Not all characters occur because they are useful. Some occur because
they have not yet been strongly selected against. And remember, the
development of a trait isn't a directed process; there's no "it would
be beneficial to acquire trait X" Rather, trait X is present and it
either does or does not help an organism or a species to pass on its
genes to more offspring.
As far as I know, root grafting occurs just because the tissue
structure of roots is the way it is. Where compatible roots touch,
they are capable of growing together. (In the same way, the structure
of the cambium layer in dicot stems allows stem grafts.) I don't think
I've ever read of any benefit to the plants involved unless maybe
interconnected roots make individual trees less susceptible to blowing
over. It is known that plants under stress release chemicals that can
signal other plants to prepare for or repel pests. Perhaps root
grafts allow the exchange of these chemical signals. Has anyone here
read anything to that effect in a trustworthy article?
Megan Syverson wrote:
>> My botany professor instructed me to address my
> question to plant-ed. I am curious about root grafts,
> and I would appreciate any response to my inquiry. My
> question is this: I have learned about the
> disadvantages of root grafting to trees; trees can
> contract such diseases as Dutch Elm Disease, and can
> support other trees that compete for their light. Why
> then, did trees develop such an adaptation; that is,
> what advantages are there to root grafts? Thank you
> for taking the time to read this.
> Megan Syverson
> Botany 130 student
> UW-Fox Valley
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