EFFECT OF COPPER TRAY TREATMENT ON EUCALYPTUS GRANDIS (HILL EX MAIDEN) SEEDLING GROWTH

Chemical pruning of the roots of seedlings growing in containers not only prevents root penetration into polystyrene containers, but also results in a changed root distribution within the plug with fewer outer ‘caged’ roots and more internal branching.

The use of a Cu based paint on hard plastic trays where root penetration is not a problem, but root distribution may be, was tested using Eucalyptus grandis. Root geometry in plug systems has been blamed for lodging some years after transplanting. This research examined the effects on root plug formation and subsequent regrowth potential of inhibited root apices.

At 14 weeks from sowing Cu tray treatment resulted in a greater seedling collar diameter, but at 21 weeks seedling height, leaf area, stem and root dry mass were not significantly different despite very different root configurations in the plug. The starch percentage in leaves, stems and roots was also not significantly different in seedlings from treated and untreated trays.

Highly significant differences in the pattern of root emergence from the plug after transplanting were recorded. Only 18% of roots emerging from untreated plugs emerged from the top one third of the plug compared with 40% of roots from treated plugs. Treated root systems also produced a greater number of lateral roots (53 compared with 34). Keeping seedlings in plugs for 21 weeks as compared with 14 weeks resulted in less than half the number of roots emerging after transplanting.