ISHS Acta Horticulturae 56: Symposium on Juvenility in Woody Perennials
JUVENILITY IN HEDGED RADIATA PINE |
| Authors: | W.J. Libby, J.V. Hood |
| Abstract:
Rooting of radiata pine (Pinus radiata D. Don) cuttings generally declines in terms of speed of rooting, percentage of cuttings that root, and root-system quality as the donor trees become older and larger. By 1971, it had been demonstrated that the level of rooting success, as judged by all three criteria, could be maintained if young trees were repeatedly pruned, or hedged. In 1971, cuttings were set from trees which had been hedged since 1965, and from trees of the same genotypes (clones) which had grown in tree form during the same period. Clonal pairs of rooted cuttings of hedged and tree-form origin were planted in three plantations in 1972, and have now completed 3 years' growth. During the 1972 growing season at one plantation, hares preferentially browsed the cuttings of tree-form origin. At a second plantation, mortality associated with summer drought was much greater among the tree-form-origin cuttings. In our 1973–74 data, trees of hedged origin consistently and significantly exceeded trees of tree-form origin in: total needle length; total length, average length, and number of primary branches; number of secondary branches; 1974 bole volume; and 1973–74 bole-volume growth. Trees of tree-form origin consistently and significantly exceeded trees of hedged origin in: occurrence of male and female strobili; and 1973 and 1974 bole volume and 1973-74 bole-volume growth per unit needle length in 1973. These latter observations are consistent with the suggestion that tree-form-origin cuttings are more mature than hedged-origin cuttings, and that more-mature cuttings allocate more photosynthate to bole per unit leaf area. Trees of the two origins were not consistently different in height, or in taper. | |
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