MARTIN SHIELDS / SCIENCE PHOTO LIBRARY MARTIN SHIELDS / SCIENCE PHOTO LIBRARY
Common bean (Phaseolus vulgaris) seedling 'sleeping' at 10:00 p.m.. The leaves are oriented in the vertical plane to reduce transpiration. In the previous photo in the sequence (noon) the leaves had moved to a horizontal position to photosynthesize. These movements are governed by an internal circadian clock (circadian rhythm) that stimulates variations in turgor pressure between day and nighttime.
Model release not required. Property release not required.