The relationship between the mitotic activity and moisture content of recalcitrant seeds ofAcer saccharinum(L.) during maturation, post-maturation drying and germination

Abstract

AbstractThe decline of embryo moisture content from approx. 82 to 53% in 1997 and 56% in 1998 in recalcitrant seeds ofAcer saccharinumduring maturation was accompanied by decreased mitotic activity in the meristems and an increase in the percentage of cells in the G1phase of the cell cycle. DNA synthesis and mitosis in the root apex ceased at approx. 53% embryo moisture content, and 67% of the cells were arrested in the G1phase. During post-maturation drying, cell division in the shoot apex and embryonic leaves continued as long as the embryo moisture content was higher than 50 and 45%, respectively. Mitotic activity in the drying embryo may be controlled by its moisture level. Increased proliferation of the root, shoot and leaf meristems of the mature seeds was already recorded at 24 h of germination, before the root protruded through the seed coat. However, the increase in the embryo moisture content was small – from 56 to 59%. In the 3 d seedlings (10–15 mm long) the mitotic index reached 8% in the root apex and 12% in the shoot apex with leaves. Placing mature seeds in moist conditions might be necessary for the switch from proliferation decline towards its activation. Thus, in contrast with orthodox seeds, the preservation of cell division capacity and increased mitotic activity may be essential for rapid germination immediately after shedding in matureAcerseeds.