The effect of cambial zone isolation upon the autolytic system in maturing tracheids of pine (Pinus silvestris L.)

The autolytic protease system in maturing tracheids of the main stem of <em>Pinus silvestris</em> was investigated after separation (using surgical methods) of the cambial zone from the layer of differentiating xylem, in combination with decapitation and IAA application. Separation of the cambium prevented autolysis of the protoplast in maturing tracheids, although the specific activity of proteases was little reduced. It was found that a radial or longitudinal concentration gradient of exogenously applied auxin was not responsible for autolysis, but that it could influence the level of extracted protein, and proteolytic activity. Similarly, decapitation modified, only to small degree, the effects of the cambium separation. Thus, the data from this experiment lead to the conclusion that integration of all cells in the region of xylem formation is a crucial factor for the start of autolytic protoplast breakdown. Possible involvement of auxin waves in the transfer of the positional information for this process is suggested.

Stock Plant Etiolation, Shading, and Banding Effects on Cutting Propagation of Carpinus betulus

In a study of stock plant etiolation and stem banding, stem cuttings of upright European hornbeam (Carpinus betulus L. `Fastigiata') were taken at 2-week intervals over 4 months following budbreak and rooted under intermittent mist for 30 days. Percent rooting and root counts declined with increasing cutting age. Stock plant etiolation and stem banding increased percent rooting and root counts throughout the study, with the combination of both treatments yielding the best rooting. In nontreated stems, > 75% rooting was achieved only within 4 weeks of budbreak. Etiolation and stem banding resulted in rooting ≥ 75% up to 3 months after budbreak. In two shading studies, stock plants were grown in a glass greenhouse under 0%, 50%, 75%, or 95% shade, or initially etiolated (100% shade) for 1.5 days. Cuttings were taken after 2.5 and 60 days and treated with IBA concentrations ranging from 0 to 4.9 mm before rooting under intermittent mist for 30 days. Percent rooting increased proportionally to the degree of shading, with a maximum response at 95% shade. Cuttings taken at 60 days were less responsive to etiolation and shading than those harvested at 25 days. Auxin concentration interacted with shading to yield, at 95% shade and 3.7 mm IBA, the highest rooting percentage and the greatest root counts and lengths. Light exclusion by etiolation, stem banding, or shading can extend the cutting propagation season by increasing rooting responses and increasing the sensitivity of stem cuttings to exogenously applied auxin. Chemical name used: 1H-indole-3-butyric acid (IBA).

Influence of postseverance treatments on the rooting capacity of Fraser fir stem cuttings

Postseverance treatments of wounding, auxin, disbudding, bottom heat, and chilling were examined for their effects on rooting stem cuttings (tips of primary axes) of young Fraser fir (Abiesfraseri (Pursh) Poir.) stock plants. Applied auxin consistently increased rooting percentages and the number and length of roots. Wounding alone did not affect the rooting response, but was beneficial in combination with applied auxin. Certain wounding treatments were better than others. Roots rarely emerged from wound margins and were usually observed at the base of cuttings. Bottom heat enhanced rooting, particularly in combination with wounding + auxin. Removal of lateral buds had a negligible effect on rooting. Following 4 and 8 weeks of artificial chilling, cuttings initially taken in early November rooted well if treated with wounding + indolebutyric acid. However, terminal budbreak was more complete following an 8-week chill. Cuttings taken in late January rooted well without additional chilling. Less chilling was required for rooting than for budbreak.