Effect of low root medium pH on net proton release, root respiration, and root growth of corn (Zea mays L.) and broad bean (Vicia faba L.)
1992
Yan, F. | Schubert, S. | Mengel, K.
The effect of low pH on net H+ release and root growth of corn (Zea mays L.) and broad bean (Vicia faba L.) seedlings was investigated in short-term experiments at constant pH. Broad bean was more sensitive to low pH than corn: the critical values (pH values below which net H+ release and root growth ceased) were pH 4.00 (broad bean) and pH 3.50 (corn) at 1 millimolar Ca2+. Both proton release and root growth were progressively inhibited as the medium pH declined. Additional Ca2+ in the root medium helped to overcome the limitations of low pH for net H+ release and root growth. Potassium (for corn) and abscisic acid (for broad bean) increased both net H+ release and root growth rate at the critical pH value. It is concluded that poor root growth at low pH is caused by a lack of net H+ release that may decrease cytoplasmic pH values. Inhibited net H+ release at high external H+ activity is not due to a shortage of energy supply to the H+ ATPase. Instead, a displacement of Ca2+ by H+ at the external side of the plasmalemma may enhance reentry of H+ into root cells.
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