Báo cáo lâm nghiệp: "Comparative study species"

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assimilation in woodland of Comparative study nitrogen species J. Pearson, E.C.M. J.L. Kershaw Clough Department of Biology (Darwin), University College London, Gower Street, London H!F6B7;U./
Current needle development in Sitka for nitrate assimilation when the capability spruce is earlier than that in Scots pine. soil is fertilized. The foliar application has The 1 yr old needles would seem to be net increased leaf NR activity when compared exporters whereas the current needles are to the unfertilized control. With the grow- net importers of nitrogen early on in devel- ing concern over N0! pollutants in the opment, especially in Scots pine (Fig. 1 atmosphere, these different leaf re- ). Sitka spruce is predominantly a root assi- sponses may be important in defining how milator of nitrate, but maintains a relatively resistant to acid rain a particular tree spe- cies might be. A low capacity for leaf nitro- low, yet constitutive capacity for shoot assimilation (Fig. 1 and Table I). gen assimilation may mean that a species would be unable to buffer itself against However, when the shoots are sprayed such aerial inputs. Table it shows that the with nitrate the leaves do show an in- pool of free amino acids is highest in crease in NR activity. Poplar exhibits the those 2 species, pine and birch, with the type of response that could be considered higher leaf NR, Such pools might repre- typical of the nitrophilous pioneer be- sent an important buffering capacity in havior. It has both a high leaf and root relation to acid rain inputs (Raven, 1988).
Certainly, of the broad leaf trees, References it that recent reports for acid rain seems damage are becoming more common for Raven J.A. (1988) Acquisition of nitrogen by the the climax species beech, which seems to shoots of land plants: its occurrence and impli- have a low leaf NR capacity. cations for acid-base regulation. New PhytoL 109,1-20 Smirnoff N., Todd P. & Stewart G.R. (1984) The occurrence of nitrate reduction in the leaves of woody plants. Ann. Bot. 54, 364-374 Acknowledgment E.E. & R.L. Stewart G.R., Specht Hegarty (1988) Inorganic nitrogen assimilation in plants The work was funded of Australian rain forest communities. special project grant Physiol. by a from the NERC. Plant. 74, 26-33