Summary
Apparatus for studying root growth in water cultures is described. When a complete nutrient solution, in which the roots were growing, was replaced by mineral-free water, root growth stopped within about 24 hours. Although the total length of the roots was less, transpiration per unit root length was also less in mineral-free water than in nutrient solution.
Measurements of the exudation rates from detopped root systems showed that in mineral-free water the osmotic pressure of the xylem sap and water conductance of the roots were reduced. The reduction in conductance was much greater than the reduction in root length, indicating that the permeability of the root tissues to water had been reduced.
The transpiration of plants in mineral-free water did not increase when the roots were cut off, in spite of the marked effect of mineral-free water on root resistance. It was concluded that root resistance was not the most important factor causing reduced transpiration and that mineral-free water considerably affected the water relations of the shoots, indicating an important role for mineral salts in this aspect of plant function.
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Drew, D.H. Mineral nutrition and the water relations of plants. Plant Soil 26, 469–480 (1967). https://doi.org/10.1007/BF01379567
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DOI: https://doi.org/10.1007/BF01379567