| Abstrakt: |
Glassiness of willow (Salix babylonica L.) can be controlled by the amount of ammoniacal nitrogen in the culture medium. In this study, glutamate dehydrogenase (EC 1.4.1.3) activity was observed in the different parts of the plant during induction of the vitrification process. The apparent affinity constants of the enzyme for ammonium were determined. The root enzyme displayed the highest affinity for ammonium (Km, 0.70 - 2.25 mM), and correlatively, its activity was linked to the amount of ammonium applied and to the development of the vitreous state. Although it has been shown that ethylene, matric potential and high cytokinin content are implicated in vitrification, the present study shows that a knowledge of the affinity constants for ammonium, when the ammoniacal nitrogen content of the culture medium is taken into account, can predict the risk of the plant material becoming vitreous. [ABSTRACT FROM AUTHOR] |
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