2.4. X-ray microanalysis
Roots of seedlings from different treatments were washed with
distilled water three times. The harvest roots were dipped in 5%
agar, inserted to a depth of 1.0 cm in a copper holder, and immediately
sliced free-hand with a razor blade to get transverse sections,
and then frozen in liquid nitrogen. The samples were freeze-dried,
gold coated in a high vacuum sputter coater and stored in a desiccator.
They were analyzed in a scanning electron microscope
(S-3000N Hitachi, Japan) equipped with an energy-dispersive Xray
detector. Five tissues, including epidermal cells, exoderm cells,
cortical cells, endoderm cells and the stellar parenchyma in each
root transverse section were analyzed. More than three transverse
sections of each treatment were observed and three location spots
of the same tissue of each section were analyzed. Both map-scan
and spot-scan were done.