ISSN:
1615-6102
Keywords:
DNA synthesis
;
Dormancy and activation
;
Electron microscope autoradiography
;
Helianthus tuberosus
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary Parenchyma cells of dormant tubers ofHelianthus tuberosus L. cv. OB1 (Jerusalem artichoke) contain a very low amount of hormones, therefore they respond to 2,4-D or IAA treatment by dividing and synthesizing RNA, DNA, and polyamines. In particular the activation of the dormant tissues induces an early synthesis of DNA, which reaches the maximum at 3 hours, much before the beginning of the S phase (12 hours). By supplying [6-3H] thymidine and carrying out electron microscopic autoradiography, we were able to determine that plastids and mitochondria were the organelles responsible for this early synthesis while the DNA in the nucleus first appeared labeled at 15 hours. In addition, ultrastructural observations carried out to compare the dormant cells with activated ones, showed an increase in the nucleolar volume, a different organization of the tubular complex of the plastids and several other ultrastructural changes which indicate that at 3 hours some fundamental metabolic processes are already active; they become even more evident later on. The implications of these results in the physiology of the tuber cells during activation are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01281166
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