Fig. 3.

Growth-mediated solar tracking of the stem and upper leaves in a sunflower plant (Helianthus annuus L., ‘Sunspot’). The drawings were plotted from observations on a 10-week-old plant (A). Photon fluence densities of sunlight on the surface of the upper leaves were measured as described by Pieruschka et al. (2011) in the morning (0700 h), at noon, and in the evening (1900 h) under three different weather conditions (7–25 September 2013; means ± s.e.m. of nine measurements each) (B).