|
4.3.3.P6
Harry and his friend Hermione’s task for class is to find the soil that allows plant roots to grow best. So she and Harry develop transparent soil, and measure the position of the tip of all plant roots over the course of a number of weeks. (no magic, recent science - see image on the right, from Reference [1])
A. The teacher then asks the class to find out whether the roots are growing randomly. Hermione, harried as ever, uses a magic spell to discover that the roots are just moving randomly. She then puts her magic wand aside and gets back to the lab manual: The lab manual asks her to make a graph of the logarithm of the average root tip depth squared as a function of the logarithm of time (log-log plot). On the axes provided below, sketch a possible plot for this random motion. Describe the relevant features of this plot.
|
 |
B. Hermione finds that the average depth z of the root is z0=3.2 mm at the start of class (1pm), and Harry observes that 4 hours later (5pm) the average depth is z1=5.2 mm. Calculate the diffusion constant for the random motion of the root in the vertical direction (in other words, find a number that describes how fast the roots are digging down into the soil).
|
C. In a different soil the root seems to grow straight down with a constant velocity (see image on right, from Ref [1]). What differences would you expect compared to random motion, if you made a log-log plot for the position of these root tips? You may use the log-log plot below to explain.
|
 |
[1] Downie H, et al. (2012) Transparent Soil for Imaging the Rhizosphere. PLoS ONE 7(9): e44276.
Comments (0)
You don't have permission to comment on this page.