• K Periasamy

      Articles written in Proceedings – Section B

    • Studies on seeds with ruminate endosperm - II. Development of rumination in the vitaceæ

      K Periasamy

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      The six genera of the Vitaceæ studied show varying extent of perichalazal growth after fertilization. Ingrowths of rumination are produced by the integumentary tissues as a result of localised growth from the raphe region at the ventral side of the seed and their location in the mature seed is determined by the extent of perichalazal growth. InLeea the perichalaza itself becomes pushed in as an ingrowth and in addition to this four more ingrowths are produced; inCissus, Vitis, Tetrastigma andAmpelocissus the number of ingrowths is only two and these are situated away from the perichalaza; inCayratia the ingrowth is a single dome-shaped structure with two small longitudinal ridges at the inner face.

      The nucellus increases after fertilization, and becomes ruminate by the ingrowths of the seedcoat. The endosperm remains quiescent and of small volume until the seed attains almost its mature size, but thereafter grows rapidly and replaces all the nucellus, thereby acquiring the same ruminate configuration. The mature endosperm contains fatty reserves and one druses in each cell.

      The mechanical tissue of the mature seedcoat is completely derived from the innermost layer of the outer integument and is of varying layers thick in the different genera. The middle layers of the outer integument become tanniferous to varying extent in the different genera. The innermost layer of the inner integument becomes tanniferous, the outermost becomes spirally thickened and these two persist in the mature seed, whereas the middle layer acts as a nutritive layer and becomes completely crushed. Raphides occur in the seedcoat of all the genera exceptLeea.

    • Studies on seeds with ruminate endosperm - III. Development of rumination in certain members of the apocynaceae

      K Periasamy

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      The unitegmic, tenuinucellate ovules ofVoacanga grandifolia andErvatamia heyneana of the Apocynaceae show massive-chalazal growth after fertilization. The integumentary part of the ovule also grows to a certain extent. Due to differential growth activity of the inner layers and the epidermis, the latter forms infoldings into the former. The epidermal layer becomes thickened in a peculiar manner, but the inner layers remain thin-walled. The endosperm develops late and becomes ruminate by replacing all the inner layers of thin-walled cells and leaving intact the epidermis alone with its infoldings as the mature seed coat. Outgrowth from around the funicle forms a prominent aril inErvatamia heyneana and a common fleshy mass around the seeds inVoacanga grandifolia.

      InTabernaemontana sp. chalazal growth is lesser, and even though the seed surface becomes irregular during early stages, the endosperm does not become ruminate.

    • Studies on seeds with ruminate endosperm - V. Seed development and rumination in two genera of the rubiaceae

      K Periasamy

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      The unitegmic, tenuinucellate ovules ofPsychotria andRandia show after fertilization a massive chalazal growth which is more pronounced in the former than in the latter. InPsychotria, the epidermis forms deep or shallow infoldings into the inner layers that grow around the young, quiescent endosperm; the infoldings are confined to the chalazal part alone and are absent in the integumentary part. InRandia malabarica, the epidermis forms shallow and irregular undulations both in the chalazal and the integumentary parts.

      The endosperm remains quiescent and of small volume during the early stages of seed development. When the seed has attained nearly its mature size, the endosperm grows rapidly in volume and attains a ruminate configuration by replacing all the surrounding tissues of the seed except the epidermis which, with its infoldings or undulations, serves as the mature seed coat.Psychotria shows a graded variation from a pronounced degree of rumination inP. congesta to complete absence of rumination inP. bisulcata, through a gradually decreasing series represented byP. dalzellii, P. elongata, P. reevesii, P. serpens andP. macrocarpa. The cell walls of the mature seed coat do not become thickened inPsychotria, but inRandia malabarica, they acquire an Ericaceous type of lignification.

    • Studies on seeds with ruminate endosperm - VI. Rumination in the araliaceae, aristolochiaceae, caprifoliaceae and ebenaceae

      K Periasamy

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      InDiospyros, the ovules are bitegmic, but after fertilization the inner integument fails to grow and exhibit any morphological changes. Seed development is of the massive chalazal type. Rumination ingrowths develop from the seedcoat which is formed by chalazal growth in basipetal continuation of the integuments. The endosperm develops early and hence the ingrowths are formed directly into its tissue.

      InApama, seed development is normal chalazal. The seedcoat becomes irregularly wavy due to unequal radial elongation and bending of the cells of the outermost layer of the inner integument. The endosperm develops late and becomes ruminate by replacing all the nucellus. Rumination is of theAnnona type in bothDiospyros andApama.

      Certain developmental stages ofViburnum foetens andArthrophyllum diversifolium indicate that development of rumination in these is of theSpigelia type and similar to what obtains in the genusPsychotria of the Rubiaceae.

    • Morphological and ontogenetic studies in palms - VI. On the ontogeny of plication in the palm leaf

      K Periasamy

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      In the palm leaf primordium, plications do not arise by schizogenous splits. If plications arise by splitting, the stomata of the palm leaf have to develop from various, morphologically indefinite internal layers instead of from the protoderm. Cell alignment in the lamina wing where plications arise is such that a simple schizogenous splitting cannot result in straight splits. The adaxial and abaxial ridges and furrows in the lamina tissue represent the earliest morphological expression of the development of plications by differential growth. In the juvenile leaf ofPhoenix, although a well developed haut is absent, the morphological equivalence of a haut is produced in the same way as in the adult leaf, and plications arise identically in the juvenile and the adult leaves.

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