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Báo cáo lâm nghiệp: " A comparison of the photosynthetic radiation response of Scots pine shoots in direct and diffuse radiation"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: A comparison of the photosynthetic radiation response of Scots pine shoots in direct and diffuse radiation. | 469s Ann. Sci. For. 1989 46 suppl. 469s-472s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA A comparison of the photosynthetic radiation response of Scots pine shoots in direct and diffuse radiation p. Oker-Blom1 H. Smolander2 and T. Lahti3 1 University of Helsinki Department of Silviculture Unioninkatu 40 B 00170 Helsinki 2 Finnish Forest Research Institute Suonenjoki Research Station SF-77600 Suonenjoki and 3 University of Helsinki Botanical Museum Unioninkatu 44 SF-00170 Helsinki Finland Introduction The directional distribution of radiation incident on a coniferous shoot has been shown to have a large effect on the rate of shoot photosynthesis e.g. Zelawski et al. 1973 . In a multidirectional radiation field the irradiance on the needle surface area of a shoot becomes more evenly distributed than in the case of a highly directional field and the rate of photosynthesis per unit of intercepted radiation should logically be higher cf. Oker-Blom 1985 . The aim of this study was to compare the rates of photosynthesis of Scots pine Pinus sylvestris L. shoots in diffuse and direct radiation and to test a shoot photosynthesis model based on the hypothesis that shoot photosynthesis can be expressed as the integrated response of the photosynthetic units of the shoot which are assumed to have an invariant photosynthetic light-response curve. Materials and Methods The material consisted of 9 1 yr old shoots collected from a young Scots pine stand. The net rate of photosynthesis of the excised shoots was measured in a direct and a diffuse spherical radiation field using an open flow IRGA-system URAS 3G . The temperature in the assimilation chamber was 20 C ambient co2 concentration was 340 ppm and the air water vapor pressure deficit was 9 1 mbar. The distribution of radiation within each shoot was simulated using a Monte Carlo method cf. Smolander et al. 1987 and using a model describing shoot geometry based on certain morphological characteristics of the shoot