Leaf looks different after export

Hello everyone,
I think I do something wrong, when I export a tree.
In Tree It the leaf looks very good, like you can see on the following picture:

treeInTreeIt.jpg (124.45 KiB) Viewed 3220 times

After exporting the tree and using it in another program (jMonkey) the leaf of the tree does not look the same. It does not have their "transparency", like you can see on the following picture:

treeInOtherProgram.jpg (67.33 KiB) Viewed 3220 times

For testing, what could be wrong, I downloaded some of the uploaded "Tree It-models" from Sketchfab (the GLB-Files), for example the "willow". Using the GLB-File in my program, the leaf looks exactly the same like it looks in Tree It. So I think it has nothing to do with the programm I use. I tried to export the willow myself from Tree It (it can be found in the examples there), but then the leaf looks "bad" again.

So I think if the example from Tree It looks "bad" after my own export but not if I use the export from Sketchfab in my program, I think I do something wrong when I export the tree by myself.

Has anyone an idea or an suggestion what am I doing wrong?
Thanks in advance.

The leaves on the first image are alpha masked, you need to enable the alpha channel/setting wherever that is on your program of choice

Thanks for the hint. Is it possible, that the alpha channel/setting could be activated in the exported file (material?)? I ask, because it seems as if my program does not have activation for alpha channel/setting. It seems as if the program uses the information from the file. When I use an TreeIt-Tree from Sketchfab (that someone else uploaded there), then everything looks great (like it looks in TreeIt). But when I use my own export then there is no alpha.

I don't know how the jmonkey engine works, but this might be useful: https://hub.jmonkeyengine.org/t/solved- ... re/34724/2

I think the textures these trees come with, have transparent backgrounds which can be used as alpha masks as well