Cytochemical and Autoradiographic Analyses on Root Primordia and Root Apices of Marsilea Strigosa

An investigation was made of the meristematic activity of the apical cell, its immediate derivatives (merophytes), and of other selected cell populations of the root of Equisetum scirpoides Michx. The plane of the first division of a derivative of the apical cell is radiallongitudinal, which provides evidence that merophytes immediately adjacent to the apical cell cannot be the ultimate root initials. The apical cell is as active mitotically in roots 20–40 mm long as it is in roots that are 0.25–1 mm in length. The mitotic activity of the apical cell and of other cell populations was determined from the mitotic index, and from determination of the durations of the cell cycle and of mitosis of the apical cell by using the colchicine method of metaphase accumulation. Microspectrophotometric measurements of DNA content indicated that there was no consistent increase in DNA (endopolyploidy) in the apical cell or in the other meristematic cells as roots increased in length. Conclusion: there is no evidence that the apical cell becomes quiescent or undergoes endopolyploidy as a root increases in length.

supporting

confidence: 52%

Section: -10mm 5-iommmentioning

confidence: 99%

mentioning

confidence: 99%

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Quantitative Studies of the Root Apical Meristem of Equisetum Scirpoides

Gifford¹,

Kurth

1982

“…D' Amato and Avanzi (1965) criticized the conclusion that the apical cell is an initiating cell based on DNA synthesis alone because, from this, one cannot distinguish the synthesis of DNA prior to mitosis from the synthesis of DNA prior to endoreduplication. By using a combination of microspectrophotometry and autoradiography, D' Amato andAvanzi (1965, 1968)and Avanzi and D'Amato (1967) reported that the apical cell is quiescent and that the chromatin of the quiescent cell is blocked at the post-DNA synthetic phase (G2). According to them, the root apical cell of species of Marsilea, Ceratopteris, Blechnum, and Polypodium divides only during the initial stage of or-ganization of the root primordium.…”

mentioning

confidence: 99%

Mitotic Activity in the Root Apical Meristem of Azolla Filiculoides Lam., With Special Reference to the Apical Cell

Nitayangkura

Gifford

Rost

1980

The meristematic activity of the apical cell and its derivatives (merophytes) in the unbranched, determinate roots of Azolla filiculoides Lam. was investigated. The plane of division of the apical cell indicates that it is the initial of each merophyte. The division plane of each newly formed merophyte is strictly periclinal to the root surface and provides confirmation that the immediate derivatives of the apical cell cannot be the ultimate root initials. The frequency of cell division as determined by the mitotic index, and by the duration of the cell cycle as determined by the colchicine method, confirmed the meristematic activity of the apical cell. As roots increase in length, the duration of the cell cycle in the total meristem increases, with the apical cell possessing the longest cell cycle, whereas the immediate derivatives maintain approximately the same cycle duration as in shorter roots. In determinate Azolla roots, cell division appears to play a major role up to a certain root length, then increase in length is produced mainly by cell elongation.

“…The root apical cell is considered to be mitotically active in ferns only during the initiation and early organization of the root apex. Subsequently, the apical cell gradually becomes mitotically quiescent and, then later, adjacent cells may also become quiescent (Avanzi and D'Amato, 1970;D'Amato, 1975). Correlated with a low frequency ofmitosis is the occurrence ofendopolyploidy.…”

mentioning

confidence: 99%

The Root Apical Meristem of Osmunda Regalis

Freeberg

Gifford

1984

Roots of the Osmundaceae differ from most ferns in having more than one apical cell. The size of the apical initial group, which includes cells that are considered to be apical cells, varies directly with root diameter in Osmunda regalis L. Mitotic indices were 6.63% for apical cells, 7.45% for the entire apical group, 6.25% for distal derivatives, and 7.15% for developing cortical cells. Cytophotometric measurements of Fuelgen‐stained nuclei indicated no endopolyploidy in the populations of cells studied. These findings demonstrate that there is no quiescent center in the roots of O. regalis.