Aluminum Toxicity Studies with Radioactive Phosphorus

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Abstract
Barley was grown in solutions with and without Al and then transferred to similar solutions containing 15 mc. of P32/ 1. After 4 hours of exposure roots of separate plants were washed in tap water, 0.001 [image] sulfuric acid, and 0.1 [image] sulfuric acid in order to distinguish between P bound by Al and P not so bound Radioautographs demonstrated a large accumulation of P32 in the roots and very little in the tops of plants grown in contact with.Al. Plants not grown in the presence of Al had considerable quantities of P32 in the tops. Tap water and 0.001 [image] acid extracted no appreciable quantity of P32 from the roots. Extraction with 0.1 [image] acid removed most of the P32. This solubility in 0.1 [image] acid indicated that the P present was bound by Al, and that inactiva-tion was largely internal. Sections of roots grown in contact with Al and washed in tap water were stained by Heidenhain''s iron hematoxylin process without a mordant. S uch modified procedure demonstrates the presence of Al wherever the stain is taken up. Al accumulation was indicated on root surfaces and throughout the cortical region with very little present in the vascular system. The distr. of Al and P as demonstrated is further evidence that Al inactivates P primarily within the roots of the plant.