Effect of different nitrogen sources on growth and nitrogen metabolising enzyme activities in peanut (Arachis hypogaea L.) cell suspension cultures
1996
Mohd Pu'ad Abdullah | Marziah Mahmood | Mohd Arif Syed (Pertanian Malaysia Univ., Serdang, Selangor (Malaysia). Dept. of Biochemistry and Microbiology)
Peanut cell suspension cultures were initiated and established from four-week-old leaf callus. These were used to study the response of growth and nitrogen metabolising enzyme activities when the sources of nitrogen supply in the media were altered. Settled cell volume (SCV) of cells growth and nitrogen metabolising enzyme activities were monitored every two days over a 14-day-culture period. The present results indicate the presence of both ammonium assimilation pathways: the glutamine synthetase (GS)/glutamate synthase (GOGAT) and the glutame dehydrogenase (GDH)/glutamine synthase (GS) in peanut cell suspension cultures. Depending on sources of nitrogen supplied and age of cultures, enzyme activities in these pathway varied throughout the culture period. Nitrate induced the activity of nitrate reductase (NR) where high activity was observed in L6 medium containing both NO3 and NH4 as well as NO3 alone especially during early part of the growth phase. The activity was not detected when NH4 or glutamine was used as the sole source of nitrogen in the medium. Ammonium appeared to be the most important source of nitrogen that influences NADH-GDH and GS activities. The NADH-GDH was high during the early part of the exponential phase of growth while GS activity was maximal during the later part. Glutamine was found to enhance the activity of NADH-GOGAT but it did not significantly influence the activity of NADH-GDH and GS ezymes. The activity profiles of these enzymes in relation to various nitrogen sources applied in the medium are discussed
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