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VARIATION IN CELL‐CYCLE TIME AND NUCLEAR DNA CONTENT IN THE APICAL MERISTEM OF HELIANTHUS ANNUUS L. DURING THE TRANSITION TO FLOWERING
Author(s) -
Marc Jan,
Palmer John H.
Publication year - 1984
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1984.tb12544.x
Subject(s) - meristem , biology , cell cycle , mitosis , helianthus annuus , metaphase , botany , microbiology and biotechnology , horticulture , chromosome , shoot , cell , sunflower , genetics , gene
The mitotic cycle in the apical meristem of Helianthus annuus L. has been investigated during the transition to flowering. Towards the end of the strictly vegetative phase 8 days after sowing the average cell‐cycle time, measured by colchicine‐induced metaphase accumulation, was 37 hr in the peripheral zone, 83 hr in the central zone and 118 hr in the rib meristem. By Day 12 the cycle had shortened in all zones. By the time of floral initiation on Day 16 the cycle time had returned to its original value in the peripheral zone and the rib meristem, while in the central zone it continued to shorten to 33 hr, approaching the cycle time of the peripheral zone. Cytophotometric measurements of nuclear DNA showed that mitotic activation of the central zone was not associated with any reduction in the proportion of nuclei with a 4 C DNA content. It was calculated that the spatial and temporal variation in cell‐cycle time was mainly a function of the length of the G 1 /G 0 phase which lasted about 19 hr in the peripheral zone, 82 hr in the rib meristem, and declined from 55 to 21 hr in the central zone.