THIS FILE COPY MUST BE RETURNED
TO
Cj#tr /)7')
/ 7/-
I NFORMAT I ON SECTION p
NORTHERN FOREST RESEARCH CENTRE
5320 • 122 STREET
EDMONTON 5, ALBERTA .
T$139%
Y
NITROGEN AND PHOSPHORUS REQUIREMENTS DURING THE EARLY
GROWTH OF WHITE SPRUCE SEEDLINGS
61
NOTES
NITROGEN AND PHOSPHORUS REQUIREMENTS DURING THE EARLY
GROWTH OF WHITE SPRUCE SEEDLINGS
Most studies of the response of conifer seedlings to various levels of mineral nutrition have employed entirely autotrophic plants. However, current forest-regeneration research and operations with first-year seedlings often require a knowledge
of the response of seedlings during their heterotrophic-to-autotrophic transition,
since this is the period during which nutrients are first applied in the greenhouse.
One feature of this growth period is that the plant utilizes internal as well as
external nutrition, and therefore may not respond to changes in the levels of externally applied nutrients. Responses to an increased supply of nitrate nitrogen have
been observed in the leaves and roots, but not in the stems, of lodgepole pine
(Pinus contorta Dougl. var. latifolia) seedlings six weeks after sowing (2). These
responses indicate that for lodgepole pine the transition begins within six weeks.
Since white spruce [Picea glauca (Moench) Voss] attains only about half the dry
weight of lodgepole pine in the same time period, an experiment was conducted to
determine whether white spruce could respond to different external levels of nitrogen
or phosphorus under environmental conditions similar to those used in the lodgepole pine study.
Plants were grown in perlite-vermiculite and harvested six weeks from sowing
in the same manner as described previously (2) for lodgepole pine. The nutrient
solutions used are given in Table 1. With the exception of the 6.2 ppm phosphorus solution, which had a pH of 7.4, the nutrient solutions had pH's of 6.1 to 6.7.
The average dry weights of the six-week-old seedlings grown under nine nitrogen regimes and at 62 ppm phosphorus are given in Table 2. Increasing the nitrogen supply, regardless of the nitrogen form, resulted in growth responses in the
leaves but not in the roots, and therefore markedly reduced the root-to-leaf weight
ratios. The nitrogen treatments did not produce significant differences in the dry
Table 1. Composition of nutrient solutions used to grow white spruce seedlings
Milliliters of stock soln./l. of aqueous nutrient
Stock solution
0.2 M Ca(NO3)24F120
0.2 M CaCl2 . 2H 20
0.2 M NH 4C1
0.2 M NI-1 4N° 3
0.2 M KH 2 PO 4
0.2 31 NaH 2 PO 4
0.2 Al KCl
0.2 Al MgSO 4 . 7H 20
FeEDTA*
Microt
Nitrate
(ppm)
Ammonium
(ppm)
Ammonium
nitrate (ppm)
Phosphate
(ppm)
5.6 56 112
5.6 56 112
5.6 56 112
6.2 62 124
0
20
0
1
10
0
0
10
2
1
20
0
0
0
1
0
9
10
2
1
1
19
0
0
10
0
(1
10
2
1
10
10
0
0
10
0
0
10
2
1
20
0
0
0
10
0
0
10
2
1
0
20
2
0
10
0
0
10
2
1
0
20
20
0
10
0
0
10
2
1
0
20
40
0
10
0
0
10
2
1
0
20
0
10
10
0
0
10
2
1
0
20
0
20
10
0
0
10
2
1
20
0
0
0
10
0
0
10
2
1
20
0
0
0
10
10
0
10
2
1
*Contains: 1.92 g of FeEDTA (13% Fe) /100 ml H2O.
tContains: (in g/1. H2O) 11 2 130 3, 2.86; MnC1f4F1•0, 1.80; ZnC12, 0.10; CuC12'21-120, 0.13; Na2Mo042H20, 0.02.
Can. J. Plant Sci. 51: 61-63 (Jan. 1971)
CANADIAN JOURNAL OF PLANT SCIENCE
62
Table 2.
Dry weights (mg/plant) and root-to-leaf ratios of six-week-old white spruce grown
under various nitrogen regimes
Nitrogen level (ppm N)
Plant part
Nitrogen form
5.6
56
112
Leaf
Nitrate
Ammonium
Ammonium nitrate
5.4 a*
5.1 a
6.0 a
9.0 b
8.2 b
8.6 b
8.3 b
9.1 b
9.1 b
Stem
Nitrate
Ammonium
Ammonium nitrate
1.1 a
0.8 a
0.9 a
0.9 a
0.8 a
1.0 a
0.9 a
0.8 a
1.0 a
Root
Nitrate
Ammonium
Ammonium nitrate
2.6 a
2.7 a
3.1 a
2.7 a
2.3 a
3.0 a
2.3 a
2.2 a
2.9 a
Whole plant
Nitrate
Ammonium
Ammonium nitrate
9.1 a
8.6 a
10.0 a
12.6 b
11.3 b
12.6 b
11.5 b
12.1 b
13.0 b
Root/leaf
Nitrate
Ammonium
Ammonium nitrate
0.48 a
0.53 a
0.52 a
0.38 b
0.28 b
0.35 b
0.28 c
0.24 c
0.32 b
*Values are the mean of four replications each consisting of 40 plants. Values in the same row that are followed by the
same letter do not differ significantly at the 95% level.
weights of the stems. The intermediate nitrogen level, i.e., 56 ppm, was quite
adequate for the early growth of white spruce with all three nitrogen sources.
Durzan and Steward (1) have indicated that for 16-month-old white spruce
after the second growing season, fresh weights are greater if nitrate rather than
ammonium is used as the nitrogen source. However, Swan (4) and McFee and
Stone (3) found the opposite to be true for the dry weights of younger plants.
In the present experiment, these two nitrogen sources gave about the same growth
responses, and ammonium nitrate produced the same or slightly greater dry weights
than either nitrate or ammonium alone (Table 2).
The phosphorus requirement of the plants was lower than the nitrogen requirement, and significant growth responses were not produced by raising the
phosphate concentration above the lowest level, i.e., 6.2 ppm P. The nitrogen
level in this series was 112 ppm as nitrate. The average dry weights (mg/plant)
for the three phosphate levels were: leaf 8.0, stem 0.9, root 2.2 and whole plant
11.0; and the average root/leaf ratio was 0.27. In this regard, Swan also found
6.2 ppm phosphorus to be adequate for the top growth of 15-week-old white spruce
with ammonium nitrate as the nitrogen source.
Assuming that the sequence of growth responses to nitrogen is similar in
lodgepole pine and white spruce, then the lack of response in the roots of white
spruce indicates that it has a longer heterotrophic growth period than lodgepole
pine, and that the growth response of these species to increased nitrogen supply
probably occurs first in the leaves, then in the roots, and finally in the stem. High
levels of nitrogen or phosphorus nutrition cannot be used for promoting root growth
of spruce during its first six weeks of growth. A nutrient solution containing 50
to 60 ppm nitrogen, as ammonium nitrate, and 6 to 7 ppm phosphorus is quite
adequate for the early growth of white spruce under conditions where the rooting
medium does not reduce the availability of these elements.
NOTES
63
DURZAN, D. J. and STEWARD, F. C. 1967. The nitrogen metabolism of Picea glauca
(Moench) Voss and Pinus banksiana Lamb. as influenced by mineral nutrition. Can. J.
Bot. 45: 695-710.
ETTER, H. M. 1969. Growth, metabolic components and drought survival of lodgepole
pine seedlings at three nitrate levels. Can. J. Plant Sci. 49: 393-402.
McFEE, W. W. and STONE, E. L. Jr. 1968. Ammonium and nitrate as nitrogen
sources for Pinus radiata and Picea glauca. Soil. Sci. Soc. Amer. Proc. 32: 879-884.
SWAN, H. S. D. 1960. The mineral nutrition of Canadian pulpwood species. 1. The
influence of nitrogen, phosphorus, potassium and magnesium deficiencies on the growth
and development of white spruce, black spruce, jack pine and western hemlock seedlings
grown in a controlled environment. Tech. Rep. No. 168, Pulp and Paper Res. Inst. Can.,
Montreal.
Harold M. Etter
Forest Research Laboratory, Department of Fisheries and Forestry, Edmonton, Alberta.
Received July 2, 1970, accepted November 9, 1970.