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Absorption of Atmospheric NO 2 by Spruce ( Picea abies ) Trees. III. Interaction with Nitrate Reductase Activity in the Needles and Phloem Transport
Author(s) -
Weber P.,
Thoene Barbara,
Rennenberg H.
Publication year - 1998
Publication title -
botanica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 0932-8629
DOI - 10.1111/j.1438-8677.1998.tb00722.x
Subject(s) - nitrate reductase , picea abies , nitrate , phloem , chemistry , cycloheximide , girdling , horticulture , puromycin , botany , abies alba , biochemistry , biology , protein biosynthesis , organic chemistry
In order to compare the effects of excess pedospheric and atmospheric nitrogen supply on nitrate reductase activity (NR. EC 1.6.6.1) excised spruce branches were exposed to nitrate solutions or were fumigated with NO 2 . Immersion of spruce branches in 6 mM nitrate caused an increase in NR activity by a factor of 14 or 19 in current‐year and in one‐year‐old needles, respectively, as compared to controls incubated in tap water. Exposure to 65 nl I −1 NO 2 increased NR activity by a factor of 1.5 in current‐year needles and by a factor of 2.5 in one‐year‐old needles as compared to non‐fumigated controls. Addition of cycloheximide (0.17 μM) or puromycin (200 μM) to the incubation solution prevented the induction of NR activity from both nitrate and NO 2 exposure. This finding indicates that induction of NR activity by both atmospheric NO 2 or increased nitrate supply of the needles is both caused by de‐novo synthesis of NR protein. The increase in NR activity in needles of branches still attached to the tree as a consequence of exposure to 65 nl I −1 NO 2 was found to be a transient phenomenon. The increase persisted for several days only and was no longer observed after one week of sustained NO 2 exposure. An interruption of phloem transport by girdling, applied subsequent to the induction of NR activity by atmospheric NO 2 , prevented the decrease in NR activity. Apparently, export out of the exposed needles and phloem transport within the stem are involved in the regulation of NR activity upon NO 2 exposure.