²⁶Al MICROANALYSIS IN THE LEAF CELL ORGANELLES OF RUZIGRASS AND BARLEY BY ACCELERATOR MASS SPECTROMETRY (AMS)

Abstract

The response to aluminum (Al) application was compared between an Al-tolerant plant, ruzigrass (Brachiaria ruziziensis), and two cultivars of barley (Hordeum vulgare L.), Al-tolerant ‘Dayton’ and Al-sensitive ‘Kearney’, of Al at 1.0 mM level. The micro content of Al transportation and accumulation in leaf cell organelles (nuclei, mitochondria, and chloroplast) was determined by the ²⁶Al tracer technique with accelerator mass spectrometry (AMS), which could detect atoms of the order of 10⁷ of ²⁶Al. In a short-time-exposure experiment, plants were immersed into 0.1 mM ²⁷Al (containing 101 dpm/300 mL ²⁶Al) for 5 hours. Then the leaves were separated and ²⁷Al and ²⁶Al were determined. Growth of shoots and roots of ruzigrass was not influenced at 1 mM AlCl₃, but the growth of barley cultivars (Dayton and Kearney) was seriously affected. There was only a small difference in Al content in shoot (about 5 g g⁻¹) among plant species or cultivars when total leaf ²⁷Al was determined by the inductively coupled plasma atomic emission spectrometry (ICP/AES) method at 0.1 mM level. While large differences in the Al content between plant cultivars in the leaf subcellular organelles were found by using ²⁶Al with the AMS method, the amount was in the order of 1–10 pg per 1 mg of organelle protein. Ruzigrass accumulated about 4 or 5 times higher content (2.8 ng mg⁻¹ of protein) of ²⁷Al in the nuclei and 2 or 3 times higher content (0.2 ng mg⁻¹ of protein) in the mitochondria than the two barley cultivars did. There was no difference in Al accumulation in the chloroplast among these three plant cultivars.

ACKNOWLEDGMENTS

We thank Dr. H. Kurata for helping with the enzyme assay of leaf cellular organelle fractions and Miss. H. Matsunaga for her assistance of leaf organelle fractionations. This work was supported in part by a Grant for Atomic Energy Research from Science and Technology Agency in Japan.