Interaction of Mineral Deficiency and Nitrogen Source on Acid Phosphatase Activity in Leaf Extracts

SUMMARY Plants were grown in sand cultures to observe the effects of mineral deficiencies, with different sources of nitrogen supply, on leaf acid phosphatase activity using phenolphthalein phosphate as substrate. Large increases ranging from 7 to 18 times normal (on fresh weight or protein basis) occurred with deficiency of phosphorus with nitrate, nitrite or ammonia nitrogen ; increases from 4 to 8 times normal occurred with deficiencies of zinc with nitrite or ammonia; and of copper with nitrite. Less pronounced increases, from z to 3 times normal on a protein basis, occurred with deficiency of zinc with nitrate; of boron with all nitrogen sources; of manganese and of iron with nitrite. Activities on both protein and fresh-weight basis were often greater with nitrite or ammonium sulphate than with nitrate. Effects of phosphorus, zinc, copper, boron, and nitrogen sources were significant. Molybdenum deficiency caused approximately z times normal activity on a protein basis in tomato, tobacco, sunflower, cauliflower, lucerne, mustard, spinach beet, and lettuce when nitrate was given. Effects with ammonia nitrogen were not consistent in molybdenum-deficient plants but 50 per cent, increases occurred in the first 5 species listed. Activities varied widely between species. It was concluded that the increases in activity were caused by increases in amounts of the enzyme produced during growth, and that different combinations of deficiencies and nitrogen supplies produce different specific responses in terms of enzyme synthesis.