Effect of soil oxygen deficit on iron nutrition of orange seedlings

Abstract

Iron deficiency chlorosis in plants is often asso- ciated with soil conditions that appear to restrict ex- change of gases with the atmosphere, such as fine texture, lack of aggregation, excessive moisture, or discontinuity in the profile in the form of plowsole, hardpan, claypan, or stratified deposits. These condi- tions can cause CO2 to accumulate in the soil and, particularly in calcareous soils, produce substantial concentrations of HCO3 ions. Solution culture studies (1, 14) have shown that NaHCO3 can cause a marked reduction in iron absorption by some kinds of plants. Thus has arisen the so-called bicarbonate hypothesis to explain the variable chlorosis of plants growing in calcareous soils.