Ottoline Leyser from the University of York says that after a plant is pruned, all the inhibited shoot tips compete with each other to grow.

VOA: special.2009.10.13

Elizabeth Blackburn compares them to the plastic tips on the ends of shoelaces.

VOA: special.2009.10.07

"We are telling parents, 'Hey this is what was available on the Internet,this is what your kids are able to do and some basic tips on if you want to increase security this is how you can do it,"

VOA: standard.2009.12.20