Seems like the most likely option is that they're. somehow 'seeing' using their leaves as light sensors. I've gotta tell you, when you see the map in question (screen grabbed from the teaser trailer. you're not going to believe that it's something to be taken seriously. On a related note, India is now publicly stating that China's claims to this bit of water are ilegitimate. Anyway, a big step forward for women, few before her have "inflamed maritime territorial disputes"
On the topic of plane propulsion, I ran into this video on a new design for engines: https://youtu.be/ojVNOj-q3SQ