The Onion

There is not really strong evidence of plant sentience. Here's one paper looking at it:

A. Plants do not show proactive behavior.

B. Classical learning does not indicate consciousness, so reports of such learning in plants are irrelevant.

C. The considerable differences between the electrical signals in plants and the animal nervous system speak against a functional equivalence. Unlike in animals, the action potentials of plants have many physiological roles that involve Ca2+ signaling and osmotic control; and plants’ variable potentials have properties that preclude any conscious perception of wounding as pain.

D. In plants, no evidence exists of reciprocal (recurrent) electrical signaling for integrating information, which is a prerequisite for consciousness.

E. Most proponents of plant consciousness also say that all cells are conscious, a speculative theory plagued with counterevidence.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8052213/

Though something interesting and perhaps counter intuitive to note is that even if we realized plants were sentient, a plant-based diet actually involved killing fewer plants due to the lessened need to grow feed (of which most of the energy is lost)