How much applicable is raspberry pi at industrial point of view?
No. In engineering point of view both Arduino and Raspberry PI's are bare minimum example boards. They do not feature the ruggedness required for an 24/7-365 industrial application.

You can add these features with extra boards. But you will still have a weak core you've build upon.
This is not entirely valid for Arduino, since you can use only the software

Go for an PLC instead. Look at CodeSys for suitable brands for example. (eg: wago)

I can link some greenhouse controllers I've found on Shodan.io, but that feels wrong. Please secure your automation!

But, I understand you're a student, and a PLC might not be available or within course context. In that case, I'd suggest you go for Raspberry PI.
Why?
- It has Ethernet by default.
- It runs linux. Which means it has no probleem running an HMI.
- It has USB, which means you can add any external interface for IO or communcations.
For examples, to use Wago CANopen Fieldbus Device. Or their Ethernet variant. Instead of using the weak unprotected GPIO's on the processor board.