28
CLASSIFICATION OF STOMATAL TYPES
A. MORPHOLOGICAL OR TOPOGRAPHICAL CLASSIFICATION:
The dicotyledons stomata were firstly classified into 4
types by Yesque in the year 1889. The names for your types
were given after the family in which these types were first
studied. The four types as defined by Yesque (1889) are as
follows:
(i) Ranunculaceous type: Stoma mother cell is cut off by a
simple U-shaped wall; mature stomata are surrounded by
several irregularly disposed epidermal cells.
(ii) Cruciferous type: The stoma mother cell is cut off in the
primordial cell by three or more cell walls inclined to
one another at an angle of about 60°; mature stomata are
surrounded by three subsidiary cells, of which one is,
smaller than the other two.
(iii) Caryophyllaceous or Labiateous type: Stoma mother cell
is cut off into the primordial cell by two U-shaped cell
walls oriented in opposite directions, the second being
attached to the concavity of the first, mature stomata are
suspended in the middle of an epidermal cell by two cell
walls perpendicular to the pore.
(iv) Rubiaceous type: Stoma mother cell is cut off in the
primordial cell by two parallel walls; mature stomata are
accompanied by two subsidiary cells parallel to the long
29
axis of the pore.
In order to remove the impression that the particular
type of stomata are not restricted to certain families only;
Metcalfe and Chalk (1950) replaced these terms by more general
descriptive ones: "anomocytic” for Mranunculaceous”, "anisocytic”
for "Cruciferous”; "diacytic” for "Caryophyllaceous” or
"labiateous” and "paracytic” for "rubiaceous”.
Since Metcalfe and Chalk (1950) proposed these terms;
they have been in use in most research papers to indicate the
structure and position of the epidermal or subsidiary cells. The
different terms of Metcalfe and Chalk (1950) are defined as
under:
(i) Anomocytic (irregular-celled)type: The stoma is surrounded
by a definite number of cells that are not different from
the remainder of the epidermis.
/
(ii) Anisoeytic (unequal celled) type: The stoma is surrounded
by three cells of which one is distinctly smaller than the
other two.
(iii) Diacytic (Cross-celled) type: The stoma is enclosed by
a pair of subsidiary cells whose common wall is at right
angles to the guard cells.
(iv) Paracytic (parallel celled) type: The stoma is accompanied
on either side by one or more subsidiary cells parallel to
30
the long axis of the pore and guard cells.
The following morphological terms have been added to this list:
(v) Actinoc.ytic type: The stoma is surrounded by a circle of
radiating cells (Metcalfe and Chalk, 1950).
(vi) Cyclocytic type: The stoma is surrounded by 4 or more cells
forming a narrow ring around the guard cells (Stace, 19650*
(vii) Tetracytic type: The stoma is surrounded by four
subsidiary cells, 2 lateral and 2 polar, the polar sometimes
smaller and roundish (Metcalfe,1961).
(viii) Stoma with a single subsidiary cell; : The stoma is
accompanied by a single subsidiary cell either shorter or
longer than the guard cells and which mostly lie parallel
to the long axis of the pore. Van Cotthem (1970) designated
this as a hemiparacytic.
B. MORPHOGENETIC OR ONTOGENETIC CLASSIFICATION:
The stoma mother cell or stomatal initial called the
meristemoid is cut off from a cell of the protoderm. The
stomatal initial undergoes one or more divisions to give rise
to a stoma. A stomatal meristemoid which divides to form two
equal guard cells is called a guard mother cell.
I. Prantl^ classification (1872); It was Prantl (1872) who
firstly recognised two main ontogenetic types of stomata as under
31
(i) Direct type: The stoma initial undergoes only two divisions,
cutting off a mesogene neighbouring cell during the first
division before the second segment form the two guard cells
during the second division.
(ii) Indirect type; The stomata initial divides three or more
times to give rise to two or more mesogene neighbouring and
encircling cells before forming the guard cells.
II. Florin's classification (1931. 1955): The gymnosperm stomata
were classified into two following ontogenetic types by
Florin (1931, 1933):
(i) Haplocheilic type: A stoma mother cell directly dunctions
as a guard mother cell which divides to produce a pair of
guard cells only without cutting off any subsidiary cells..
(ii) Syndetocheilic type: A stomatal initial functions as a guard
mother cell after cutting off one or more subsidiary cells.
Florin (1931, 1933) did most of his work on fossil material
and, therefore, his conclusions many times were based upon the
structure of mature stomata. After the publication of Florin's
(1931, 1933)work, many research workers used these ontogenetic
terms for the description of mature stomata too on the basis of
presence or absence of subsidiary cells. Then, later on it was
proved that neither the presence of many subsidiary cells did
not always necessarily involved a syndetocheilic ontogeny; nor
did the absence of subsidiary cells involved always a haplocheili
32
ontogeny. Florin (1933), therefore, proposed to replace the
terms "mesogenous" for syndetocheilic and "perigenous" for
haplocheilic to indicate that the epidermal cells around the
stoma (neighbouring or subsidiary cells) develop or not from
the same stomatal initial as the guard cells.
(iii) Mesoperigenous: This term is coined by Pant (1965) to
this ontogenetic classification of the stomatal types to
denote that the surrounding cells are of dual orogin, at
first typically one mesogene neighbouring cell and guard
mother cell are formed from the meristemoid, while the
remaining perigene are those which happen to lie on the
other side of the meristemoid.
III. Pant’s classification (1965): Pant (1965) divided these
three maintypes mesogenous, mesoperigenous and perigenous
into ten subtypes as follows:
1.
Mesogenous are further subdivided depending upon the number
of cutting faces of the meristemoid which corresponds to
the number of subsidiary cells:
(i)
(ii)
Unilabrate
Dolabrate
(a) Mesoparacytic
(b) Mesodiacytic
(c) Pyrrosia type
(iii)
(iv)
Trilabrate
Tetralabrate
33
2. Mesoperigenous subdivided on the basis of plane of division
of the guard mother cell:
(i) Plagiogyria type (at right angles)
(ii) Tetracentron type (parallel)
(iii) Ranunculus type (at any angle)
3. Perigenous type.
IV. Maroti*s classification (1966): Maroti (1966) used thjfcfie two
ontogenetic terms,viz.:
(i) Haplochell
(ii) Syndetocheil
V. Paliwal's classification (1969): Paliwal (1969) classified the
monocot stomata into following five categories depending
upon the number of perigenes:
(i) Asahkoshik (Aperigenous)
(ii) Dwisahkoshik (Biperigenous)
(iii) Chatusahkoshik (Tetraperigenous)
(iv) Shatsahkoshik (Hexaperigenous)
(v) Bahusahkoshik (Multiperigenous)
(VI) Payne's classification (1970): Payne (1970) recognised two
new following mesogenous stomatal patterns in the dicotyledons
(i) Helicocytic: Stoma is surrounded by a helix of four or
more mesogene subsidiary cells.
(ii) Allelocytic: Stoma is surrounded by an alternating comple
of three or more C-shaped mesogene subsidiary cells of
graded sizes. Allelocytic stoma is known as:
(a)
Paralleloc.vtic when the guard cells are developed
34
parallel to the subsidiary cells and (b) Mall elocy tic
when the guard cells are developed at right angles to
the subsidiary cells.
(VII) Frvns-Claessens and Van Cotthea^s classification (1973):
Fryns-Claessens and Van Cotthem (1973) classified the
stomata of vascular plants into following 26 ontogenetic
categories:
A. Perigenous stomata:
Type: 1.
aperigenous
2.
monoperigenous
3*
diperigenous
4.
tetraperigenous
5.
hexaperigenous
6.
polyperigenous (Cycloperigenous)
B. Mesoperigenous stomata:
Type:
7.
anomo-mesoperigenous
8.
dia-mesoperigenous
9.
hemipara-mesoperigenous
10.
eupolo-mesoperigenous
11.
copolo-mesoperigenous
12.
anisoperigenous
13.
stauro-mesoperigenous
14.
para-mesoperigenous
15.
cyclo-mesoperigenous
35
C. Mesogenous stomata:
Type:
16. desmo-mesogenous
17. Euperi-mesogenous
18. Coperi-mesogenous
19. Duploperi-mesogenous
20. Dia-mesogenous
21. Para-mesogenous
22. Cyclo-mesogenous
23. allelo-mesogenous
0
\
¥
V
24. aniso-mesogenous
25. helieo-mesogenous
26. Tetra-mesogenous
DISPERSION7OF STOMATA
On the lamina, the stomata are more or less uniformely
dispersed over the whole surface in between the veins, sometimes
over the finer veins but mostly not over the main veins. The
stomata are very rarely present over the major veins. In other
words, the dispersion of the stomata is homogeneous in most
plants. This may not be always true, as stomata are sometimes
more numerous on certain parts of leaves and competely absent
from other pats. Sometimes, stomata are dispersed in distinct
groups. The dispersion of stomata is more or less homogeneous in
other foliar organs like lamina, such as stipule, bract,
bractiole, calyx, corolla etc. Usually, the stomata are separated
from one another by one or more epidermal cells, but sometimes
two or more stomata occur grouped together in close contact with
36
each other; such stomata in literature are called contiguous.
The stomata are either sunken or situated in grooves or
grouped together and often covered by thick layer of hairs in
xerophytes. The stomata present in intercoastal zones and form
longitudinal rows. Ecological factors such as humidity, wind,
temperature and position of the leaf on the plant etc. also
influence the number of stomata.
ORIENTATION OF STOMATA:
In foliar organs such as lamina, stipule, bract,^corolla
etc, the orientation of stomata may be irregular, while in the
cylindrical organs like stem, petiole, peduncle, style, filament
of the stamen etc, the orientation of the stomata may be parallel
to the long axes or occassionally transverse or oblique. So in
many of the dicotyledons, the stomata are oriented at randam.
While in fern and monocotyledon leaves, the stomata are oriented
more or less parallel to the long axes. Rarely, the stomata are
oriented perpendicular to the mid-rib. If the orientation of
stomata is consistent, then it may be a useful charactor for the
identification of certain taxa.
THE FORM OE THE EPIDERMAL PELLS AND THEIR WALLS
There are no special descriptive terms to indicate the
form of epidermal cells and their anticlinal walls. In this
investigation shape of the epidermal cells such as triangular,
tetragonal, polygonal, irregular, elongated prosenchymatous,
37
isodiametric of the epidermal cells are described, The anticlinal
walls are described. The anticlinal walls may be thick or thin,
sometimes distinctly pitted, straight, arched, curved, lobed
arcuate or sinuous. The anticlinal walls may be homogeneous and
evenly or unevenly thickened or stratified. The degree of
undulations has also been described for anticlinal epidermal
walls. The amount of undulations of the cell walls appeared to
have of taxonomic significance in certain plant group, although
it is a quite variable character influenced by a number of
ecological factors. Stace (1965) pointed out these ecological
factors. Shading, air, soil and humidity are regarded to cause a
stronger undulation of the antidinal walls, the position of the
leaf on the stem also seems to be of some influence.
Table showing the families studied number of genera and
species according to Willis (1966), species studied by previous
workers and genera and species studied during the present
investigation:
Sr.No.
1.
Rubiaceae
Family
Genera and
species according
to Willis
(1966) of a
family
Genara
Species
500
6000
Species
investigated
by
previous
workers
No. of Gene
and species
studied
during
present
investigati
Genera
Tognini,1897
(1)
Pant & Mehra,
1965(14)
Bir-Bahadur
et al. 1971 (26)
21
Speci
33
38
900
13000
Plumbaginaceae
10
500
Inamdar and
Patel, 1971 (1)
2
4.
Primulaceae
20
1000
Yerma, 1 972(1 )
4
5.
Myrsinaceae
35
1000
6.
Sapotaceae
7.
Ebenaceae
8.
Scrophulariaceae
9.
Orobanchaeeae
2.
Compositae
3.
Pognini,1897
34
(1)
Pant & Yerma,
1963(1)
Ramayya & Rao,
1968(1)
4
3
-
800
3
500
-
1
220
3000
-
17
14
180
-
2
4
170
-
1
11. Gesneriaceae
120
2000
-
2
12. Bignoniaceae
120
650
15
63
14. Acanthaceae
250
2500
Pant and Mehra, 15
1963(1)
Paliwal,1966(14)
Inamdar,1970(31)
2
15. Yerbenaceae
75
3000
Pant & Kidwai,
1964(1)
Inamdar, 1 969
(14)
13
2
180
3500
Tognini, 1897(1) 18
Ramayya & Rao
1969(3)
Inamdar & Bhatt
1972(32)
4
3
270
2345
36,733
10* Lentibulariaceae
13. Pedaliaceae
incl. Martyniaceae
16. Labiatae
17. Plantaginaceae
Potal 17
Bhatnagar and
Gupta,1969(1)
6
35-75
1
Tognini,1897(1) 11
Inamdar,1969(1 )
Paliwal,1969
(species not
mentioned)
1
Inamdar 1969Q0 3
«
74
1
1
150
23
The data on the past work of these seventeen gamopetalous
families has been summarised in the above table. It is very
clear from this data that out of 2345 genera and 36,733 species,
work has been carried out only on 74 genera and 150 species. Henc
there is ample scope for further research on the structure and
ontogeny of stomata in these seventeen gamopetalous families.
Therefore, the present investigation has been undertaken on the
structure and development of stomata on 114 genera and 237 specie
belonging to the seventeen gamopetalous families. In addition
to these 237 species of 17 gamopetalous families, 3 species of
Begonia have also been investigated for comparing the results
with those of G-esneriaceae. Therefore, in all 240 species have
been worked out.