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Báo cáo lâm nghiệp: " Effects of water deficit on leaf in fast-growing tree species growth and initiation"

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Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Effects of water deficit on leaf in fast-growing tree species growth and initiation...

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Nội dung Text: Báo cáo lâm nghiệp: " Effects of water deficit on leaf in fast-growing tree species growth and initiation"

Effects of water deficit on leaf and initiation growth in fast-growing tree species W.J. Davies 1 J.S. Pereira 2 J.C. Metcalfe 1 Lancaster LA1 4YQ, Institute of Environmental and Biological Sciences, University of Lancaster, U.K., and 2 Department of Forestry, Instituto Superior de Agronomia, P-1399 Lisboa Codex, Portugal outside in 51 plots of nutrient-rich soil. Plots Introduction were covered with plastic to prevent surface evaporation from the soil or rewetting by rain or Eucalyptus globulus is becoming increas- dew. Plants were either watered to drip point ingly important in Mediterranean regions every day or received no water from d 0. Leaf for pulpwood production. Although the areas were calculated from regression equa- tions constructed using caliper measurements plant is highly drought tolerant, its high of leaf length and width and direct values of leaf productivity seems to be particularly sensi- areas obtained with a Li-cor leaf area meter. tive to water shortage (Pereira et al., Gas exchange studies were conducted using a 1986). These researchers have shown portable C0 porometer (H. Walz Messund 0 IH 2 that biomass production in young E. Regeltechnick, Effe!trich, F.R.G.). globulus growing in the field in Portugal can be increased by a factor of 3 under irrigation, and this has been related to an increase in foliage area (Borralho et al., Results and Discussion 1987). Most of our knowledge on the growth of Stomatal conductance and photosynthesis seedlings to date comes from field tree both clearly reduced by soil drying were experiments such as the above. In order (Fig. 1Although the stomata opened at to further our understanding of seedling the beginning of the photoperiod, they growth, the early growth patterns of juve- stayed open for less time as water stress nile E. globulus have been investigated developed and, after 10 d without water, under conditions of water deficit, in were almost closed in the afternoon. conjunction with detailed measurements Photosynthesis appeared to decline of gas exchange. linearly with conductance. In the longer term, a decline in biomass production under water shortage will result from Materials and Methods reduced assimilation rates and a decrease in leaf area, and Borralho et aL (1986) Experiments were conducted in Lisbon, Portu- recently reported that non-irrigated E. gal, where E. globulus seedlings were grown
had a smaller surface area per leaf initiation is important and, as demon- globulus unit of leaf than did irrigated plants. strated in Fig. 3, the initiation of new Provided the soil water deficit was not leaves at the apex of the dominant shoot is restricted with developing water stress. too severe, growth of the youngest leaves Indeed, Hsiao (1973) proposed that bud could still continue (Fig. 2), thus the reduc- tion in dry matter production appears to be formation and leaf initiation were more a result of more than purely a cessation of sensitive than leaf growth to water deficit and these results tend to confirm that growth. Our current studies suggest that
view. In addition, Pereira et al. (1987) production of three clones of E. globulus in the juvenile phase. In: Structural and Functional have attributed the decreased foliage area Responses to Environmentat Stresses: Water observed with water shortage to de- Shortage (Kreeb K.H., Richter H. & Hinckley creased leaf number. Our understanding T.M., eds.), SF’H Academic Publishing, The of the control of new leaf formation is limit- Hague ed at present and further research is being Hsiao TC. (1973) Plant responses to moderate water stress. Annu. Rev. Plant Physiol. 24, 519- directed in this area. 570 Pereira J.S., Pereira H., AraOjo M.C., Linder S., Ericsson T, Borralho N. & Leal L. (1989) Opti- misation of biomass production in E. globulus References plantations. A case study. In: Biomass Produc- tion by Fast Growing Trees. (Pereira J.S. & Borralho N., Araujo M.C. & Pereira J.S. (1987j Landsberg J.J., eds.), Kluwer, Dordrecht, in Influence of water supply in crown structure and press

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