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

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 speciesgrowth and initiation...
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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 growthin fast-growing tree species W.J. Davies 1 J.S. Pereira 2J.C. Metcalfe1 Lancaster LA1 4YQ, Institute of Environmental and Biological Sciences, University of Lancaster,U.K., and2 Department of Forestry, Instituto Superior de Agronomia, P-1399 Lisboa Codex, Portugal outside in 51 plots of nutrient-rich soil. PlotsIntroduction were covered with plastic to prevent surface evaporation from the soil or rewetting by rain orEucalyptus globulus is becoming increas- dew. Plants were either watered to drip pointingly important in Mediterranean regions every day or received no water from d 0. Leaffor pulpwood production. Although the areas were calculated from regression equa- tions constructed using caliper measurementsplant is highly drought tolerant, its high of leaf length and width and direct values of leafproductivity 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 a1986). These researchers have shown portable C0 porometer (H. Walz Messund 0 IH 2that biomass production in young E. Regeltechnick, Effe!trich, F.R.G.).globulus growing in the field in Portugalcan be increased by a factor of 3 underirrigation, and this has been related to anincrease in foliage area (Borralho et al., Results and Discussion1987). Most of our knowledge on the growth of Stomatal conductance and photosynthesis seedlings to date comes from fieldtree both clearly reduced by soil drying wereexperiments such as the above. In order (Fig. 1Although the stomata opened atto further our understanding of seedling the beginning of the photoperiod, theygrowth, the early growth patterns of juve- stayed open for less time as water stressnile 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 declineof gas exchange. linearly with conductance. In the longer term, a decline in biomass production under water shortage will result fromMaterials 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-globulusunit 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 budcould still continue (Fig. 2), thus the reduc-tion in dry matter production appears to be formation and leaf initiation were morea result of more than purely a cessation of sensitive than leaf growth to water deficit and these results tend to confirm thatgrowth. Our current studies suggest thatview. In addition, Pereira et al. (1987) production of three clones of E. globulus in the juvenile phase. In: Structural and Functionalhave attributed the decreased foliage area Responses to Environmentat Stresses: Waterobserved with water shortage to de- Shortage (Kreeb K.H., Richter H. & Hinckleycreased leaf number. Our understanding T.M., eds.), SF’H Academic Publishing, Theof the control of new leaf formation is limit- Hagueed at present and further research is being Hsiao TC. (1973) Plant responses t ...