TAILIEUCHUNG - Báo cáo lâm nghiệp: "Nitrogen recycling"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài:Nitrogen recycling. | 654s Ann. Sci. For. 1989 46 suppl. 654s-659s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Nitrogen recycling in the apple Malus domestics Borkh. . Titus Department of Horticulture University of Illinois Urbana 1161801 . This paper summarizes the work of several graduate students and Research Associates with whom I have worked in recent years. Most of this work has been published but here I attempt to integrate these results into a comprehensive scheme. Some of this research was carried out at the University of Illinois Urbana Illinois . Other aspects were completed at University College Dublin Ireland. Our early work dealt with the uptake and translocation of various forms of nitrogen by young fruit trees. While this area of nitrogen metabolism is important the primary concern in this paper is the seasonal transformations of nitrogen in various tissues of an apple tree in which we have been engaged for the last several years. In looking into some early literature the recognition that the roots of the apple Malus domestica Borkh. could reduce nitrogen Eckerson 1931 and that amino acids are synthesized in apple roots Thomas 1927 took on new significance to us. And a report on the forms of nitrogen found in the tracheal sap of the apple was especially interesting Bollard 1957 . Our present concepts of nitrogen recycling in the apple began to take shape with the work of Spencer who concentrated her research on the biochemical and enzymatic changes in apple leaf tissue during autumnal senescence. She found that one of the first indications of senescence in apple leaves was the decline in leaf protein which began in the second week of August when day length first became less than 14 h Spencer and Titus 1972 . This decline of protein was not attributed to declining RNA or DNA since both continued to increase for an additional 30 days. The ability of apple leaf discs to incorporate i4C leucine into protein was unimpaired during the time when .

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