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Chlorate Toxicity and Nitrate Reductase Activity in Tomato Plants
Author(s) -
HOFSTRA J. J.
Publication year - 1977
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1977.tb01524.x
Subject(s) - chlorate , nitrate reductase , nitrate , chemistry , ammonium , enzyme , nitrogen , botany , biochemistry , biology , inorganic chemistry , organic chemistry
Chlorate damage was studied in tomato plants ( Lycopersicum esculentum cv. Moneymaker) that were supplied with a nitrogen‐free nutrient solution or with a nutrient solution, containing either nitrate or ammonium as a nitrogen source. Damage was low in ammonium‐fed plants and high in nitrate‐fed plants and in nitrogen‐less plants. Nitrate reductase activity could be detected in all treatments, although the activity was highest in the nitrate‐fed plants. The hypothesis that chlorate can be used as a substrate by the enzyme nitrate reductase in higher plants, was studied and proved to be true for the tomato plants, as was found earlier for Escherichia and Chlorella . The affinity of the enzyme for chlorate was lower than for nitrate, the K m being 4 m M and 0.15 m M respectively. Induction of the enzyme by chlorate could not be detected. The enzyme activity was lowered in leaf discs after a 7 h treatment with chlorate and the inhibition was proportional to the chlorate concentration of the medium. The results were discussed in terms of competition between nitrate and chlorate at the uptake and the enzyme site and with regard to a possible influence of chlorate on synthesis and breakdown of the enzyme.