Effect of plant growth regulators and different nitrogen sources on NADP-isocitrate dehydrogenase activity of radish cotyledons

NADP-isocitrate dehydrogenase (NADP-ICDH) activity of radish (Raphanus sati vus L.) seedlings pretreated with various plant growth regulators: KiN, GA, and ABA and different nitrogen sources viz. KNO3, NH4Cl and NH4NO3 in ligh t and dark was investigated. ICDH activity was significantly higher in ligh t than in dark; addition of different nitrogen sources reduced it to a grea ter extent in NO3 supplementation. Among hormonal treatment only KiN showed slight promotion with KNO3 and NH4NO3. On the other hand in light KNO3 and /or NH4NO3 promoted ICDH activity and among hormones, KiN significantly pro moted the activity in KNO3 and NH4NO3 supplemented seedlings while ABA was effective in NH4CL. It is suggested that in non-photosynthetic tissues, NAD P-ICDH provides both reductant and carbon skeleton for glutamate synthesis.