Competing sinks?

Just because two plants are sufficiently closely related to graft them together doesn't necessarily mean it's a good idea to graft them together.

I must confess that, beyond the novelty value, I don't quite get the amazing tomato-potato.

It seems more sensible from a plant physiology point of view to just plant a tomato next to a potato and have two sets of leaves each providing for one sink rather than have two large sinks competing for the same resources. I initially wondered if maybe the potatoes ripened first and then maybe the tomatoes but the inset photograph seems to show them both ripe together.

Given that tobacco is also in the Solanaceae family I wonder how long it will be before we see tomacco for real? Oh wait someone already did that.