trees not lighting correctly in maya xstream

[Ralph Lengler]

I'm doing an animated short film which involves a large landscapes with nature, mainly trees but also agricultural fields and that stuff.

First, it appears that some tree species don't take up (enough???) light, notably the cherry tree, or the eucalyptus, etc. The interesting thing is that if a transparent object (a glass-like object) is in front of this tree, then all of a sudden is this tree renders with the correct luminance. Which made me conclude that this is a problem of the sort transparencies go to a certain color and that this color (in the maya camera environment tab this background color needs to be BLACK, because otherwise you will just run into whole bunch of other render problems).

Now my question is where can I change such a setting????

Second much more important question, some trees and plants seem to have a color shift into the blue whereas and are more washed-out looking, while others don't exhibit this behavior, while in Standalone vue you don't get that. Is there a possibility to color correct this?