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- Author or Editor: Nina L. Bassuk x
Abstract
Only a few species are capable of colonizing extreme environments, whereas more moderate environments can support many more. The diversity of species in a habitat is thus controlled by the environment, whether by soil fertility, altitude or any other factor. This diversity reflects the number of species adapted to grow in a habitat, and the nature of this adaptation must be examined in light of the physiological effect of the environmental factors making up the habitat, and their variation in time and space (11).
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).
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).
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).
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.
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).
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).
Abstract
A modification of the traditional technique of etiolation and blanching, using Velcro adhesive fabric strips as the blanching material, was used with success in improving cutting propagation of a wide range of difficult-to-root woody species. Stockplants were etiolated under black cloth at budbreak, followed by banding for a period of 4 weeks, to produce a cutting with an etiolated base. Rooting of softwood cuttings from 18 of 21 species tested was improved significantly by these stockplant pretreatments. The use of Velcro as the banding material facilitated blanching, permitted the application of rooting hormone as a part of the blanching procedure, wounded underlying stem tissues, and resulted occasionally in the formation of adventitious roots on intact shoots.
Landscape trees are frequently planted in heavily compacted soils, such as around newly constructed buildings or in urban areas. Under such conditions, trees frequently die, or decline prematurely. Techniques for ameliorating these conditions were studied: vertical drainage mat panels, gravel-filled sumps, soil trenching and peat-amended backfill. Acer saccharum Marsh. `Seneca Chief, ` a species sensitive to compaction stresses, and the less sensitive Pyrus calleryana Decne. `Red Spire' were planted in a compacted clay loam. Shoot growth, root distribution and soil oxygen levels were measured over two growing seasons. Oxygen levels varied with treatment, but were not limiting to root growth. Shoot growth of pears was greatest for soil trenches. Except for the gravel-filled sumps, all other treatments also showed increased shoot growth compared to controls. Maple mortality was generally high and inversely correlated with field drainage.
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.