Interesting question! As I understand the aging process, DNA is constantly being damaged by cosmic rays, by chemical pollution, etc. DNA has the ability to repair most such damage, but not all. Eventually the damage builds up so there are "errors" in the DNA, and new tissue isn't as good as the old tissue. (Being made of old tissue now, the subject is a bit personal for me!) So, logic tells me that plant DNA would follow this same path, and eventually the tip cuttings would not grow properly - too small leaves, missing microstructure in the leaves, etc. Am I correct?