Growth analyses on in vitro, ex vitro and auxin-rooted hypocotyl cuttings of Pinus contorta Dougl. ex Loud.

Three different types of rooted hypocotyl cuttings showed relative growth rates close to those recorded as maximal for seedlings of Pinus contorta Dougl. ex Loud. However, slight differences in growth rate were noted depending on how the cuttings had been rooted. (I) Cuttings rooted in vitro initially formed a large wound tissue at the base from which roots subsequently developed. (II) Cuttings rooted ex vitro formed roots without previous formation of a wound tissue at the root-shoot connection. I and II produced plants with in average two roots per plant and the plants grew at similar relative growth rates (6.86 and 6.88 % per day respectively). (III) Auxin-rooted cuttings also formed roots (21 per plant) without previous formation of a wound tissue and had a slightly higher growth rate (7.65 % d ). The growth rate of auxin-rooted cuttings was not significantly different from the 8.67 % d obtained in seedlings. The conclusions drawn from these experiments were that; (1) rooted cuttings have the capacity to grow almost as fast as seedlings, (2) wound tissue produced prior to rooting or an extended period before the roots develop does not have a negative affect on the growth capacity of the cuttings, (3) the number of roots per cutting did not affect growth rate.