[Omeryar]

I don't have the answer directly but i may be able to shed some light or make your question more complicated.....
If the orks spores come from a plant like a fern then they would be positivly affected by the nid spores and grow really fast.
If the orks are a fungus then the nid spores would have a negative effect on the ork growth rate. Fungus is much closer related to animals than plants. So the mutating effects of the nid spores would effect and mutate them. But keep in mind that a fungus only thrives by eating dead things. The nid spores make the plant life grow really fast so that they can consume it to add to the hive fleets bio mass. The nids can clear a planet of life in a matter of days leaving nothing behind. So the fungus would have nothing to eat.

Though, if the nid spores do increase the growth rate of the orks then i can see the nids finally meeting their match or fighting to a stand still.

 

[Leech]

to leech: if i can ask where did you get your information?

Let me think, Mycetic spores were an option in the old Epic Hive war and have been endlessly stated as being like drop pods.

The affect on plant growth I think was in White dwarf and/or the 3rd edition Tyranid codex. Also in one or more codexes it has been said that Tyranids introduce all kinds of spores to mutate and or create new types of alien life.

When Tyranids infect local plant life they mutate it, meaning Orks would become hybrids of some sort of they were to be infected, if no hybrids or then that means they don't speed up their growth. Often the effect of more plant growth is caused by just making the atmosphere better suited to it, as well as spores. Meaning a lack of Orks going mad or reproducing alot.

Though nobody can say how Tyranid affect the atmosphere or planet exactly with their spores to make more plants. So it's hard to say if Orks would be affected. It is likely Tyranid would use other means if Orks started multiplying too quickly.

 

[Jarl Bloodwolf]

see ive heard the drop pod thing to. but ive gotten my information from lexicanum.com (idk how reliable it is but if its still runing than games workshop has to agree with whats on it), the ork codex and the nid codex. idk i thought it was a cool question to ask and aparently all those who have given an answer of one form or another agree with me (in that its an interesting question, not that the spores would increase the growth rate of orks)

 

[Hive Node]

I'm not really sure but I know tyranids would be good gardeners

 

[Jarl Bloodwolf]

hahahaha that they would lol that they would