Ammonium and nitrate uptake and nitrate reductase activity of photoautotrophic callus cultures of the fern Platycerium coronarium (Koenig) DESV

Abstract

The uptake of nitrate and ammonium by callus of Platycerium coronarium from the culture medium was examined. Nitrate reductase activity of photoautotrophic callus cultures under CO2 enrichment was significantly lower compared to the cultures without CO2 enrichment, but higher than that of heterotrophic callus cultured on medium with 2% (wt/vol) sucrose. When sucrose concentration of the heterotrophic culture was lowered to 0.2%, nitrate reductase activity increased. The level of nitrate reductase activity increased by about 25% in the heterotrophic callus with an increase in 2,4-D from 2 μM to 10 μM, despite a decline in fresh weight gain. However, photoautotrophic cultures with 1% CO2 enrichment showed 20% decline in nitrate reductase activity and 45% decline in fresh weight gain with a similar increase in 2,4-D level. The rate of uptake of nitrate from the culture medium was unrelated to the level of nitrate reductase activity in the callus. For photoautotrophic callus under CO2 enrichment, the presence of 1% (vol/vol) CO2 generally resulted in the highest rate of nitrate uptake. The rate of uptake of ammonium was higher for callus cultured on 2 μM 2,4-D compared to that on 10 μM 2,4-D. © 1995 Society for In Vitro Biology.