tailieunhanh - Báo cáo lâm nghiệp: "Biochemical aspects of inorganic nitrogen assimilation by woody plants"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài:Biochemical aspects of inorganic nitrogen assimilation by woody plants. | 648s Ann. Sci. For. 1989 46 suppl. 648s-653s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Biochemical aspects of inorganic nitrogen assimilation by woody plants . Stewart J. Pearson . Kershaw and . Clough Department of Biology Darwin Building University College London Gower street London WC1E 6BT . Introduction For the majority of woody plants the mineralization of organic nitrogen in soil provides their source of nitrogen for growth. The relative activities of ammonifiers and nitrifiers as influenced by a complex interaction of abiotic and biotic factors will determine the availability of ammonium and nitrate ions both spatially and temporarily. Nitrification rates show considerable variation in different forest soils and for the most part this is unrelated to total nitrogen pH or carbomnitrogen ratio Robertson 1982 . Not surprisingly woody plant species exhibit differences in their capacities to utilize nitrate and ammonium ions see . Chandler 1981 . These differences relate in part at least to the prevalent form of available nitrogen in their ecological niche. However the assimilation of ammonium and nitrate ions carries different potential costs with respect to energy and water requirements with ammonium ions being the more cost-effective nitrogen source Raven 1985 . Differences in cost effectiveness of nitrate and ammonium ions may be important with respect to the growth of understorey trees and shrubs in light- and water-limited environments particularly as these species have high maintenance costs. In this report we will consider the characteristics of inorganic nitrogen assimilation in woody plants. The occurrence and localization of nitrate reductase and glutamine synthetase isoforms will be discussed. Nitrate reduction Nitrate assimilation in higher plants is catalyzed by 2 enzymes pyridine nucleo-tide-linked nitrate reductase and ferredoxin-linked nitrite reductase. The capacity for nitrate reduction is widespread among .