الفهرس 
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Abstract
Experiments were conducted in the field, under controlled conditions in growth chambers, and in the greenhouse to study the environmental and biological factors affecting nitrate reductase in navy beans (Phaseolus vulgaris L.)
These factors included plant part studies, stage of development, variety, availability of nitrate, soil water stress, and other chemical substances, particularly simazine and chlorate. The role of nitrate as an inducing factor was studied. The possible biological interaction between enzymatic assimilation of nitrate and atmospheric nitrogen fixation was investigated.
The distribution of enzyme activity, nitrate and protein varied greatly in different parts of the plant. The leaves showed higher enzyme activity than did the root, nodules, stems, and petioles at the same phys.io1ocicai age.
The enzyme could not be detected in leaf tissues of bean plants grown in sterile cultures with anunonium sulphate in the absence of nitrate, Plants starved of nitrate for short