Analytical studies on the shoot apex of Helianthus annuus

1969 ◽  
Vol 47 (9) ◽  
pp. 1367-1375 ◽  
Author(s):  
T. A. Steeves ◽  
M. Anne Hicks ◽  
J. M. Naylor ◽  
Patricia Rennie
Keyword(s):  
Helianthus Annuus ◽  
Shoot Apex ◽  
Culture Medium ◽  
Deoxyribonucleic Acid ◽  
Vegetative State ◽  
Central Zone ◽  
Apical Region ◽  
Cell Nuclei ◽  
Liquid Culture Medium ◽  
Vegetative Shoot Apex

The vegetative shoot apex of Helianthus annuus contains a central zone in which the cell nuclei are relatively large and stain faintly in the Feulgen reaction. Excised apices in the vegetative state were supplied with thymidine-H3 through their sterile, liquid culture medium. Autoradiography after 24 or 48 hours of feeding revealed no significant incorporation of the labeled precursor into central zone nuclei, but extensive incorporation in peripheral regions of the apex. It is concluded that during vegetative growth deoxyribonucleic acid (DNA) synthesis and mitosis are arrested in the central zone or reduced to an extremely slow rate. Microspectrophotometry, however, indicates that the central zone nuclei are not held at the 2C level. With the onset of flowering, cytological zonation disappears in the apex and the incorporation of thymidine-H3 is uniformly heavy throughout the apical region.

The ultrastructure of the central zone cells of the shoot apex of Helianthus annuus

1981 ◽  
Vol 59 (11) ◽  
pp. 2009-2015 ◽  
Author(s):  
V. K. Sawhney ◽  
P. J. Rennie ◽  
T. A. Steeves
Keyword(s):  
Endoplasmic Reticulum ◽  
Helianthus Annuus ◽  
Shoot Apex ◽  
Ultrastructural Study ◽  
Central Zone ◽  
Peripheral Zone ◽  
Striking Difference ◽  
Vegetative Shoot ◽  
Helianthus Annuus L ◽  
Vegetative Shoot Apex

An ultrastructural study of the vegetative shoot apex of Helianthus annuus L. cv. Peredovic has shown that in most respects the cytoplasmic components of the central zone cells were similar to those of the mitotically active peripheral zone cells. For example, the mitochondria, dictyosomes, endoplasmic reticulum, ribosomes, and microtubules were not different either in their structure or in distribution in the two types of cells. The only striking difference found was the presence of starch-containing plastids in the central zone, primarily in the two tunica layers in this region, and their absence from peripheral and immediately subjacent regions of the meristem. Starch-containing plastids were observed in the differentiating pith cells. Plasmodesmata were observed in the central zone and in walls between central and peripheral zone cells.

Further analytical and experimental studies on the shoot apex of Helianthus annuus: variable activity in the central zone

1979 ◽  
Vol 57 (8) ◽  
pp. 971-980 ◽  
Author(s):  
E. L. Davis ◽  
Patricia Rennie ◽  
Taylor A. Steeves
Keyword(s):  
Helianthus Annuus ◽  
Mitotic Activity ◽  
Shoot Apex ◽  
Experimental Studies ◽  
Central Zone ◽  
Peripheral Zone ◽  
Intact Plants ◽  
Cast Doubt ◽  
Young Leaves ◽  
Mitotic Frequency

The cytologically distinctive central zone of the vegetative shoot apex of Helianthus annuus L. cv. Peredovic has a mitotic frequency considerably lower than that of the surrounding peripheral zone in intact plants. Apices excised and grown in culture for 5 days before being supplied with [H3]thymidine reveal a correspondingly low level of DNA synthesis in the central zone when autoradiographed. In similarly cultured apices, mitotic activity in the central zone is less than that recorded for intact plants. Labelling immediately after excision of the apex indicates that the central zone cells are activated by the operation and quiescence returns during the following 5 days. This activation is confirmed by mitotic counts 2 days after excision. The removal of only two young leaves from the apical buds of otherwise intact plants results in a comparable stimulation of mitotic activity in the central zone. These observations cast doubt upon the significance of mitotic activity in living shoot apices when these have been exposed for observation by removal of leaves. They also raise questions about the validity of labelling techniques which involve the partial dissection of the shoot apex.

Quiescent cell populations in apical meristems of Helianthus annuus

1974 ◽  
Vol 52 (10) ◽  
pp. 2195-2201 ◽  
Author(s):  
Haviva D. Langenauer ◽  
Edward L. Davis ◽  
Peter L. Webster
Keyword(s):  
Dna Synthesis ◽  
Helianthus Annuus ◽  
Shoot Apex ◽  
Central Zone ◽  
Quiescent Cell ◽  
Shoot Meristem ◽  
Cell Populations ◽  
Quiescent Center ◽  
Apical Meristems ◽  
Shoot Apical Meristems

Quiescent cell populations in both root and shoot apical meristems of Helianthus annuus are compared. Histoautoradiographs prepared after 12-h provision of [3H]thymidine in the growth medium demonstrate the presence of a quiescent center located subterminally in the apical meristem of cultured and attached Helianthus roots. Similar techniques (using [3H]-thymidine in the medium for 24–48 h) show that while cells of the shoot meristem undergo DNA synthesis, a central zone that does not incorporate the precursor exists at the summit of the cultured vegetative shoot apex. Central zone cells contain larger nuclei than do surrounding cells in the shoot apex, while quiescent-center nuclei are smaller than those in the surrounding meristem of the root apex.Growth of excised roots in medium without carbohydrates causes temporary arrest of proliferative activity in most of the meristem. When sucrose is provided after this treatment, cells of the meristem as well as most cells of the root quiescent center are stimulated into DNA synthesis. In shoots cultured in sucrose-deficient medium, few cells continue to synthesize DNA, but subsequent transfer to medium with carbohydrates stimulates no cells of the central zone into DNA synthesis, although progression through the cycle is resumed by other cells of the meristem. These and other considerations suggest that the quiescent regions in root and shoot apical meristems are not comparable.

Experimental studies on the shoot apex of Helianthus annuus: the effect of surgical bisection on quiescent cells in the apex

1977 ◽  
Vol 55 (5) ◽  
pp. 606-614 ◽  
Author(s):  
E. L. Davis ◽  
T. A. Steeves
Keyword(s):  
Dna Synthesis ◽  
Helianthus Annuus ◽  
Shoot Apex ◽  
Experimental Studies ◽  
Central Zone ◽  
Quiescent Cells ◽  
Cytological Features

When the shoot apex of Helianthus annuus cv. Peredovic is bisected surgically, two new apices are regenerated, each of which, 3 weeks after the operation, contains a quiescent central zone similar to that of the original apex. The operation destroys some cells of the original zone and stimulates others to become active in DNA synthesis. Regenerating apices, supplied with [H3] thymidine and autoradiographed at the end of the 2nd day after the operation, reveal no evidence of a quiescent zone. Evidence for the establishment of quiescence appears by the end of the 3rd day and becomes clearer on the 4th and 5th days after the operation. There is no evidence that the residual zone cells play any particular role in regeneration. It is suggested that quiescence in regard to DNA synthesis and mitosis appears sooner than the cytological features associated with quiescence in the sunflower shoot apex.

scholarly journals Involvement of deoxyribonucleic acid polymerase β in nuclear deoxyribonucleic acid synthesis

1978 ◽  
Vol 173 (1) ◽  
pp. 309-314 ◽  
Author(s):  
T R Butt ◽  
W M Wood ◽  
E L McKay ◽  
R L P Adams
Keyword(s):  
Dna Synthesis ◽  
Dna Polymerase ◽  
Deoxyribonucleic Acid ◽  
Nuclear Dna ◽  
Dna Polymerase Beta ◽  
Cell Nuclei ◽  
High Molecular Weight Dna ◽  
Dna Polymerase Alpha ◽  
Polymerase Beta

The effects on DNA synthesis in vitro in mouse L929-cell nuclei of differential extraction of DNA polymerases alpha and beta were studied. Removal of all measurable DNA polymerase alpha and 20% of DNA polymerase beta leads to a 40% fall in the replicative DNA synthesis. Removal of 70% of DNA polymerase beta inhibits replicative synthesis by 80%. In all cases the nuclear DNA synthesis is sensitive to N-ethylmaleimide and aCTP (arabinosylcytosine triphosphate), though less so than DNA polymerase alpha. Addition of deoxyribonuclease I to the nuclear incubation leads to synthesis of high-molecular-weight DNA in a repair reaction. This occurs equally in nuclei from non-growing or S-phase cells. The former nuclei lack DNA polymerase alpha and the reaction reflects the sensitivity of DNA polymerase beta to inhibiton by N-ethylmaleimide and aCTP.

Correlation between deoxyribonucleic acid and volume in liver cell nuclei during post-natal growth

1960 ◽  
Vol 20 (1) ◽  
pp. 208-211 ◽  
Author(s):  
A.O. Pogo ◽  
B.G.T. Pogo ◽  
J.R.Cordero Funes
Keyword(s):  
Liver Cell ◽  
Deoxyribonucleic Acid ◽  
Cell Nuclei

A single-cell analysis of the Arabidopsis vegetative shoot apex

2021 ◽  
Author(s):  
Tian-Qi Zhang ◽  
Yu Chen ◽  
Jia-Wei Wang
Keyword(s):  
Single Cell ◽  
Shoot Apex ◽  
Single Cell Analysis ◽  
Cell Analysis ◽  
Vegetative Shoot ◽  
Vegetative Shoot Apex

Variation in the Amounts of Deoxyribonucleic Acid in the Cell Nuclei and its Correlation with Mitotic Activity: Compensatory Hypertrophy of the Kidney

Nature ◽  
1955 ◽  
Vol 175 (4459) ◽  
pp. 684-685 ◽  
Author(s):  
J. FAUTREZ ◽  
G. CAVALLI ◽  
E. PISI
Keyword(s):  
Mitotic Activity ◽  
Deoxyribonucleic Acid ◽  
Compensatory Hypertrophy ◽  
Cell Nuclei

Ontogenetical and experimental studies of the floral apex of Portulaca grandiflora. 1. Histology of transformation of the shoot apex into the floral apex

1969 ◽  
Vol 47 (1) ◽  
pp. 133-140 ◽  
Author(s):  
Siti Raswati Soetiarto ◽  
Ernest Ball
Keyword(s):  
Shoot Apex ◽  
Experimental Studies ◽  
Floral Meristem ◽  
Vegetative Shoot ◽  
Floral Organs ◽  
Mature Flower ◽  
Floral Apex ◽  
Portulaca Grandiflora ◽  
Floral Primordia ◽  
Vegetative Shoot Apex

The vegetative apex was a low dome consisting of two layers of tunica surmounting a very small corpus. Foliar primordia originated as periclines in the flanks of T2. The transition apex became first a steep cone and then a hemisphere. All floral primordia—the two bracts, the two sepals, the several whorls of petals, the several whorls of stamens, and the carpels—originated in the manner of leaves, as periclines in T2 on the flanks of the apex. All appendages, including carpels, were therefore lateral. In the early transition, the apex had a brief stage in which there were three tunica layers, but the inner one was lost with the onset of the sepals. The bracts and the first sepal continued the normal positions of primordia for the vegetative phyllotaxy of 3/8, but with the second sepal, this phyllotaxy was lost, and petals, stamens, and carpels were produced in whorls. While leaves, bracts, sepals, and petals were produced in acropetal sequence, stamens were produced in basipetal sequence, and carpels appeared simultaneously. After carpels were formed, the rest of the floral apex underwent a brief period of expansion growth, achieving a diameter comparable to that of a shoot apex, but its substance was eventually incorporated into the carpel margins, which later produced the ovules. This agrees with the determinate nature of the floral apex. During the development of the first series of floral organs, the floral apex underwent continued increase in area, finally achieving a diameter several times that of the vegetative shoot apex. Its size and form were such that they were compared to those of some inflorescence apices. After development of the first series of floral organs, the subjacent tissues to the floral meristem underwent divisions and elongation at right angles to the axis, causing at first a flattening of the meristem, and eventually a cup-shaped form, with the carpels attached in the bottom of a bowl. The mature flower was thus perigynous, but this development arose quite differently from the perigyny as it is known from ontogenetic studies in the Rosaceae.

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