Maturation in Larch

Abstract

The time course of maturation in eastern larch (Larix laricina [Du Roil K. Koch) was examined by grafting scions from trees of different ages onto 2-year-old root stock and following scion development for several years. Height, diameter, foliar chlorophyll content, and rooting ability of scion-derived cuttings all varied linearly as a function of log10 age. Chlorophyll content (milligrams per gram of dry weight) increased while height, diameter, and ability to root decreased with age (P < 0.01). The tendency toward orthotropic growth and branch formation per centimeter of main stem decreased abruptly between age 1 and 5 years (P < 0.01). Total chlorophyll content of both long and short shoot foliage increased by 30 to 50% with increasing age, but the chlorophyll a/b ratio did not change. Also, juvenile long shoot needles were significantly longer than mature (P < 0.01). Surprisingly, the juvenile scions produced more total strobili over two successive years, but the mature scions produced a significantly higher proportion of male strobili (P < 0.001 year 1; P < 0.02 year 2). The age-related changes in foliar traits were not associated with changes in DNA methylation between juvenile and mature scions. Using HPLC, we found that 20% of foliar DNA cytosine residues were methylated in both scion types.

Maturation in Larch

“…In a wide variety of conifers and other woody plants, foliar characteristics also change in association with the onset of maturation (18). Changes in needle form, dimensions, pigment (Chl and anthocyanin) content, surface waxes, and CO2 fixation have all been reported in the conifers Cupressus, Pinus, Picea, and Larix, and in English ivy (Hedera helix) (2,16,17,28). Following germination, conifers generally exhibit indeterminate growth resulting in acicular needles throughout most of the first growing season.…”

“…We (17) previously reported on a number of changes associated with increasing age in Eastern larch, including changes in needle dimensions, a reduction in total foliar surface area, and an increase in Chl content. Chl content on a needle dryweight basis increases almost 50% between 1 and 74 years ( 17).…”

The effect of phase change on annual growth increment in eastern larch (Larix laricina (Du Roi) K. Koch)

“…However, the earlier decline in annual increment observed for a dominant tree on a relatively good site is probably not due to the limiting effect of competition or nutrients (Forward and Nolan, 1964) Sweet, 1973;Greenwood, 1984). A similar experiment was carried out using the larch trees in the stand described above (Greenwood et al, 1989). Grafting success was not affected by the age of the donor tree.…”

“…That a newly germinated seedling cannot produce a maximum annual increment in height and diameter after 1 yr is intuitively obvious, but maximum growth potential is clearly necessary for the seedling to establish itself. In addition, scions from 1 yr old trees produced 2-3 times more branches per unit length of stem than older ones (Greenwood, 1984;Greenwood et al, 1989), which may also be a result of the vigorous growth potential of young trees. After 5-10 yr, the plant will have become well enough established to realize its growth potential to the fullest extent.…”

“…The height and diameter increments of the grafted scions after the first growing season are shown in Fig. 2A (Greenwood, 1984 (Greenwood et al, 1989).…”