153
DISCUSSION
Diversity of stomata
:
Stebbins and Khush
(1961), who have studied the stomatal
apparatus in 192 species belonging to 49 families, emphasize
the concept of the constancy of stomatal structure within a
family and accordingly they have grouped the different
families under four broad categories of stomata recognised
by them, but they also have cited some families as exceptions
which may fall in more than one category.
(1966,
Tomlinson
1969) seems to have also accepted this concept in group­
ing the different genera of Commelinaceae and different famili­
es of the orders Commelinales and Zingiberales.
However, more
than one type of stoma have been reported even on the same
surface of the leaf in some families like ftlismataceae-Baldellia
(Slafit,
1963) and Sagitt aria guayensis var.
(Crovindra jalu ,
lappula
1967), Cyperaceae-Hypoly trum (Baas, 1969),
Gramineae-Stipa neesiana (JVrrilJaga-Maffei, 1966) and pennise turn
(Yadav, 1969) and in the members of the orders Pandanales and
Spathiflorae
(Pant and Kidwai,
1966).
During the course of
the present investigation a diversity of stomata has been
encountered in some members of almost all the families
investigated. Such a diversity may be (a) ontogenetic or (b)
due to organizational changes in a mature stomatal apparatus.
15b
(a)
A guard cell mother cell may organize into a
stoma without any subsidiary cells
(anomocytic stoma) or the
surrounding epidermal cells may cut off subsidiary cells as
a guard cell mother cell produces a stoma. The resultant
stoma may be paracytic, tricytic or tetracytic.
(b)
The organizational changes in a mature stomatal
apparatus are brought about in any one of the following ways;
(i) The epidermal cells surrounding a stoma may cut off
subsidiary cells or they themselves assume the form of the
subsidiaries; for example an anomocytic stoma may become
paracytic or unilaterally flanked by one or two lateral
subsidiary cells.
(ii) An increase in the number of subsidiary cells may
take place by wall formation in lateral and/or polar subsi­
diaries in some members of Liliaceae, Amaryllidaceae, Araceae,
Orchidaceae, Commelinaceae etc.
Alternatively the adjacent
epidermal cells may assume the form of subsidiary cells
/
„
and
(cf. Liliaceae, Amaryllidaceae, Cannaceae ^ Zingiberoeae)
or both the processes may operate simultaneously as in some
members of the families Dioscoreaceae and
Zingiberaceae.
Some of such stomata may look partly or completely amphicyclic
paracytic or tetracytic.
Pant and Kidwai (1966) have also
reported partly amphicyclic tetracytic stomata in
Schizmatoglottis and Anthurium and completely amphicyclic
tetracytic stomata in Monstera. Philodendron, Pothos and
Rhaphidophora calophyHum.
An increase in the number
of subsidiary cells by wall formation .
is reported in Limnophyton (Stant, 1963) and in Stipa
neesiana(ArriBaga - Maffei, 1966), Baas
(1969) reports
additional lateral subsidiary cells in Hypolytrum but he
does not explain how the additional lateral subsidiaries
are formed,
(iii)
Sometimes subsidiary cells of a stomatal
apparatus may become epidermal cell like, or they may be
absent causing deviations from the basic types.
Thus a
tetracytic siomcimay become tricytic, paracytic or rarely a
stoma with one subsidiary cell,
A few forms such as a
stoma with one lateral and two polars or with only two
polars may also be met with.
The various forms of stomata
are sometimes int^graded through a series of transistional
forms.
Pant and Kidwai (1966) have also reported that
though the stomata are typically paracytic in Typha and
Sparganium, some stomata are without one or both lateral
subsidiary cells.
In light of the present investigation and the available
data on the occurrence of more than one type of stoma even
on the same surface, the concept of constancy of the mature
stomatal apparatus in different families of monocotyledons
as emphasized by Stebbins and Khush (1961) cannot be
!■
supported.
Stebbins and Khush (1961) have discussed the primitive
and advanced stomatal types,
Recording to them^stoma
with
several subsidiaries is the most primitive type from which ike
stomatal types with two subsidiaries and without subsidiaries
156
are derived independently but the types with taosubsidiaries
are advanced over the types with no subsidiaries.
This may
be true where the stomiltal type is constant for a family
but it is difficult to visualize one type as advanced over
the other^ when more than one type of stoma occur on the same
organ or surface or at times side by side.
Therefore, the
conclusion of these authors cannot be supported atleast in
the view of the present study.
For a further discussion
please see under Orchidaceae.
Abnormalities :
(a)
Cytoplasmic connections t During the course of
this investigation, cytoplasmic connections between nearby
stomata are observed in some members of the familiesa
Liliaceae and Amaryllidaceae.
They are sporadic in Allium.
Asphodelus. Asparagus plumosus. Amaryllis belladona and
Crinum asiaticum but are frequent in Asparagus gonoclados,
A. racemosus var. javanleus and A. sprengeri.
In all the
plants studied they are commonly found between two nearby
stomata but rarely as many as four stomata have been seen
thus associated.
Plasmodesmata have been reported in guard cell walls
by Kulha (1900), Gardiner and Hill (1901), Kienitz - Gerloff
(1902) and Esau (19^1).
Recently Litz and Kimmins (1968)
also reported them between guard cells and accessory cells
of Phaseolus vulgaris, Nicotiana tabacum and Datura stramonium.
However, no other author has, so far, reported cytoplasmic
connections between guard cells of neighbouring stomata in
157
monocotyledons.
Inamdar, Gopal and Chohan (1969) have, of
course, made a mention of such cytoplasmic connections in
polyscias of the dicotyledonous family Araliaceae.
Litz and Kimmins (1968) are of the opinion that the
cytoplasmic connections between guard cells and accessory
cells serve as path ways for the exchange of material and
that the guard cells are not physiologically isolated from
other epidermal cells.
It is premature to attribute any
definite significance without proper evidence to the
cytoplasmic connections, but they may be interpreted as
translocation channels.
Further, the protuberances from the
walls of guard cells are often formed in the direction of
strands.
It is, therefore, likely that they may help in
determining the directions in which protuberances may extend*
(b) Contiguous stomata :
They have been observed in
some members of Liliaceae, Amaryllidaceae, Dioscoreaceae,
Araceae, and Orchidaceae.
They may be juxtaposed, super­
imposed or may be arranged variously.
Most commonly two
stomata are contiguous but rarely three are thus found. They
are produced by 2-3 meristemoids placed side by side or end
to end.
Sometimes a guard cell mother cell is cut off by
an adjacent epidermal cell in
vicinity of a mature stoma.
It develops into a stoma and the two stomata become contiguous
which may be variously arranged.
Paliwal (1965) has also
reported the formation of contiguous stomata in this manner
in Pisum sativum.
Contiguous stomata have also been reported
in some members of Gramineae (Stebbins and Shah, 1962; Yadav,
158
1969)5
Alismataceae (Stant, 1963, see Fig* No. 103) and
Araceae (Pant and Kidwai, 1966).
The formation of contiguous
0
stomata does not support Bunning*s theory of inhibition zone. ^
k
(c) Degeneration of guard cells :
During the present
investigation, degeneration of stomatawas observed in Allium,
Asphodelus. Asparagus racemosus var .javanicus.Dioscorfea wallichL't
and Sansevieria.ffuch stomata are represented by a central
band of thickening and the shrivelled remains of guard cells
are sparingly seen.
Rarely the stoma is seen as a circular
plate. Pant and Kidwai (l966) have also reported the degenera­
tion of guard cells in Monstera. Pothos, RhaphidTophora
celatocaulis and Typhonium.
a
Similarly occasionallyAstoma is with only one guard cell
which may l?e either due to the degeneration of one guard
cell of a stoma, or the failure of the guard cell mother
cell to produce guard cell initials and itself assuming the
form of a guard cell.
Stomata with one guard cell are
reported in Alocasia, Spirodela and Typhonium (Pant and
Kidwai, 1966).
Very rarely a mature stoma is flanked by a guard cell
as observed on the perianth of Asparagus racemosus var.
%
javanicus.
As far as the author is aware no earlier author \
has reported such a phenomenon in monocotyledons.
(d) Unequal guard cells : An interesting case of a
stoma with unequal guard cells has been encountered on the
ovary of Crinum asiaticum with no pore between them. Pant and
159
Kidwai (1966) have also figured such a phenomenon in
Alocasia (cf. Fig. 51,
p. 321).
On the other hand, rarely
the two guard cells of a stoma are arranged irregularly on
the perianth of Asparagus racemosus var. javanicus.
Development j
In the present investigation the stomatal apparatus
is mostly studied on leaves but it is extended to the
vegetative and floral organs of some members of the families,
Liliaceae and Amary11idaceae.
Though there is a diversity
of stomatal types on leaves, the different types show,
perigenous development. Similarly the different types of
stomata on the same surface in various organs of the same
plant also follow a similar mode of developmenty
i.e.,
perigenous - as far as could be traced.
The present observations then support the findings of
S^ebbins and Khush (1961) who conclude that the developmental
modes in monocotyledons are constant even as to the minute
detail from organ to organ within the same plant, pant and
^idwai (1966) have also reported only perigenous development
in the members of the orders, pandanales and Spathiflorae.
Because of the occurrence of more than one type of stoma
even on the same surface of an organ and the various
abnormalities that have been encountered during the study,
the question arises "Can the structure and/or ontogeny of
stomata be useful criteria in taxonomical studies?".
At the
outset one becomes sceptical to use the stomatal characters
l6o
as an aid to the classification because of the diversity
stomata on the same surface of an organ.
of
Since only
perigenous development is, so far, reported for monocotyledonous
stomata, the ontogeny has, whatsoever, no significance in
the classification.
Inspite of the diversity, the mature structure
of
stomatal apparatus on the leaf may help to group tentatively
the different families investigated on the basis of the most
frequent type as follows
(a)
:
Stoma paracytic :
A1ismataceae
Pontederiaceae
(b)
Stoma tetracytic j
Agavaceae
Cannaceae
Comnelinaceae (in part)
Hypoxidaceae
(Curculigo)
Musaceae
Orchidaceae
(in part)
Zingiberaceae
(c)
Stoma tricytic :
Dioscoreaceae
(Dioscorea bulbifera)
161
(d)
Stoma anomocytic •
/Unary 11 idac eae
Agavaceae (Polianthes)
Dioscoreaceae
Iridaceae
Liliaceae
Orchidaceae (in part)
Subsi.cU<=*-rvj
(e)
Stoma with more than 4Acells all around :
Commelinaceae (in part)
tkai
It may be noted^the above groupings are somewhat
different from those of Stebbins and Khush (1961) and
Tomlinson (1969).
My observations are discussed familywise in the text to
follow,in light of the relevant literature published.
attempt has also been made wherever possible,
An
to discuss
the taxonomical implications of the families, on the basis
of^present findings.
FAMILY
= = = »»»
: sORCHIDACEAE
s ss as as as s = = = s
The only available information on the stomatal features
of Orchidaceae is through the works of Strasburger (1866) and
Stebbins and Khush (1961).
The latter authors have studied
only four species belonging to four genera in this family.
They reported that stomata lack subsidiary cells in the
Orchidaceae and treated the family along with other families
in which stomata are also devoid of subsidiary cells (see
l6z
Table No, lt p, 5*0.
in
Since they do not cite any exceptions
Orchidaceae it may be assumed that only one type, i.e.,
anomocytic,
is found in this family.
However, during this
investigation anomocytic stomata are found in Habenaria,
Peristylus and Satyrium. predominantly paracytic in Nervilia
and tetracytic in Aerides. Arundina. Dendrobium and Vanda,
Further, more than one type of stoma occur in all the genera
except Dendrobium. Habenaria. Peristylus and Satyrium,
Inamdar (1968) has also reported anomocytic stomata in
Habenaria marginata.
It is, therefore, evident that the
present observations are only partly in agreement with the
broad conclusions drawn by Stebbins and Khush (1961),
According to these authors stomatal types with more
than two subsidiary cells are primitive from which, types
with two subsidiary cells and with no subsidiary cells are
independently derived.
also be tested in
The validity of this conclusion may
light of the present findings. In their
more or less phylogenetic
classification Engler and Prantl
(cf. Pfitzer 1889) and Schlechter (1926) have
Habenaria
treated
Satyrium and Platenthera (peristylus) as
primitive genera, and Pogonia (Nervilia). Arundina.
Dendrobium. Aerides and Vanda as more advanced. Further,
the last four genera are epiphytic and the first three and
Pogonia (Nervilia) are terrestrial.
Hutchinson (l959)also
considered epiphytes as of more recent origin implying
thereby that they are more advanced than the terrestrials.
2.63
Terrestrial species of Habenaria, Peristylus and
Satyrium are anomocytic, and that of Nervilia is pre­
dominantly paracytic, but epitphytic species of Arundina,
Aerides, Pendrobium and Vanda are predominantly tetracytic.
Therefore,
the primitive genera have anomocytic or pre­
dominantly paracytic stomata; but more advanced epiphytic
genera have the tetracytic ones.
More than one type of
stoma even on the same surface, at times side by side, are
found in these advanced genera also.
It is,
therefore,
difficult to visualize one type as more advanced over the
other as they occur on the same surface. The conclusion of
Stebbins and Khush (1961), therefore, needs a serious
consideration to evaluate primitive or advanced nature of
stomata.
The taxonomical positions of various genera with
respect to the classifications of Bentham and Hooker f.
(1965), Engler and Prantl (pfitzer, 1889) and Schlechter
(adapted from Hutchinson, 1959 and Lawrence, 1967) are
given below;
Bentham and Hooker f.
Tribe Epidendreae
Subtribe Dendrobieae
Genus Pendrobium
Subtribe Coelogyneae
Genus Arundina
Tribe Vandeae
Subtribe Sarcantheae
Genera Vanda
Ae rides
164
Tribe Neottieae
Subtribe Arethuseae
Genus Pogonia
Tribe Ophrydeae
Subtribe Habenarieae
Genus Habenaria*
Subtribe Diseae
Genus Satyrium
Schlechter*s classification (1926)
ft
Subfamily Honc^adrae
Division I Basitonae
Tribe Ophrydoideae
Genus Habenaria
Division II Acrotonae
Tribe Polychondreae
Genus Pogonia
Tribe Kerosphaereae
Series A. Acranthae
Genera Dendrobium
Arundina
Series B. Pleuranthae
Subseries Monopodiales
Genera Vanda
Aerides
*
including peristylus
l64a
Engler and prantl (pfitzer, 1889)
Monandrae
A. Basitonae
Tribe Ophrydeae
Germs Habenar ia
Platenthera
Satyr iutn
B. Acrotonae
Tribe Neottieae
Genus Nervilia
Tribe Thunieae
Genus Arundina
Tribe Dendrobieae
Genus Dendrobium
Tribe Sarcantheae
Genera Vanda
Aerides
165
Stomata are anomocytic in the investigated members of
the tribe Ophrydeae, predominantly paracytic in the members
of the tribe Neottieae and tetracytic in the members of
Kke-
remaining tribes.
This may suggest that^segregation of
different genera into various tribes in these systems of
classifications may also find support in a broad sense oti the
C1926J)
basis of stomatal types,
Schlechter*s class ification^finds
more support on the basis of the structure of the stomatal
apparatus as he has included the genera Arundina, Aerides,
Dendrobium and Vanda in the tribe Kerosphaereae,
The most
predominant type in Nervilia is paracytic followed by
tricytic with tetracytic and anomocytic in equal proportions.
This may suggest that the tribe Neo^ttjjeae occupied an
intermediate position between the tribes having predominantly
tetracytic and the tribes with anomocytic stomata.
The
taxonomic position of Nervilia in different systems of
classification seems to support the present findings.
However, the conclusions, based on the study of a meagre
material of 13 species belonging to 7 genera, are, of course,
encouraging and a
detailed study of several species of
various genera (since the family is a large one) may yield
tangible results.
It may be possible to group various genera
on the basis of stomatal structure, as done by Tomlinson (1969)
for Coiranelinaceae.
On the basis of available stomatal
information, it is possible to suggest a tentative grouping
of various genera investigated as
iVuL Coded
:
166
Stomata anomocytic
:
Habenaria
FeristylusSatyr ium
Stomata predominantly paracytic
Stomata predominantly tetracytic
:
Nervilia
:
Polar subsidiary cells mostly
elongated at right angles to the
long axis of stoma ...............................................
Dendrobium
Polar subsidiary cells not as above..
Vanda
derides
Arundina
FAMILY
;
ZINGIBERACEAE
The only available information on stomata in this
family is through the works of Stebbins and Khush (1961)
and Tomlinson
(1969).
The former authors, who have studied
the stomatal apparatus in five species of this family,
included Zingiberaceae in Category I,
i.e., a stoma surrounded
by 4-6 subsidiary cells but they cite
(Table j, p.
55)
Amomum and Zingiber (one species each) as exceptions in the
family having only paracytic stomata.
On the other hand,
the latter author has investigated the stomatal features in
a large number of plants of Zingiberaceae and according to
him (p. 352),
stomata are usually with a pair of lateral
subsidiary cells and often also with a pair of terminal
(polar) subsidiary cells,
implying thereby that they may be
paracytic or tetracytic.
His figures D and F (p, 344)
clearly depict tetracytic stomata, but he classifies
\u. CoAegovnjC01-), i.e..
ZingiberaceaeAparacytic stoma
(see p. 4o4).
167
In the present investigation only tetracytic stomata
L.
are found in Globa and Zingiber but in other genera, where
diversity is observed, tetracytic stomata predominate, and
deviations from the normal structure of this type are also
met with.
They may be due to increase or decrease in the
number of subsidiary cells as described earlier, Tomlinson
(1969) also reports the modification of other epidermal cells
adjacent to the stoma in Boesenbergia and Camptandra.
The present observations, therefore, largely agree
with those of Sfcebbins and Khush (1961).
However, these
authors report paracytic stomata in Zingiber but they are
only tetracytic in Zingiber cernuum investigated during this
study.
Tomlinson (1969), following Nakai (l9**T) put the genus
Costus into a separate family Costaceae on anatomical
grounds.
However, the stomata are tetracytic in Costus as
in other members of Zingiberaceae,
I, therefore, feel that
the stomatal apparatus does not furnish any additional
\Xa.
evidence to supportAseparation of Costus from Zingiberaceae,
On the contrary, all the investigated genera seem to be
closely related within Zingiberaceae on the basis of the
stomatal structure.
Tomlinson (1969) reports that the stoma in Costus
englerianus is provided with irregularly arranged subsidiary
cells in addition to lateral and terminal subsidiary cells.
In Costus speciosus, however, additional cells are regularly
arranged as laterals and/or polars.
168
Of the Zingiber ace ae and Costaceae investigated byTomlinson (1969) Globba bulbifera is the only species investi­
gated by both of us.
The present study, therefore, provides
additional information on stomata in those species of this
family which are so far not worked out.
FAMILY
5
CANNACBAE
Tomlinson (1969) described the stomata in this family
as paracytic (p. 364 and 4o4).
lUe
On^other hand^Stebbins and
Khush (1961) reported them to be tetracytic in this family,
but according to Paliwal (1969) there are 3-7 subsidiary
edul is.
cells in Canna ..
During the present investigation, more than
one type of stoma are found on the same surface on the leaf
of Canna sp.
Inspite of diversity, the predominant type is
tetracytic, followed by paracytic one.
My observationsare,
therefore, largely in agreement with those of Stebbins and
Khush (1961).
FAMILY
32 =s as S3 SS S3
j
MARANTACEAE
—23S333333S
As early as 1866, Strasburger reported stomata without
subsidiary cells (cf. Paliwal, 1969) in Maranta.
Later on
Stebbins and Khush (1961) and Tomlinson (1969) described
paracytic stomata in Marantaceae.
The present investigation
concurs with the observations of these authors.
However,
in addition, a few tetracytic-like stomata, (because the
adjacent epidermal cells at polar ends of the stoma
the form of subsidiary cells) are also encountered. Tomlinson
'1 1 ‘
'
n
(
H.'
••
,
'
>
v *v ■ /
;
y'
.
169
(1969) on p. 404, 1 ef reports a few stomata in Marantaceae,
surrounded by modified epidermal cells.
In the present
plant no such cells have been observed, unless the polar
subsidiary cells in a few tetracytic sonata fit in this
category.
FAMILY
sssstscsss
:
MUSACEAE
ssasesssB
Stebbins and Khush (1961) reported stomata with more
than two subsidiary cells as a predominant condition in the
family Musaceae.
Tomlinson (1969.
P. 404) specifically
mentions that they are tetracytic in Musaceae. The present
observations thus agree
FAMILY
SSS888
with those of these authors.
: HAEMODORACEAE
S8S3BSS8:SS88B
The genus Sansevieria is included in the family
Haemodoraceae - tribe Ophiopogoneae by Bentham and Hooker f.
(1965).
However, Rendle (1953) put this genus in
Liliaceae, sub^f airily Dracaenoideae along with Yucca. Dracaena
and Cordyline.
Bailey (1949) includes Agave, Polianthes.
Yucca. Dracaena. Cordyline and Sansevieria in Agavaceae, a
circumscription of the genera also adopted by Hutchinson
(1959).
Since stomata are predominantly tetracytic in Agave.
Cordyline and Yucca a character also found in Sansevieria.
the alignment of the present genus with these genera in
Agavaceae can, then, atleast be strengthened on the basis of
the stomatal apparatus.
Stebbins and Khush (1961) seam teViave
followed Hutchinson’s classification, and therefore, the
170
inclusion of Sansevieria in Agavaceae by these authors can
be presumed.
In that case, then, stomata are at least not
without subsidiary cells in this genus, and other investigated
members of Agavaceae contrary to the report of these authors,
that stomata are without subsidiary cells in this family.
FAMILY
{
SBCtSCK
IRIDACEAE
SS 32 tS SS SS SS SS S3 SB
The earliest report on the stomata in this family is
that of Strasburger (1866) who reported them to be without
any subsidiary cell. Stebbins and Khush (1961) who investi­
gated stomata in four species belonging to
four genera of
this family recorded that the stomata are without any
subsidiary cells.
These observations were confirmed by
Paliwal (1969) while observing stomata on Belamcanda
chinensis.
The present investigation also concurs with the
findings of the earlier workers.
The transformation of a guard cell mother cell into an
ordinary epidermal cell is an interesting feature not
reported by earlier authors.
The writer has also observed a
similar phenomenon in some members such as Crinum lafcifolium.
Pancrat fAim etc., of an allied family - Amaryll idaceae.
FAMILY
: AMARYLLIDACEAB
The genera Agave. Amaryllis. Crinum. Curculigo.
Pancratium. Polianthes and Zephyranthes are treated as members
of Amaryllidaceae by Bentham and Hooker f.
Diels (1936) and Rendle (1953).
(19^5), Engler and
However, the circumscription
171
of the family Amaryllidaceae is restricted by Hutchinson
(1959) including all the genera investigated except Agave.,
Polianthes and Curculigo
The first two genera belong to
Agavaceae and the last genus to Hypoxidaceae,
Stebbins and Khush (19&1), who have followed Hutchinson*s
classification, have studied ten species in Amaryllidaceae,
fifteen in Agaveae and two in Hypoxidaceae.
They hold that
stomata in first two families are anomocytic (except
Doryanthes in Agavaceae which has a pair of lateral subsidiary
cells) but Hypoxidaceae has stomata with a pair of laterals
(paracytic).
The present study, based on eleven species of
Amary1lidaceae (Sensu Bentham and Hooker,
f.) reveals that,
though more than one type of stoma occur in most of the
organs of various species studied, anomocytic stomata are
predominant in Amaryllis. Crinum, Pancratium. Zephyranthes
and Polianthes but tetracytic in Agave and Curculigo.
Anomocytic stomata have also been reported in Zephyranthes
ajax. Z. lancasteri. Z. rosea (Shanks. 1965) and Amaryllis
vittata (Paliwal, 19(>9).
My observations thus concur with
those of Stebbins and Khush (1961) but for the last two
VIZ.j
SClnhCl u.vc.t*lt<30 .
genera,AThe separation of Agave and Curculigo from
Amaryllidaceae to the Agavaceae, therefore, finds a support
on the basis of the structure of stomata.
Cordyline.
Sansevteria and Yucca, which are also included in Agavaceae
(Sensu Hutchinson 1959) have also predominantly tetracytic
stomata (please see under Liliaceae and Haemodoraceae). The
present study, therefore, indicates that in most of the
members of Agavaceae (Sensu Hutchinson, 1959) tetracytic
172
stomata are most frequent and, therefore, the data on
stomatal structure may indicate Agavaceae as a homogeneous
family.
However, Polianthes, included in Agavaceae by
Hutchinson (1959) becomes an exception in the family having
predominantly anomocytic stomata as in other amaryllidaceous
species (Sensu Hutchinson).
FAMILY
SBS8SS
:
DIOSCOREACEAE
BSSBSSaESSBSSB
The only isolated information about stomata in this
family is through the work of Stebbins and Khush (1961), who
based their observations only on two species, belonging to
two genera.
According to these authors, stomata are
anomocytic.
The present investigation, based on an intensive study
of six species of Dioscorea, reveals the occurrence of more
than one kind of stoma on the same surface. The predominant
type is anomocytic in all species of Dioscorea, except D.
bulbifera in which it is tricytic.
Inspite of diversity, the
present investigation, therefore, largely concurs with the
findings of Stebbins and Khush (1961).
Hutchinson (1959) derives Dioscoreales from Liliales
whereas Rendle (1953) considers the family nearly phylogenetically allied to
Amaryllidaceae from which it can be
distinguished by the habit, net-veined leaves and generally
unisexual flowers.
In the families Liliaceae, Amaryllidaceae
(Sensu Hutchinson) and Dioscoreaceae (except D. bulbifera),
173
stomata are mostly anomocytic and the stomatal apparatus
may suggest an evidence in considering the phylogenetic
relationship between these families.
FAMILY
ssmsss
:
TACCACEAE
SSCSSKSSSS
The only report on the stomatal apparatus in this family
is that of Stebbins and Khush (1961) who recorded anomocytic
stomata as a sole type in this family (cf. Table No. 1^ p. 5*0.
Though my findings broadly agree with these observations, the
occurrence of stomata with one subsidiary cell is an addi­
tional information.
FAMILY
sssbbb
:
LILIACEAE
ss ss ss ac s: as as s: sb
Allium. Asparagus, Chlorophytum. Gloriosa. Iphigenia.
Ruscus. Scilla, Smilax. Urginea and Yucca belong to Liliaceae
(Sensu Bentham and Hooker f,, 19&5; Engler and
Diels, 1936).
However, Hutchinson (1959) has transferred Ruscus and Smilax
to monogeneric families Ruscaceae and Smilacaceae respectively
and Cordyline and Yucca to Agavaceae.
Bailey (19-4-9) has
also adopted more or less a similar circumscription of these
genera.
Stomata are predominantly paracytic on the leaves
of Smilax. and tetracytic on those of Ruscus. Cordyline and
Yucca, against the predominant anomocytic type on the leaves
of Allium. Asphodelus, Iphigenia. Scilla, the cladodes of
various species of Asparagus and vegetative and floral organs
of Asparagus racemosus var. .javanicus. Chlorophytum and
Gloriosa.
The stomata' of Ruscus. Smilax. Cordyline and
Yucca, therefore, provide a new evidence in support of the
taxonomical treatment of the genera adopted by Hutchinson
(1959) who based it purely on external morphology.
On the other hand, tribes Allieae (Allium sp.),
Agapantheae and Gillesieae, which have an umbellate spathaceous
inflorescence are put in Amaryllidaceae by this author and
the transfer of these tribes from Liliaceae to Amaryllidaceae
has also found favour by some morphologists on palynological
data (See Lawrence 1967, P* ^15); however stomatal structure
dc^ not lend any indication to support the inclusion of Allium
into Amaryllidaceae, since only anomocytic stomata are found
in Liliaceae and Amaryllidaceae (Sensu Hutchinson 1959; also
cf. Stebbins and Khush, 1961).
Apart from the fibrous leaves and xerophytic nature of
Cordyline and Yucca, the characters which are also found in
Agave and Sansevieria, the inclusion of all these genera in
the family Agavaceae by Hutchinson (1959) can «lso find a
favourable support on the structure of stomata, since all the
genera share a common stomatal character - predominantly
tetracytic,
According to Stebbins and Khush (1961), stomata are
predominantly anomocytic, i.e,, without any subsidiary cells
in Liliaceae, Smilacaceae and Agavace
(except Doryanthes).
My observations are in agreement with those of these authors
for Liliaceae (Sensu Hutchin$o«/L959) only, but not for
ca
Smila^ceae
and Agavaceae since stomata are predominantly
175
paracytic and tetracytic in these families respectively. It
appears there is no information about stomata in Ruscus,
implying thereby that these authors may not have investigated
it from this view point.
The present investigation on
stomata on the cladode of Ruscus is a further contribution
to support the separation of Ruscus from Liliaceae and its
inclusion to Ruscaceae
(Hutchinson, 1959).
FAMILY
BCBBSS
:
PONTEDERIACEAE
SSSBSS8SSSSSS8
Stebbins and Khush (1961) put Pontederiaceae along with 'tke
families in which a stoma with two subsidiary cells is a
predominant feature.
Though a diversity of stomatal types
is observed in^present plant,^most abundant type is paracytic.
My observations therefore, are largely in agreement with
those of these authors.
Taxonomically Pontederiaceae is included in Liliales
along with other families such as Liliaceae, Smilacaceae,
Ruscaceae etc., by Hutchinson (1959) who remarks, "The
Pontederiaceae are a difficult family to place.
They appear
to me to be aquatic Liliaceae tending towards Aroid type,
the spiciform inflorescence have a spathe—like reduced leaf
(leaf-sheath) ....
M
Swartz (1930) also treated the family as closely related
to
Liliaceae but considered the characters of endosperm,
the variability and reduction in the androecium and the floral
zygomorphy to be of sufficient importance to also justify
placing it close to
#
the family Commelinaceae.
Lawaace ('13Q>'2).
176
On the basis of the stomatal apparatus, it is evident
that Pontederiaceae are quite distinct from Liliaceae
(Sensu Hutchinson, 1959) because of the predominantly
paracytic stomata in the former family and anomocytic ones
in the latter family.
Similarly Swartz*s view that it can
be placed close to
Commelinaceae on the basis of floral
qrootvoLs
morphology, also cannot be substantiated on the guard. that
stomata are predominantly tetracytic in most of the genera
of Commelinaceae investigated by Tomlinson (1969), and my
observations on the study of some plants of this family.
However, Pontederiaceae may indicate a relationship
with some araceous members like Amorphophallus, Arisaema.
Cryptocoryne, Sauromatum etc. (see alsp p. 14% ), in which
paracytic type is also most frequent.
The findings, then,
to some extent, may substantiate Hutchinson*s view, but it
will be premature to draw any conclusion on the basis of the
meagre data available and on the basis of stomata alone. A
detailed investigation of many species of the families of
assumed affinities with Pontederiaceae will be of utmost
importance to provide ample data to th^row light on the
phylogenetic relationships of these families.
FAMILY
“• “
25 25 25 85
:
COMMELINACEAE
SR
25 52 25 85 52 26 SS S S
25 85 SB
A considerable amount of literature is available on
the stomatal apparatus and its ontogeny in Commelinaceae
through the works of Strasburger (1866), Campbell(1891),
Benecke (1892), Porsch (1905), Drawert (1941), Stebbins and
177
Jain (i960) Stebbins and Khush (1961) and Tomlinson (19^6*
P
1969).
From their investigations on 4 species belonging to
4 genera of this family, Stebbins and Khush (1961) reported
that stomata are surrounded by four subsidiary cells, one on
each of the four sides of paired guard cells, constructing
a beautiful square in Tradescantia, Rhoeo and Zebrina but
six subsidiary cells have been reported by them in Commelina,
two additional cells being present on the sides.
However,
a comparatively much better and a more detailed account of
the stomatal apparatus, based on an extensive study, is
furnished by Tomlinson (1969).
He classified the investiga­
ted species on the basis of the structure of stomata
assuming it to be a constant feature for a particular group
of genera
as follows :
2 -
celled stomata : Cuthbertia,
4 -
celled
(Tricerate11a)
stomata: Aploleia. Belosynapsis, Callisia,
Campelia Cochliostema. Coleotrype,
Cyanotis. Dichorisandra, Forrestia.
Gibas is. Hadrodemas. Palisota. Rhoeo,
Setcreasea, Siderasis, Tinantia,
Tripogandra. Zebrina.
6 - celled stomata
: Aneilema. Anthericopsis, Athyrocarpus.
Ballya. Commelina, Floscopa,
Geogenanthus. Murdannia. Pollia,
Polyspatha, Stanfieldiella.
The present observations on the stomatal apparatus on
leaves of Cyanotis . and Tinantia fully concur with those of
178
Tomlinson
(19&6) •
The most frequent type of stomata with
six subsidiary cells in Commelina also largely confirms the
findings of Stebbins and Khush (1961) and Tomlinson (1969)
but rarely deviations leading to 4-5 and
-7-fcelled stomata
have also been observed in various species of Commelina,
Tomlinson (1969) recorded 6-celled stomata in Murdannia
(see p. 33 and figure 9 (M) on p. 38) but figures 9 P and T
of Murdannia zeylanica and M. graminea respectively show
4«- celled stomata.
However, this author has treated the
genus with other genera having 6 - celled stomata, on the
basis of the investigation in five species (cf, p, 33).
I have observed only 4-celled stomata in M. semiteres and
M. nudiflora.
The last species is also investigated by
Tomlinson (1969).
My observations on Murdannia are, there­
fore, different from those of Tomlinson (1969).
Prom the present study, it is evident that the stomatal
apparatus is constant in Cyanotis, Murdannia and Tinantia
but it is vaiiable in various species of Commelina. the
y*
variant forms often occurring side by side on the same surface,
Tomlinson
the
(1969) has grouped the different genera on
basis of the number of subsidiary cells.
The following
is a tentative segregation of the genera presently
investigated.
Stomata with 4-subsidiary cells :
Epidermal cells mostly tangentially elongated;
lateral subsidiary cells generally elongated at
right angles to the long axis of stoma ........
Tinantia
179
Epidermal cells elongated in the
direction of the long axis of the leaf;
lateral subsidiary cells parallel to
guard cells s
Lateral subsidiary cells as long
as the guard cells............ .
Cyanotis
Murdannia semiteres
Lateral subsidiary cells as long
as the stomatal apparatus .......
Murdannia nudiflora
Stomata more commonly with 6
subsidiary
cells rarely varying
from 4-8 cells
.............. .......
Commelina
Tomlinson (196<5 p. 383) has described an increase in the
number of subsidiary cells in Geogenanthus.
In the present
study also a wall formation has been noted in the polar
subsidiary cells of Commelina suffruticosa increasing their
number (cf. PLATE 6l F).
Tomlinson (1969) has listed the species examined by him,
of which Cyanotis axillaris, Cyanotis cristata and Murdannia
nudiflora are also studied by me.
This list therefore, is
supplemented by four more species of Commelina and one species
each of Murdannia and Tinantia. on which the information
regarding stomatal apparatus is now made available.
The present investigation has also brought to light a
few marked deviations, which so far are not reported by
earlier workers
180
FAMILY
:
ARACEAE
The earliest account on the structure of stomata in
this family seems to be that of Strasburger (1866) who
described stomata of Pothos with four subsidiary cells. Later
on the structure of the mature stomata of some members of
Araceae was described by Solereder and Neyer (1928, 1933),
Webber (i960), Stebbins and Khush (1961) and Pant and Kidwai
(1966).
From their investigations on seven species belonging to
seven genera of Araceae, Stebbins and Khush (1961) reported
that the most predominant type in the family is the stoma with
more than two subsidiary cells except in Irisaema in which
the stoma is paracytic
(see Table No. 3, p. 5^).
However,
Pant and Kidwai (1966) seem to be the first authors to make
detailed observations on the stomata in 17
species of Araceae,
which are somewhat at variance from those of Stebbins and
Khush (1961),
According to Pant and Kidwai (1966) paracytic
stomata occur in Alocasia,
ftmorphophallus, Arisaema, Caladium,
Colocasia, etc., tetracytic in Anthurium, Monstera, Philodendron,
Po thos , Schismatoglot t is .
anomocytic in Pistla.
and Rhaphid ophora calophyHum and
However, they have also observed
tetracytic, tricytic and anomocytic stomata in Amorphophallus and
tricytic in Alocasia, Caladium, Colocasia, Pothos, Philodendron,
Typhonium and Zamioculcas.
Anomocytic stomata have also been
recorded by them in Pothos, Typhonium and Zamioculcas.
It is
evident from these data, that they have observed more than
one type of stoma atleast in some of the genera, though the
181
prevalent type in many of them is paracytic, in others
tetracytic but anomocytic only in one genus.
The present investigation deals with Amorphophallus.
Arisaema, Cryptocoryne and Sauromatum.
The last two genera
are not worked out by Pant and Kidwai (1966),
My observa­
tions on Amorphophallus agree with those of these authors in
having predominantly paracytic stoma,
Amphicyclic paracytic
stoma found in Amorphophallus and Cryptocoryne is not reported
by these authors.
Similarly anomocytic and tricytic stomata,
reported by these authors in Amorphophallus have not been
encountered
in the present study.
From the above discussion, it is also clear that though
my observations are somewhat at variance with those of
Stebbins and Khush (1961) and pant and Kidwai (1966), in
general they largely concur with those of the latter authors.
Inspite of
a diversity in stomatal types on the same
surface of the leaves in some genera,
it is possible to
group
different genera, whose stomatal apparatus is known, on the
basis of the predominant type.
Paracytic
Anomocytic
Tetracytic
Alocasia
Pistia
Anthurium
Amorphophallus
Monstera
Arisaema
Philodendron
Caladium
Pothos
llephidophora calophyllum
Colocasia
Cryptocoryne
l|aphidophora celatpcaulis
Cttp
Schim|pglottis
182
Sauromatum guttatum
Synogonium
Typhonium
Xanthosoma
From the above given datum, it is clear that pre­
dominantly paracytic genera are more than the tetracytic ones
whereas only one genus is anomocytic.
The information,
therefore, is immensely useful in correcting the report of
Stebbins and Khush (1961).
V
Since Arisaeroa neglectum, Crypfocoryne and Sauromatum
are not investigated by Pant and Kidwai (1966) the present
study provides additional information about the stomatal
n.
apparatus in three uni^yestigated
species of the family.
fAMILY
5
ALISMATACEAE
Stebbins and Khush (1961) recorded paracytic stoma in
Alismataceae, a conclusion based on an investigation of only
two species belonging to two genera.
From a more detailed
anatomical study of fourteen species of the Alismataceae
(including Sagittaria sagittifolia and Limnophyton obtusifolium).
sjjjint (1963) found that stomata are mostly paracytic but
occasionally they are with more than two subsidiary cells as
in Baldellia.
She also reported that several instances about
wllldt"
the presence of tetracytic stomata in the familyAhad been
recorded earlier (see p. 12).
According to her, stomata are
paracytic in Sagittaria (S. sagittifolia.
and S. japonica
cited), Alisma, Dasmasonium, Echinodorus. Limnophyton
183
obtusifollum, Luronium and Ranalisma but they are paracytic
and tetracytic in Baldellia.
This suggests that stomata are
only paracytic in Sagittaria sagittifolia and Limnophyton
obtusif olitwt. Govind|ra jolu
(1967) observed that though the
prevalent stomatal type is paracytic in Sagittaria guayensis
var, lappula, occasionally stomata are tetracytic.
This
seemed to be first report regarding the occurrence of more
than one type of stoma in the genus Sagittaria.
Figures 6
and 7. depicting stomata of S. lancifolia (see Stant 1963. P.
11), are tricytic and tetracytic respectively, and they
indicate a diversity, of stomata in the genus Sagittaria.
Similarly the figures 11
and 14 of Govindjrajulu1 s work (1967)
clearly show paracytic and tetracytic stomata respectively,
but a tetracytic stoma shown in figure 3^ deserves critical
consideration, since one of the polars apparently resembles
an epidermal cell and, therefore, that stoma is probably a
tricytic and not a tetracytic one.
From a critical study of the works of Stant
Govinc^ajalu
(1963) and
(1967), it is evident that more than one type
of stoma are present on the same surface in Sagittaria. In
the present investigation, diversity of stomata has also been
observed on the leaf of Sagittaria sagittifolia.
This^thert,
becomes an additional example of diversity of stomata in the
genus Sagittaria.
In Sagittaria sagittifolia. though there is a diversity,
the predominant type is paracytic, tetracytic and tricytic
types being rare.
The present observations vary in certain
aspects from those of Stebbins and Khush (1961) and Stant
18k
(1963) but they largely conform to the findings of these
authors that the most abundant type is paracytic.
Similarly paracytic, tetracytic and tricytic stomata are
encountered on the leaf of Limnophyton obtusifolium, but the
first type is most prevalent.
This investigation, then, is
also largely in conformity with findings of Stebbins and
Khush (1961) and Stant
(1963).
The latter author, however,
has depicted a group of paracytic stomata and contiguous
stomata placed end-to-end (in figure 103, on p. 3*0 for
Limnophyton. Contiguous stomata have not been observed in the
species I have studied.
The present study, therefore, constitutes a supplementary
data on stomata for the family.
I have also been able to
bring out some information on Limnophyton presumably over­
looked by Stant (1963) during the course of her study.