This work was carried out to study the effects of roots pruning with cupper sulphate, cupper
oxychlorate and ethephon (2-cloroethtlphosphonic acid) on growth and quality of
Pinus taeda
L. seedlings
produced in tubes. The treatments with cupper sulphate or cupper oxychlorate were applied on the tubes
(before their filling with the substrate for plantation), by immersing them into a mixture of equal parts of
water and latex paint, at cupper doses of 0, 12, 24, 36, and 48g L
-1 of solution (paint + water). The ethefon
was sprayed to the aerial part of seedlings (10-15cm height) at 0, 50, 75, 100, and 125 mg (a.i.) L
-1. The
experiment followed a completely randomized block design with five replicates. Considering the cupper
sources, only cupper sulphate reduced the attributes of root dry matter (mainly by inhibiting the development
of lateral roots), collar diameter, seedlings height, and aerial dry matter, with the increase of product dose.
The increment of cupper sulphate doses resulted in a higher increase of copper concentration in the substrate
than the increase of cupper oxychlorate doses. The increment of cupper oxychlorate doses did not reduce the
total root dry matter, but increased the number of lateral roots at the median and higher portion of the root system. Cupper sulphate significantly reduced the emission of lateral roots, as opposed to the effect of
cupper oxychlorate. Therefore, the use of increasing doses of cupper oxychlorate seems to show a more
positive effect on root pruning, compared to cupper sulphate, since a seedling with a large number of lateral
roots of small length is desirable aiming the seedling establishment after transplantation. The increase of
ethefon dose sprayed at seedlings aerial part increased the principal root dry matter and the number of later
roots at the median (linear effect) and lower (quadratic effect) parts of root system. There was no effect of
ethefon on the other seedling growth attributes.
