GIRDLING AND APPLYING CHEMICALS PROMOTE RAPID ROOTING OF SYCAMORE CUTTINGS

Rokrt C. Han ’ SOUTHERN EXPERIMENT STATION

Shoots of 6- and lPyear-old sycamore Martindale 1957, McAlpine et al. 1972, Briscoe (Platanus occidentalis L.) were girdled 1973) or from rejuvenated stump sprouts of and treated with rooting powder 4 weeks mature trees ( Kormanik. and Brown 1974 1, before cuttings were taken. The powder, but little is known of the rooting potential of which contained auxiw, sucrose, and cap nonjuvenile material (Farmer 1974 1. For most tan, was also applied basally to nongirdled forest trees including sycamore, successful cuttings immediately before iwertion in a rooting decreases with age, and satisfactory rooting medium. Thirteen days later, 100 methods for rooting cuttings of older material percent of the girdled cuttings had rooted; have not been reported. Rooting cuttings of they produced an average of 21 per older trees is important because juvenile char- cutting. Only 22 percent of the nongirdled acteristics are not reliable for selecting su- cuttings rooted during this period; the perior trees and because presents in- average number of toots per cutting was compatibility problems and affects rootstock. four. For IZyear-old slash pine, girdling and ap Additional keywords: Vegetative propaga- plying chemicals to shoots 2 months before tion, growth substances, P&anus occi: taking cuttings proved to be a promising meth- dentalis L od of stimulating rooting (Hare 19751. The treatment, which is similar to air-layering, INTRODUCTION improves rooting by forcing the shoot to ac- cumulate food reserves and by inducing callus Sycamore improvement programs would be formation. Unlike air-layering, however, this facilitated by reliable techniques of asexual system promotes rapid rooting by removing propagation. Sycamore cuttipgs readily the cutting to an optimal environment once when taken from juvenile orteti (Nelson and callus is formed; It also eliminates damp moss, *The author ia Plant Physiologist, Foresi Servica+USDA. which is known to leach out growth substances Southern Forest Experiment Station. GuMport Mirrkripol 39501. (Cameron 19681. The procedure offers tree breeders a way to avoid grafting when building tion t-test; each of ihe 50 pairs consisted of one up clone banks and seed . girdled and one nongirdled cutting taken from %‘he present experiment describes an at- the same ortet and crown position and placed tempt to use the girdling technique to root adjacent to one another in the. propagating cuttings from 6- and 13-year-old sycamore. bed. All cuttings were removed after 13 days and tallied for survival, number of roots, and MATERIALS AND METHODS the presence of callus. Because of the over- whelming response to girdling, no statistical The rooting powder applied was developed analysis was necessary. previoqs$ for sycamore and other hardwoods. It. codtained 1 percent each IBA (indolebutyric RESULTS AND dISCUSSION acid) and PPZ ( 1-phenyl-3-methyl-5-pyraza- lone), 20 percent powdered sucrose, and 5 The cuttings were all living when lifted percent captain in talc (l-l-20-5). Cuttings after 13 days. All of the girdled cuttings had were obtained from twenty-two g-year-old rooted (table 1); the average number of roots trees and from three 13-year-old trees growing per cutting was 21.5 (fig. 1). In contrast, only in southern Mississippi. On May 7, 19115, when 22 percent of the nongirdled cuttings rooted the had fully expanded, two pairs of during this time; they averaged 4.3 roots each. shoots were tagged in the middle and lower Although all girdled cuttings rooted, there crown of each tree. Each pair consisted of was evidence of clonal differences in response shoots of similar size from t’he same branch to treatment. Girdled cuttings from the four or from one nearby. One member of each pair best trees averaged 49 roots per cuttifig; those was girdled by removing a ring of 1 to 2 from the four worst averaged only seven. Only cm wide from the previous year’s about two trees showed 100 percent rooting of cut- 25 cm below the tip of the shoot. An aqueous tings that did not receive the girdling treat- slurry of the rooting powder was applied to ment. the distal portion of each wound with a camel’s hair brush; next, the girdles were covered Table l.-Rooting responses of girdled and non- girdled sycamore cuttings after (13) with Saran film and then with tinfoil. Al- days in the propagating bed though aluminum foil, which is cheaper than tinfoil, w,ould probably be satisfactory, tinfoil has better wrapping properties. On June 3, cuttings were taken at the distal end of the girdled shoots and 25 cm below the shoot tip of the nongirdled ones. On the same 8 22 100 22.4 22.7 4.1 day, cutting pairs were tied together and 13 3 100 15.2 16.7 6.0 transported to the greenhouse in plastic bags ’ Average number of roots per rooted cutting. where they were dipped in water, treated basally with rooting powder, and inserted At the time they were taken from the tree, side-by-side in the propagating bed. Non- all girdled cuttings were heavily callused, and girdled cuttings received the l-l-20-5 powder. some had small roots. By lifting time, half of Girdled ones were given O-0-20-5; IBA and the nongirdled cuttings that had not rooted PPZ were omitted to avoid possible auxin in- showed some callus. Although some of these hibition of root growth where pre-formed roots might have rooted after a longer period in were present. The cuttings were inserted 7 the propagation bed, their root systems would cm deep in perlite-vermiculite rooting m,&itim; be smaller than those on girdled cuttings, and spacing was 15 by ‘15 cm. Misting nozzles survival after planting would probably be automatically controlled by evaporation from poorer. a screen supplied moisture; bottom heat was Girdled cuttings from l&year-old trees usu- provided to maintain temperatures of 24” to ally had fewer roots than those. from 6-year-old 27’ C in the medium. Greenhouse temperatures trees (table 1). However, root systems of ranged from 18O. to 32” C. The experimental cuttings from the older trees were adequate design was appropriate for a paired obseiva- for planting (fig. 1) .

2 more time. Improvfd chemical treatments a;e being investigated to induce adequate and rapid rooting without girdling. another pos- sibility is to build up clones by rooting girdled cuttings from previously grafted material.

LITERATURE CITED Briscoe, C. B. 1973. Extended planting seasons for syca- more and cottonwood. USDA For. Serv. Res. Note SO-140, 3 p. South. For. Exp. Stn., New Orleans, La. Cameron, R. J. 1968. The leaching of auxin from air layers. N.Z. J. Bot. 6: 237-239. Farmer, R. E., Jr. 1974. Vegetative propagation and the ge- netic improvement of North American hardwoods. N.Z. J. For. Sci.. 4:211- 220. Hare, R. C. 1975. Girdling promotes rooting of slash pine cuttings. Proc. Thirteenth Sou’th. Figure l.-Cuttings from u 13-year-old sycmno~e For. Tree Improv. Conf., p. 226-229; aftet 13 days in the propagating bed (girdled left, nongirdted right). Kormanik, P. P., and C. L. Brown. 1974. Vegetative propagation of some se- With this technique, rapid greenhouse root- lected hardwood forest species in the ing of nonjuvenile foliated sycamore cuttings southeastern United States. N.Z. J. appears feasible if the shoots are accessible. For. Sci. 4 ~228-234. However, for large trees whose branches are difficult to reach, it may be necessary to shoot McAlpine, R. G., D. D. Hook, and P. P. the cuttings from the tree without girdling. Kormanik. These cuttings will require more time in the 1972. Horizontal planting of sycamore cut- tings. Tree Plahters’ Notes 23(2) : propagating bed and will have sparser root systems than girdled cuttings. Using l-l-20-5 5-7. rooting powder, we obtained 22 percent rooting Nelson, T. C., and D. L. Martindale. within 13 days for nongirdled cuttings; pos- 1957. Rooting American sycamore cuttings. sibly, 50 percent would have rooted if given J. For. 55:532.