Abstract
The lower shoots in horizontally placed apple trees exhibited much weaker development as well in light as darkness. Removing a narrow strip of bark along both sides of a horizontally placed apple tree improved markedly the growth of the lower buds. In poplars the same effect was received by surrounding the lower buds with semicircular incisions. The inhibition of the lower buds was also released by removing the apical bud and the upper ones. The presented results and those published earlier show that the mechanism responsible for inhibition of the lower buds acts in two steps: 1) gravity influences directly the system composed of a bud and the adjacent tissue of the stem. 2) the lower buds partly inhibited in the step "1" are further inhibited by a correlative mechanism which supresses all weaker buds. The second "step" reaction takes place also after a tree have been reverted back to the normal vertical position.
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