Effet d'un traitement par l'acide abscisique sur la division cellulaire, les teneurs en ADN et l'élongation du bourgeon cotylédonaire de plants de pois décapités

1987 ◽  
Vol 65 (5) ◽  
pp. 907-915 ◽  
Author(s):  
Arlette Nougarède ◽  
Pierre Rondet ◽  
Pierre Landré ◽  
Jacques Rembur
Keyword(s):  
Cell Cycle ◽  
Abscisic Acid ◽  
Pisum Sativum ◽  
Shoot Apex ◽  
S Phase ◽  
Main Axis ◽  
Cortical Cells ◽  
Exogenous Aba ◽  
Pisum Sativum L ◽  
Subapical Region

When applied to pea (Pisum sativum L. var. nain hâtif d'Annonay) cotyledonary bud at the time of decapitation, cis-abscisic acid (ABA) induced a decrease in the mitotic indices of the meristem and subapical regions of the bud, in comparison with decapitated but not ABA treated control plants. ABA treatment delayed the entry of the G0–1 nuclei of the inhibited bud into the S phase and then into mitosis. Whatever the ABA concentration (10−3 to 10−7 M), the overall growth of the bud and the elongation of the cortical cells in its subapical region were not affected during the first 48 h. ABA induced an inhibition of bud elongation, all the more important since it was applied later after decapitation. When applied on a 48-h released bud, ABA induced an inhibition of elongation of the bud, a decrease in its mitotic activity, as well as a concentration of the shoot apex nuclei in the G1 phase of the cell cycle. However, this exogenous ABA treatment could not entirely replace the main axis in maintaining the inhibited state of the bud.

Excision and replication of extrachromosomal DNA of pea (Pisum sativum)

1983 ◽  
Vol 3 (2) ◽  
pp. 172-181
Author(s):  
J Van't Hof ◽  
C A Bjerknes ◽  
N C Delihas
Keyword(s):  
Cell Cycle ◽  
Pisum Sativum ◽  
S Phase ◽  
Velocity Sedimentation ◽  
Extrachromosomal Dna ◽  
Chromosomal Dna ◽  
Root Tips ◽  
Dividing Cells ◽  
G2 Phase ◽  
Pea Roots

Experiments with cultured pea roots were conducted to determine (i) whether extrachromosomal DNA was produced by cells in the late S phase or in the G2 phase of the cell cycle, (ii) whether the maturation of nascent DNA replicated by these cells achieved chromosomal size, (iii) when extrachromosomal DNA was removed from the chromosomal duplex, and (iv) the replication of nascent chains by the extrachromosomal DNA after its release from the chromosomal duplex. Autoradiography and cytophotometry of cells of carbohydrate-starved root tips revealed that extrachromosomal DNA was produced by a small fraction of cells accumulated in the late S phase after they had replicated about 80% of their DNA. Velocity sedimentation of nascent chromosomal DNA in alkaline sucrose gradients indicated that the DNA of cells in the late S phase failed to achieve chromosomal size. After reaching sizes of 70 X 10(6) to 140 X 10(6) daltons, some of the nascent chromosomal molecules were broken, presumably releasing extrachromosomal DNA several hours later. Sedimentation of selectively extracted extrachromosomal DNA either from dividing cells or from those in the late S phase showed that it replicated two nascent chains, one of 3 X 10(6) daltons and another of 7 X 10(6) daltons. Larger molecules of extrachromosomal DNA were detectable after cells were labeled for 24 h. These two observations were compatible with the idea that the extrachromosomal DNA was first replicated as an integral part of the chromosomal duplex, was cut from the duplex, and then, once free of the chromosome, replicated two smaller chains of 3 X 10(6) and 7 X 10(6) daltons.

scholarly journals Excision and replication of extrachromosomal DNA of pea (Pisum sativum).

1983 ◽  
Vol 3 (2) ◽  
pp. 172-181 ◽  
Author(s):  
J Van't Hof ◽  
C A Bjerknes ◽  
N C Delihas
Keyword(s):  
Cell Cycle ◽  
Pisum Sativum ◽  
S Phase ◽  
Velocity Sedimentation ◽  
Extrachromosomal Dna ◽  
Chromosomal Dna ◽  
Root Tips ◽  
Dividing Cells ◽  
G2 Phase ◽  
Pea Roots

Experiments with cultured pea roots were conducted to determine (i) whether extrachromosomal DNA was produced by cells in the late S phase or in the G2 phase of the cell cycle, (ii) whether the maturation of nascent DNA replicated by these cells achieved chromosomal size, (iii) when extrachromosomal DNA was removed from the chromosomal duplex, and (iv) the replication of nascent chains by the extrachromosomal DNA after its release from the chromosomal duplex. Autoradiography and cytophotometry of cells of carbohydrate-starved root tips revealed that extrachromosomal DNA was produced by a small fraction of cells accumulated in the late S phase after they had replicated about 80% of their DNA. Velocity sedimentation of nascent chromosomal DNA in alkaline sucrose gradients indicated that the DNA of cells in the late S phase failed to achieve chromosomal size. After reaching sizes of 70 X 10(6) to 140 X 10(6) daltons, some of the nascent chromosomal molecules were broken, presumably releasing extrachromosomal DNA several hours later. Sedimentation of selectively extracted extrachromosomal DNA either from dividing cells or from those in the late S phase showed that it replicated two nascent chains, one of 3 X 10(6) daltons and another of 7 X 10(6) daltons. Larger molecules of extrachromosomal DNA were detectable after cells were labeled for 24 h. These two observations were compatible with the idea that the extrachromosomal DNA was first replicated as an integral part of the chromosomal duplex, was cut from the duplex, and then, once free of the chromosome, replicated two smaller chains of 3 X 10(6) and 7 X 10(6) daltons.

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