Photosynthesis in orchid roots?

[Jadeco]

I have recently taken botany, and our textbook (Introductory Plant Biology by Kingsley R Stern, James Bidlack, and Shelley Jansky) pointed out that, initially, the primary function of phalaenopsis orchid roots was believed to hold water since their roots are so thick, but recent research has shown that they heavily involve photosynthesis. I wish I still had the textbook to cite any sources and give exact quotes.