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Effects of nitrogen and phosphorus on root and shoot growth of Cotoneaster divaricata Rehd. & Wils.
Scientia Horticulturae, 15 (1981) 77--85 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
77
EFFECTS OF NITROGEN AND PHOSPHORUS ON ROOT AND SHOOT GROWTH OF COTONEASTER DIVARICATA REHD. & WiLS.
M.E.C. GRACA and D.F. HAMILTON Department o f Horticulture, Purdue University, West Lafayette, I N 47907 (U.S.A.) Journal Paper No. 8047. Purdue University, Agricultural Experiment Station, West Lafayette, IN 47907, U.S.A. (Accepted for publication 24 September 1980)
ABSTRACT Graca, M.E.C. and Hamilton, D.F., 1981. Effects of nitrogen and phosphorus on root and shoot growth of Cotoneaster divaricata Rehd. & Wils. Scientia Hortic., 15: 77--85. Root and shoot growth rates of Cotoneaster divaricata were determined using a growing system of polyvinyl chloride pipe cylinders in which longitudinal sections could be removed for periodic root observations. Plants were fertilized with nitrogen (N), phosphorus (P), and potassium (K). N, as NH4NO3, was applied weekly at levels of 0, 250 or 500 mg/l and P, as H3PO4, was incorporated in the medium at levels of 0, 5 or 50 mg/1. K, as KC1, was maintained in the medium at a 150 mg/1 level by soil tests conducted weekly. Shoot growth was increased after N application. However, no difference was observed between N levels. P increased shoot growth only at the highest N level applied. Although root growth was not increased by either N or P, high N levels inhibited root growth, whereas P stimulated root growth. No correlation (r = 0.19) was observed between shoot and root growth.
INTRODUCTION D u r i n g p r o d u c t i o n o f c o n t a i n e r - g r o w n w o o d y p l a n t s , a m a j o r c o n c e r n is t h e g r o w t h o f s h o o t s w h i l e r o o t g r o w t h is o f t e n n e g l e c t e d . G r o w t h o f w o o d y p l a n t s is d e t e r m i n e d b y m a n y e n v i r o n m e n t a l f a c t o r s , i n c l u d i n g m i n e r a l n u t r i t i o n . T h e m a i n o b j e c t i v e o f f e r t i l i z a t i o n is t o e n s u r e a c o n s t a n t n u t r i e n t supply rather than to modify growth by vastly altering the nutritional regime. F o r f i e l d - g r o w n p l a n t s , o n e or t w o f e r t i l i z a t i o n s d u r i n g e a c h g r o w i n g - c y c l e are u s u a l l y s u f f i c i e n t t o s a t i s f y t h e p e a k n u t r i t i o n a l n e e d s as well as c o n s t a n t n u t r i t i o n a l d e m a n d s . In c o n t r a s t , c o n t a i n e r - g r o w n p l a n t s r e q u i r e f r e q u e n t i r r i g a t i o n a n d f e r t i l i z a t i o n b e c a u s e o f t h e s m a l l s o i l - v o l u m e in w h i c h t h e r o o t s y s t e m is c o n f i n e d . F u r t h e r m o r e , c o n t a i n e r i z e d p l a n t s are ~ s u a l l y f e r t i l i z e d w i t h N a t h i g h levels r e s u l t i n g in m o r e s h o o t t h a n r o o t g r o w t h . C o n s e q u e n t l y , in t h e t r a n s i t i o n f r o m c o n t a i n e r t o l a n d s c a p e , t h e p e r c e n t a g e o f p l a n t s t h a t
0304-4238/81/0000--0000/$02.50 © 1981 Elsevier ScientificPublishing Company
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become successfully established may be greatly reduced relative to fieldgrown plants. Achieving o p t i m u m nutrient levels that will maintain a proper balance between shoot and r o o t growth often is difficult. According to Gilliam and Wright (1978), the major problem in nursery production o f containerized w o o d y plants is in determining N levels that will p r o m o t e maximum shoot growth. Early investigations have shown that an increased N fertilization increased s h o o t / r o o t ratio (Turner, 1922; Reid, 1929; Mitchell, 1939). W o o d y landscape plants also exhibit a growth pattern distinct from most herbaceous crops. Bud break and initiation of new growth in spring m a y be from pre-formed buds, i.e. buds formed during the previous growing-sea~on. This new growth may constitute the total growth for the season. R o o t growth of these plants, on the other hand, normally occurs in spring and fall, (McDougall, 1916). Applying fertilizer to obtain the desired response with b o t h shoot and r o o t growth is often difficult. This difficulty is mainly due to the marked periodicity of shoot and r o o t growth. In some species, root growth can b e detected before shoot growth (Wareing, 1971; Mertens and Wright, 1978). Other studies have shown that the r o o t activity frequently appears to be inhibited during the period of active flushing of the shoots (Wareing, 1971). This inhibitory effect of shoot growth on roots appears to be due to the fact that while the shoots are extending rapidly they monopolize all the available photosynthates. On the other hand, root development is considered b y some to be more dependent u p o n adequate P and K than on N (Mitchell, 1939), b u t insufficient information is available regarding the nutrient levels necessary to optimize b o t h r o o t and shoot growth in container-grown plants. Therefore, the objectives of this study with Cotoneaster divaricata Rehd. & Wils. were to determine the effects of various N and P levels on (a) shoot and r o o t growth rates, (b) foliar nutrient composition, (c) growth periodicity of shoots and roots. MATERIALS AND METHODS Single-stem rooted cuttings (8 cm) of Cotoneaster divaricata were taken from stock plants grown in full sunlight, and inserted into flats containing soil : sphagnum peat : perlite (1:2:2 v/v). The propagating-medium was amended with Dolomite, CaMg (CO3)2, MgSO4 and fritted-trace elements: Mn, 7.58%; Fe, 18.08%; Cu, 3.08%; Zn, 7.08%; B, 3.08%; Mo, 0.28%. Basal portions of cuttings were dipped in 2% indole-3-butyric acid talc (IBA), and then inserted into the rooting-medium. Flats containing cuttings were placed under intermittent mist (10 s/10 min) and maintained at 24 + 3°C under natural photoperiod. After 4 weeks, 36 rooted cuttings were selected for uniformity of shoot and r o o t development and transplanted into vertical poly-
79 vinyl chloride pipe cylinders, 5.0 cm diameter × 32 cm long, containing a m e d i u m o f peat and perlite (1:1 v/v). Dolomite [CaMg(CO3)2], MgSO4 and Hoagland and Arnon (1950) m i c r o n u t r i e n t solution were added t o the medium. In order to measure r o o t growth, a section was cut f r o m one side of each length o f pipe according t o Murdoch et al. (1974). The removed section was then replaced and secured with electrical tape. A sheet of transparent acetate plastic was rolled and inserted into each pipe and a piece of saran cloth was wired to the b o t t o m o f each pipe t o retain t he growing-medium. The pipe sections with transplanted cuttings were then placed at a 45 ° angle with the window side d o w n against a shelf for support. The e x p e r i m e n t a l design was an N × P factorial with N, as NH4NO3, applied weekly at 0, 250 or 500 mg/1 and P, as H3PO4, i n c o r p o r a t e d once at 0, 5 or 50 mg/1 before transplanting. K, as KC1, was maintained at 150 mg/1, added as liquid when needed as de t e r m i ne d by soil testing. A random i zed complete block design with 4 replications was used. One week after transplanting, one s hoot and one r o o t were selected for weekly growth measurements which c o n t i n u e d for 9 weeks. The rate of new growth was calculated by subtracting the previous week's i ncrem ent f r o m the cumulative length. Moisture was maintained by watering plants every o t h e r day with 50 ml of tap water. Soil mix was leached at 15-day intervals t o prevent build-up o f soluble salts. To determine the nut r i e nt status of the medium, a n u t r i e n t analysis was carried o u t at the beginning and end of the e x p e r i m e n t . Plants were harvested after 9 weeks. Harvesting was c o m p l e t e d by separating new shoots (new growth), base (old stem and ol d leaves), and roots f r o m each plant. Fresh weight of c o m p o n e n t s was obtained, followed b y r o o t length measured by t he T e n n a n t (1975) m e t h o d . This m e t h o d consists of measuring r o o t length by counting t he n u m b e r o f intercepts in horizontal and vertical rows of a r o o t system placed on a grid. The n u m b e r of intercepts is th en substituted in t he following formula: R o o t length = 1 1 / 1 4 × n u m b e r of intercepts × grid unit. Samples were dried in a forced-air oven at 70°C for 3 days. Dry weight of samples was d e t e r m i n e d gravimetricaily and the tissue was ground with a 20-mesh screen Wiley mill. Following grinding, samples were wet-ashed with sulfuric acid. Total reduced N was det er m i ned by Nesslerization and NO~ t h r o u g h electrode analysis. P was de t e r m i ne d by the a m m o n i u m - p h o s p h o m o l y b d a t e m e t h o d with 1, 2, 4-amino napht ol sulfonic acid as the reducing agent (Jackson, 1958). K was det er m i ned with a Model 9200 Unicam flame spectrophotometer. RESULTS AND DISCUSSION S h o o t growth of C o t o n e a s t e r divaricata was consistently greater t han r o o t growth, e x c e p t for the ni nt h week (Fig. 1). Rapid increases in s h o o t growth
80
6.Oz~ Shoot Growth 5.0-
Root Growth
0
oE 4.Ow ~ 3.0-
I'I
.
i
4
6
8
WEEKS
Fig. 1. Effects of nitrogen and phosphorus on shoot and root growth of C o t o n e a s t e r divaricata.
were the result of N applications (Figs. 2 and 3). However, within treatments, no increase in growth was observed from 250 and 500 mg/1 N (Fig. 2). These results agree with findings b y Gilliam and Wright (1978), who reported that 300 mg/1 N are necessary for maximum growth of 'Helleri' holly (Ilex crenata Thunb. 'Helleri') and Burford holly (Ilex cornuta Lindl. & Paxt. Burfordii) during the first full season following propagation, while further increases in N did n o t continue to accelerate growth. A ..¢ I0.0 I= ¢) v -I0 n,,
I 8.0
6.0
0
H
LSD
5 %
N 0 mg/I N 250
mg/I
N 500
m9 / I
I-
8
4.0
2.0
0
2
4
6
8
WEEKS
Fig. 2. Effect of nitrogen on rates of shoot growth of C o t o n e a s t e r divaricata.
81
A £ o v
3o
~
h
RootGrowth
0 "r I--
2.0
O n~ (.9 1.0--
0.0
o - - - - - - ~
I
i
I
0
250
500
N (rag/I)
Fig. 3. Shoot and root growth of Cotoneaster divaricata at different levels of nitrogen. Shoot growth response to P addition occurred only at the highest N level (Fig. 4). However, there was no significant difference between 5 and 50 mg/1 P (Fig. 4). R o o t growth was n o t increased by N (Fig. 3). Lack of a root-growth response suggests t h a t N absorbed by roots is readily translocated to the shoot, where it is used in protein synthesis and consequently shoot growth. Mitchell (1939) also observed that increased N produced more stimulation of shoot than of root growth in white pine (Pinus s t r o b u s L.). Likewise, r o o t growth did not improve when P was applied (Table I). These data support research by Wright (1979), who reported t h a t P applications did n o t increase root growth in I l e x crenata Thunb. 'Helleri' and 'Rotundifolia'.
5.0 "E c~ v
4.0
I
LSD
5 %
-iI-0 n~ (D I0 0 --r" o9
5.0
2.0
~~. LO
z~ 5 mg/I • 0 mg/I
I
I
I
0
250
500
N (rag/I)
Fig. 4. Effects of nitrogen and phosphorus combinations on shoot growth of Cotoneaster divaricata.
82 TABLE I E f f e c t s o f n i t r o g e n a n d p h o s p h o r u s o n r o o t a n d s h o o t g r o w t h o f Cotoneaster divaricata. M e a n s e p a r a t i o n w i t h i n c o l u m n s b y T u k e y t e s t a t 5% level. C o r r e l a t i o n c o e f f i c i e n t r = 0 . 1 9 T r e a t m e n t (mg/1)
Growth rate per week (cm)
N
P
Shoot
Root
0 5 50
1.49 a 2.07 ab 1.38 a
1.24 a 1.96 a 0.29 a
250
0 5 50
3.73 c 3 . 1 1 bc 3.61 c
1.11 a 1.31 a 1.14 a
500
0 5 50
2 . 8 8 bc 4.12 c 4.08 c
1.04 a 1.11 a 1.36 a
TABLE II E f f e c t s o f n i t r o g e n o n s h o o t a n d r o o t g r o w t h o f Cotoneaster divaricata; m e a n s o f 4 r e p l i c a t i o n s ; m e a n s e p a r a t i o n w i t h i n c o l u m n s b y T u k e y t e s t a t 5% level Nitrogen mg/1
0 250 500
F r e s h w e i g h t (g)
Root length (m/g)
Shoot
Root
Root
Plant
3.33 a 7.33 b 7.87 b
3.70 a 4.91 a 3.72 a
13.18 a 12.56 a 11.39 a
6.80 a 5.11 ab 3.72 b
Density cm/cm 3
30.25 a 39.84 a 27.02 a
TABLE III Effec~ o f p h o s p h o r u s o n s h o o t a n d r o o t g r o w t h o f Cotoneaster divaricata; m e a n s o f 4 r e p l i c a t i o n s ; m e a n s e p a r a t i o n w i t h i n c o l u m n s b y T u k e y t e s t at 5% level Phosphorus mg/1
0 5 50
F r e s h w e i g h t (g)
Root length (m/g)
Shoot
Root
Root
Plant
5.94 a 6.39 a 6.19 a
3.91 a 4.55 a 3.89 a
12.08 a 10.94 a 14.11 a
5.05 a 4.68 a 5.90 a
Density cm/cm 3
31.65 a 32.15 a 33.30 a
Also, no correlation was f o u n d bet w e e n shoot and r o o t growth as a function of N and P (r = 0.19). Contrary to these findings, Mertens and Wright (1978) f o u n d t h a t in two cultivars of Japanese holly (Ilex crenata Thunb. 'Helleri' and 'Rotundifolia'), m a x i m u m shoot growth was accompanied by
83 minimum r o o t growth and vice versa, when grown at 150 or 300 mg/1 N levels. They also observed t h a t active root growth preceded shoot flushing by one or two weeks. In Cotoneaster, however, shoot growth was apparent before r o o t growth began (Fig. 1). As with shoot and r o o t growth, there was a significant increase in shoot fresh weight from 0 to 250 mg/1 N, but no significant response was observed at 500 mg/1 N (Table II). R o o t fresh weight was not increased by N applications (Table II). Although root length did n o t increase significantly, it was observed t h a t as N increased there was a slight reduction in root length (Table II). This effect is illustrated best on a per-plant basis, where a significant decrease was obtained from 0 to 500 mg/1 (Table II). These results suggest that root growth varies inversely when N concentration increases. There was no significant increase in the density of the root system caused by either N or P (Tables II and III). At 500 mg/1 N, root density tended to be less than at 0 mg/1 (Table II). Conversely, increased P tended to increase root density slightly (Table III), suggesting t h a t root development is more dependent upon P than upon N. Additions of P did not affect shoot and root fresh weight. The same response was observed for r o o t length per gram of root, and root length per gram of plant (Table III). Furthermore, as shoot growth occurred before root growth, plants may have had ample carbohydrate reserves negating immediate response to N and P applications. From results of foliar analysis, Smith (1978) recommended a range of 2--4.5% for N, 0.2--0.6% for P, and 1.5--3.5% for K as o p t i m u m nutritional TABLE IV E f f e c t s o f n i t r o g e n a n d p h o s p h o r u s levels o n f o l i a r n u t r i e n t c o m p o s i t i o n o f Cotoneaster divaricata; m e a n s o f 4 r e p l i c a t i o n s ; m e a n s e p a r a t i o n w i t h i n c o l u m n s b y T u k e y t e s t at 5% level T r e a t m e n t (mg/1) Nitrogen
Dry weight o f s h o o t (g)
Phosphorus
C o m p o s i t i o n (%)
NO3 (mg/1)
N
P
K
0 5 50
1.36a 1.74abc 0-99 a
1.17cd 1.39bcd 0.99 d
0.19a 0.17a 0.14 a
1.76a 1.68a 1.55 a
0 0 0
250
0 5 50
3.08 d 2.29 b c d 2.66 cd
2.28 a 2 . 0 0 abc 2.26 a
0.14 a 0.15 a 0.21 a
1.44 a 1.41 a 1.67 a
10 15 16
500
0 5 50
2.35 bcd 3.07 d 3.23 d
2.79 a 2.35 a 2 . 1 8 ab
0.20 a 0.16 a 0.16 a
1.54 a 1.39 a 1.39 a
50 76 51
84 ranges. In o u r e x p e r i m e n t , raising N levels w i t h i n t h e range r e c o m m e n d e d b y S m i t h ( 1 9 7 8 ) increased N c o n t e n t in t h e t i s s u e ' ( T a b l e IV). A d d i t i o n s o f P w e r e n o t s u f f i c i e n t t o raise foliar P c o n t e n t t o its r e c o m m e n d e d o p t i m u m level. Soil analysis at t h e e n d o f t h e e x p e r i m e n t revealed a r a n g e f r o m 6.1 t o 8.5 mg/1 in t h o s e t r e a t m e n t s w h e r e P was applied, a n d t h e i r results w e r e w i t h i n t h e o p t i m u m soil r a n g e ( l o w e r limit n e a r 0.9 mg/1 t o an u p p e r l i m i t higher t h a n 9 . 7 m g / 1 ) r e p o r t e d b y Flint (1962). Foliar K c o n t e n t did n o t v a r y significantly a m o n g t h e t r e a t m e n t s , a n d t h e y w e r e w i t h i n t h e range described by Smith (1978). CONCLUSIONS S h o o t g r o w t h o f C o t o n e a s t e r divaricata was i m p r o v e d b y a p p l i c a t i o n o f N. H o w e v e r , within N levels, t h e r e w e r e n o significant d i f f e r e n c e s b e t w e e n 250 a n d 500 mg/1. S h o o t g r o w t h i n c r e a s e d in r e s p o n s e to P a p p l i c a t i o n o n l y in t h e p r e s e n c e o f N. High N levels t e n d e d t o have negative e f f e c t s o n r o o t g r o w t h at least initially, b u t p o s s i b l y n o t later. T h e r e f o r e , 250 mg/1 N is n e c e s s a r y f o r m a x i m i z a t i o n o f s h o o t g r o w t h o f C o t o n e a s t e r divaricata at t h e p h a s e o f d e v e l o p m e n t studied. R o o t g r o w t h p e r i o d i c i t y was n o t significantly a f f e c t e d b y e i t h e r N or P a d d i t i o n s . Also, n o c o r r e l a t i o n (r = 0.19) was f o u n d b e t w e e n s h o o t a n d r o o t g r o w t h w i t h t h e ' t r e a t m e n t s studied. T h e s e findings suggest t h a t n u t r i e n t s at t h e levels a p p l i e d are r e a d i l y t r a n s l o c a t e d to s h o o t s t o p r o m o t e g r o w t h i R o o t g r o w t h did n o t o c c u r e v e n t h o u g h t e r m i n a l b u d s were f o r m e d . This r e l a t i o n s h i p b e t w e e n s h o o t a n d r o o t g r o w t h is i m p o r t a n t t o n u r s e r y m e n f o r m a n i p u l a t i o n o f r o o t a n d s h o o t g r o w t h b y t i m i n g o f fertilizer applications. In C o t o n e a s t e r divaricata, h o w e v e r , t i m i n g o f f e r t i l i z a t i o n b y r o o t a n d s h o o t g r o w t h p e r i o d i c i t y m a y b e difficult. REFERENCES
Flint, H.L., 1962. Effects of different soil levels and methods of applications of growth of selected woody ornamental species in containers. Proc. Am. Soc. Hortic. Sci., 81: 552--555. Gilliam, C.H. and Wright, R.D., 1978. Container fertilization of selected Ilex. Am. Nurseryman, 147(11): 8, 62--63. Hoagland, D.R. and Arnon, D.I., 1950. The water culture method for growing plants without soil. Calif. Agric. Exp. Stn. Circ. 347, p. 32. Jackson, M.L., 1958. Soil chemical analysis. Prentice-Hall, Englewood Cliffs, NJ, pp. 200--210. McDougall, W.B., 1916. The growth of forest tree roots. Am. J. Bot., 3: 384--392. Mertens, W.C. and Wright, R.D., 1978. Root and shoot growth rate relationships of two cultivars of Japanese holly. J. Am. Soc. Hortie. Sci., 103: 722--724. Mitchell, H.L., 1939. The growth and nutrition of White pine (Pinus strobus L.) seedlings in cultures with varying nitrogen, phosphorus, potassium and calcium. Black Rock For. Bull., 9: 40--133. Murdoeh, C.L., Criley, R.A. and Fukuda, S.X., 1974. An experience method for the study of root growth in containers of solid media. HortScience, 9: 221.
85 Reid, M.E., 1929. Growth of seedlings in light and in darkness in relation to available nitrogen and carbon. Bot. Gaz., 87: 81--117. Smith, E.M., 1978. Foliar analysis survey of woody ornamentals. Ornamental Plants-1978, A Summary of Research. Ohio Agric. Res. Dev. Center, Res. Circ., 236:30--33. Tennant, D., 1975. A test of a modified line intersect method of estimating r o o t length. J. Ecol., 63: 995--1000. Turner, T.W., 1922. Studies of the mechanism of the physiological effects of certain mineral salts in altering the ratio of top growth to root growth in seed plants. Am. J. Bot., 9: 415--445. Wareing, P.F., 1971. The physiology of conifers, Part I. The growth of the shoot and root. J. Hortic. Soc., 96: 394--403. Wright, R.D., 1979. Effects of nitrogen and phosphorus rates on growth of Ilex. HortScience, 14(3): 32.
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EFFECTS OF NITROGEN AND PHOSPHORUS ON ROOT AND SHOOT GROWTH OF COTONEASTER DIVARICATA REHD. & WiLS.
M.E.C. GRACA and D.F. HAMILTON Department o f Horticulture, Purdue University, West Lafayette, I N 47907 (U.S.A.) Journal Paper No. 8047. Purdue University, Agricultural Experiment Station, West Lafayette, IN 47907, U.S.A. (Accepted for publication 24 September 1980)
ABSTRACT Graca, M.E.C. and Hamilton, D.F., 1981. Effects of nitrogen and phosphorus on root and shoot growth of Cotoneaster divaricata Rehd. & Wils. Scientia Hortic., 15: 77--85. Root and shoot growth rates of Cotoneaster divaricata were determined using a growing system of polyvinyl chloride pipe cylinders in which longitudinal sections could be removed for periodic root observations. Plants were fertilized with nitrogen (N), phosphorus (P), and potassium (K). N, as NH4NO3, was applied weekly at levels of 0, 250 or 500 mg/l and P, as H3PO4, was incorporated in the medium at levels of 0, 5 or 50 mg/1. K, as KC1, was maintained in the medium at a 150 mg/1 level by soil tests conducted weekly. Shoot growth was increased after N application. However, no difference was observed between N levels. P increased shoot growth only at the highest N level applied. Although root growth was not increased by either N or P, high N levels inhibited root growth, whereas P stimulated root growth. No correlation (r = 0.19) was observed between shoot and root growth.
INTRODUCTION D u r i n g p r o d u c t i o n o f c o n t a i n e r - g r o w n w o o d y p l a n t s , a m a j o r c o n c e r n is t h e g r o w t h o f s h o o t s w h i l e r o o t g r o w t h is o f t e n n e g l e c t e d . G r o w t h o f w o o d y p l a n t s is d e t e r m i n e d b y m a n y e n v i r o n m e n t a l f a c t o r s , i n c l u d i n g m i n e r a l n u t r i t i o n . T h e m a i n o b j e c t i v e o f f e r t i l i z a t i o n is t o e n s u r e a c o n s t a n t n u t r i e n t supply rather than to modify growth by vastly altering the nutritional regime. F o r f i e l d - g r o w n p l a n t s , o n e or t w o f e r t i l i z a t i o n s d u r i n g e a c h g r o w i n g - c y c l e are u s u a l l y s u f f i c i e n t t o s a t i s f y t h e p e a k n u t r i t i o n a l n e e d s as well as c o n s t a n t n u t r i t i o n a l d e m a n d s . In c o n t r a s t , c o n t a i n e r - g r o w n p l a n t s r e q u i r e f r e q u e n t i r r i g a t i o n a n d f e r t i l i z a t i o n b e c a u s e o f t h e s m a l l s o i l - v o l u m e in w h i c h t h e r o o t s y s t e m is c o n f i n e d . F u r t h e r m o r e , c o n t a i n e r i z e d p l a n t s are ~ s u a l l y f e r t i l i z e d w i t h N a t h i g h levels r e s u l t i n g in m o r e s h o o t t h a n r o o t g r o w t h . C o n s e q u e n t l y , in t h e t r a n s i t i o n f r o m c o n t a i n e r t o l a n d s c a p e , t h e p e r c e n t a g e o f p l a n t s t h a t
0304-4238/81/0000--0000/$02.50 © 1981 Elsevier ScientificPublishing Company
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become successfully established may be greatly reduced relative to fieldgrown plants. Achieving o p t i m u m nutrient levels that will maintain a proper balance between shoot and r o o t growth often is difficult. According to Gilliam and Wright (1978), the major problem in nursery production o f containerized w o o d y plants is in determining N levels that will p r o m o t e maximum shoot growth. Early investigations have shown that an increased N fertilization increased s h o o t / r o o t ratio (Turner, 1922; Reid, 1929; Mitchell, 1939). W o o d y landscape plants also exhibit a growth pattern distinct from most herbaceous crops. Bud break and initiation of new growth in spring m a y be from pre-formed buds, i.e. buds formed during the previous growing-sea~on. This new growth may constitute the total growth for the season. R o o t growth of these plants, on the other hand, normally occurs in spring and fall, (McDougall, 1916). Applying fertilizer to obtain the desired response with b o t h shoot and r o o t growth is often difficult. This difficulty is mainly due to the marked periodicity of shoot and r o o t growth. In some species, root growth can b e detected before shoot growth (Wareing, 1971; Mertens and Wright, 1978). Other studies have shown that the r o o t activity frequently appears to be inhibited during the period of active flushing of the shoots (Wareing, 1971). This inhibitory effect of shoot growth on roots appears to be due to the fact that while the shoots are extending rapidly they monopolize all the available photosynthates. On the other hand, root development is considered b y some to be more dependent u p o n adequate P and K than on N (Mitchell, 1939), b u t insufficient information is available regarding the nutrient levels necessary to optimize b o t h r o o t and shoot growth in container-grown plants. Therefore, the objectives of this study with Cotoneaster divaricata Rehd. & Wils. were to determine the effects of various N and P levels on (a) shoot and r o o t growth rates, (b) foliar nutrient composition, (c) growth periodicity of shoots and roots. MATERIALS AND METHODS Single-stem rooted cuttings (8 cm) of Cotoneaster divaricata were taken from stock plants grown in full sunlight, and inserted into flats containing soil : sphagnum peat : perlite (1:2:2 v/v). The propagating-medium was amended with Dolomite, CaMg (CO3)2, MgSO4 and fritted-trace elements: Mn, 7.58%; Fe, 18.08%; Cu, 3.08%; Zn, 7.08%; B, 3.08%; Mo, 0.28%. Basal portions of cuttings were dipped in 2% indole-3-butyric acid talc (IBA), and then inserted into the rooting-medium. Flats containing cuttings were placed under intermittent mist (10 s/10 min) and maintained at 24 + 3°C under natural photoperiod. After 4 weeks, 36 rooted cuttings were selected for uniformity of shoot and r o o t development and transplanted into vertical poly-
79 vinyl chloride pipe cylinders, 5.0 cm diameter × 32 cm long, containing a m e d i u m o f peat and perlite (1:1 v/v). Dolomite [CaMg(CO3)2], MgSO4 and Hoagland and Arnon (1950) m i c r o n u t r i e n t solution were added t o the medium. In order to measure r o o t growth, a section was cut f r o m one side of each length o f pipe according t o Murdoch et al. (1974). The removed section was then replaced and secured with electrical tape. A sheet of transparent acetate plastic was rolled and inserted into each pipe and a piece of saran cloth was wired to the b o t t o m o f each pipe t o retain t he growing-medium. The pipe sections with transplanted cuttings were then placed at a 45 ° angle with the window side d o w n against a shelf for support. The e x p e r i m e n t a l design was an N × P factorial with N, as NH4NO3, applied weekly at 0, 250 or 500 mg/1 and P, as H3PO4, i n c o r p o r a t e d once at 0, 5 or 50 mg/1 before transplanting. K, as KC1, was maintained at 150 mg/1, added as liquid when needed as de t e r m i ne d by soil testing. A random i zed complete block design with 4 replications was used. One week after transplanting, one s hoot and one r o o t were selected for weekly growth measurements which c o n t i n u e d for 9 weeks. The rate of new growth was calculated by subtracting the previous week's i ncrem ent f r o m the cumulative length. Moisture was maintained by watering plants every o t h e r day with 50 ml of tap water. Soil mix was leached at 15-day intervals t o prevent build-up o f soluble salts. To determine the nut r i e nt status of the medium, a n u t r i e n t analysis was carried o u t at the beginning and end of the e x p e r i m e n t . Plants were harvested after 9 weeks. Harvesting was c o m p l e t e d by separating new shoots (new growth), base (old stem and ol d leaves), and roots f r o m each plant. Fresh weight of c o m p o n e n t s was obtained, followed b y r o o t length measured by t he T e n n a n t (1975) m e t h o d . This m e t h o d consists of measuring r o o t length by counting t he n u m b e r o f intercepts in horizontal and vertical rows of a r o o t system placed on a grid. The n u m b e r of intercepts is th en substituted in t he following formula: R o o t length = 1 1 / 1 4 × n u m b e r of intercepts × grid unit. Samples were dried in a forced-air oven at 70°C for 3 days. Dry weight of samples was d e t e r m i n e d gravimetricaily and the tissue was ground with a 20-mesh screen Wiley mill. Following grinding, samples were wet-ashed with sulfuric acid. Total reduced N was det er m i ned by Nesslerization and NO~ t h r o u g h electrode analysis. P was de t e r m i ne d by the a m m o n i u m - p h o s p h o m o l y b d a t e m e t h o d with 1, 2, 4-amino napht ol sulfonic acid as the reducing agent (Jackson, 1958). K was det er m i ned with a Model 9200 Unicam flame spectrophotometer. RESULTS AND DISCUSSION S h o o t growth of C o t o n e a s t e r divaricata was consistently greater t han r o o t growth, e x c e p t for the ni nt h week (Fig. 1). Rapid increases in s h o o t growth
80
6.Oz~ Shoot Growth 5.0-
Root Growth
0
oE 4.Ow ~ 3.0-
I'I
.
i
4
6
8
WEEKS
Fig. 1. Effects of nitrogen and phosphorus on shoot and root growth of C o t o n e a s t e r divaricata.
were the result of N applications (Figs. 2 and 3). However, within treatments, no increase in growth was observed from 250 and 500 mg/1 N (Fig. 2). These results agree with findings b y Gilliam and Wright (1978), who reported that 300 mg/1 N are necessary for maximum growth of 'Helleri' holly (Ilex crenata Thunb. 'Helleri') and Burford holly (Ilex cornuta Lindl. & Paxt. Burfordii) during the first full season following propagation, while further increases in N did n o t continue to accelerate growth. A ..¢ I0.0 I= ¢) v -I0 n,,
I 8.0
6.0
0
H
LSD
5 %
N 0 mg/I N 250
mg/I
N 500
m9 / I
I-
8
4.0
2.0
0
2
4
6
8
WEEKS
Fig. 2. Effect of nitrogen on rates of shoot growth of C o t o n e a s t e r divaricata.
81
A £ o v
3o
~
h
RootGrowth
0 "r I--
2.0
O n~ (.9 1.0--
0.0
o - - - - - - ~
I
i
I
0
250
500
N (rag/I)
Fig. 3. Shoot and root growth of Cotoneaster divaricata at different levels of nitrogen. Shoot growth response to P addition occurred only at the highest N level (Fig. 4). However, there was no significant difference between 5 and 50 mg/1 P (Fig. 4). R o o t growth was n o t increased by N (Fig. 3). Lack of a root-growth response suggests t h a t N absorbed by roots is readily translocated to the shoot, where it is used in protein synthesis and consequently shoot growth. Mitchell (1939) also observed that increased N produced more stimulation of shoot than of root growth in white pine (Pinus s t r o b u s L.). Likewise, r o o t growth did not improve when P was applied (Table I). These data support research by Wright (1979), who reported t h a t P applications did n o t increase root growth in I l e x crenata Thunb. 'Helleri' and 'Rotundifolia'.
5.0 "E c~ v
4.0
I
LSD
5 %
-iI-0 n~ (D I0 0 --r" o9
5.0
2.0
~~. LO
z~ 5 mg/I • 0 mg/I
I
I
I
0
250
500
N (rag/I)
Fig. 4. Effects of nitrogen and phosphorus combinations on shoot growth of Cotoneaster divaricata.
82 TABLE I E f f e c t s o f n i t r o g e n a n d p h o s p h o r u s o n r o o t a n d s h o o t g r o w t h o f Cotoneaster divaricata. M e a n s e p a r a t i o n w i t h i n c o l u m n s b y T u k e y t e s t a t 5% level. C o r r e l a t i o n c o e f f i c i e n t r = 0 . 1 9 T r e a t m e n t (mg/1)
Growth rate per week (cm)
N
P
Shoot
Root
0 5 50
1.49 a 2.07 ab 1.38 a
1.24 a 1.96 a 0.29 a
250
0 5 50
3.73 c 3 . 1 1 bc 3.61 c
1.11 a 1.31 a 1.14 a
500
0 5 50
2 . 8 8 bc 4.12 c 4.08 c
1.04 a 1.11 a 1.36 a
TABLE II E f f e c t s o f n i t r o g e n o n s h o o t a n d r o o t g r o w t h o f Cotoneaster divaricata; m e a n s o f 4 r e p l i c a t i o n s ; m e a n s e p a r a t i o n w i t h i n c o l u m n s b y T u k e y t e s t a t 5% level Nitrogen mg/1
0 250 500
F r e s h w e i g h t (g)
Root length (m/g)
Shoot
Root
Root
Plant
3.33 a 7.33 b 7.87 b
3.70 a 4.91 a 3.72 a
13.18 a 12.56 a 11.39 a
6.80 a 5.11 ab 3.72 b
Density cm/cm 3
30.25 a 39.84 a 27.02 a
TABLE III Effec~ o f p h o s p h o r u s o n s h o o t a n d r o o t g r o w t h o f Cotoneaster divaricata; m e a n s o f 4 r e p l i c a t i o n s ; m e a n s e p a r a t i o n w i t h i n c o l u m n s b y T u k e y t e s t at 5% level Phosphorus mg/1
0 5 50
F r e s h w e i g h t (g)
Root length (m/g)
Shoot
Root
Root
Plant
5.94 a 6.39 a 6.19 a
3.91 a 4.55 a 3.89 a
12.08 a 10.94 a 14.11 a
5.05 a 4.68 a 5.90 a
Density cm/cm 3
31.65 a 32.15 a 33.30 a
Also, no correlation was f o u n d bet w e e n shoot and r o o t growth as a function of N and P (r = 0.19). Contrary to these findings, Mertens and Wright (1978) f o u n d t h a t in two cultivars of Japanese holly (Ilex crenata Thunb. 'Helleri' and 'Rotundifolia'), m a x i m u m shoot growth was accompanied by
83 minimum r o o t growth and vice versa, when grown at 150 or 300 mg/1 N levels. They also observed t h a t active root growth preceded shoot flushing by one or two weeks. In Cotoneaster, however, shoot growth was apparent before r o o t growth began (Fig. 1). As with shoot and r o o t growth, there was a significant increase in shoot fresh weight from 0 to 250 mg/1 N, but no significant response was observed at 500 mg/1 N (Table II). R o o t fresh weight was not increased by N applications (Table II). Although root length did n o t increase significantly, it was observed t h a t as N increased there was a slight reduction in root length (Table II). This effect is illustrated best on a per-plant basis, where a significant decrease was obtained from 0 to 500 mg/1 (Table II). These results suggest that root growth varies inversely when N concentration increases. There was no significant increase in the density of the root system caused by either N or P (Tables II and III). At 500 mg/1 N, root density tended to be less than at 0 mg/1 (Table II). Conversely, increased P tended to increase root density slightly (Table III), suggesting t h a t root development is more dependent upon P than upon N. Additions of P did not affect shoot and root fresh weight. The same response was observed for r o o t length per gram of root, and root length per gram of plant (Table III). Furthermore, as shoot growth occurred before root growth, plants may have had ample carbohydrate reserves negating immediate response to N and P applications. From results of foliar analysis, Smith (1978) recommended a range of 2--4.5% for N, 0.2--0.6% for P, and 1.5--3.5% for K as o p t i m u m nutritional TABLE IV E f f e c t s o f n i t r o g e n a n d p h o s p h o r u s levels o n f o l i a r n u t r i e n t c o m p o s i t i o n o f Cotoneaster divaricata; m e a n s o f 4 r e p l i c a t i o n s ; m e a n s e p a r a t i o n w i t h i n c o l u m n s b y T u k e y t e s t at 5% level T r e a t m e n t (mg/1) Nitrogen
Dry weight o f s h o o t (g)
Phosphorus
C o m p o s i t i o n (%)
NO3 (mg/1)
N
P
K
0 5 50
1.36a 1.74abc 0-99 a
1.17cd 1.39bcd 0.99 d
0.19a 0.17a 0.14 a
1.76a 1.68a 1.55 a
0 0 0
250
0 5 50
3.08 d 2.29 b c d 2.66 cd
2.28 a 2 . 0 0 abc 2.26 a
0.14 a 0.15 a 0.21 a
1.44 a 1.41 a 1.67 a
10 15 16
500
0 5 50
2.35 bcd 3.07 d 3.23 d
2.79 a 2.35 a 2 . 1 8 ab
0.20 a 0.16 a 0.16 a
1.54 a 1.39 a 1.39 a
50 76 51
84 ranges. In o u r e x p e r i m e n t , raising N levels w i t h i n t h e range r e c o m m e n d e d b y S m i t h ( 1 9 7 8 ) increased N c o n t e n t in t h e t i s s u e ' ( T a b l e IV). A d d i t i o n s o f P w e r e n o t s u f f i c i e n t t o raise foliar P c o n t e n t t o its r e c o m m e n d e d o p t i m u m level. Soil analysis at t h e e n d o f t h e e x p e r i m e n t revealed a r a n g e f r o m 6.1 t o 8.5 mg/1 in t h o s e t r e a t m e n t s w h e r e P was applied, a n d t h e i r results w e r e w i t h i n t h e o p t i m u m soil r a n g e ( l o w e r limit n e a r 0.9 mg/1 t o an u p p e r l i m i t higher t h a n 9 . 7 m g / 1 ) r e p o r t e d b y Flint (1962). Foliar K c o n t e n t did n o t v a r y significantly a m o n g t h e t r e a t m e n t s , a n d t h e y w e r e w i t h i n t h e range described by Smith (1978). CONCLUSIONS S h o o t g r o w t h o f C o t o n e a s t e r divaricata was i m p r o v e d b y a p p l i c a t i o n o f N. H o w e v e r , within N levels, t h e r e w e r e n o significant d i f f e r e n c e s b e t w e e n 250 a n d 500 mg/1. S h o o t g r o w t h i n c r e a s e d in r e s p o n s e to P a p p l i c a t i o n o n l y in t h e p r e s e n c e o f N. High N levels t e n d e d t o have negative e f f e c t s o n r o o t g r o w t h at least initially, b u t p o s s i b l y n o t later. T h e r e f o r e , 250 mg/1 N is n e c e s s a r y f o r m a x i m i z a t i o n o f s h o o t g r o w t h o f C o t o n e a s t e r divaricata at t h e p h a s e o f d e v e l o p m e n t studied. R o o t g r o w t h p e r i o d i c i t y was n o t significantly a f f e c t e d b y e i t h e r N or P a d d i t i o n s . Also, n o c o r r e l a t i o n (r = 0.19) was f o u n d b e t w e e n s h o o t a n d r o o t g r o w t h w i t h t h e ' t r e a t m e n t s studied. T h e s e findings suggest t h a t n u t r i e n t s at t h e levels a p p l i e d are r e a d i l y t r a n s l o c a t e d to s h o o t s t o p r o m o t e g r o w t h i R o o t g r o w t h did n o t o c c u r e v e n t h o u g h t e r m i n a l b u d s were f o r m e d . This r e l a t i o n s h i p b e t w e e n s h o o t a n d r o o t g r o w t h is i m p o r t a n t t o n u r s e r y m e n f o r m a n i p u l a t i o n o f r o o t a n d s h o o t g r o w t h b y t i m i n g o f fertilizer applications. In C o t o n e a s t e r divaricata, h o w e v e r , t i m i n g o f f e r t i l i z a t i o n b y r o o t a n d s h o o t g r o w t h p e r i o d i c i t y m a y b e difficult. REFERENCES
Flint, H.L., 1962. Effects of different soil levels and methods of applications of growth of selected woody ornamental species in containers. Proc. Am. Soc. Hortic. Sci., 81: 552--555. Gilliam, C.H. and Wright, R.D., 1978. Container fertilization of selected Ilex. Am. Nurseryman, 147(11): 8, 62--63. Hoagland, D.R. and Arnon, D.I., 1950. The water culture method for growing plants without soil. Calif. Agric. Exp. Stn. Circ. 347, p. 32. Jackson, M.L., 1958. Soil chemical analysis. Prentice-Hall, Englewood Cliffs, NJ, pp. 200--210. McDougall, W.B., 1916. The growth of forest tree roots. Am. J. Bot., 3: 384--392. Mertens, W.C. and Wright, R.D., 1978. Root and shoot growth rate relationships of two cultivars of Japanese holly. J. Am. Soc. Hortie. Sci., 103: 722--724. Mitchell, H.L., 1939. The growth and nutrition of White pine (Pinus strobus L.) seedlings in cultures with varying nitrogen, phosphorus, potassium and calcium. Black Rock For. Bull., 9: 40--133. Murdoeh, C.L., Criley, R.A. and Fukuda, S.X., 1974. An experience method for the study of root growth in containers of solid media. HortScience, 9: 221.
85 Reid, M.E., 1929. Growth of seedlings in light and in darkness in relation to available nitrogen and carbon. Bot. Gaz., 87: 81--117. Smith, E.M., 1978. Foliar analysis survey of woody ornamentals. Ornamental Plants-1978, A Summary of Research. Ohio Agric. Res. Dev. Center, Res. Circ., 236:30--33. Tennant, D., 1975. A test of a modified line intersect method of estimating r o o t length. J. Ecol., 63: 995--1000. Turner, T.W., 1922. Studies of the mechanism of the physiological effects of certain mineral salts in altering the ratio of top growth to root growth in seed plants. Am. J. Bot., 9: 415--445. Wareing, P.F., 1971. The physiology of conifers, Part I. The growth of the shoot and root. J. Hortic. Soc., 96: 394--403. Wright, R.D., 1979. Effects of nitrogen and phosphorus rates on growth of Ilex. HortScience, 14(3): 32.