[. Bot. 48: 6 57-666
Johansen, D.A.
l Korsmo, E.
1940.
1954.
Plant Nicrotechniaue.
Anatomy of Weeds.
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¥iUI1z, P.A.
Rickett; H.W.
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-- --
NcGraw-·Hill, New York.
Grondahl & Sons, Oslo, Norway.
University of California
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Bot.
Robbir1s, W.W., Bellue, N.K. arid Ball, v'l.S. 1951.. Weeds of
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Sacremento.
Ulbrich, E. 1934, Chenopodiaceae. In Engler and Prantl, Die
Naturlichen Pfl&~zenfamilien, 2nd ed. Bd. l6c: 379-584.
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North America. Bartonia 27: 1-46.
30