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Ontogeny of the paracytic stoma: Variations and modifications
Abstract
It was generally believed that the topography of the cells surrounding the guard cells in the mature condition indicate their
mode of development. However, it has now been established that more than one ontogenetic type may correspond to a single mature
type, or it may lead to the development of varied stomatal types. The paracytic stoma was studied from this viewpoint. It
was found that it may be formed through one of at least eight different modes. These are classified and reviewed. The need
to undertake studies on the ontogeny of this type of stoma in various groups of plants has been emphasized.
... There may also have been differences in our interpretation of surface features ( Figure 1) as compared to other workers (see [22], esp. Plate 1; [31] However, when making comparisons between species with differing stomatal ontogenies a M.I. approach might be more appropriate. Finally, we suggest that differences in both how epidermal features are measured and how stomatal indices are calculated could be one reason for high variability observed in me-ta-analysis of responses of plants to paleoclimatic CO 2 variability [30]. ...
... Any differences in stomatal index must have resulted from environmental cues that affected the likely-hood that an epidermal cell would develop into a stomate. In the leguminosae generally, and with peanut in particular, subsidiary cells arise from para-mesogenous stomatal development.The result of the para-mesogenous stomatal developmental process is that the entire stomatal complex, consisting of a pair of guard cells bounded by a two unequally sized subsidiary cells, traces its lineage to a single meristematically active epidermal cell sometimes called a meristemoid ([31], and references therein.) Traditionally, calculation of S.I. includes the subsidiary cells as part of the population of epidermal cells[34]. ...
Peanut,
(Arachis hypogaea L.) cvar. C76-16, was grown either in
the field, or in open gas exchange chambers under elevated or ambient CO2 concentrations. Stomatal density and other selected epidermal parameters
associated with leaf development and gas exchange
were measured on recently fully expanded canopy leaves. It was
hypothesized that exclusion of solar UV by chambers would affect stomatal
density, but no clear statistically significant chamber effect on stomatal
density was found. However, elevated [CO2] did lead to a reduction
in both adaxial and abaxial stomatal developmental initiation and in stomatal
density. Since each stomate was bounded by companion cells resulting from
developmental events, non-random stomatal spacing as the “one cell spacing rule”
appears to result from ontogeny rather than a long hypothesized chemical signal
inhibiting adjacent meristemoid differentiation into guard cells. A method of
visualizing epidermal patterns is also described.
... In other taxa, one lateral subsidiary cell is a mesogene cell and the other is a perigene cell (e.g. Payne, 1970;Farooqui, 1982), although it is impossible to distinguish between them in the mature epidermis. The 'living fossil' genus Equisetum, a member of the non-lycopsid pteridophyte lineage that is paraphyletic in morphological analyses but monophyletic in molecular analyses (Fig. 1), apparently possesses axial cell files that form meristemoids following asymmetric divisions (Table 1). ...
I. II. III. IV. V. VI. VII. VIII. References SUMMARY: We evaluate stomatal development in terms of its primary morphogenetic factors and place it in a phylogenetic context, including clarification of the contrasting specialist terms that are used by different sets of researchers. The genetic and structural bases for stomatal development are well conserved and increasingly well understood in extant taxa, but many phylogenetically crucial plant lineages are known only from fossils, in which it is problematic to infer development. For example, specialized lateral subsidiary cells that occur adjacent to the guard cells in some taxa can be derived either from the same cell lineage as the guard cells or from an adjacent cell file. A potentially key factor in land-plant evolution is the presence (mesogenous type) or absence (perigenous type) of at least one asymmetric division in the cell lineage leading to the guard-mother cell. However, the question whether perigenous or mesogenous development is ancestral in land plants cannot yet be answered definitively based on existing data. Establishment of 'fossil fingerprints' as developmental markers is critical for understanding the evolution of stomatal patterning. Long cell-short cell alternation in the developing leaf epidermis indicates that the stomata are derived from an asymmetric mitosis. Other potential developmental markers include nonrandom stomatal orientation and a range of variation in relative sizes of epidermal cells. Records of occasional giant stomata in fossil bennettites could indicate development of a similar type to early-divergent angiosperms.
The majority of existing ontogenetic classifications of stomatal complexes is considered to be, in fact, a mixture of structural and ontogenetic ones. Purely ontogenetic classifications should be based on only three characters: a) orientation of guard cells' mother cell division in relation to the plane of the preceding cell division; b) orientation of the divisions of cells other than guard cells' mother cell and c) number of cell divisions leading to mature stomatal complex formation. This method would result in three independent and reciprocally supplementary stomatal classifications. The first one consists of only Payne's anomo-, dia-, and parameristic types. The second one contains both Payne's allelo- and helicocytic types and new concentro-, radi-, and tangenticytic stomatal types. For the third classification, monomeristic and bimeristic types, and so forth, are proposed. Two neglected unnamed Strasburger's and Prantl's stomatal types are reintroduced as initial, resp. terminal.
Nuclear magnetic resonance spectroscopy of paramagnetic molecules has proven to be a powerful tool in investigating the geometric and electronic structures of biological molecules and, more generally, of chemical compounds incorporating paramagnetic metal ions. The magnetic perturbations due to the unpaired electrons are such that nuclei located in the near vicinity of the paramagnetic center exhibit unusual chemical shifts and relaxation rates which distinguish them from the diamagnetic background.
The leaf anatomy of 81 species of Syzygium was examined. General generic and subgeneric descriptions of Syzygium leaf anatomy are given. Four stomatal types (anisocytic, anomocytic, cyclo-staurocytic and paracytic) that occur exclusively
or in combinations are recognised. Two major vascular systems are differentiated by the presence or absence of adaxial phloem
partition. Phylogenetic inferences using maximum parsimony and Bayesian methods for separate and combined analyses of DNA
(ETS and ITS) sequences and morphological (leaf anatomy and macromorphology) data were conducted. Results of the combined
analyses gave slightly higher support value for clade than analyses based on DNA sequences. The subgenera Perikion, Sequestratum and Syzygium are strongly supported, but the subgenus Acmena is moderately supported in the Bayesian but not in the parsimony analysis of combined data sets. The relationships among
subgenera are not fully resolved. All the leaf anatomical characters examined are homoplastic. We did not find any unique
leaf anatomical characters allowing delimiting of the four subgenera in Syzygium. However, a combinations of non-unique leaf anatomical characters, including stomatal types, crystal types and frequency,
and midrib vascular system (adaxial phloem partition) are diagnostic for subgeneric groups.
Baranova, M. (V. L. Komarov Botanical Institute, Prof. Popov Str. 2, 197376 St. Petersburg, Russia. Principles of comparative
stomatographic studies of flowering plants. Bot. Rev.58(1): 49–99, 1992.—Numerous unsolved taxonomic problems have caused systematists to go beyond the traditional methods of herbarium
taxonomists and begin to utilize laboratory disciplines such as cytology, palynology, chemotaxonomy, and anatomy. The anatomy
of wood and of leaves, among other things, have been used to provide data for systematic studies. The study of the morphology
and ontogeny of the stomatal complex in leaves has been one fruitful area for research. The reader is warned that the taxonomic
value of such leaf epidermal characters is very different in different taxa just as is true for traditional morphological
characters. The terminology used for describing stomates and the whole stomatal complex or apparatus, as it has developed
since the time of Vesque (1889) is given. The classifications of Vesque and Metcalfe and Chalk for angiosperms, and that of
Florin for gymnosperms are given in detail. The problems inherent in including the ontogenetic development of the stomatal
complex in the description and terminology of types are discussed. It is concluded that morphological classification of stomates
is best based on their appearance in the mature leaf, excluding any attempt to include ontogeny as well. Fourteen morphological
types of stomates are now recognized: anomocytic, anisocytic, paracytic, diacytic, actinocytic, encyclocytic (cyclocytic),
tetracytic, pericytic, desmocytic, polocytic, staurocytic, hemiparacytic, laterocytic, and stephanocytic. Other kinds seen
in the literature are subtypes of these. In actuality, intermediates between these types exist in nature, and it is not always
easy to distinguish these types. Nonetheless, stomatal types and their ontogenies have been used with success in the resolution
of many taxonomic problems. The author outlines the many difficulties encountered in the utilization of such data. Even so,
examples from the Celastraceae, Chloranthaceae, Polemoniaceae, Hydrophyllaceae, Boraginaceae, Convolvulaceae, Solanaceae,
other dicotyledonous families, and some monocotyledonous families are given. The paracytic stomatotype is regarded as probably
primitive in both dicotyledons and monocotyledons. Other types of stomates have repeatedly been derived from the paracytic
type, so that the presence of similar advanced stomatotypes is not a sure indication of close relationship.
In 1950 Metcalfe & Chalk showed the need for new technical terms 'devoid of taxonomic or ontogenetic implications' to replace those of Vesque. Their new terms and some others, proposed by Metcalfe and Stace, are now generally used. All previous classifications of stomatal types included only those of Angiosperms and Gymnosperms. The eight new forms described in this and a previous paper ( Van Cotthem, 1968) include five known only from the Filices and bring the number of known stomatal types to 15, of which two have been subdivided;
During the past 125 years the history of early angiosperms, interpreted through the fossil leaf record has been largely an
exercise in paleofloristic studies, ignoring evolution. Imprecise identifications of ancient leaves “matched” to extant genera
and families have been used as the basis for reconstructions of paleocommunities and paleoclimates. However, as the result
of careful morphological studies of leaf form, venation and cuticular features new insights into the evolution of angiosperms
are now available. In this paper considerations are given to the usefulness and shortcomings of leaf form, venation and cuticular
analysis as diagnostic tools of plant identification. Many techniques for the study of the morphology of modern and fossil
leaves are included in this paper as well as tables outlining features of leaf venation and the epidermis. Careful morphological
studies of leaf form (such as the venation and epidermal characters emphasized in this paper) will provide better understanding
of the relationships of living angiosperms and transform the fossil leaf record into useful data that can be used to study
the evolution of the angiosperms.
The compilation of new data on stomatal ontogeny from the literature and the finding of a rather unknown type inMarcgravia have shown the need of a new classification of the ontogenetic types of stomata. Pant (1965) recognized 10 main types; this
number is now enlarged to 26 and a modified terminology is chosen. From the name of each type not only the ontogenetical pattern
but also the morphological nature of the adult stoma can be deduced. Thus the gap between morphological and ontogenetical
classifications has been bridged.
Two important differences from Pant’s classification and definitions are introduced.
In this classification any other new type can be included; all the possibilities for the introduction of supplementary data
are left open.
The present paper deals with the epidermal structure and ontogeny of stomata for four species of the Zygophyllaceae and Simarubaceae. The mature stomata are anomocytic, paracytic, perigenous and with a single subsidiary cell. Abnormalities noticed here are contiguous stomata and stomata with a single guard cell. The development of paracytic stomata and stomata with a single subsidiary cell is mesogenous type, while that of anomocytic stomata resembles perigenous type. Six types of glandular and eglandular trichomes have been observed. The structure and ontogeny of stomata is similar in the species investigated. Balanites is more closely related to the Zygophyllaceae than Simarubaceae.
The ontogeny of stomata is described for threee species of the family Salvadoraceae. The mature stomata are anisocytic, paracytic, anomocytic, perigenous and with a single subsidiary cell. The development of anisocytic and paracytic types and those with a single subsidiary cell conforms to the syndetocheilic or mesogenous type. The ontogeny of anomocytic stomata is haplocheilic or perigenous. Sometimes in the anisocytic type, one of the subsidiary cells undergo tangential division and the mature stomata show 3—4 subsidiary cells. Abnormalities noticed here are (a) stomata with a single guard cell, (b) stomata with aborted guard cells and (c) stomata with unequal guard cells. Contiguously placed and group of stomata have been oberved.
The structure and development of stomata in 10 Amaryllidaceous members are described. The study is made on the leaves and floral organs of Amaryllis belladona, Crinum asiaticum, C. bulbispermum, C. latifolium, C. pratense, Pancratium sp., Polianthes tuberosa, and Zephyranthes atamsco, and on leaves of Agave sp. and Curculigo orchioides. In most of the organs of the different plants studied more than one type of stoma occur, even on the same surface. However, the stomata are largely anomocytic in Amaryllis, Crinum, Pancratium, Polianthes, and Zephyranthes, but they are tetracytic in Agave and Curculigo. An increase in the number of subsidiary cells in teracytic, tricytic, paracytic, and stomata with one subsidiary cell has been noted. It may be due to wall formation in the subsidiary cells or by the neighbouring perigenes assuming their form. The range of variation in different types of stomata in each organ has been studied. Abnormal features such as juxtaposed or superimposed contiguous stomata, connections between guard cells of nearby stomata, transformation of meristemoids into epidermal cells are observed. The development of different types of stomata in different organs of the same plant is perigenous. The systematic position of different genera is discussed in light of the present findings. A method of preparing epidermal imprints by the use of Depex, a mounting medium, and white of an egg is also described.
The structure and ontogeny of stomata in vegetative and floral organs of three species of Kalanchoe is described. The mature anisocytic stomata are mono-cyclic or completely or incompletely amphicyclic, rarely paracytic, transitional between paracytic and anisocytic and with a single subsidiary cell. The development of all the types is syndetocheilic or mesogenous from organ to organ but the mature stomatal apparatus varies from organ to organ as regards the number and arrangement of subsidiary cells. Abnormal stoma with a single guard cell and arrested development were observed on all organs. An abnormal stoma with a single guard cell develops directly from the meristemoid.
Hitherto published accounts of the development of stomata in Equisetum are conflicting about the sequence of divisions and about the formation of a sub-stomatal cell from a meristemoid. The present study of the development of stomata in a species identified as E. ramosissimum subspecies ramosissimum supports the observations of Strasburger (1867) and Pant and Mehra (1964) on the basis of sections cut in various planes through internodes of the plant.
The ontogeny and structure of stomata in 22 genera and 51 species of the Polemoniales are described. Five main types of stomata noticed are: anisocytic, anomocytic, diacytic, paracytic, and stomata with a single subsidiary cell. Three modes of stomatal development: syndetocheilic or mesogenous, haplocheilic or perigenous, and meso-perigenous or syndeto-haplocheilic are observed. Abnormalities seen are: stomata with single guard cells, arrested development and contiguous stomata variously oriented. Contiguous stomata result from adjacently placed meristemoids or readjustment during maturation. Stomata with a single guard cell are formed as a result of degeneration of one of the guard cells before or after pore formation. The stomatal apparatus varies in different organs of a plant in form, number, orientation and arrangement of the subsidiary and also the surrounding cells. Three lines leading to Polemoniales, Boraginales, and Solanales are distinet.
The leaf epidermal characters of 89 species belonging to 42 genera of the Celastraceae sensu lato (including Hippocrateaceae) are described in detail. The range and pattern of variation in stomatal type and presence and type of crystalliferous epidermal cells can be used to support the broad family concept of Celastraceae. The stomata may be anisocytic, complex anisocytic, anomocytic, cyclocytic, bi- and/or tricyclic, complex cyclocytic, laterocytic, complex laterocytic, paracytic, parallelocytic, helicocytic, or of an intermediate type. The laterocytic stomata are most common, and are here recognized for the first time as a distinct stomatal type characterized by the lateral position of the subsidiary cells (3 or more) but yet different from the paracytic and cyclocytic type. The general implications of the epidermal diversity for the grouping of genera in a natural classification are discussed. Special attention is devoted to the taxonomic position and/or delimitation of the following genera: Kokoona and Lophopetalum; Sarawakodendron; Perrottetia; Salada and the related genera Cheiloclinium, Peritassa and Tontelea; Hippocratea and the putatively related genera Antodon, Apodostigma, Cuervea, Elachyptera, Helictonema, Hemiangium, Hylenea, Loeseneriella, Prionostemma, Pristimera, Reissantia and Simirestis; Cassine sensu lato (including Elaeodendron, Crocoxylon and Mystroxylon); Denhamia and Maytenus; Euonymus; Goupia; Siphonodon and Pottingeria. Finally a tentative discussion of the wider affinities of Celastraceae is given and the scope for future studies is indicated.
Existing descriptions of patterns of stomatal development in monocotyledons are very few, often inaccurate and sometimes misleading. The terminologies developed therefrom are probably not very useful. In this article the situation is clarified with respect to information obtained from the examination of the development of the stomatal complex in about 100 species of monocotyledons representing most families. Certain families lack divisions of cells surrounding the guard cell mother cell (meristemoid). Others possess such divisions which may be categorized as either oblique or non-oblique. Many families lack oblique divisions, others are characterized by oblique divisions. There seems to be a correlation between the presence of oblique divisions and the shortness of the protodermal cells. In some families the sequence of divisions is quite precise, in others it is quite variable. Available evidence shows that there are no major groups of monocotyledonous families characterized by a particular pattern of divisions in the development of the stomatal complex and that speculations about the phylogenetic significance of these patterns are premature. It is suggested that the stomatal complex has value as a systematic character only in combination with a variety of other characters and only by consideration of groups which are already known to be natural. Our present appreciation of the affinities of monocotyledonous groups should be used as a source of comparative information about the development of the stomatal complex in monocotyledons and not vice versa.
1. A long-standing discrepancy in the literature pertaining to the location of the radiating bands in the stomatal apparatus of the genus Equisetum was discussed, with the citation of six authors who stated that they were part of the subsidiary cell wall, and another six authors who stated that they were part of the guard cell wall. 2. Macerations were made of desilicified and cleared material of twelve species of Equisetum, which revealed that these bands are always located on the subsidiary cell wall, thus confirming Sanio's original report.
The present paper describes the distribution, structure, ontogeny, function of foliar nectaries and structure and ontogeny
of stomata inBignonia chamberlaynii Sims. The mature nectaries are patelliform and originate from a single papillate epidermal cell. They consist of 1-layered
base (foot), 2-layered stalk and 1-2-layered palisade-like epithelial cells which secrete sugary fluid.
Tha mature stomata are anisocytic, anomocytic, paracytic, perigenous (tetracytic and amphicyclic), with a single subsidiary
cell. The ontogeny of anisocytic, paracytic and stomata with a single subsidiary cell conforms to the mesogenous type, while
that of the anomocytic, tetracytic and amphicyclic ones is perigenous. Abnormalities noticed here are contiguous (juxtaposed
and superposed) stomata, stomata with a single guard cell and aborted guard cells.
Epidermal structure and development of stomata were studied in the vegetative and fioral organs of
Zornia diphylla (L.) Pers. and Z. zeylonensis Pers. Most of the intercostal cells in leaflet, stipule, and
bract are large-sized mucilaginous idioblasts. The swollen base of the idioblast compresses the basal
part of the adjacent subsidiary or ordinary cell, which hence has a narrow base in contrast to that of
the idioblast.
Para-mesogenous, aniso-, and tetra-mesoperigenous stomata occur in all organs of the above
species. In addition, the outer epidermis of the ovary wall shows aperigenous (anomocytic) stomata.
Stomata of the first three types are dolabrate, irrespective of their mesogenous or mesoperigenous
development. These types are related, the differences between them depending on the nature of the
placement of the second wall of the meristemoid. The present study lends support to an earlier
contention that anomocytic (aperigenous) stomata may result from suppression of the divisions of the
meristemoid of paracytic type. It is suggested that stomata flanked by two lateral, parallel, meso-
genous subsidiaries which do not meet each other at least at one pole (incomplete), should be termed
aniso- or tetra-mesoperigenous according to the total number of subsidiary cells of dual origin.
Using macerated pieces of epidermal tissue from living plants and herbarium specimens, stomatal complexes of 192 species belonging to 49 families of monocotyledons were studied. Four categories are recognized, 2 with 4 or more subsidiary cells surrounding the guard cells, 1 with 2 subsidiaries, and 1 with none. Development of the 2-subsidiary type, studied in acetocarmine preparations of Juncus effusus and Sagittaria montevidensis, resembles that in Gramineae previously described. No correlation was found between type of stomatal complex and either leaf shape or type of xylem vessel, but some correlation exists between this character and type of seed germination, vascular anatomy of seedling, growth habit of mature plant, and geographic distribution. Types with 4 or more subsidiaries are most commonly phanero phytes with tropical distribution, many vascular bundles in the cotyledon, and hypogeal germination. Complexes with 2 subsidiaries occur in many families of a diverse nature, but the most primitive plants with this type are hydrophytes or helophytes with tropical or temperate distribution, 1 vascular bundle in the cotyledon, and epigeal germination. Stomatal complexes without subsidiaries are almost confined to the Liliales and their more specialized derivatives. These plants are predominantly geophytes with temperate or tropical distribution, 2 bundles in the cotyledon, and epigeal germination. Reasons are advanced for suggesting that the type with many subsidiaries is the most primitive and the other 2 types have been derived from it independently by reduction of the number of subsidiary cells.
The structure and development of stomata on the vegetative and floral organs of
Vigna unguiculata Walp., and the vegetative organs of Phaseolus radiatus L. and
P. aconitifolius Jacq. are described. Paracytic, anisocytic, and anomocytic stomata
are present on the same surface of different organs of the plants investigated except
on the stem and petiole of V. unguiculata, the bract of P. radiatus, and the petiole,
stipule, and stipel of P. aconitifolius where the last type is absent. Stomata with only
one subsidiary cell are found on the leaf, petiole, sepal, and petal of V. unguiculata.
Diacytic stomata occur on the stipel of P. radiatus and the stem, stipule, and stipel of
P. aconitifolius. Paracytic stomata are by far the commonest on each organ. The frequency
of different types of stomata on different organs in the plants investigated is
tabulated. The ontogeny of different kinds of stomata on each organ is mesogenous,
but the perigenous type may be found on the petal and pericarp of V. unguiculata and
the stipule of P. radiatus. The variation in stomata is due to: (a) a diversity in stomatal
types even on the same surface, and (b) an increase in the number of subsidiary cells.
The subsidiary cells divide, or additional subsidiary cells are derived from adjacent
epidermal cells. The present study also supports the inclusion of the species concerned
in the tribe Phaseolae.
The development of stomata and other interesting anatomical features of leaves, sheathing stipules and perianth lobes of 5 species of Magnolia and 4 species of Michelia were studied.
Very often the mature foliar stomata are paracytic with 2 parallel subsidiaries and 1 or more parallel encircling cells but the stomata in the sheathing stipules and perianth lobes are usually anomocytic. A fairly constant feature of the foliar stomata of these plants is the partial overlapping of the subsidiary cells by the guard cells.
Epidermal cells of a few species contain calcium oxalate druses. In Magnolia grandiflora and M. pumila the epidermal cells possess peculiar rod-shaped bodies of uncertain chemical nature.
Polygonal or lobed thick walled brachysclereids occur singly or in groups in the various investigated species. Thin walled vesiculose sclereids are found in the leaves of all plants but they are absent in other organs of some species.
The 2 parallel subsidiary cells and encircling cells of stomata develop from the same initial. The development of stomata is, therefore, typically mesogenous (syndetocheilic). According to Rao (1939) the encircling cells in some of these plants are formed by divisions of the subsidiary cells and although this is partly true the encircling cells of a majority of stomata are formed directly from the stomatal meristemoids.
According to Paliwal & Bhandari (1962) the anomocytic stomata of the perianth lobes of Magnolia grandiflora, M. stellata and Michelia champaca are haplocheilic which implies that they are perigenous. However, we find that the irregular ring of cells around the guard cells of stomata in these parts and in the sheathing stipules, develop as a result of divisions in the mesogene subsidiary cells indicating thereby that these stomata are mesogenous and their development is essentially similar to that of foliar stomata.
The stomata in Gnetum ula Brongn. occur in large numbers on the abaxial surface of the leaves and are orientated in various directions. A few were seen in some preparations on the adaxial surface also, especially in the region of the midrib.
Stomatal development follows the syndetocheilic type of Florin. According to the terminology of ontogenetic types suggested by Pant, they may be described as mesogenous dolabrate; they are mesoparacytic (rubiaceous) and amphicyclic. In this respect, and in several details, the present findings support the observations of Takeda, and differ rather widely from those of Maheshwari & Vasil.
Twin stomata were also met with frequently, as well as several stomata lying together contiguously. The structural features of these are described and commented upon briefly in the paper.
Various characteristics make the epidermis of certain monocotyledonous plants, particularly the cereal grasses, favorable for studies of certain phases of developmental morphology and genetics. In the Commelinaceae, Araceae, Gramineae, and other families, development of the stomatal complex involves the following epigenetic sequence of events. In certain localized rows or areas, the cytoplasm of the protodermal cells becomes polarized, so that it is denser and contains more inclusions at the distal end of the cell. The nucleus then divides by a mitotic figure oriented across the cytoplasmic gradient. The chromosomes of this figure are similar at the two poles until early telophase, when the proximal nucleus becomes larger and more weakly staining than the distal one, both with the Feulgen technique and with acetocarmine. The distal nucleus eventually divides to form the two guard cells, but before doing so it induces division of two or more of the surrounding epidermal cells. Since in these cells there is also a cytoplasmic gradient, with a denser cytoplasm adjacent to the guard mother cell, these induced divisions are asymmetrical, with the nucleus in the center of the epidermal cell becoming larger and more weakly staining than that near the guard mother cell. In this way, subsidiary cells are formed. In the Commelinaceae, the subsidiary cells lateral to the guard mother cell are always formed before those proximal and distal to it, and a particular epidermal cell adjoining a guard mother cell always contributes a lateral subsidiary before a proximal or distal one. In Allium and other Liliaceae differentiation of the guard mother cell and guard cells is similar, but no subsidiary cells are formed. Some possible clues to the explanation of this sequence are offered, and pertinent experiments are suggested.
Zugl.: Stockholm, Univ., Diss., 1931.
In both Gnetum gnemon and G. ula the atomatal development in the collars and axes of the male and female cones and the outer two envelopes of the ovule is of the haplocheilic type. In the leaf some stomata do show parallel subsidiary cells, but they arise from the surrounding epidermal cells and do not seem to have a common origin with the guard cells. This conflicts with earlier accounts and is of interest in relation to the types of stomata met with in other gymnosperms, living and fossil.
The epidermal structure and development of stomata in vegetative and reproductive organs of Ephedra foliata and Gnetum ula is described. The epidermal cells are polygonal, isodiametric, or elongated with thick or thin straight, arched, or slightly sinuous anticlinal walls. The cuticle is thin or thick. Papilla-like unicellular outgrowths are present in Ephedra foliata . The mature stomata are orientated parallel to the longitudinal axes or irregularly. The mature stomata are anomocytic, paracytic, with a single subsidiary cell, cyclocytic, and actinocytic. Arrested development, contiguous stomata, and stomata with aborted guard cells have been observed. The ontogeny of stomata on different organs of these two plants is typically haplocheilic or perigenous but the stomatal apparatus varies from organ to organ.
The epidermal structure and ontogeny of stomata in 19 species of Centrospermae and two of Polygonales are described. The cells of the epidermis are polygonal, isodiametric, or elongated in various directions and arranged irregularly. The anticlinal epidermal walls are thick, sinuous, straight, or arched. Eleven types of glandular and eglandular trichomes have been observed. Six types of stomata: anomocytic, paracytic, stomata with a single subsidiary cell, diacytic, anisocytic, and transitional between diacytic and paracytic, have been noticed in the species investigated. The ontogeny of anomocytic stomata is haplocheilic or perigenous, while that of the other five types is syndetocheilic or mesogenous. Abnormal stomata with a single guard cell, unequal guard cells, aborted guard cells, and arrested development are common. Groups of stomata are also frequent but contiguous stomata are rather rare.
The cuticle, epidermis and stomatal ontogeny of Casuarina equisetifolia Forst. is described. The cuticle shows well marked impressions of the epidermal cells and stomata. The epidermis of leaf and stem shows transversely oriented, tetracytic, mesoperigenous stomata with two lateral mesogene subsidiaries and two polar perigene neighbouring cells. Although the epidermal structure of Casuarina shows a good deal of resemblance with that of the Bennettitales, it may not indicate any phylogenetic relationships since there are important differences in the structure and reproduction of the plants of these two groups.
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