Place carrots, celery, turnips and onion in bottom of 4-qt. slow cooker. Sprinkle chicken all over with salt and pepper. Place chicken on top of vegetables. Slowly pour broth around chicken and vegetables.
Cover slow cooker; cook on low 6 hrs. Transfer chicken to bowl; let cool slightly.
Using 2 forks, shred chicken. Stir chicken back into slow cooker. Stir in rice, parsley and lemon juice. Cook on low until heated through, about 10 min.