Epsilon Archive for Student Projects

Abstract

By taking up nutrients and water, root growth has an important influence on
plant growth and productivity. Thereby, root growth is influenced by its
surrounding soil conditions, which vary spatially even on a small scale. Hence,
different parts of the root system are exposed to different penetration resistances in
the soil. As root cells are connected by their cell walls, information about growth
conditions can be transferred throughout the root system, which is why roots can
react to the soil conditions of their neighbouring roots.
By doing in-vivo measurements in a hydroponic system, this study investigated
the responses of unimpeded roots to local mechanical stress of their neighbouring
roots. To do so, the primary or seminal roots were exposed to vertical or horizontal
obstacles. Using a time-lapse imaging system under infra-red light in combination
with particle image velocimetry the underlying processes of root growth, such as
the growth direction, the growth rate, the cell elongation rate, and the growth zone
length were quantified.
In this study, the primary and seminal roots showed contrasting responses of root
growth rate and root growth direction. While the primary roots did not response to
a restriction in growth of the seminal roots, seminal roots reacted to the applied
stress in the same way as the impeded roots, even if the stress did not occur in their
environment. In the case, where the roots found a way to work around the
anticipated stress, they compensated for the impaired root with an increase in
growth rate.
The fact, that the primary root did not show this response, might be due to their
different functions in the root system. Furthermore, the relative root growth rate
was stronger associated with the relative length of growth zone than with the
relative elemental elongation rate. Nevertheless, the elemental elongation rate
might be the driver for short-term adjustments.
Keywords: kinematics analysis, time-lapse imaging, root growth rate, root curvature, soil
heterogeneity, local mechanical stress