scholarly journals Cell Division in the Formation of the Stomatal Complex of the Young Leaves of Wheat

1966 ◽  
Vol 1 (1) ◽  
pp. 121-128
Author(s):  
J. D. PICKETT-HEAPS ◽  
D. H. NORTHCOTE

During the formation of stomata in the young leaves of wheat the cells divide in a characteristic manner; two of the cell divisions are asymmetrical and produce cells of unequal sizes. A study of the fine structure of the cells during mitosis has shown that a band of microtubules appears at each preprophase stage. This band, although it is not present in the subsequent stages of mitosis, indicates the location on the wall of the mother cell where the cell plate will join it at the final division of the cytoplasm at telophase. Thus the future plane of cell division is indicated by these microtubules at preprophase. Microtubules are also found at the growing edge of the cell plate and appear to function in directing the vesicles which are brought up to extend the plate. The cell plate which is formed to cut off the subsidiary cells on either side of the guard mother cell is curved, and the microtubules present in conjunction with this plate during its formation could function to align and hold it on the required position. The relationship of the guard mother cell to the divisions of the adjacent epidermal cells which form the subsidiary cells is discussed, and related to general problems of growth and differentiation.

1969 ◽  
Vol 22 (2) ◽  
pp. 375 ◽  
Author(s):  
JD Pickett-Heaps

The relationship between preprophase microtubules and asymmetrical cell division in the formation of the stomatal complex of C. cyanea was investigated. Polarization of nuclei and other cell organelles adjacent to the guard mother cell occurred in most cases without a preprophase band of microtubules being present; the grouping of preprophase microtubules appeared immediately prior to cell division, and its situation, even during abnormal stomatal development, predicted the plane of future division. The results show that preprophase microtubules cannot be the cytoplasmic agents involved in orienting and positioning the nucleus prior to division. Clear evidence was obtained indicating that preprophase microtubules move intact into the spindle. Some aspects of abnormal stomatal development are discussed, and the results are related to some other work on stomatal differentiation.


1968 ◽  
Vol 16 (2) ◽  
pp. 177 ◽  
Author(s):  
A Mahmood

The use of the term cambium, or equivalent terms, in modern literature is discussed. The term cambial zone adopted in this paper includes the cambial initial and the dividing and enlarging cells. The tissue mother cell produced at each division of the initial produces a group of four cells in xylem or two cells in phloem. Theoretical constructs have been made for xylem and phloem production by associating the concepts that xylem and phloem are produced in alternate series of initial divisions and that a new primary wall is deposited around each daughter protoplast at each cell division. Correlations are derived from the theoretical constructs for the thickness of primary wall layers lying in the tangential direction and of those lying in the radial direction at progressive histological levels. Deductions from theoretical constructs are made when the initial is producing xylem, when it changes its polarity from xylem to phloem production, and when the reverse change occurs. Most of the theoretical deductions are supported by photographic evidence. The chief point of this study is the demonstration of generations (multiplicity) of primary parental walls. The term intercellular material proposed in this paper includes the cell plate plus any remnants of ancestral primary walls between the current primary walls surrounding the adjacent protoplasts. This term is still applicable to cells where secondary wall deposition is taking place or has been completed.


1971 ◽  
Vol 49 (1) ◽  
pp. 226-229 ◽  
Author(s):  
Virginia G. Fonte ◽  
Robert L. Searls ◽  
S. Robert Hilfer

1991 ◽  
Vol 39 (1) ◽  
pp. 43 ◽  
Author(s):  
DJ Carr ◽  
SGM Carr

The mode of stomatal development is studied in cotyledons, seedling and adult leaves of species of eucalypts and three species of Angophora. In the cotyledons of all species examined the early stomatal initials are unilabrate or dolabrate. The stomatal initials in seedling leaves of species of the Corymbosae and Clavigerae are anisocytic. In the 4th seedling leaf in species of a group we have previously called Monocalyptus the stomatal initials are also anisocytic. All other eucalypts retain the early cotyledonary mode of origin of stomata throughout life. These two modes of origin, whether anisocytic or by unilabrate and dolabrate initials, are set in all eucalypts from the 4th seedling leaf onward. Secondary characteristics of the adult stomata, e.g. number of subsidiary cells, are more complex than those of the seedling leaves; rarely, the relatively simple pattern of the seedling leaves may persist in the adult leaves of a given species. In species in which the initials in adult leaves are unilabrate or dolabrate, groups of stomata may share one or more subsidiary cells or be juxtaposed without an intervening subsidiary cell. The sister cell(s) of the guard mother cell may precociously develop a thicker cuticle than ordinary epidermal cells, and this may be apparent at maturity. The abaxial stomata of the cotyledons (but not of seedling or adult leaves) are regularly aligned parallel to the main venation. The existence of three main types of origin of stomata characteristic of three large non-interbreeding groups of eucalypts is of interest in the taxonomy of the genus.


Development ◽  
1995 ◽  
Vol 121 (12) ◽  
pp. 3947-3958 ◽  
Author(s):  
R. Rogge ◽  
P.J. Green ◽  
J. Urano ◽  
S. Horn-Saban ◽  
M. Mlodzik ◽  
...  

An allele of the yan locus was isolated as an enhancer of the Ellipse mutation of the Drosophila epidermal growth factor receptor (Egfr) gene. This yan allele is an embryonic lethal and also fails to complement the lethality of anterior open (aop) mutations. Phenotypic and complementation analysis revealed that aop is allelic to yan and genetically the lethal alleles act as null mutations for the yan gene. Analysis of the lethal alleles in the embryo and in mitotic clones showed that loss of yan function causes cells to overproliferate in the dorsal neuroectoderm of the embryo and in the developing eye disc. Our studies suggest that the role of yan is defined by the developmental context of the cells in which it functions. An important role of this gene is in allowing a cell to choose between cell division and differentiation. The relationship of the Egfr and Notch pathways to this developmental role of yan is discussed.


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