THE NITROGEN NUTRITION OF THE PEACH TREE. [Manuscript received August 8, 1966] Summary

Transcription

1 THE NTROGEN NUTRTON OF THE PEACH TREE. * STORAGE AND MOBLZATON OF NTROGEN N YOUNG TREES By B. K. TAYLORt nd THE LATE L. H. MAY:j: [Mnuscript received August 8, 1966] Summry The chemicl composition nd distribution of storge nitrogen in young pech trees nd the importnce of this stored nitrogen for new growth were investigted. Young pech trees, which were grown in snd culture for two growing sesons, ccumulted nitrogen in proportion to supply during the first yer, nd the results suggested tht this stored nitrogen ws utilized for new growth during the second growing seson irrespective of the externl nitrogen supply. Tree growth in erly spring ws significntly correlted with the level of storge nitrogen in tree tissues, but fter November tree growth ws mrkedly dependent upon the externl nitrogen supply. f fertilizer nitrogen ws not pplied, the supply of storge nitrogen in tree tissues ws exhusted by the end of November. Reccumultion of storge nitrogen begn in tree tissues in December nd ws rpid if the externl nitrogen supply ws high. Storge nitrogen in dormnt trees consisted minly of soluble orgnic nitrogen nd free rginine ws the principl constituent of this frction. The level of rginine in woody tissues of the dormnt trees ws the most sensitive indictor of the nitrogen sttus of the trees. Approximtely 60-80% of the storge nitrogen in dormnt 2-yer-old trees ws found in root tissues, irrespective of the nitrogen tretment.. NTRODUCTON The mount of new shoot growth mde by young pple trees is function of the nitrogen content of the trees t the beginning of the growing seson nd the externl nitrogen supply, providing tht no other fctor is limiting growth (Roberts 1921; Hrley, Moon, nd Regeimbl1949; Olnd 1959; Yokomizo et l. 1964). Similrly, it hs been concluded from studies on the sesonl chnges in concentrtion of totl nitrogen nq other nitrogenous constituents in tissues of mture pech trees tht nitrogen ccumultes in woody tissues in lte summer, utumn, nd winter in proportion to nitrogen supply, nd tht this stored nitrogen is mobilized for new growth during the next growing seson (Schneider 1958; Rdu 1961; Tylor 1967). However, this ltter conclusion must be regrded s tenttive s in ech cse the dt were expressed on concentrtion rther thn bsolute (per tree) bsis. The experiment described in Prt of this series (Tylor 1967) clerly indicted tht lrge orchrd trees were unsuitble for further investigtion of the role of storge * Prt, Aust. J. Bil. Sci., 1967,20, t Deprtment of Plnt Physiology, Wite Agriculturl Reserch nstitute, University of Adelide; present ddress: Victorin Deprtment of Agriculture, Horticulturl Reserch Sttion, Ttur, Vic. t Deprtment of Plnt Physiology, Wite Agriculturl Reserch nstitute, University of Adelide. Aust. J. Bil. Sci., 1967,20,

2 390 B. K. TAYLOR AND L. H. MAY nitrogen in tree growth. When lrge trees re used s experimentl mteril nlyticl dt cnnot usully be expressed on n bsolute bsis, growth responses re difficult to mesure, nd tree nutrition cnnot be controlled precisely. t is necessry to tke ech of these fctors into ccount when criticlly studying the reltionship between stored nutrients nd plnt growth nd in the experiment reported in this pper the problem ws overcome by growing young trees in snd culture. The present investigtion ws crried out to determine how importnt storge nitrogen is for the growth of young pech trees nd to determine the chemicl composition nd distribution of storge nitrogen in dormnt trees. However, becuse of their smll size) nd presumbly smll storge volume, the growth of young trees might not be s dependent upon the level of storge nitrogen s would the growth oflrge mture trees.. METHODS () Experimentl Design The experiment ws crried out from June 1963 to Mrch During the first yer three levels of nitrogen were supplied to the trees. Further nitrogen tretments were superimpose on these during the second growing seson, viz: First yer Second yer N NNo NN3 NN9 N3 NNo NN3 N3N9 N g NgNo N9N N9N9 where No indictes tht no nitrte nitrogen ws supplied, nd Nl, N, nd Ng indicte tht nitrte nitrogen ws supplied t 20, 60, nd 180 p.p.m. respectively. Overll, there were 108 trees in the experiment, i.e. 9 tretments X 4 replictes X 3 hrvests. The experiment ws lid out ccording to rndomized block design, where ech block ws replicte nd consisted of fctoril of tretments X hrvests. (b) Preprtion of Trees prior to Tretment (i) Source of Trees.-n June 1963, 135 one-yer-old pech trees (Golden Queen scion on Elbert rootstock) were selected t commercil nursery for uniformity of size, for the presence of lef buds on tree stems, nd for freedom from disese nd dmge. (ii) Plnting Procedure.-At plnting, tree roots were wshed clen, dried between sheets of blotting pper, nd the trees were weighed. Tree roots were severely pruned to remove s much of the storge tissue of ech root system s possible. The roots of the pruned trees were then serilly immersed in solutions of 5 25% sodium hypochlorite (2 min) nd 200 p.p.m. terrmycin hydrochloride (30 min) in n ttempt to prevent subsequent infection of trees with Agrobcterium tumefciens (crown gll). However, glls were detected subsequently on bout 20% of the trees. Pruned trees were plnted in 4-gl metl pots (lined with epoxy resin) which contined 26 kg sieved, stem-sterilized river snd. Potted trees were plced in glsshouse nd tree tops were cut bck to within 6 in. of the grft union. Both root nd top prunings were weighed. The snd ws thoroughly leched with distilled wter nd

3 THE NTROGEN NUTRTON OF THE PEACH TREE. 391 mulch of 3 kg sterilized grvel ws plced on the surfce of ech pot. Distilled wter ws supplied s required to ech pot until tretments were commenced. (c) Appliction of Nitrogen to Pruned Trees Trees were strtified ccording to their fresh weight fter pruning. The strtified trees were divided into four equl groups, ech of which constituted rnge of tree weights nd ws designted "replicte". Within ech replicte the nine nitrogen tretments were llocted to trees t rndom. Tree positions within ech replicte were chnged in rndom mnner t monthly intervls during the growing seson but the positions of the replictes in the glsshouse were not chnged. n both yers of the experiment, 2 litres of complete nutrient solution with or without nitrogen (s nitrte) were pplied to ech tree every second dy, or dily during het-wve conditions. The nutrient ws poured onto the surfce of ech pot, llowed to percolte through the snd, nd excess liquid drined into hlf-gllon polythene continer plced underneth ech pot. When required the lechte ws remde to volume with distilled wter nd recycled. However, once fortnight, the old nutrient solutions were discrded, the snd in ech pot ws thoroughly leched with distilled wter, nd fresh nutrient solutions were pplied. n the first yer, nutrient pplictions were commenced on July 27, 1963, nd were continued until the end of June They were continued fter the cesstion of shoot growth in Mrch 1964 to llow for possible further uptke of nitrogen during utumn nd erly winter. n JUly nd August 1964, distilled wter only ws pplied to the trees t rte of 2 litres per tree per week. One-third of the trees were hrvested in July 1964, nd, in the first week of August 1964, the reminder were repotted into fresh snd which hd been sieved, cid-wshed (see Hewitt 1952), nd stem-sterilized. The trees were repotted so tht growth during the second yer would not be influenced by the level of nutrients which hd ccumulted in the snd during.the first yer. t ws ssumed tht the cidwshing tretment would remove ll vilble nitrogen from the snd. The ph of the cid-wshed snd ws 6 8±O 03. Second-yer tretments were commenced on September 5,1964, when the trees were t the "pink-tip" stge of bud-burst, nd were continued until ll trees hd been hrvested in Mrch (d) Generl Tree Mngement After bud-burst in the first yer, ll shoots were removed except one which becme the new stem of the tree. Root suckers were pinched off nd leves which bscissed during the first yer were discrded. During the second yer, flower buds were removed t bud-burst nd root suckers were pinched off, but this tissue ws dded bck to the pots in n ttempt to mintin the nitrogen blnce. n ddition, the leves which bscissed during the seson were collected nd plced in pper bgs ttched to ech pot. n both yers of the experiment, trees were spryed with Bordeux mixture t bud-burst to control "curl lef" fungus. nsecticides were lso pplied when necessry.

4 392 B. K. TAYLOR AND L. H. MAY (e) Sesonl Tree Growth Mesurements Mesurements of tree growth were mde t intervls of 3-4 weeks during the first nd second growing sesons. During the first yer, the totl length of tops per tree nd the stem dimeter per tree t fixed point (two redings t right ngles to one nother) were mesured, while in the second yer, the totl length of new shoots, the totl number of new shoots, nd the stem dimeter t the sme fixed point were recorded for ech tree. (f) Hrvesting Procedures Trees were hrvested t the times set out in the following tbultion: Hrvest Hrvest No. of Trees Remrks No. Dte Hrvested July 13-19, End of first yer; (3 tretments X 12 replictes) dormnt lefless trees 2 November 23-26, Midwy through second (9 tretments X 4 replictes) growing seson 3 Mrch 1-5, End of second (9 tretments X 4 replictes) growing seson At ech hrvest, trees were thoroughly wshed, blotted dry, weighed, nd quickly subdivided into the following prts: (1) Roots; (2) Stock+stem+1-yer-old shoots; (3) Lef+flower buds (replictes bulked), or new shoots." The stock consisted of the bove-ground portion of the rootstock. The number of buds, flowers, leves, nd shoots per tree ws lso recorded. Subdivided tissues were weighed, quick-frozen in dry ice, chopped finely, plced in lbelled muslin bgs, nd stored t f root glls were present on tree they were cut off nd oven-dried t for 16 hr. Abscissed lef tissue ws similrly treted. (g) Preprtion of Tissue Smples for Anlysis Frozen tissues were freeze-dried, weighed, nd ground to pss sieve with pores 1 mm in dimeter. Mter mixing well, duplicte subsmples of ech tissue were tken for dry mtter nlysis (oven-dried t for 16 hr) nd the dry weight of ech tree nd its prts ws clculted. The remining tissue ws plced in screw-lid glss jrs nd stored t until required. Oven-dried tissues were ground in the sme wy but were stored t room temperture. (h) Nitrogen Anlyses Tree tissues were nlysed in duplicte for their content of the following nitrogenous constituents-totl nitrogen, nitrte nitrogen, soluble nitrogen, rginine nitrogen, totl oc-mino nitrogen, mmonium nitrogen, nd mide nitrogen. Abscissed leves nd root glls were only nlysed for totl nitrogen. Aprt from totl nitrogen,

5 THE NTROGEN NUTRTON OF THE PEACH TREE. 393 root glls were ssumed to contin the sme concentrtion of other nitrogenous constituents s helthy roots. Even if this ws not correct, little error is involved since the dry weight of the gll tissue per tree ws usully very smll prt of the totl dry weight of the roots. (i) Totl Nitrogen.-The microkjeldhl method of McKenzie nd Wllce (1954) ws used except tht the quntity of concentrted sulphuric cid used in the digestion step ws incresed to 2 ml, nd the distilltions were crried out in n pprtus described by Jennings (1962). (ii) Nitrte Nitrogen.-Anlyses were crried out ccording to the phenoldisulphonic cid procedure of Humphries (1955). (iii) Soluble Nitrogen.-n greement with other workers (Sturt 1935; Olnd nd Yemm 1956; Olnd 1959), it ws found tht queous solutions extrcted significntly greter quntities of soluble nitrogen from plnt tissues (freeze-dried pech shoots) thn did 80% queous ethnol. Citrte buffer (0'05M, ph 5 0) ws used for the routine extrction of soluble nitrogen. The procedure ws s follows: Freeze-dried ground tissue (0 5-1 g) ws extrcted for 24 hr t 2 C with 54 ml buffer in stoppered 100-ml centrifuge tube (the extrct ws occsionlly shken during this time). Mter centrifuging, the superntnt ws poured through glss wool filter into 250-ml volumetric flsk. This process ws repeted three times except tht the extrction period ws reduced to 1 hr. Successive extrcts were bulked nd mde to volume with citrte buffer. After mixing, ml liquots of ech extrct were tken to dryness in vcuo in rotry evportor (wter-bth temp. 35 C) nd ech residue ws tken up in distilled wter nd mde to volume in lo-ml volumetric flsk. The level of soluble nitrogen in 2-ml liquots ws determined by microkjeldhl nlysis using the sme method nd equipment s described for totl nitrogen nlyses. However, preliminry heting strip ws necessry before digestion (extrct cidified first) to reduce the volume of liquid in the flsk, otherwise extrcts frothed during digestion nd nitrogen ws lost. (iv) nsoluble Nitrogen.-The concentrtion of insoluble nitrogen in the tissues ws found by clculting the difference between the concentrtion oftotl nd soluble nitrogen in ech tissue. (v) Arginine Nitrogen.-The concentrtion of rginine nitrogen in the citrte buffer extrcts ws estimted by the method of Gilboe nd Willims (1956). n some cses it ws necessry to dilute the extrcts with distilled wter before nlysis otherwise pigments present in the extrcts interfered with the test. (vi) Totl X-Amino Nitrogen.-The concentrtion of totl X-mino nitrogen in the citrte buffer extrcts ws determined by the method of Rosen (1957). The cette-cynide regent ws freshly prepred before use (Grnt 1963). (vii) Ammonium nd Amide Nitrogen.-Cold 80% ethnol ws used to extrct mmonium nd mide nitrogen from freeze-dried tissues. Citrte buffer ws not used s extrctnt becuse the method of ssy for these nitrogenous frctions ws ph-dependent nd the use of buffered extrcts would hve complicted the ssy procedure. Extrctions were crried out in the sme wy s described erlier for soluble nitrogen except tht the initil extrction period ws for 4 hr nd totl of 200 ml 80% ethnol ws used per extrction. Ech extrct ws cidified with

6 394 B. K. TAYLOR AND L. H. MAY o N Hel, tken to dryness in vcuo in rotry evportor, nd the residue ws dissolved in distilled wter nd mde to volume in 25-ml volumetric flsk. The concentrtion of these frctions in ech extrct ws determined by the method of Pucher, Vickery, nd Levenworth (1935), except tht the Nessler's regent ws prepred nd used s described by Jennings (1962).. RESULTS Dt recorded for trees infected with root glls were not seprted out prior to sttisticl nlysis becuse vlues for these trees fell within the rnge recorded for helthy trees. () Tree Growth during the First Yer The fresh nd dry weights of the trees nd their prts, the number of shoots, leves, lef nd flower buds per tree, the totl length of tops, nd the stem dimeter per tree were ll significntly incresed with incresed nitrogen supply (e.g. Fig. 1). S{) No V// / /6 N3 7,/0_ u..0 ;]0 rx---x-x-x-x- e N, X, / ; ; f.: g 10 - j _,- 1% N.S. 0 1",,0 g ' 0 ' : i;j "'?l >: 5%t t ± i < /,/ 6/ N3..., N g / ll. 0/ / 0/ X_X-X f//" ----, / t SEPT. OCT. NOV. DEC. JAN. FEB. OCT. NOV. DEC. JAN. FEB. MAR. JUL. Fig..-nfluence of nitrogen tretment on the totl length of tops per tree nd the stem dimeter per tree during the first growing seson. ncresed nitrogen supply lso incresed the top/root rtio on dry weight bsis, indicting tht the size of tree tops incresed more so thn the size of the roots. Nitrogen deficiency symptoms were first observed in November on trees in Nl nd N3 tretments. (b) Tree Growth during the Second Growing Seson (i) At Hrvests 2 nd 3 Tree growth, expressed s fresh weight or dry weight per tree (e.g. Fig. 2), ws dependent on, nd in proportion to, the nitrogen tretments pplied in both yers of the experiment, nd in most cses differences between tretments were significnt.

7 THE NTROGEN NUTRTON OF THE PEACH TREE. 395 Similrly, the growth of ech tree prt usully showed response to both sets of tretments. As noted for the hrvest 1 dt, the top/root rtio on dry weight bsis incresed with incresing nitrogen supply. 6'0 N,No 6 0 N3 NO 6 0 NgN O 5' ',0 3'0 2'0 ',0, A-' X _x : J A SON 0 J F M ',0 o.l----.l X e A x x A ====-t e 1-0.l---,----' x x_x A-A A 0-- ASONDJ FM Q 6'0 ffi 5-0 :;: ' 0 >- '" o "- 3'0 o l- Z 2.0 ::J o :;: " x '" 9 0 N,N3 : %_t==--" '0 5'0 3'0 20 N3 N3 6'0, A.l x X A! 0-0 5' '0 o N g N 3,------/' x x/x : x:::::::::=:: 0_0 JASONOJFM 6'0 5,0 4'0 o N,Ng, ---, e::-!=--- _ '0 5'0 4'0 3'0 o N3 N9 6'0 A A x/./. x -:::::--!-o A A 5 0 NgN g, A, /. x x_. -o_o A Fig. 2.-nfluence of nitrogen tretment on the dry mtter content of tree tissues during the second growing seson. X Roots. Stock+stem+l-yer-old shoots. ::, Buds, new shoots. o Abscissed leves... Whole tree. Folige colour rnged from drk green for the N 9 tretment to yellowish green for the No tretment. Percentge lef bscission per tree ws inversely proportionl

8 396 B. K. TAYLOR AND L. H. MAY Hr FRST-YEAR TREATMENT 1;--1;--1;--1; N g 1;/ ::.;::=:=:=: :' MAN EFFECT MEANS " SECOND-YEAR TREATMENT ; 1;_1;--1;---1; N g / / 0_ N3 / / _X--X--X--X No 'Hi ' 0 -..,,5 1-0 r.::; Q Ul :c z g c!::.j 0 5 3'0 2 5,.5 ' 0 i i OCT. NOV. DEC. JAN. FEB. MAR. NTERACTON MEANS FRST-YEAR TREATMENT x SECOND-YEAR TREATMENT / b. -A / 0 '0-.'.-1; NgN g / /x,_,-.x.-.=.: -,---0 N N l (j.:1;----.1;--.1;------x NN: _ 1i ---.1; N / i. 9N3.;/ A --!J. j,' h--;--; '"_---o----o----o --; o N3 N 3 NgN O f'...,:o='&-----x----- t/1 ','0? N, N 3 / ; / /' /X_X-- x -X N,No 0'5 i i OCT. NOV. DEC. JAN. FEB. MAR. Fig. 3.-nfiuence of nitrogen tretment on the totl length of new shoots per tree during the second growing seson. 0 5 "'0::1 r j OCT. NOV. DEC. JAN. FEB. MAR.

9 THE NTROGEN NUTRTON OF THE PEACH TREE. 397 to nitrogen supply during the second yer nd ws indictive ofthe severity of nitrogen stress in the trees. 0 8 FRST-YEAR TREATMENT - N 0.7' ' ffi... 0'] 0 :z: )( 0 8 c L!::J $ 8...J ' 0 ] / x--x/x r MAN EFFECT MEANS.--/0 0-0 N 0/0""- 3 x-x N, /'/ i SEPT. OCT. NOV. DEC. JAN. FEB. NTERACTON MEANS FRST-YEAR TREATMENT x SECOND-YEAR TREATMENT _._,,,,c:-=-":;::-:-:j::; &= '_, :::-::---6==&-!,/'/ l',// / /x / /... x x... 0 / / # /' / /... 0 J"/ 0... /... 0/'1" g';;:::--o. / o -=--- / '0 -- / x _x---x / / x//-x x /.x-----' /-":::: 7-:.::-Xx---x--x-x N.S! NgNg N g N 3 N3.Ng NgNO N,Ng N3N 3 N3 NO N,N 3 N,No ' SECOND-YEAR TREATMENT A_N9 /' / / 00 0_ON3 :.--===.::::::::-x_x-x-x-x =' 0/ No N.5 0 ] L L-_-L L-_-L.L..-_--' SEPT. OCT. NOV. DEC. JAN. FEB. Fig. 4.-nfluence of nitrogen tretment on the stem dimeter per tree during the second growing seson. SEPT. OCT. NOV. DEC. JAN. FEB. Significnt negtive interctions were found between first nd second yer tretments for ll dt recorded t hrvest 3; i.e, the greter the nitrogen supply in

10 398 B. K. TAYLOR AND L. H. MAY the first yer, the smller the effect of nitrogen ppliction in the second yer on tree growth, nd vice vers. (ii) Sesonl Chnges in Growth Sesonl chnges in the totl length of new shoots, in stem dimeter, nd in the totl number of new shoots per tree re shown in Figures 3, 4, nd 5. MAN EFFECT MEANS FRST-YEAR TREATMENT A-----A----A-----A-----A Ng SECOND-YEAR TREATMENT A/ 0/0-0-0_0-0 N3 / x x---x---x-----x N, x A /; N3 A x--x---x-----x No x / x A----A-----A-----A Ng ',0 5'0 g t Cl 2'0 ',0 OCT. NOV. DEC. JAN. FEB. MAR. NTERACTON MEANS FRST-YEAR TREATMENT x SECOND-YEAR TREATMENT.!=-..:.::-...:-=:--A ""'-4J.-"""':'=-..J.'=- -=-"':=:.b..0/ ----A---A------A 6'/'/ :///" /'/0 /.:><_0..-x- - -x- - -x- - -x A /.///.--o---o-----o---o ll/ 80 l -'< X '1. x x/ / / x---x---x-----x x/ x N 5 o: 1, x/ NgNg N g N 3 NgNO N3N 9 N,N g N3N 3 N3 NO N,N3 N,No ',0 i " OCT. NOV. DEC. JAN. FEB. MAR. Fig. 5.--nfluence of nitrogen tretment on the totl number of new shoots per tree during the second growing seson. OCT. NOV. DEC. JAN. FEB. MAR. t is evident from Figure 3 tht the totl length of new shoots per tree ws dependent on, nd in proportion to, the level of nitrogen supplied in both yers of the experiment. This result supports the hypothesis tht the trees ccumulted

11 THE NTROGEN NUTRTON OF THE PEACH TREE. 399 nitrogen in proportion to supply during the first yer nd tht the stored nitrogen ws used for new growth during the second growing seson. At the beginning of the growing seson the influence of the first-yer tretments on tree growth ws more pronounced thn tht ofthe second-yer tretments (cf. min effect mens). However, fter November, the current nitrogen supply hd pronounced effect on tree growth [cf. NsN9 nd N9Ns tretments (Fig. 3) for exmple], nd, since nitrogen deficiency symptoms were first seen in November on trees which did not receive ny fertilizer nitrogen, it is suggested tht the supply of storge nitrogen in these trees ws exhusted by this time. Similrly, sesonl chnges in the stem dimeter per tree (Fig. 4) nd the totl number of new shoots per tree (Fig. 5) were dependent on, nd in proportion to, the nitrogen supply in both yers of the experiment. TABLE 1 CORRELATON BETWEEN GROWTH OF NEW SHOOTS N THE SECOND GROWNG SEASON AND TOTAL NTROGEN CONTENT PER TREE PROR TO COMMENCEMENT OF GROWTH Loglo dt tems in Regression Tretments Pooled in Regression r Degrees of Freedom Dry weight of new shoots t hrvest 2 NlNo, NNo, N9No 0'966*** 10 v. nitrogen per tree t hrvest 1 NlN, NN, N9N 0'970*** 10 NlN9, NN9, N9N9 0'828*** 10 Length of new shoots t hrvest 2 NlNo, NNo, N9No 0'843*** 10 v. nitrogen per tree t hrvest 1 NlN, NN, N9N 0'946*** 10 NlN9, NN9, N9N9 0'784** 10 Dry weight of new shoots t hrvest 3 NlNo, NNo, N9No 0'979*** 10 v. nitrogen per tree t hrvest 1 NlN, NN, N9N 0'987*** 10 NlN9, NN9, N9N9 0'834*** 10 Length of new shoots t hrvest 3 NlNo, NNo, N9No 0'828*** 10 v. nitrogen per tree t hrvest 1 NlN, NN, N9Ns O' 714*** 10 NlN9, NN9, N9N t _._--- ** P<O Ol. *** P<O OOl. t Not significnt. (iii) Oorreltion between Tree Growth nd the Nitrogen Oontent per Tree As expected, highly significnt positive correltion ws found between the mount of new shoot growth per tree t hrvests 2 nd 3 nd the nitrogen content per tree t hrvest 1 if the externl nitrogen supply in the second yer ws low (Tble 1). However, if high level of nitrogen ws supplied during the second yer then the level of correltion ws reduced nd in one cse ws not significnt. (c) Nitrogen Oontent of Tree Tissues (i) Oomposition of Storge Nitrogen in Dormnt Trees The influence of nitrogen supply on the mount of ech nitrogenous constituent in dormnt tissues, reltive to vlues in the Nl tretment, is shown in Tble 2.

12 400 B. K. TAYLOR AND L. H. MAY Nitrte ws not detected in ny of the tissues. t is evident tht the mount of ech constituent usully incresed with incresing nitrogen supply nd tht levels of soluble nitrogen incresed more rpidly thn levels of insoluble nitrogen. From this ltter result it is concluded tht the storge nitrogen which ccumulted in the young pech trees consisted minly of soluble nitrogenous compounds. Since the mount of rginine nitrogen in most tree tissues showed the gretest reltive increse of ny of the nitrogenous constituents with incresing nitrogen supply, it is concluded tht estimtion of levels of rginine nitrogen in the pech trees gve the most sensitive indiction of the nitrogen sttus of the trees. The TABLE 2 NFLUENCE OF NTROGEN TREATMENT ON THE AMOUNTS OF NTROGENOUS CONSTTUENTS N TREE TSSUES AT HARVEST 1 Vlues re percentges reltive to the N 1 tretment Tree Tissue Nitrogen Ammo- Totl Totl nsoluble Soluble Tret- nium Arginine Amide ",-Amino ment Nitrogen Nitrogen Nitrogen Nitrogen Nitrogen Nitrogen Nitrogen Roots Nl loo'o loo'o loo'o loo'o loo O loo'o loo O N N Stock + Nl loo'o loo O loo'o loo'o loo'o stem + N yr-old N shoots Lef+ Nl loo'o loo'o loo O loo O loo O loo O flower N loo O buds lll Whole Nl loo'o loo O loo O loo'o loo O loo'o tree N N gretest reltive increse in rginine nitrogen ws found in the stem plus stock plus l-yer-old shoot frction nd therefore this is the most suitble type of tissue to use in ny ssessment ofthe nitrogen sttus of dormnt trees. Similr results were obtined if the dt were expressed on concentrtion bsis. Rtios of mounts of nitrogenous constituents in tree tissues t hrvest 1 re shown in Tble 3. As expected from Tble 2, the level of soluble nitrogen s proportion of the totl nitrogen content incresed with incresing nitrogen supply. Almost ll of the soluble nitrogen in the tissues ws orgnic in nture nd consisted minly of rginine nitrogen. The rginine nitrogen content of the soluble nitrogen frction incresed with incresing nitrogen supply, indicting tht the composition of this frction ws dependent upon the nitrogen supply. f this supply ws low, then greter proportion of the soluble nitrogen which ccumulted consisted of mide

13 THE NTROGEN NUTRTON OF THE PEACH TREE. 401 nitrogen. Generlly, however, the levels of mide nitrogen constituted very smll prt of the soluble nitrogen frction. The totl ex-mino nitrogen content of the TABLE 3 RATO OF AMOUNTS OF NTROGENOUS CONSTTUENTS N TREE TSSUES AT HARVEST Expressed s percentges Rtio Nitrogen Tretment Nl N N9 Lest Significnt Difference 5% 1% 0 1% Level Level Level Soluble nitrogen/totl nitrogen Roots Stock + stem + 1-yer-old shoots Lef+flower buds Whole tree nsoluble nitrogen/totl nitrogen Roots Stock + stem + 1-yer-old shoots Lef+flower buds Whole tree Arginine nitrogen/soluble nitrogen Roots Stock+stem+1-yer-old shoots Lef + flower buds Whole tree Totl -Amino nitrogen/soluble nitrogen Roots Stock + stem + 1-yer-old shoots Lef+flower buds Whole tree Ammonium nitrogen/soluble nitrogen Roots Stock + stem + 1-yer-old shoots Lef+flower buds Whole tree Amide nitrogen/soluble nitrogen Roots Stock+stem+ l-yer-old shoots Lef + flower buds ll O Whole tree Arginine + mmonium + mide nitrogen/soluble nitrogen Roots ll O Stock + stem + 1-yer-old shoots Lef + flower buds Whole tree soluble nitrogen frction ws not influenced by the nitrogen tretment. rrespective of the tretment pplied, lmost ll of the soluble nitrogen in the tissues ws ccounted for s rginine, the mides, nd mmoni.

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16 TABLE 5 GAN OR LOSS (MG) OF TOTAL NTROGEN BY EACH TREE PART AND TREE DURNG THE SECOND GROWNG SEASON At Hrvest 2 At Hrvest 3 (hrvest 2 - hrvest 1 vlues) (hrvest 3 - hrvest 2 vlues) Nitrogen Tretment Stock + Stock + Roots Stem+ New Abscissed Whole Stem + New Abscissed Roots l-yer-old Shoots Leves Tree 1-yer-old Shoots Leves Shoots Shoots NNo NN NN NNo NN NN N9N O N9N N9N Whole Tree !Jj pi r o ::0 j

17 THE NTROGEN NUTRTON OF THE PEACH TREE. 405 from smll differences in tree size, nd therefore nitrogen content, t ech hrvest. t is lso evident from Tble 5 tht the uptke of totl nitrogen per tree t hrvests 2 nd 3 ws pproximtely directly proportionl to the externl nitrogen supply. "2 0'8 0'6 D o N1 NO tt=== "2 N3 NO 0'8 0'6 0'4 0'2 ==: e 4 " '6 0'4 0'2 o ',("66), X,,,,,,,,,,,, NgN O "-, e --X 4 ===X 19 61'2 z w l'j f- Z w 0'8..J rn :3 0'6 o J) 0'4 f z is 0'2 :; " x 0 " 9 N1 N3,! i' "2 N3 N '6 0, 0'2 o. er---i 4 " ' ',(1-66), x '\ N g N 3,,,,,,,,,,, "-, e:> X----J( l. 4_1l. e-e "2 N 1N g "2 N3 N9,,0 "2 'S1-66) x " " NgNg,,, "'''' 0' '4 0'2 /,:::><t -, ---.,,! o g 0' /: e.,,/-4 lj.'><e_e 0 8 0' e>\ :_l. 4 e_e Fig. 7,-nfluence of nitrogen tretment on the mount of soluble nitrogen in tree tissues during the second growing seson. X Roots. Stock+stem+l-yer-old shoots. /:::, Buds, new shoots..a Whole tree, During the second hlf of the growing seson, the nitrogen content of the roots nd old tree tops incresed in ll tretments except in roots of trees in the N9NO

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20 408 B. K. TAYLOR AND L. H. MAY nitrogen did not ccumulte in tree tissues t this time, presumbly becuse the demnd for nitrogen exceeded the supply. (3) nsoluble Nitrogen (Fig. 8).-The mount of insoluble nitrogen in tree tissues during the second growing seson ws proportionl to the level of nitrogen supplied 5 0 N1 NO 5'0 N3 NO 5 0 NgNO 3'0 3'0 := A==- =.-!!!!d ',0 :.. 2'0 1-0 J o " ' 0 z «o ',0 OJ o x '" o ASONDJFM N1 N3 :t ASONDJFM 5 0 1'0 N3 N3,.==---=-=- -x &- J ',0 ASONDJFM N g N 3 :.. ASONDJ FM 5 0 N 1N g 5 0 N3N NgN g. " :========4: ',0 :...====--=-. 2'0 ', Fig. 10.-nfluence of nitrogen tretment on the mount of totl ",-mino nitrogen in tree tissues during the second growing seson. X Roots. Stock+stem+l-yer-old shoots. 6 Buds, new shoots. Whole tree. in both yers of the experiment. Since the mount of insoluble nitrogen incresed throughout the growing seson in most tissues it ws not utilized in growth processes. However, there is evidence tht smll mounts of insoluble nitrogen in the stock plus stem plus l-yer-old shoots of ll tretments were mobilized during the first hlf of the growing seson, nd presumbly this nitrogen ws trnslocted to the growing

21 V. DSCUSSON The results strongly suggest tht tree growth during the first hlf of the second growing seson ws mde lrgely t the expense of nitrogen which hd ccumulted in woody tissues of the trees during the first yer. However, prt from the influence of storge nitrogen on tree growth, tree size t the beginning of the second growing seson could lso hve influenced subsequent growth, since tree size nd the nitrogen content per tree t tht time were both in proportion to the nitrogen tretment pplied in the first yer. Nevertheless, the results of the nitrogen nlyses clerly show tht stored nitrogen in tree roots nd old tops ws exported to the new shoots during the first hlf of the growing seson, thus confirming the importnce of storge nitrogen for tree growth. Anlysis of growth dt obtined t the end of the second growing seson indicted tht there ws significnt negtive interction between first nd second yer tretments, irrespective of the wy in which tree growth ws mesured. For exmple, trees in the NN9 tretment responded more mrkedly to the externl nitrogen supply thn did those in the N9N9 tretment, but this ws not due to greter uptke of nitrogen per tree in the former tretment. Apprently, fctors other thn nitrogen supply limited the growth of nitrogen-rich trees during the second yer. The finding tht the storge nitrogen of dormnt pech trees consists minly of soluble orgnic nitrogen nd tht free rginine is the principl constituent of this frction grees well with the results of Olnd (1959) for pple. Thus, s might be expected, the nture nd chemicl composition of storge nitrogen in different woodjt species of the fmily Roscee pper to be similr. About two-thirds of the storge nitrogen in dormnt, 2-yer-old trees ws held in root tissues irrespective of the previous nitrogen tretment. This uneven points. n the ltter hlf of the growing seson the mount of insoluble nitrogen in the new shoots of trees in the N N 0, N 3N 0, N 9N 0, nd N 9N 3 tretments fell, presumbly due to loss of insoluble nitrogen in the bscissed leves (the extent of this loss ws not mesured). (4) Arginine Nitrogen (Fig. 9).-The mount of rginine nitrogen in the trees fell shrply to very low level during the first hlf of the growing seson nd remined low during the reminder of the seson. (5) Totl -Amino Nitrogen (Fig. lo).-the mount of totl -mino nitrogen in tree tissues ws proportionl to the nitrogen supply in the first nd second yers of the experiment. During the first hlf of the growing seson, the mount of totl -mino nitrogen in tree tissues of ll tretments declined, except in the new shoots where smll increses occurred, but during the second hlf of the growing seson the mount of totl -mino nitrogen incresed in tree tissues in proportion to the externl nitrogen supply (except in the N9N3 tretment). These sesonl chnges were similr to those found for the mount of soluble nitrogen in tree tissues, nd, since rginine did not ccumulte in tree tissues during the ltter hlf of the growing seson, it is suggested tht the soluble nitrogen which ccumulted in the storge tissurs t this time consisted lrgely of other free mino cids nd mides. THE NTROGEN NUTRTON OF THE PEACH TREE. 409

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