Knowledge about plant nutrition and photosynthesis is key to the scientific literacy of citizens. However, numerous studies have shown the existence of about 50 alternative ideas related to this content. In this work, carried out based on a reflection-action process, two studies based on the ideas of our 12-18 year old students are presented, as well as those of the Teacher Training Master of the Complutense University of Madrid (Spain); we propose a new approach to teach these topics and others related. In addition, the most interesting ideas from an analysis on some of the main university manuals of Plant Physiology on the subject of photosynthesis are shown to finally propose a teaching model of this content that has been applied and evaluated in two Educational Centres of the Community of Madrid, getting good results.