DISTRIBUTION OF PHYSIOLOGICALLY INACTIVE ZINC IN MAIZE GROWING ON A BLACK EARTH SOIL

Physiologically inactive zinc occurred in the roots and leaves but not the stems of maize seedlings when grown for 30 days in pots on a black earth soil. Expanded leaves had very high zinc concentrations (60-200 µg/g), yet expressed symptoms of zinc deficiency, which indicated that most of the zinc in these tissues was inactive. By contrast, stem tissue, which was 36% leaf sheaths and 64% new leaves and meristems, contained low levels of zinc (17 µg/g) when unfertilized and normal levels (27 µg/g) when fertilized with 10 µg/g zinc. Stem growth indicated that this zinc was active. Fertilizer phosphorus (200 µg/g) induced phosphorus/zinc imbalance and inactivated zinc further in roots, certain expanded leaves, and the stem. Zinc and phosphorus deficiencies and zinc inactivation were prevented by fertilization with both zinc (10 µg/g) and phosphorus (200 µg/g). This system is proposed as a model for the study of chemical and biochemical forms of active and inactive zinc in maize. © 1978, CSIRO. All rights reserved.