STORAGE OF HARDWOOD PLANTING STOCK: EFFECTS OF VARIOUS STORAGE REGIMES AND PACKAGING METHODS ON ROOT GROWTH AND PHYSIOLOGICAL QUALITY

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1 No SORAGE OF HARDWOOD PANING SOCK: EFFECS OF VARIOUS SORAGE REGIMES AND PACKAGING MEHODS ON ROO GROWH AND PHYSIOOGICA QUAIY D. P. WEBB nd F. W. von AHEN Gret kes Forest Reserch Centre, P.O. Box 49, Sult Ste. Mrie, Ontrio, Cnd P6A 5M 7 (Received for puliction 25 Jnury 198) ABSRAC Results of two experiments conducted etween 1977 nd 1979 on overwinter storge of seven temperte zone hrdwood species commonly plnted in southern Ontrio indicte tht temperture of storge nd method of pckging cn mrkedly ffect physiologicl qulity of plnting stock. Root growth cpcity nd overll growth potentil of cold-stored stock t.5 nd 5 C were comprle with those of norml spring-lifted controls. Storge t tempertures of 5 nd 1 C resulted in low root growth cpcity nd ws generlly detrimentl to seedling performnce in comprison with spring-lifted nursery control stock tht hd een exposed to winter chilling out of doors. At 1 C there ws considerle root nd ud growth during the storge period from Novemer to April. Of the five pckging methods exmined, seedlings totlly enclosed, or seedlings with only their roots enclosed within Krft gs with plstic liner, with moist pet surrounding the roots, showed the lest shoot wter stress nd generlly hd the highest root growth cpcity. Root growth cpcity of stored seedlings of Acer scchrum Mrsh., Acer scchrinum., Frxinus mericn., Quercus rur., Juglns nigr., nd Betul ppyrifer Mrsh, ws significntly correlted with shoot xylem wter potentil t time of removl from storge. Shoot xylem wter potentil ppers promising s rpid mesure of physiologicl qulity. It is recommended tht utumn-lifted nursery stock of Frxinus mericn, Acer scchrinum, Quercus rur, ili mericn., Betul ppyrifer, nd Acr scchrum e stored t temperture of.5 C nd Juglns nigr t 5 C with reltive humidity of 7-85%. Roots should e surrounded y moist pet nd the totl seedling tightly enclosed within Krft g with polyethylene liner. INRODUCION Silviculturl techniques hve een developed for the successful estlishment of wide rnge of uplnd temperte zone hrdwood species on open field sites in southern Ontrio (von Althen, 1979). Although improved growth of most hrdwood species cn N.Z. J. For. Sci. 1.(1): (198).

2 84 New Zelnd Journl of Forestry Science Vol. 1 e otined y culturl tretments such s site preprtion nd weed control, these tretments hve een only prtilly successful with some species such s sugr mple (Acer scchmm Mrsh.). he dependence of survivl nd susequent shoot growth of outplnted seedlings upon the rpid estlishment of vigorous root system is now well recognised. However, dmge to root systems nd poor root growth remin frequent cuses of seedling stgntion nd contriute to the ineffectiveness of mny culturl prctices (yr nd Hoffmnn, 1967; We nd Dumroff, 1978; We nd von Althen, 1978). Growth check following plnting is especilly common with numer of hrdwood species nd hs led to severl investigtions of root development nd seedling estlishment (Frmer, 1975; rson, 197, 1975, 1977; Rietveld nd Willims, 1978; We, 1976,, 1977; We nd von Althen 1978). hese studies indicte tht erly shoot extension of severl species of hrdwood plnting stock is strongly correlted with the plnt's ility to produce new roots t time of outplnting. Recent ttempts to estlish sugr mple on open-field sites in southern Ontrio hve shown tht time of spring plnting is criticl to successful estlishment (We nd von Althen, 1978). his species undergoes n erly spring flush of root growth (ylor nd Dumroff, 1975) nd under current plnting prctice in Ontrio, seedlings re lifted nd plnted fter this urst of root ctivity hs occurred (Dumroff nd We, 1978). Improved estlishment of this species ws otined y plnting seedlings with high cpcity for root growth otined from erly spring lifting of nursery stock or from cold storge of utumn-lifted stock (von Althen nd We, 1978). Cold storge of utumn-lifted sugr mple, silver mple (Acer scchrinum.), nd ss wood (ili mericn.) hs proven useful technique for the mintennce of high roots growth cpcity nd overll seedling growth potentil (We, 1976, 1977). Plnting of cold-stored utumn-lifted sugr mple plnting stock overcme the shoot growth stgntion or check condition common to norml plntings of this species nd llowed extension of the plnting seson into June with little loss of shoot growth (von Althen nd We, 1978). At present little informtion is ville on the environmentl conditions required for overwinter storge of hrdwood nursery stock nd their effects on physiologicl qulity. he present pper outlines results of two experiments on the effect of vrious storge tempertures nd pckging methods on physiologicl qulity of seven of the more commonly plnted hrdwood species in Ontrio. MAERIAS AND MEHODS Experiment No. 1 his experiment consisted of seedlings from six species nd trnsplnts from one species exposed to five storge tempertures X three pckging tretments. Nursery stock of 2 + white sh (Frxinus mericn.), 2 + silver mple, 2 + red ok (Quercus rur.), 1 + lck wlnut (Juglns nigr.), nd 3 + nd sugr mple ws otined from the Ontrio Ministry of Nturl Resources, St. Willims Nursery, St. Willims, Ontrio nd 2 + sswood ws otined from Midhurst Nursery, Midhurst, Ontrio on 23 Novemer At time of lifting ll stock ws lefless nd dormnt, nd ws trnsported directly to Sult Ste. Mrie, Ontrio. Ech

3 No. 1 We nd von Althen Storge of Hrdwood Plnting Stock 85 species ws grded for size nd rndomly llocted to the vrious storge tempertures nd pckging tretments. emperture tretments consisted of 1, 5,.5, 5, nd 1 C ±.5 C. Reltive humidities t these tretments were etween 7 nd 85%. Within ech temperture tretment, seedlings were sujected to the following three pckging methods: (1) Seedling roots were surrounded with moist pet nd enclosed in Krft gs with polyethylene liners seled round the stem just ove the root collr, (2) Seedlings were totlly enclosed in seled Krft gs with polyethylene liners with moist pet surrounding the roots, nd (3) Seedlings were totlly enclosed in seled Krft gs with polyethylene liners without pet. Nursery stock of ech species ws lifted the following spring from the nursery fter norml winter exposure nd ws included s the spring-lifted controls. In April of 1978, 12 seedlings from ech of the storge tretments nd spring-lifted controls were oserved for the numer of new white lterl roots tht hd formed during storge, visul presence of terminl nd lterl ud swell, nd presence of fungl growth. Fresh nd dry weights of the roots nd shoots were mesured nd moisture contents were clculted. Xylem wter potentil ws determined on the terminl 1 cm of the shoot using the pressure chmer technique of Scholnder et l. (1965). Root growth cpcity mesurements were otined on 12 seedlings of ech species nd ge clss for ech tretment ccording to We (1977). Seedlings were plnted in 2 cm plstic pots in soilsndpet mixture (2:1:2 vv) nd plced in the greenhouse under extended photoperiods of 16 hours nd temperture of pproximtely 18 C (night) nd 28 C (dy). After 3 dys, the seedlings were removed from the pots y gently wshing the soil from the roots with fine spry of wter. Root growth cpcity, i.e., the numer of new white first nd second order lterl roots produced during the 3-dy growth period, ws recorded. he presence of terminl nd lterl ud flush nd of folir dmge ws lso ssessed. Experiment No. 2 Nursery stock of white sh (2 + ), silver mple (2 + ), red ok (2 + ), lck wlnut (1 + ), sugr mple (3 + ), nd white irch (Betul ppyrifermzrsh.) (2 + ) ws otined from the Ontrio Ministry of Nturl Resources, St. Willims Nursery on 27 Novemer Seedlings of ech species were grded for size nd rndomly ssigned to* one of the following five pckging tretments. 1. Seedlings were stored re root with no coverings. 2. Seedling roots were enclosed in Krft gs with plstic liners. Bgs were then seled round the stem just ove the root collrs. 3. Seedling roots were enclosed in Krft gs with plstic liners with moist pet surrounding the roots. Bgs were then seled round the stems just ove the root collrs. 4. Seedlings were totlly enclosed in seled Krft gs with plstic liners nd with moist pet round the roots. 5. Seedling roots were surrounded y moist pet, wrpped in wx pper, nd enclosed in urlp.

4 86 New Zelnd Journl of Forestry Science Vol. 1 Blck wlnut seedlings were cold stored t 5 C nd reltive humidity of 84%; ll other species were stored t.5 C nd reltive humidity of 71%. For ech species except white irch, stock ws lifted in the spring from the nursery fter norml winter exposure nd ws included s the spring-lifted controls. In April of 1979, eight seedlings from ech of the storge tretments nd springlifted controls were oserved for the numer of new white lterl roots tht hd formed during storge, for the presence of terminl nd lterl ud swell, nd for the presence of fungl growth. Xylem wter potentil ws determined on the terminl 1 cm of the shoot nd on one min lterl root per seedling, using the pressure chmer technique of Scholnder et l. (1965). Root growth cpcity mesurements were mde on 16 seedlings for ech tretment s outlined in Experiment No. 1. he dt were sujected to nlysis of vrince nd the significnce of tretment mens (P ^.5) ws identified y ukey's procedure. Non-mesurement dt were sujected to Chi-squre test of significnce. RESUS AND DISCUSSION Experiment No. 1 Growth During Storge Previous results from cold storge of utumn-lifted hrdwood nursery stock (We, 1977) indicted tht ud swell nd new root development would tke plce in storge within the rnge of tempertures employed in the vrious storge tretments of this experiment. As expected, terminl nd lterl ud swell nd lterl root initition occurred. Significnt differences were otined etween species nd etween tempertures of storge (les 1 nd 2). he method of pckging hd no significnt effects. Seedlings with ud swell nd root initition in storge were restricted minly to storge tretments of 1 nd 5 C. ittle ud swell or root initition ws oserved either t 5 nd 1 C or in spring-lifted controls. Bud swell in storge t.5 C or lower ws confined to sswood nd sugr mple (3 + ), wheres root growth occurred only with sugr mple nd silver mple t these tempertures. Moisture content of the roots nd shoots ws highly vrile nd no significnt effects were oserved etween species, storge tempertures, or pckging method, [n contrst, shoot xylem wter potentil differed significntly etween species, storge tempertures, nd pckging methods (le 3). Seedling shoot moisture stress ws lowest for seedlings in the.5 C temperture tretment enclosed within the g with plstic liner nd roots surrounded y moist pet. Fungl growth on seedlings in the vrious tretments ws miniml nd ws restricted to the pckging tretments tht enclosed the seedling within the g. Only in the cse of lck wlnut ws fungl growth oserved on the roots nd this ws restricted to the lower.5 nd 5 C tretments where, on severl seedlings, root dmge nd root exudtion were oserved. Growth Response After 3 Dys in Greenhouse Environment Seedlings from the vrious storge tretments tht hd een exposed to the greenhouse environment for 3 dys showed vrile flushing of terminl nd lterl

5 No. 1 We nd von Althen Storge of Hrdwood Plnting Stock 87 ABE 1 Percent of seedlings with terminl or lterl ud swell t time of removl from overwinter storge (Nov-April) Storge temperture ( C) Species Control Frxinus mericn Acer scchrinum Quercus rur ili mericn Juglns nigr Acer scchrum (3 + ) Acer scchrum (2 + 2) Dt re mens of 36 trees. terminl; lterl ABE 2 Men numer of new white lterl roots per seedling t time of removl from overwinter storge (Nov-April) Storge temperture ( C) Species Control Frxinus mericn Acer scchrinum Quercus rur ili mericn Juglns nigr 4.5* Acer scchrum (3 + ) ^ D 1.5 c c c 1.6. e Acer scchrum (2 + 2).6 2.^.3 c. c.1 c. c Within species, mens with similr letters re not significntly different. * Dt re the mens of 36 trees.

6 New Zelnd Journl of Forestry Science Vol. 1 ABE 3 Effects of vrious storge tretments on shoot xylem wter potentil retment Shoot xylem wter potentil ( kp) Species A. scchrinum 1872& A. scchrum (2 + 2) 1869 F. mericn mericn 1173 A. scchrum (3 + ) 988 Q. rur 982 J. nigr 885 emperture 5 C 18 1 C C C 114 Control C 749 Pckging Method 1 Roots in moist pet enclosed in Krft g with polyethylene liner (shoots exposed) 1987c 2 Seedling in g with liner, no pet Seedling in g with liner, roots surrounded with moist pet 885 & Men of 48 determintions. Men of 63 determintions. c Men of 15 determintions. Verticl lines connect mens tht re not signicntly different. uds (le 4). Significnt differences were oserved etween species nd storge tempertures. Pckging tretments hd no significnt effects. he optimum temperture for reking ud dormncy of most woody species is etween 1 nd 1 C nd it is generlly thought tht the degree of chilling required is restricted to n upper temperture vlue elow which ny temperture is eqully effective, except for extremely low tempertures, which my retrd the process of dormncy removl (Smish, 1954). In the present experiment, tempertures of 1, 5, nd.5 C were eqully effective in reking ud dormncy s shown y the ud flush dt in le 4. Although chilling temperture of 5 C roke ud dormncy of most species exmined, it ws less effective. Fewer numers of seedlings roke ud fter tretment t 5 C thn t the wrmer chilling tempertures. he 1 C tretment did not pper effective in dormncy removl. he smll numers of seedlings tht flushed terminl or lterl uds fter storge t this temperture my hve done so in response to the 16 hr photoperiods of the greenhouse environment. Bud flush in storge comprle to tht with spring-lifted controls ws otined t tempertures of 5 nd.5 C. In some species, e.g., lck wlnut, significntly

7 No. 1 We nd von Althen Storge of Hrdwood Plnting Stock 89 ABE 4 Percent of seedlings tht flushed terminl nd lterl uds fter 3 dys' growth in greenhouse conditions Storge temperture ( C) Species Control Frxinus mericn ' 78^ Acer scchrinum Quercus rur ili mericn Juglns nigr Acer scchrum (3 + ) Acer scchrum (2 -f 2) Dt re mens of 36 trees. terminl; lterl. higher numer of seedlings flushed terminl uds t the non-freezing storge tempertures thn in spring-lifted control plnts. his my hve een result of possile difference etween optimum temperture for reking dormncy of terminl nd lterl uds s demonstrted in pech y Erez nd vee (1971) where mximum rest-reking efficiency ws found t 8 C for terminl uds nd t 6 C for lterl uds. he lowest temperture t which mximum numers of seedlings showed norml lef development ws.5 C for ll species with the exception of lck wlnut where 5 C ws more suitle (le 5). No significnt differences were otined etween seedlings stored t these tempertures nd nursery-lifted controls. Root growth fter 3 dys in greenhouse conditions, like the other prmeters mesured, vried with species nd temperture of storge (le 6). No significnt effects of pckging method were oserved. Storge tempertures of 5 nd 1 C were usully inhiitory to root growth, the effect eing similr to tht of temperture on ud dormncy removl. With sugr mple, in contrst to the other species, the higher temperture of 1 C ws lso inhiitory to": root growth. his temperture is considerly ove the minimum for root growth of this species nd most new roots were produced in storge rther thn fter trnsfer to greenhouse conditions. No significnt differences in the numer of new roots produced ws oserved etween

8 9 New Zelnd Journl of Forestry Science Vol. 1 ABE 5 Percent of seedlings showing norml lef development fter 3 dys' growth in greenhouse conditions Storge temperture ( C) Species Frxinus mericn +1 1* Control 1 Acer scchrinum Quercus rur il i mericn Juglns nigr Acer scchrum (3 + ) Acer scchrum (2 -j- 2) Dt re men of 36 trees. ABE 6 Root growth cpcity of hrdwood nursery stock stored t vrious tempertures Storge temperture ( C) Species Control Frxinus mericn 148.7* Acer scchrinum W D Quercus rur 14.8 K 12.^ D c. c 2.1. il i mericn U ' Juglns nigr K D. c. c 12.8^ e Acer scchrum (3 + ) ' Acer scchrum (2 + 2) o.o U o.o Within species, mens followed y the sme letter re not significntly different. * Dt represent men numer of new lterl roots produced fter 3 dys' growth in greenhouse conditions. seedlings stored t tempertures of 5 nd.5 C nd spring-lifted controls. However, lck wlnut produced significntly higher numers of new roots t 1 nd 5 C thn in controls. In generl, storge temperture of.5 C ws the most eneficil for mintennce of physiologicl qulity of silver mple, sugr mple, white sh, sswood, nd red ok, lthough 5 C ws eqully eneficil to red ok. A storge temperture of 5 C ws est for lck wlnut.

9 No. 1 We nd von Althen Storge of Hrdwood Plnting Stock 91 Experiment No. 2 his experiment ws designed to exmine rnge of possile pckging methods for cold storge of hrdwood nursery stock t tempertures found to e the most eneficil for mintennce of physiologicl qulity. In the previous experiments, method of pckging hd no significnt effects on root growth cpcity nd seedling qulity of cold-stored stock. However, significnt effect on shoot xylem wter potentil ws oserved. It ws felt tht the lck of significnt effect on root growth cpcity ws the result of the high vriility in root growth cpcity mesurements. In the current experiment, seedling smple size for root growth mesurements were incresed to llow for greter precision in mesurement nd sttisticl nlysis. Growth During Cold Storge Bud swell nd new root initition during storge were miniml over ll tretments nd were confined to seedlings of sugr mple nd silver mple. In the other species the storge temperture ws sufficient to mintin seedlings in stte of quiescence or imposed dormncy. No ud or root growth ws noted. Fungl growth in storge ws not prolem. Significnt differences in shoot nd root xylem wter potentil were oserved etween pckging tretments in ll species tested (le 7). As oserved in the previous experiment, seedlings enclosed in Krft gs with plstic liner with the roots surrounded y moist pet exhiited the lest mount of shoot wter stress nd generlly were not significntly different from the spring-lifted controls. Seedlings stored re root, with oth roots nd stems exposed to the storge environment, exhiited the gretest mount of shoot wter stress. In this tretment, ll species except silver mple exhiited shoot xylem wter potentils of 65 kp, the mximum limit of the pressure chmer. Shoot xylem wter potentil vlues of 65 kp were ssocited with desiccted shoots. With white irch, ll pckging tretments tht exposed the shoots to the storge environment resulted in shoot dmge nd in low shoot xylem wter potentil vlues in the terminl 1 cm of the shoot. Growth Response After 3 Dys in Greenhouse est Environment Pckging tretments significntly ffected root growth cpcity of ll species tested (le 8). In generl, seedlings enclosed within the g nd roots surrounded y moist pet produced the highest numer of new roots fter 3 dys' growth in greenhouse conditions. Root growth cpcity of seedlings in this tretment ws equl to or higher thn tht in spring-lifted control stock. Most species showed no significnt differences etween tretments tht enclosed the totl seedling or root portion of the seedling within the g with or without pet. However, white irch demonstrted significntly greter root growth cpcity when stored with the entire seedling enclosed within the g nd moist pet surrounding the roots in comprison with the other tretments. Root growth cpcity ws strongly correlted with shoot xylem wter potentil (Fig. 1). iner regression nd correltion coefficients re sed on six pirs of smple mens requiring n r vlue of.754 nd.874 t P^.5 nd.1, respectively,

10 VD ABE 7 Shoot nd root xylem wter potentil ( kp) of cold-stored hrdwood nursery stock sujected to vrious pckging tretments Pckging tretment (see Mterils & Methods pge 85) Species Bre root 1 Seedlings Roots Roots totlly enclosed in g in g in g with Roots wrpped no pet moist pet moist pet in urlp Control 2 Frxinus mericn Acer scchrinum Quercus rur Betul ppyrifer Juglns nigr Acer scchrum Shoot Root Shoot Root Shoot Root Shoot Root Shoot Root Shoot Root ,. D 36, ^ , D , , 238^ 3438, c Mens followed y the sme letter in ech horizontl line re not significntly different. < o c 238, c , c 544, 195 c u 233, 1169 c , c , , u c 475,. 356, c , 2 S3 Cu S 1

11 o ABE 8 Root growth cpcity of cold-stored hrdwood nursery stock sujected to vrious pckging tretments Pckging tretment (see Mterils & Methods pge 85) Seedlings totlly Roots in g Roots in g enclosed in g Roots wrpped Bre root no pet moist pet with moist pet in urlp Species Control ror er 5 < O Frxinus mericn.* e 4.4 c P Acer scchrinum Quercus rur 27.2^., 29.6\ D 7.3, e x.4 ed ed CO ft S Betul ppyrifer.3, Juglns nigr., o 8- Acer scchrum ^ Within species, mens followed y the sme letter re not significntly different. * Dt represent men numer of new lterl roots produced fter 3 dys' growth in greenhouse conditions. 43.9, P 13 QfQ O

12 New Zelnd Journl of Forestry Science Vol. 1 for significnce. hus, lthough the correltion coefficients pper high they re just significnt t the designted level of proility nd should e interpreted in tht light. Further dt re required prticulrly for intermedite vlues to reinforce these reltionships. Although significnt correltions were otined with shoot xylem wter potentil nd root growth cpcity for ll species tested, root xylem wter potentils were mrkedly higher (less negtive) thn shoot xylem wter potentils nd were not significntly correlted with root growth cpcity. he significnt correltion of shoot xylem wter potentil with root growth cpcity of the hrdwood species exmined in this study indictes tht shoot xylem wter potentil my e useful nd reltively rpid mesure of seedling physiologicl qulity. Mesurements of xylem wter potentil using the pressure chmer technique of Scholnder et l. (1965) is reltively simple nd dptle to field use. Studies re in progress to exmine the fesiility of using shoot xylem wter potentil for possile routine monitoring of physiologicl qulity of cold-stored hrdwood nursery stock. i.o h r.? 1 1? ~~^! y y.->' ^ _ y ?7 1 ^' J* S A> 1 sr y Vi [ A \f : '' ' V v \. 1 'Sj? _l 2 X ' ** M V Acer Acer Frxinus Quercus Betul Juglns scchrinum scchrum mericn rur ppyrifer nigr 1 l 3 4 Root G r owt h C p c i t y Y = -1.26X Y = X Y=-.78X Y = X Y = X Y = X l I 5 6 r =-.91 r»-.93 r*-.85 r = -.97 r =-.91 r=-.96 p>5 p>.1 l FIG. 1 iner regression of root growth cpcity nd shoot xylem wter potentil.

13 No. 1 We nd von Althen Storge of Hrdwood Plnting Stock 95 CONCUSIONS he present study demonstrtes tht temperture of overwinter storge nd method of pckging cn mrkedly ffect physiologicl qulity of rnge of temperte zone hrdwood species. Root growth cpcity nd overll growth potentil of stock stored t.5 nd 5 C were comprle with those of norml spring-lifted nursery stock tht hd een exposed to winter chilling out of doors. Root growth cpcity of coldstored seedlings of sugr mple, silver mple, white sh, red ok, lck wlnut, nd white irch ws significntly correlted with shoot xylem wter potentil t time of removl from cold storge. Shoot xylem wter potentil my offer useful nd rpid mesure of seedling physiologicl qulity. It is recommended tht utumn-lifted nursery stock of white sh, silver mple, red ok, ss wood, white irch, nd sugr mple e stored t temperture of.5 C nd lck wlnut t 5 C with reltive humidity of 7-85%. Roots should e surrounded y moist pet nd the totl seedling tightly enclosed within Krft g with polyethylene liner. ACKNOWEDGMENS he ove report forms prt of co-opertive study undertken y the Ontrio Ministry of Nturl Resources nd the Gret kes Forest Reserch Centre, Cndin Forestry Service. Specil thnks re extended to Mr R. upert, St. Willims Nursery nd Mr E. F. Johnston, South-western Region, Ontrio Ministry of Nturl Resources for encourgement, technicl ssistnce nd supply of nursery stock. he technicl ssistnce of Mr D. Mries nd Mr G. Mitchell is grtefully cknowledged. REFERENCES DUMBROFF, E. B. nd WEBB, D. P. 1978: Physiologicl chrcteristics of sugr mple nd implictions for successful plnting. For. Chron. 54: -5. EREZ, A. nd AVEE, S. 1971: he effect of climte conditions on dormncy development of pech uds. I. emperture. J. Am. Soc. Hort. Sci. 96: FARMER, R. E. Jr. 1975: Dormncy nd root regenertion of northern red ok. Cn J. For. Res. 5: ARSON, M. M. 197: Root regenertion nd erly growth of red ok seedlings: influence of soil temperture. For. Sci. 16: : Pruning northern red ok nursery seedlings: effects of root regenertion nd erly growth. Cn. J. For. Res. 5: : Growth of outplnted northern red ok nursery stock relted to shoot chrcteristics in the seeded. ree Plnt. Notes 28: YR, H. nd HOFFMANN, G. 1967: Growth rtes nd growth periodicity of tree roots. p in J. A. Romerger nd P. Mikol (Ed.). Interntionl Review of Forestry Reserch, Vol. 2, Acd. Press, New York. RIEVED, W. J. nd WIIAMS, R. D. 1978: Dormncy nd root regenertion of lck wlnut seedlings: Effects of chilling. USDA For. Serv. Res. Note NC244. 3p. SAMISH, R. M. 1954: Dormncy in woody plnts. Annu. Rev. Plnt Physiol. 5: SCHOANDER, P. F., HAMME, H.., EDDA, D., BRADSREE, E. D. nd HEMMINGSEN, E. A. 1965: Sp pressure in vsculr plnts. Science 148: AYOR, J. S. nd DUMBROFF, E. B. 1975: Bud, root, nd growth-regultor ctivity in Acer scchrum during the dormnt seson. Cn. J. Bot. 53: von AHEN, F. W. 1979: Preliminry guide to site preprtion nd weed control in hrdwood plnttions in southern Ontrio. Cn. For. Serv., Sult Ste. Mrie, Ont. Report O-X p.

14 96 New Zelnd Journl of Forestry Science Vol. 1 von AHEN, F. W. nd WEBB, D. P. 1978: Effects of root regenertion nd time of plnting on sugr mple plnttion estlishment, p in P. E. Pope (Ed). Proc. Cent. Hrdwood For. Conf. Novemer 14-16, 1978, West fyette, Indin. WEBB, D. P. 1976: Root growth in Acer scchrum Mrsh, seedlings: Effects of light intensity nd photoperiod on root elongtion rtes. Bot. Gz. 137: : Effects of cold storge durtion on ud dormncy nd root regenertion of white sh (Frxinus mericn.) seedlings. Hort. Science 11: : Root regenertion nd ud dormncy of sugr mple, silver mple nd white sh seedlings: Effects of chilling. For. Sci. 23: WEBB, D. P. nd DUMBROFF, E. B. 1978: Root growth in seedlings of Acer scchrum. IUFRO Root Physiology nd Symiosis, Nncy, Frnce (in press). WEBB, D. P. nd von AHEN, F. W. 1978: Estlishment of high qulity hrdwoods on open-field sites in southern Ontrio, p in H. Oswld (Ed.). Symposium on estlishment nd tretment of high-qulity hrdwood forests in the temperte climtic region. Proc. IUFRO Div. 1, Sect. Group SI.5-. Nncy-Chmpenoux, Frnce, Sept