The original basal stem section influences rooting in Pinus banksiana cuttings

We tested the hypothesis that, during propagation, the basal stem of Pinus banksiana Lamb, cuttings contains a nonauxin endogenous root‐forming stimulus (ERS) whose effects are not replaced by auxin treatment; i.e., that auxin treatment of cuttings and surgical removal of their basal stems during propagation act additively on rooting, without significant interaction, as determined by analyses of variance. We studied the effects of ERS by severing the original basal (1 cm) stem from cuttings at days 3, 6 and 9 of a 30‐day period of propagation. To study treatment interaction, we applied the auxin N‐phenyl indolyl‐3‐butyramide to some surgically treated cuttings. Results for all variables (proportion of rooted cuttings, number of roots per cutting and fresh weight of basal stem plus roots, if any) indicated that removing the basal stem reduced rooting and that auxin treatment increased rooting, without significant treatment interaction. The results thus supported the hypothesis that P. banksiana seedling cuttings contain ERS. However, neither the present nor previous tests have shown that ERS is a chemical stimulus rather than, for example, a biophysical or anatomical one.