The effects of sodium chloride stress upon the transport of calcium in roots of Hordeum vulgare and intracellular ion concentrations in root hairs of Arabidopsis thaliana.

摘要

The effects of sodium chloride (NaCl) on calcium (Ca) transport and intracellular ion concentrations was examined in this study. The first study was about the how NaCl affects Ca loading into the xylem. I used radioactive Ca, applied at different parts of excised barley roots, as a tracer to measure Ca flux. Various salt solutions were applied to the roots and the Ca flux was monitored. In a separate experiment, I used a vibrating microelectrode to measure the influx of Ca at the epidermis of the roots, to see if NaCl affected Ca uptake. The results indicate that Ca radial transport is more sensitive to NaCl stress in the older regions of the root than in the younger regions. In the second study, I measured the effects of NaCl stress upon the growth, cytosolic Ca concentration, and cytosolic pH of root hairs of Arabidopsis thaliana . The ions were measured with the fluorescent dyes Indo-1 (for Ca) and BCECF (for pH). Root hairs were exposed to NaCl for a few minutes or for several days, and then they were loaded with the dye and the ions were measured. I report that NaCl stress has no effect on cytosolic pH, and that cytosolic Ca is not dramatically affected when the root hairs are exposed to NaCl for a few minutes. However, cytosolic Ca was dramatically reduced in root hairs of plants grown for several days with NaCl, as was growth. Root hairs grew better in medium with elevated Ca, when the plants were salt-stressed. In the third study, I used the fluorescent dyes SBFI (for Na) and PBFI (for potassium, K) to measure Na uptake in root hairs. Sodium was taken up very quickly, within minutes, and was retained in root hairs of plants grown for several days with NaCl. Additional Ca in the medium caused a reduction in the amount of na taken up. Due to technical difficulties, K could not be measured in root hairs which contained Na.