Results
Roots architecture
Figure 1 = Root architecture
Mycorrhizae
Figure 2 = Root architecture + mycorrhizae
Diffusion of exudates
figure 3 = evolution of the signal
We calculated the response time based on three diffusion values ranging from 0.0018 cm² / day to 0.18 cm² / day to cover a wide range of possible values for the diffusion in a unknown homogeneous medium for unknown substances. Values less than 0.0018 have not been calculated because below this value the model calculated that the roots touch each other before the chemical signal has been transmitted, in fact the root contact seems to be established in the modeling after 28 days. With a diffusion coefficient of 0.18 whicch is the maximum estimated value, the signal is transmitted after 11 days. We can therefore exclude the possibility that the change of direction of the roots of the experiment is caused by the transmission of a chemical signal because it could not reach the root segment before the change of direction.
Discussion
Limits of the experimental systems
Crosstalk between the model and the experiment
In the model, we considered that the plants were enought separeted so that there is no direct contact between their roots in the period of time taken into account. From the data we got, it seems that the growth rate of mycho
Improvement of the diffusion model
The model created seems robust on the scale of phenomena studied. Plausible results are observed for all scales of values analyzed. The most obvious improvement is the determination of the parameters. Indeed the diffusion coefficients, the rate of production of signal molecules and the concentration necessary for detection have been chosen arbitrarily and must be adapted to the medium, the signal and the types of roots studied. Only one type of plant has been analyzed by modeling, even if the results are similar before any type of plant should be run the model with different root phenotype In order to validate this assumption. More differentiation of roots in the root-collecting model could be used to characterize the signal transmission time for each type of root and thus improve the specificity of the results that remain very general in this model.
Conclusions