Suddenly, you orgasm and feel release. You've ejaculated into the plant's tube. And you feel slightly less bloated.
But once again you feel sexual pleasure as the tube around your penis, perhaps along with the effects of the stuff inside you, makes you orgasm again. Again you find release into the tube and with your sperm a little more of the liquid flows too.
Hours later, you're spent, you've had many orgasms into the plant. You're no longer bloated as the liquid has flowed back into the plant through your penis, along with a lot of your sperm.
The tube detaches and you feel a sudden pain in your butt as the remains of the plant in your body crawl out again, their job done. They shrivel and dry up and you stand there, seemingly back to normal except for the memories of your experience.