Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Carbon and phosphorus relations in and non-mycorrhizal pine seedlings...
Nội dung Text: Báo cáo lâm nghiệp: "Carbon and phosphorus relations in and non-mycorrhizal pine seedlings"
Carbon and phosphorus relations in mycorrhizal
and non-mycorrhizal pine seedlings
J.V.D. Rousseau C.P.P. Reid
Department of Forestry, University of Florida, IFAS, Gainesville, FL, U. S.A.
Introduction greater biomass than did
150% non-
grown under the
mycorrhizal seedlings
low phosphorus regime (LP-N) (Fig. 1a,
Several physiological and developmental
b). Mycorrhizal seedlings grown under the
responses to mycorrhizal fungus inocula- low P regime (LP-M) also had a 75%
tion and applied phosphorus were exam-
greater photosynthetic rate, but less than
ined to determine which responses were
greater biomass than did the LP-N
30%
similar to enhanced phosphorus nutrition
seedlings. Mycorrhizal seedlings grown
and which were more unique to the
under the high phosphorus regime (HP-M)
mycorrhizal association. showed no difference in photosynthetic
rate over the HP-N seedlings. However,
HP-M seedlings had 12% less biomass
than HP-N seedlings.
Materials and Methods
The phosphorus content and foliar and
fine-root P concentrations were, respec-
Pinus taeda L. seedlings, initially grown for 10
tively, 8, 4 and 2 times greater in HP-N
wk under low P conditions, were subjected to a
than in LP-N seedlings (Fig. 1c, d, e).
2 x 2 factorial design of 2 P levels {0.1 and 10.0
11 of P) with and without inoculation of Piso- LP-M seedlings showed similar but less
91g
lithus tinctorius (Pers.) Coker and Couch. After dramatic increases over the LP-N seed-
an additional 7 wk, photosynthesis by all seed-
lings in P content and foliar P concen-
lings was measured followed by harvesting and
tration. However, there was a substantial
determination of P content and dry weight of
increase in the fine-root P concentration of
foliage, stem and roots.
the LP-M over the LP-N seedlings, even
exceeding levels of the HP-N seedlings.
For seedlings grown under high phos-
Results
phorus conditions, inoculation with mycor-
rhizal fungus significantly increased the
foliar P concentration.
Non-mycorrhizal seedlings grown under
the high phosphorus regime (HP-N) had a Mycorrhizal development, as measured
55% greater photosynthetic rate and by the percentage of short-roots infected,
100% for the LP-M The similarity of the photosynthetic rates
seedlings
was near
and almost 80% for the HP-M of LP-M plants with HP-N and HP-M
seedlings
plants, without a concomitant increase in
(Fig. 1 f).
dry matter, may suggest a substantial
respiration cost of the mycorrhizas.
Mycorrhizal inoculation of seedlings
Discussion and Conclusions grown with the high phosphorus fertilizer
1 ) only a small increase in
regime caused:
phosphorus content and concentration
Mycorrhizal development in seedlings within the plant; 2) no change in photo-
grown under low P conditions had a quali-
synthetic rate; and 3) an actual 12%
tative effect similar to adding phosphorus
decrease in biomass. This biomass loss
fertilizer to non-mycorrhizal plants for all
by mycorrhizal plants may represent
parameters examined. In quantitative increased respiration costs of the mycor-
terms, adding high phosphorus had a far rhizal root system.
greater effect than inoculation, with two
important exceptions, photosynthesis and
fine-root phosphorus concentration. The
high level of fine-root phosphorus concen- References
tration in mycorrhizal seedlings indicates
that phosphorus was being preferentially
Harley J.L. & McCready C.C. (1952) The up-
stored in the mycorrhizal fungus, an idea
take of phosphate by excised roots of the
originally suggested by the biochemical beech. 11. Distribution of phosphorus between
evidence of Harley and McCready (1952). host and fungus. New Phytol. 51, 343-348
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