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FEULGEN MICROSPECTROPHOTOMETRIC STUDIES OF PANDORINA MORUM AND OTHER VOLVOCALES (CHLOROPHYCEAE) 1 2

1979; Wiley; Volume: 15; Issue: 2 Linguagem: Inglês

10.1111/j.1529-8817.1979.tb02987.x

1529-8817

Annette W. Coleman,

Marine and coastal plant biology

ABSTRACT The nuclear DNA content during normal vegetative growth and division has been examined in three species of Volvocales, Chlamydomonas reinhardtii Dangeard, Pandorina morum Bory, and Volvox carteri f. nagariensis Iyengar. The results are consistent with the nuclear cycle reported in the literature for Eudorina. Nuclear DNA content does not increase during the prolonged cell growth phase. At the time of colony formation, nuclear DNA doubles, the nucleus divides, and this alternation continues until the final 2 n complement of progeny nuclei is formed. The 4‐ and 8‐nucleate stages of dividing gonidia of V. carteri have a nuclear DNA content in the same range as the somatic cells; they are not polyploid or polytene. Four normal clones of Pandorina, having 2, 5 or 12 chromosomes, all had similar amounts of DNA per nucleus, suggesting that the species has a nuclear genome of fairly constant size rather than consisting of many strains representing a polyploid series. One unique clone, a hybrid with double the chromosome number of either its parents, had twice as much DNA as the normal clones. The Feulgen spectrophotometric method is sufficiently sensitive to detect 2‐fold differences in DNA content at the level of 2 × 10 −13 g of DNA /nucleus, and its use avoids the complications associated with the presence of organelle DNA.