NUCLEAR-DNA CONTENT VARIATION IN SEEDS FROM 22 HALF-SIB FAMILIES OF JACK PINE (PINUS-BANKSIANA, PINACEAE)

In order to understand the amount of DNA content variation and its pot ential roles, both absolute DNA amount and cell cycle phases in 22 hal f-sib families of jack pine were examined using flow cytometry. When t he variability due to differences in speed of germination was taken in to account, embryos from superior families (classified on the basis of height growth during field trials) had significantly higher levels of all nuclei classes greater than 4C. Mean DNA contents per nucleus wer e significantly lower in embryos from superior families compared to in ferior ones. Analysis of megagametophyte tissue showed that the mother trees of these embryos expressed a similar pattern. Absolute DNA valu es were also established on the emerging radicle and the hypocotyl + c otyledons region (HC) separately in five of the families. Nuclei isola ted from the emerging radicles had significantly lower levels of DNA t han those isolated from the KC region. For three of these families, ab solute DNA Values from nuclei of the hypocotyl + cotyledons region wer e established on individual embryos with varying cotyledon numbers. In all three families total DNA amount per nucleus decreased with increa sing cotyledon number. A better understanding of differences observed in DNA content during germination, as well as in total DNA content per nuclei among different half-sib families of jack pine, may help in th e identification of factors that influence growth and adaptation of th is species.