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Wen-Quan Sun and Nina L. Bassuk

The effects of silver thiosulfate (STS) on stored and freshly made cuttings of `Royalty' rose (Rosa hybrids) were examined in relation to rooting and subsequent budbreak. STS pretreatment at 0.5 mm during storage stimulated budbreak but decreased the percentage of cuttings that rooted and the number of roots. IBA at 4.9 to 9.8 mm inhibited budbreak but this effect was partially reversed by STS. Spraying the cuttings with 1.0 mm STS once daily during the first 5 days of the rooting period also reduced rooting but prevented IBA-induced leaf senescence. Ethephon and spermine, each applied at 0.5 mm before rooting, had no effect on rooting or budbreak. Chemical names used: (2-chloroethyl)-phosphonic acid (ethephon); indole butyric acid (IBA); N,N'-bis(3-aminopropyl) -l,4-buanediamine (spermine).

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Brian K Maynard and Nina L. Bassuk

New shoot growth of Carpinus betulus `fastigiata' was treated with stockplant etiolation and stem banding treatments and sampled for anatomical study at intervals over a 16-week period of greening following etiolation. Shading effects on the anatomy of the stem were also investigated. Numerous anatomical changes were noted with stem age and stockplant treatment. Among these were etiolation effects on the lignification of the secondary xylem, thickness of the periderm, and an increase in the percentage of sclereid-free gaps in the perivascular sclerenchyma, Stem banding increased the widths of the cortex and pith. Concomitant propagation studies revealed significant etiolation, shading, and banding effects on rooting percentages and root numbers. Using multiple linear regression methods rooting capacity was modelled best by linear combinations of the widths of the pith, non-lignified secondary xylem, cortical parenchyma and periderm, as well as the percentage of gaps in the sclerenchymatic sheath remaining non-sclerified. It is proposed that the development of sclereids in potential rooting sites reduces rooting potential. The exclusion of light during initial shoot development retards sclereid development by up to 3 months following treatment, which correlates well with observed increases in the rooting potential of etiolated and/or banded stems.

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Brian K. Maynard and Nina L. Bassuk

Three experiments were undertaken to examine the effect of stockplant etiolation, shading, and stem banding, prior to cutting propagation, on the auxin dose-response of rooting in stem cuttings of Carpinus betulus `fastigiata'. A 2 × 2 factorial of etiolation and banding utilized stockplants forced in a greenhouse, etiolated for 1 week and banded with Velcro™ for 1 month. In a separate study shading was applied up the time of harvesting cuttings. IBA was applied to cuttings as an aqueous ethanol quick dip in concentrations ranging from 0 to 80 mM. Rooting percentage and number were best described, up to a peak response, by a linear function proportional to the logarithm of applied IBA. The inhibition of rooting by supra-optimal IBA was directly proportional to IBA concentration. Cuttings prepared from shoots which had been etiolated or banded rooted better at low IBA and at their respective optimal IBA levels. Cuttings from shoots receiving both etiolation and banding yielded higher rooting percentages and more roots per rooted cutting on average. Etiolation and banding served to increase both initial and maximum rooting capacities, and to reduce the sensitivity of cuttings to supraoptimal auxin-induced inhibition of adventitious root initiation. The auxin dose-response interacted with shading to yield the best rooting at 95% shade and 3.7 mM IBA.

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Wen-Quan Sun and Nina L. Bassuk

Softwood shoots of apple (Malus domestica Borkh.) rootstocks M.9 and MM.106 were banded with Velcro for up to 20 days before cuttings were propagated. Percent rooting and the number of roots per cutting were significantly improved by banding for 10 to 20 days, with and without IBA application. As the duration of stem banding increased from 0 to 20 days, percent rooting and the number of roots of both M.9 and MM.106 cuttings increased linearly or curvilinearly. Stem banding also stimulated budbreak of cuttings. In M.9, banding resulted in a higher survival rate and increased new shoot growth of transplanted cuttings after 4 months. Percent budbreak and new shoot growth were highly correlated with the number of roots per cutting in both cultivars. The effects of stem banding on budbreak and subsequent growth of the cuttings were largely due to the enhanced rooting of cuttings. Chemical names used: 1H-indole3-butyric acid (IBA).

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Patricia A. Lindsey and Nina L. Bassuk

The development of a rapid, accurate, yet nondestructive technique for expressing whole-tree leaf area would be extremely useful in studying various growth phenomena in trees. The objective of this research was to evaluate the accuracy of an image analysis process adapted for estimating the leaf surface area of four broad-leafed tree species (Amelanchier L. `Robin Hill Pink', Tilia americana L. `Redmond', Sophora japonica L. `Regent', Fraxinus americana L. `Autumn Purple' and Fraxinus pennsylvanica Marsh.). Video images of photographs taken of each tree canopy were quantified by an image analyzer into unitless surface area values or silhouette areas. The relationship between estimated leaf area as calculated from silhouette area and actual leaf area of these trees as determined by a leaf area meter was highly correlated. Use of this technique would enable a researcher, simply from serial photographs of the canopy, to retroactively estimate leaf or canopy area at crucial interim periods.

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Susan D. Day and Nina L. Bassuk

Four techniques for compaction amelioration were studied: 1) Vertical drainage panels; 2) vertical gravel-filled sump drains; 3) soil trenches filled with sandy loam; and 4) peat amended back fill. The control was backfilled with existing soil on the site. Vertical drainage mats and vertical gravel-filled sump drains were shown to increase O2% in surrounding soil; however, all O2 levels regardless of treatment were above what is considered limiting. Shoot and root growth of Pyrus calleryana `Redspire' was greatest for treatments that alleviated mechanical impedance (soil trenches and amended back fill) and least for treatments that did not (controls and vertical drains). Vertical drainage mats which alleviated mechanical impedance to a lesser degree showed intermediate growth.

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Brian K. Maynard and Nina L. Bassuk

Effects of stockplant etiolation, stem banding, exogenous auxin, and catechol on the rooting response of softwood cuttings of paperbark maple (Acer griseum Pax.) were studied. Etiolated cuttings rooted better than light-grown cuttings, while stem banding did not affect rooting percentage (light-grown, 10%; light-grown + banding, 18%; etiolated, 41%; etiolated + banding, 37%). IBA did not promote, but catechol inhibited rooting (control, 31%; IBA, 37%; catechol, 17%; IBA + catechol, 21%). Root number was increased by IBA and unaffected by catechol. The distance from the cutting base to the first emerged root was measured as an indication of auxin toxicity. IBA interacted with etiolation and stem banding to increase this distance, which was greater in catechol-treated cuttings. Chemical names used: 1,2-benzenedio1 (catechol); 1H-indole-3-butanoic acid (IBA).

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Brian K. Maynard and Nina L. Bassuk

New shoot growth of Carpinus betulus L. fastigiata was subjected to stock plant etiolation and stem banding (a 2.5-cm square of Velcro applied to the shoot base) treatments and sampled for histological study at intervals over a 16-week period of shoot development following etiolation. Effects of partial shading on histology of the stem were also investigated. Numerous histological changes were noted with stem development and stock plant treatment. Among these were a reduction in lignification of the secondary xylem and thickness of the periderm, and an increase in the percentage of sclereid-free gaps in the perivascular sclerenchyma with etiolation. Concomitant propagation studies revealed significant etiolation, shading, and banding effects on rooting percentages and root numbers. Rooting capacity was modelled using linear combinations of the widths of nonlignified secondary xylem, cortical parenchyma and periderm, as well as the percentage of gaps in the sclerenchymatic sheath remaining free of sclereids. It is proposed that the development of sclereids in potential rooting sites reduces rooting potential. The exclusion of light during initial shoot development retards sclereid development by up to 3 months following treatment, which correlates well with observed increases in the rooting potential of etiolated stems.

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Wen-Quan Sun and Nina L. Bassuk

Single-node `Royalty' rose (Rosa hybrida L.) cuttings were used to examine the relationship between adventitious root formation, budbreak, and ethylene synthesis following IBA treatment. IBA was applied as a lo-second basal quick dip before rooting, and AIB, GA3, STS, and ethephon were applied either as basal dips or foliar sprays. IBA application increased rooting and inhibited budbreak of cuttings. IBA 2 600 mg·liter-1 greatly inhibited budbreak during 4 weeks of rooting. IBA treatment stimulated ethylene synthesis, which was inversely correlated with budbreak of cuttings. Ethephon also significantly inhibited budbreak. Budbreak of rose cuttings was completely prevented by repeated ethephon sprays used to maintain high endogenous ethylene levels during the first 10 days. Treatment with STS, an ethylene-action inhibitor, improved budbreak. The inhibition of budbreak by IBA treatment resulted primarily from elevated ethylene levels. Root initiation and root elongation of cuttings initially inhibited budbreak, but later promoted budbreak. Chemical names used: indole-3-butyric acid (IBA); gibberellic acid (GA3); silver thiosulfate (STS); AIB, aminoisobutyric acid (AIB); (2-chloroethyl)-phosphoric acid (ethephon).

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Brian K. Maynard and Nina L. Bassuk

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).