Báo cáo lâm nghiệp: Allocation of dry matter in Eucalyptus in response to nitrogen supply grandis seedling

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Báo cáo lâm nghiệp: "Allocation of dry matter in Eucalyptus in response to nitrogen supply grandis seedling"Allocation of dry matter in Eucalyptus grandis seedlingsin response to nitrogen supply P.G. Jarvis 2R.N. Cromer1 CSIRO Division of Forestry and Forest Products, Box 4008, Queen Victoria Terrace, A.C.2600, P ro andAustralia, andDepartment2 of Forestry and Natural Resources, University of Edinburgh, The Kings Buildings,Mayfield Road, Edinburgh EH9 3JU, U.K Material and MethodsIntroduction Seedlings of Eucalyptus grandis were grown inIt is well established that a high level of a naturally lit glass house with day/night tem-nutrient supply increases shoot growth peratures of 27i21°C, for 8 and 16 h, respec-relative to root growth in trees and a shift tively. Seedlings were grown in 5 aeroponicin carbon allocg±ian to roots was observed ’growth units’ designed to permit seedlings to grow at constant relative growth rates (Rg) andin seedlings of Eucalyptus delegatensis stable internal nutrient concentrations (Ingestadwith increasing nutrient stress (Cromer et and Lund, 1986). Nutrient solutions, made upa/., 1984). This shift can have a major so that nitrogen was the element most limitingeffect on stemwood production but similar growth, were added to circulating solutions at relative addition rates between 0.04 and 0.12 2studies have not been reported for E d- This technique enabled stable seedling . 1grandis. nitrogen concentrations [N] and R to be main- 9 Despite reports of (often dramatic) tained during experimental periods of 40-60 d in 4 growth units. Seedlings from each growthincreases ingrowth of E. grandis following unit were harvested on 4 occasions at intervalsapplication of nutrients, we have little of 7-14 d depending upon growth rate. of mecha-understanding physiological responsible for such responses. It isnismsrecognised that leaf area is a major deter-minant of plant productivity but the impor- Resultstance of leaf development in comparisonwith dry matter partitioning and rate of assimilation is not well understood2C0 Rg and [N] were relatively stable over time(see Cannel, 1985). In this paper, for each treatment (data not shown). Allo- we ex-amine the way in which rate of nitrogen cation of dry matter to stems and rootssupply to E. grandis seedlings affects allo- was examined in relation to leaf mass andcation of dry matter. data from each harvest and treatment This resulted in a strong linear correla-combination were pooled and tested using tion (r2= 0.988) between Ln f and Lnan allometric relationship (Ledig, 1983): IN! but with a major influence of [N] onLn W!=a+/3!Ln W (1) allocation as shown in Fig. 2. The regres- sion slope was not significantly differentwhere W is stem mass, W is leaf mass, S from unity and the ratio of W! to W wasa is a constant and 0 is the slope. A 1.0 when [N] approximated 16 6 mg.g-I . Atstrong linear correlation (r 0.992) was 2 = values of [N] above this, root to leaf ratiofound between Ln W and Ln W as shown S was less than 1.0.in Fig. 1. Leaf growth was in ...