TAILIEUCHUNG - Báo cáo lâm nghiệp: "The effect of nitrogen content on the of Scots pine needles and shoots photosynthesis"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: The effect of nitrogen content on the of Scots pine needles and shoots photosynthesis. | 473s Ann. Sci. For. 1989 46 suppl. 473S-475S Forest Tree Physiology E. Dreyer etal. eds. Elsevier INRA The effect of nitrogen content on the photosynthesis of Scots pine needles and shoots H. Smolander1 and p. Oker-Blom2 1 The Finnish Forest Research Institute Suonenjoki Research Station SF-77600 Suonenjoki and 2 University of Helsinki Department of Silviculture Unioninkatu 40 B SF-00170 Helsinki Finland Introduction A close dependency between photosynthetic capacity and nitrogen content of leaves has been shown . DeJong 1982 . For coniferous trees however a large variation in the relationship has been found. It has been proposed that the reason for this could be that the nitrogen content by affecting needle growth changes the pattern of mutual shading within a shoot which is the basic element used in studying photosynthesis of coniferous trees Linder and Rook 1984 . The aim of this study was to analyze separately the effect of nitrogen content on the photosynthetic capacity of individual needles and on within-shoot shading. Needle photosynthesis was approximated by measuring the photosynthesis of thinned shoots in a diffuse radiation field. Within-shoot shading was quantified in terms of the mean silhouette area to total needle area ratio of a shoot which determines the relative interception rate per unit of needle area on the shoot Oker-Blom and Smolander 1988 . Materials and Methods One yr old experimental shoots were collected from 5 young Scots pine Pinus sylvestris L. stands in Suonenjoki 62 09 N 27 05 E between 5 and 30 June 1988. The sites of the stands varied from poor sandy soil with Callu-na vulgaris vegetation to a fertile site with grass-herb vegetation. A randomly selected shoot from the uppermost whorl of each tree was used in measurements of photosynthesis. Morphological characteristics and silhouette to total needle area ratios were measured for a shoot from the uppermost whorl and for 1st order and 2nd order shoots just below. The .

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