Definition of PLACOID. : of, relating to, or being a scale of dermal origin with an enamel-tipped spine characteristic of the elasmobranchs. ADVERTISEMENT.Greek plak-, plax flat surface.First Known Use: 1842.efinition of PLACOID. : of, relating to, or being a scale of dermal origin with an enamel-tipped spine characteristic of the elasmobranchs. ADVERTISEMENT. Greek plak-, plax flat surface. First Known Use: 1842.
A tree pruner is a class 1 lever. The fulcrum is where the two blades cross, and the load is what you are cutting. The effort is applied to the two handles.
1 We would then choose to root prune the trees during dormancy to help prepare the trees for digging outside of their optimal season.  Root pruning a tree will often slow down the growth of the tree. I often like to say that trees are not multi-taskers. Most trees are only capable of doing one thing at a time. They can either put out new roots or put out new leaves, but not both at the same time.