Adrian Goodman's Research Interests
LOCAL RESPONSES TO MECHANICAL STIMULATION
Plants can also respond locally to
mechanical stimulation. In sunflowers, the more highly stressed
areas such as the base of the stem and roots, have been shown to respond the most to
(Goodman and Ennos,
Local mechanical stimulation had limited effects on the morphology of maize nodal roots; there was no significant effect of flexing on the diameter of primary nodal roots when compared to untreated roots. However, there were significant differences in root mass between treatments; there was a large decrease of 43% in the fresh and 41% in the dry mass of the fine roots in the flexed roots compared with the untreated roots. Surprisingly there was only a small effect on the mass of the primary nodal roots: only at the fifth node was there a significant increase of 15% in the dry mass of flexed roots compared to those which received no mechanical stimulation.
The effects of root flexure on the mechanical properties of the roots was more dramatic. Roots at both nodes four and five were significantly more rigid (Fig. 1), stronger and composed of a stiffer material than those which received no mechanical stimulation.
Fig. 1 The effects of mechanical stimulation on the mechanical properties of untreated and flexed maize roots. At nodes 4 and 5 there were significant differences in the rigidity between unstimulated (white bar) and flexed maize roots (hatched bar).
After flexing, the primary nodal roots at the fifth node showed increases of 75% in the rigidity (Fig. 1), 60% in the bending strength and 70% in the bending modulus of the flexed roots compared to unstimulated roots.
This study shows that :
The ecological significance of this may be that adaptive 'fine tuning' of individual roots to mechanical stimulation may produce plants which are better able to withstand overturning forces and prevent anchorage failure. This local response may also enable plants to respond, more effectively, to fluctuations in the mechanical impedance of the soil, which may result from compaction by animals or vehicles, or by the presence of naturally compacted horizons.
This could allow future studies to:
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and Ennos, 2001).