In this session, we begin by reviewing what we have covered in our previous live sessions. Next, we discuss the non-living signals of plants (and gain a better appreciation of plants). We discuss how cells talk (sending cells, target cells, non-target cells). We show the types of signaling, and discuss phytochromes (pigment that detects light, inactive and active, inside of plants). We cover phototropism using an experiment by Darwin and discuss auxin (hormone responsible for phototropism, leading to cell elongation on the “dark” side of the plant). We review signaling (permeable and impermeable). We discuss photoperiodism (how plants respond to time) and seed germination (gibberellin). We discuss the ripening hormone (ethylene) and gravitropism (negative versus positive gravitropism). We conclude this session with multiple choice practice questions.