Abstract:

Experiments were conducted with potted jujube to study the changing of NR activity in different organs and periods as well as the effect of different nitrogen forms on NR activity.The result showed:leaf was the main organ which assimilated NO^-₃.The new-leaf has the highest NR activity,then was the mid-leaf.The activity of down-leaf was the lowest.NR activity of fine-root was higher than other roots but lower than leaves,the activity of absorption roots could not be observed.Further,the diurnal variation of NR activity in vivo showed a peak curve and maximal NR activity appeared at about 11:00 or so.The change of seasons showed NR activity in leaves was higher in August comparing with other seasons and NR activity of roots appeared three peak in Jun,Aug and Oct.In addition,the effect of different nitrogen forms on NR activity indicated a peak appeared after 4 h daubing leaves with 40 mmol·L^-1 KNO₃.NR activity in vivo could be raised by lower concentration of KNO₃(<80 mmol·L^-1)and be increased no more with higner concentration of KNO₃(>80 mmol·L^-1).NR activity could also be improved by daubing urea.In addition,NR activity was not significant effected after daubing Glu or Gln,however,was remarkablely decreased by Gly.Fertilization in soil showed urea could maintain the higher NR activity in leaves and increased the ability of assimilation NO^-₃.

Key words: winter jujube, NR activity, nitrogen form, diurnal variation, season variation