Maturation in larch. I. Effect of age on shoot growth, foliar characteristics, and DNA methylation
1989
Greenwood, M.S. | Hopper, C.A. | Hutchison, K.W.
The time course of maturation in eastern larch (Larix laricina [Du Roi] 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 log(10)age. Chlorophyll content (milligrams per gram of dry weight) increased while height, diameter, and ability to root decreased with age (P less than 0.01). The tendency toward orthotropic growth and branch formation per centimeter of main stem decreased abruptly between age 1 and 5 years (P less than 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 less than 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 less than 0.001 year 1; P less than 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.
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