Precipitation of Calcium and Strontium Sulfates around Plant Roots and its Evaluation1
- G. L. Malzer and
- S. A. Barber2
The flux of Ca2+, Sr2+, and SO42- to corn (Zea mays L.) roots was investigated to determine if accumulation at the root caused precipitates to form and if so to determine the influence of precipitate formation on Ca and Sr uptake. Autoradiographic techniques using 45Ca and 35S showed both Ca2+ and SO42- accumulated at root surfaces when supply by mass-flow exceeded uptake. Petrographic studies of the roots confirmed the formation of CaSO4 precipitates.
The influence of the root precipitate on the relative Ca and Sr uptake was studied by comparing uptake by plants grown where precipitates occurred with those grown without precipitate formation. The corn plants were grown in solution culture. In order to have CaSO4 precipitation without SrSO4 precipitation a Ca/Sr molar ratio of 3670 was used. When SrSO4 precipitation without CaSO4 precipitation was desired the molar ratio was 0.45. The Ca and Sr in solution were labeled with 45Ca and 85Sr either from 9 days to harvest or for only 7 hours before harvest. Harvests were made after 13, 17, and 24 days.
Plant age at sampling did not affect the 45Ca/85Sr ratio absorbed, however the length of the labeling period did. When labeled for 7-hours, and CaSO4 precipitate was present 45Ca uptake was reduced 16 to 20% relative to 85Sr uptake as compared to uptake where no precipitate was present. When labeled from day 9, no differences occurred. When SrSO4 precipitated, 85Sr translocation was reduced 10 to 20% compared to 45Ca with the long labeling treatment.
With a Ca/Sr ratio of 3670, the roots selectively accumulated Sr, however with a Ca/Sr ratio of 0.45, the roots selectively accumulated Ca. The Ca/Sr ratio present in the root was not correlated with the Ca/Sr ratio translocated to the shoot.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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