BACKGROUND:Phototropism is the response a plant exhibits when it is faced with a directional blue light stimulus.Though a seemingly simple differential cell elongation response within a responding tissue that results in organ curvature,phototropism is regulated through a complex set of signal perception and transduction events that move from the plasma membrane to the nucleus.In nature phototropism is one of several plant responses that have evolved to optimize photosynthesis and growth.OBJECTIVE:In the present work we will review the state of the field with respect to the molecules and mechanisms associated with phototropism in land plants.METHODS:A systematic literature search was done to identify relevant advances in the field.Though we tried to focus on literature within the past decade (1998-present),we have discussed and cited older literature where appropriate because of context or its significant impact to the present field.Several previous review articles are also cited where appropriate and readers should seek those out.RESULTS:A total of 199 articles are cited that fulfill the criteria listed above.CONCLUSIONS:Though important numerous and significant advances have been made in our understanding of the molecular,biochemical,cell biological and physiologic mechanisms underlying phototropism in land plants over the past decade,there are many remaining unanswered questions.The future is indeed bright for researchers in the field and we look forward to the next decade worth of discoveries.