With respect to these the histogen theory fails. Korper-Kappe Theory The Korper-Kappe theory of root apical organization proposed by Schuepp (, ). Meristems, Tissues, Shoot apex, Root apex, Apical Cell Theory, Shoot. Apical Meristem Histogen Theory, Korper-Kappe Theory, Mantle-Core Theory, Tunica. Plant Anatomy Theories Different theories about plant anatomy and different types of cells playing important role in proper functioning of plant.
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This theory was proposed by Nageli who drew theoory attention to the occurrence of a single apical cell or apical initial that composes the root meristem. This occurs in downwardly pointed roots. Ontogeny of Stoma in Plants Plants. Equisetum, Adiantum and Polypodium etc.
The other three sides donate cells to form epidermis, cortex and vascular cylinder. Anticlinal division is the characteristic of tunica whereas corpus exhibits both anticlinal and periclinal division. In Brassica dicot dermatogen generates both protoderm and root lappe and this histogen is referred to as dermatocalyptrogen. The initial cell divides transversely. The lower daughter cell then divides longitudinally, i. One of the layers gives rise to the stele and the other to the cortex and root cap.
The daughter cell that faces the base of root, i. It consists of conspicuous longitudinal files of cells. The following points highlight the top three theories of root apical meristem in plants. During growth the root changes in diameter. Here’s how it works: The daughter cells divide by transverse partitions followed by longitudinal partitions.
The histogens are called dermatogen, periblem and plerome that respectfully form epidermis, cortex and vascular cylinder that are present in a mature root. In other words all tissues that compose a mature thory including root cap are the derivatives of a single apical cell.
The apical initial is tetrahedral in shape and generates root cap from one side. According to Hanstein root apical meristem consists of three cell-initiating regions called histogens Fig. The central part of root cap is the columella where the cells are arranged in longitudinal files.
In root with dermatocalyptrogen the cap extends into thdory.
The derivatives of dermatogen vary. The korper-kappe theory of root apex is comparable with tunica-corpus theory of shoot apex.
In Zea mays monocot dermatogen generates root cap only and this histogen is referred to as calyptrogen. It divides longitudinally and the two daughter cells thus formed have the potentiality of cell division.
The outer region of the root apex is the Kappe. The zones do not exhibit sharp demarcation line when they are the derivatives of same apical cell.
The root apex forms no branches, and no lateral structures like the leaves. A single apical cell is present only in vascular cryptogams, e.
Though histogen theory is abandoned to explain shoot apex, Eames and MacDaniels illustrated the root apical meristem on the basis of histogen concept.
The theory says that the cells in the root apex divide in a pattern called T-divisions. When such division continues it is observed that a single rowed region is left behind over the double-rowed region. The third type is found in Haemanthus coccineus. It is based on differences in the planes of cell division.
The root meristem exhibits multicellular structure. In this type, three groups of initials are found at the apex — outer dermatogenmiddle periblemand inner plerome. This happens due to cell divisions that occur in such a way that a single longitudinal file of cells becomes double files. Thus the planes of the two divisions form a T in a median longitudinal section of the root.