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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 soil temperature on gas exchange and morphological structure of shoot and root in 1 yr old Scots pine (Pinus sylvestris L.) seedlings. | 459s Ann. Sci. For. 1989 46 suppl. 459s-463s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Effects of soil temperature on gas exchange and morphological structure of shoot and root in 1 yr old Scots pine Pinus sylvestris L. seedlings J. Lippu and p. Puttonen Department of Silviculture University of Helsinki Unioninkatu 40 B 00170 Helsinki Finland Introduction Low soil temperature is one of the environmental factors affecting early growth and survival of forest seedlings in boreal ecosystems. With regard to gas exchange and growth soil temperature is often underoptimal in spring and early summer Soderstrom 1974 . In cold soils the viscosity of water increases and the permeability of roots to water decreases Lopushinsky and Kaufmann 1977 which leads to decreased gas exchange and growth. The aim of this study was to examine certain structural and physiological attributes of acclimation in Scots pine Pinus sylvestris L. seedlings at different soil temperatures. The following structural factors were examined 1 timing and amount of shoot growth 2 amount of needle and root growth. The following physiological factors were examined 1 net co2 assimilation rate A 2 transpiration E and 3 conductance to water vapor g . Materials and Methods One yr old Scots pine seedlings growing 30 d at 13 c 18 h photoperiod 250 pmol m-2-s-Ị irradiance and 7 mbar vapor pressure deficit in a mixture of low humified Sphagnum peat and perlite were exposed to 3 different soil temperature treatments 8 c 12 c and a changing temperature from 5.5 to 13.0 C . Soil temperature was controlled by immersing sealed pots into a water bath thermostated by a Lauda RS-102 thermostat. Net co2 assimilation A transpiration E and leaf conductance to water vapor g were measured by an LI-6200 portable photosynthesis system LI-COR Inc. which includes an LI-6250 infrared gas analyzer an LI-6200 control console and a leaf chamber. The relative height growth rate RHGR was calculated using the equation RHGR 1
