THE EFFECT OF NITROGEN ON FINE WHITE ROOT PERSISTENCE IN CHERRY (PRUNUS-AVIUM)

The persistence of white roots in cherry (Prunus avium) grown under two levels of nitrogen (high and low), was studied directly using a non-destructive borescope system. Plant growth and nitrogen uptake was increased by the extra nitrogen. Persistence times of white roots were significantly affected by several factors such as nitrogen level, time of appearance and depth in the pot. Suberisation of white roots tended to be late in the growing season, and roots produced in the middle of May persisted as white for significantly longer (5.9 weeks) than those produced in early July (2.5 weeks). Also, roots that appeared at the foot of the pot remained white for longer (5.6 weeks) than roots at the surface of the pot (2.7 weeks). Results also suggest that white root persistence was greater for trees with the lower rate of application of nitrogen (4.5 weeks under low nitrogen compared to 3.6 under high nitrogen).