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Figure 3 | BMC Biology

Figure 3

From: How 5000 independent rowers coordinate their strokes in order to row into the sunlight: Phototaxis in the multicellular green alga Volvox

Figure 3

Quantification of the phototactic movements depending on the applied light intensity. (a) and (b) The viewing direction, the direction of the light vector and the direction of the gravity vector is indicated. (a) In the vertical setup A, the direction of the light vector is identical to the direction of the gravity vector. The observation chamber was divided into six areas with area 1 being closest to the light source. (b) In the horizontal setup B, the direction of the light vector is perpendicular to the direction of the gravity vector. The observation chamber was divided into three areas with area 1 being closest to the light source. (c) Schematic representation of the light intensities used in setups A and B. (d)-(h) Phototactic movements were quantified by calculating the photoaccumulation index (PI). The higher the PI value, the stronger the photoaccumulation. (d) The PI was calculated separately for each area (setup A) and was plotted against the time after the light was turned on (light intensity: 0.16 ╬╝mol m-2 s-1). (e) The PI for area 1 in setup A was plotted against the time after the light was turned on using eight different light intensities. (f) The PI for area 1 in setup A was plotted against the different light intensities. Seven different times were analyzed separately at intervals of 5 s. (g) The PI for area 1 in setup B was plotted against the time after the light was turned on using 17 light intensities. (h) The PI for area 1 in setup B was plotted against the different light intensities. Three different times were analyzed separately at intervals of 10 s. (d)-(h) The color assignment is indicated. Error bars refer to the standard deviation of the y-value (n = 3).

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