Báo cáo lâm nghiệp: Carbon and phosphorus relations in and non-mycorrhizal pine seedlings

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Báo cáo lâm nghiệp: "Carbon and phosphorus relations in and non-mycorrhizal pine seedlings"Carbon and phosphorus relations in mycorrhizaland non-mycorrhizal pine seedlingsJ.V.D. Rousseau C.P.P. ReidDepartment 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 theresponses to mycorrhizal fungus inocula- low P regime (LP-M) also had a 75%tion and applied phosphorus were exam- greater photosynthetic rate, but less thanined to determine which responses were greater biomass than did the LP-N 30%similar to enhanced phosphorus nutrition seedlings. Mycorrhizal seedlings grownand 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-Nwk 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 10.011 of P) with and without inoculation of Piso- LP-M seedlings showed similar but less91glithus 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 substantialdetermination of P content and dry weight of increase in the fine-root P concentration offoliage, 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 underthe high phosphorus regime (HP-N) had a Mycorrhizal development, as measured55% greater photosynthetic rate and by the percentage of short-roots infected, 100% for the LP-M The similarity of the photosynthetic rates seedlingswas nearand 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 seedlingsDiscussion and Conclusions grown with the high phosphorus fertilizer 1 ) only a small increase in regime caused: phosphorus content and concentrationMycorrhizal development in seedlings within the plant; 2) no change in photo- ...