Maturation in Douglas-fir: II. Maturation characteristics of genetically matched Douglas-fir seedlings, rooted cuttings and tissue culture plantlets during and after 5 years of field growth.

Seedlings, rooted cuttings from juvenile stock plants, and cotyledon-derived tissue culture plantlets were propagated from several coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) full-sib families so that the rooted cuttings and plantlets were clonally identical. The stock types (seedlings, rooted cuttings and plantlets) were planted in the field in spring 1987. In fall 1991, after five complete growing seasons, the plants were measured and these values compared to maturation "markers" identified for Douglas-fir in the companion paper (Ritchie and Keeley 1994). Nodal branch lengths and nodal branch diameters decreased in the order seedlings > rooted cuttings > plantlets. The decreases were about 21% for nodal branch lengths and 24% for nodal branch diameters. Seedlings carried significantly more total branches (nodal + internodal) than the other two stock types. Height growth was similar for the three stock types, but plantlet height increment was beginning to decrease during the fourth year. We conclude that vegetative propagules of Douglas-fir exhibited traits of mature trees. These were particularly marked in the cotyledon-derived plantlets.

Physiology and morphology of Douglas-fir rooted cuttings compared to seedlings and transplants.

Cuttings of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) from three open-pollinated families were rooted in two types of tray, and then grown for 1.5 years in a bareroot nursery. During their second winter they were sampled periodically and tested for cold hardiness, dormancy status, root growth potential and various morphological characteristics. Two-year-old seedlings and transplants were tested concurrently for comparison. Rooted cuttings, seedlings and transplants cold hardened at similar rates during early winter, achieving the same level of midwinter hardiness (LT(50) = -18 degrees C) in early January. However, rooted cuttings remained hardier later into the spring than did seedlings or transplants. Rooted cuttings exhibited deeper dormancy in early winter than seedlings or transplants but these differences disappeared after January. Root growth potentials of all three stock types remained above threshold values established for transplants throughout winter. Rooted cuttings had greater stem diameter, higher stem diameter to height ratio, and greater root weight than either seedlings or transplants. This may reflect lower growing densities for the rooted cuttings. Root/shoot ratios of rooted cuttings were greater than for seedlings and similar to those of transplants. Rooted cuttings also had deeper and coarser root systems, which probably reflects lack of wrenching at the nursery.