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Open access

J. K. Lathrop and R. A. Mecklenburg

Abstract

The annual cycle of root-regeneration potential (RRP) of 3 year old Taxus hunnewelliana Rehd., plants was evaluated by recording the number of new root initials produced 6 weeks after bare root transplanting. During the summer (June, July and August) few root initials were produced. The RRP increased throughout the fall (September to December) reaching a peak in January. This was followed by a drop in RRP through the spring and early summer (February to June).

Root dormancy of 1 year old Taxus cuspidata Sieb. and Zucc., can be broken in February by an exposure to 7 weeks of chilling at 35°F. Shoot bud dormancy can be broken by an exposure to 3 weeks of chilling at 28°F. The chilling treatment breaking root dormancy appears to be sensed primarily by the root system. Chilling shoots only increased growth of dormant roots but does not substitute for the chilling requirement of the dormant root.

The annual cycle of root-regeneration potential can be partially explained by root dormancy or root-shoot competition for photosynthate. The root-regeneration potential for transplanted Taxus hunnewelliana appears to be controlled by the same factors as the annual cycle of rooting for stem cuttings.

Free access

Larry J. Shoemake, Michael A. Arnold, and Fred T. Davies Jr.

A series of six experiments was conducted over eight years to investigate impacts of provenance on transplant establishment in landscapes and the role of adventitious root regeneration in differential genotypic responses during establishment of Platanus occidentalis L. Fall, spring, and summer transplants of container-grown half-sib families (HSF = seedlings derived from a single mother tree with unknown male parentage), including two selections native to Brazos County, Texas (Brazos-C, Brazos-D), one native to Cookeville, Tenn. (Cookeville), two Kentucky/Tennessee HSF from the Westvaco Corp. (WV-10, WV-14), and two Texas HSF from the Texas Forest Service tree improvement program (TFS-09, TFS-24), were established to determine field/landscape growth responses. Subsequent studies were conducted to investigate differential leaf gas exchange responses of TFS-09 and Cookeville during moderate water deficits and to determine root regeneration potential (RRP) responses of TFS-09, Brazos-C, WV-14, and Cookeville HSF following fall, spring, and summer transplant. To investigate consistency of within-family genotypic responses and to determine relationships among adventitious root initiation from shoot cuttings, RRP, and landscape establishment, five seedlings of TFS-09 and five from Cookeville HSF were clonally propagated and ramets tested under field and RRP conditions similar to those with seedling-derived plants. Regionally native HSF consistently grew taller, had larger trunk diameters, and often had greater survival during the first 3 years in the landscape than HSF not native to the region in which the studies were conducted. Rapidity of root regeneration among HFS at the time of transplant was the best root growth related predictor of successful landscape establishment. Some growth advantages were found using genetically improved HSF, but not as consistent an improvement as with the use of seedlings from regional provenances. Within-family variation in landscape performance was greater with nonregional Cookeville clones than with regional TFS-09 clones, however there was overlap among the more vigorous Cookeville clones and the least vigorous TFS-09 clones. Increased rapidity of root regeneration and drought adaptations related to leaf morphology and gas exchange characteristics may be involved in enhanced growth responses of Texas regional genotypes. No consistent relationships were found among adventitious rooting responses from shoot cuttings and subsequent RRP of the same genotypes from root tissues or their growth during the first 3 years in landscapes.

Free access

Phillip C. Flanagan and W.T. Witte

Previous research at this facility has shown that copper sulfate, when incorporated with latex paint and applied to the interior surfaces of tube trays, was effective in chemically root pruning Quercus acutissima seedlings. Only 20% of deflected roots continued to grow after contacting Cu treated tube walls compared to controls. Treated plants showed a reduction of fibrous roots on the plug surface. Height and caliper were not affected by Cu treatments during chemical root pruning in the tube tray. Time required for regeneration of new roots was not affected by Cu treatments. Seedlings from each treatment were planted and grown two seasons under field conditions to observe effects on growth and root regeneration. No treatment effects occurred for height or caliper. Oak seedlings chemically root pruned with Cu exhibited more lateral growth and branching than control plants.

Open access

Daniel K. Struev and Bruno C. Mosre

Abstract

Dipping root systems of scarlet oak seedlings (Quercus coccinea Juench.) in 3-indolebutyric acid potassium salt (K-IBA), 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 2,4,5-trichloropropanoic acid (2,4,5-TP), β-naphtoxy acetic acid (NOAA), or naphthaleneacetic acid (NAA) induced a 6-fold increase in adventitious root regeneration, as compared to control seedlings. Time to first root initiation was increased and root elongation rate was decreased for auxin-treated seedlings relative to untreated controls. Under field conditions, one-year-old seedlings treated with NAA at 3000 mg/liter or K-IBA at 1000 or 3000 mg/liter regenerated more roots and developed greater root length than did control plants. Toothpicks impregnated with a 1000 mg/liter K-IBA solution and inserted into tap roots stimulated a 16-fold increase in roots and an 18-fold increase in root length as compared to control seedlings.

Open access

R.J. Kelly and B.C. Moser

Abstract

Root regeneration of tulip tree (Liriodendron tulipifera L.) was greater when seedlings were transplanted in the spring than in the fall. Indolebutyric acid–potassium salt (IBA) applied to the roots increased root regeneration with the greatest response at 1000 to 3000 mg liter−1 in the spring and 3000 mg liter−1 in the fall. Root regeneration and shoot growth increased as time of chilling at 2°C prior to transplanting increased from 0 to 1680 hours; 1008 hours satisfied the chilling requirement. Photoperiod did not directly influence root regeneration during either season. Root regeneration and shoot growth of shoot-pruned plants interacted with season, IBA treatment, and level of stem pruning. Decreasing sunlight intensity by 20%, 47%, or 74% reduced root regeneration and shoot growth. IBA improved root initiation over untreated plants at all light intensities tested, but subsequent growth of these roots decreased with decreased light.

Open access

R. J. Kelly and B. C. Moser

Abstract

Root regeneration and shoot growth of seedlings of Liriodendron tulipifera (tulip tree) increased as temperature of either the soil or aerial growing environment increased from 10° to 21°C. Indolebutyric acid-potassium salt, (IBA), applied to the tap roots at 1000 mg liter−1, increased root regeneration and shoot growth when both air and soil temperatures were held at either 15.5° or 21°. When air temperature was maintained at 21° and soil temperature was varied from 10° to 21°, root regeneration and shoot growth increased as soil temperature increased. IBA increased root regeneration only when soil temperature was 21°.

Open access

Lisa M. Perkins and Gary J. Kling

Abstract

Root systems of two Magnolia taxa were treated with spray applications of auxins to determine their effects on root regeneration. Spray application of 500 ppm of IBA doubled the number of adventitious roots regenerated from the cut ends of main roots in 1-year-old cuttings of Magnolia × Soulangiana (Soul.-Bod). Higher concentrations of IBA inhibited root regeneration. Auxin applications did not increase the number of lateral or branch roots. Root systems of Magnolia × Soulangiana were treated with spray applications of ethanol to determine effect of IBA on root regeneration. A significant negative linear relationship was found between ethanol concentration and the number of adventitious roots initiated at the cut ends of main roots. Ethanol concentrations of 12.5% to 70% had no effect on the number of lateral roots. Root regeneration of Magnolia × ‘Betty’ was not stimulated with soil drench applications of 250 to 1000 ppm IBA. IBA and NAA concentrations of 1000 to 4000 ppm were inhibitory. Chemical names used: 1H-indole-3-butyric acid (IBA), 1-napthaleneacetic acid (NAA).

Open access

C. I. Lee and N. Zieslin

Abstract

An inverse correlation between number of roots regenerated and diameter of root segments (except fibrous roots) was found in Rosa ⨯ Noisettiana cv. Manettii. Length of regenerated roots was proportional to the diameter of root segments. The root-regenerating potential varied among scion cultivars. Manetti root segments regenerated best with rose scion cultivar ‘Cara Mia’, and least with ‘Golden Wave’.

Open access

Daniel K. Struve and Bruno C. Moser

Abstract

Three- to 4-cm caliper pin oak (Quercus palustris Muenchh.), a species considered easy to transplant, had greater total root length and more first, 2nd, and 3rd order lateral roots than similar sized scarlet oak (Q. coccinea Juench.), a species considered difficult to transplant. One-year-old seedlings initiated roots 2 weeks earlier in spring and regenerated more roots after 12 weeks than did scarlet oak. Girdled, dormant scarlet oak seedlings regenerated similar numbers of roots as ungirdled plants, while girdled, dormant pin oak seedlings regenerated fewer roots. Removing buds from dormant seedlings decreased root regeneration by pin oak, but had no effect with scarlet oak.

Free access

Michael A. Arnold and Eric Young

After receiving 0, 600, 1200, or 1800 hr. of chilling at 5C, one-year-old Malus domestica Borkh. seedlings were given 10 sec. root dips either 10,000 ppm K-IBA solution or water control. Following chilling and IBA treatments, 20 seedlings of each combination were placed in forcing conditions of 20 ± 2C root temperatures and either 20 or 5 ± 1C shoot temperatures. Five seedlings of each treatment were harvested after 0, 7, 14, and 21 days of forcing. Five C prohibited budbreak and bark slipage for up to 21 days. Under 20C, budbreak, shoot elongation and root growth all occurred earlier, faster, and reached a higher level with increased chilling. Twenty C root and 5C shoot temperatures during forcing resulted in large increases in the growth of adventitious shoots on lateral roots, but had little effect on the formation of adventitious shoots on the tap root. K-IBA prohibited development of adventitious shoots on roots, reduced shoot elongation more so than budbreak, and increased root regeneration across chilling hours. K-IBA inhibition of adventitious shoots did not alter the overall pattern of root regeneration enhancement by chilling.