Measurement of Radish Root Enlargement under Mechanical Stress
1977
Kibreab, Tadesse | Danielson, Robert E.
Evaluation of the force that can be exerted by enlarging plant roots, and comparison with that required to deform the soil, will help to identify the influence of soil mechanical properties on plant growth. A growth chamber study was made to evaluate the rate of enlargement of radish (Raphanus sativus L.) roots as influenced by level of applied pressure and to determine the maximum pressure against which the roots could expand. Special cells were designed to measure the growth rate of the roots against the applied pressure. The procedure involved compressing the storage root by gas pressure against a liquid; and the liquid and root being separated by a membrane. The storage root enlarged against the membrane. The secondary roots extended outside of the pressure cell into an aerated nutrient solution and the leaves were exposed to light and air under controlled conditions of an environmental chamber. Volume change of the roots was periodically determined and after harvest the final volume and weight was obtained. Osmotic potential of root extracts was also determined. The rate of root enlargement decreased with applied stress. Volume and weight at harvest decreased in a logarithmic manner with applied pressure. The limiting pressure for radish root enlargement was estimated to be about 8.5 bars. Osmotic potential of root extract was closely related to applied pressure. It is suggested that the origin of forces exerted by the root is from higher turgor pressure induced by osmotic concentration of sap.
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