North American Fruit Explorers mailing list at ibiblio

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Plants and animals are different.  Most "advanced" animals (such as 
mammals) are designed to age.  Normal cells that are grown in tissue 
culture will reproduce a certain number of times and then die.  Only 
cancerous cells and certain stem cells can be kept growing 
indefinitely, and the stem cells either die or get weird.  (Cancerous 
cells can be kept in culture indefinitely, and do not give up and die.  
This suggests why our normal cells are designed to die.)

When animals reproduce, the age of the new zygote is reset.  There are 
a bunch of theories about how, but no one is really sure, which is why 
Dolly was being watched for signs of premature aging.

For whatever reason, plants don't work that way.  Most plant cells are 
"immortal", meaning that if conditions are right, they can grow and 
reproduce forever.  Many plants use cloning as a normal form of 
reproduction - known as vegetative propagation when people assist.  So 
the difference between grafting a fruit tree and Dolly is that the 
grafted fruit tree only suffers from the potential for accumulated 
viruses, genetic damage, etc., and not from planned obsolescence.

Ginda Fisher


On Sunday, February 16, 2003, at 01:26  PM, Thomas Olenio wrote:

> Hello,
>
> What is the difference between grafting fruit trees and Dolly the 
> cloned
> sheep?
>
> I believe part of Dolly's problem was premature aging, due to her 
> cellular
> clock being set from the starting point of a mature sheep.  Yet grafted
> trees do not seem to suffer the same fate.
>
> Earlier fruiting may be tied to the advanced cellular clock of the 
> scion,
> but it does not seem to shorten the lifespan of the tree.
>
> Anyone know the reason?
>
> Later,
> Tom
>
> --
> Southwest Ontario
> Canada Hardiness Zone 6a
> (similar to US zone 5)