Winter wheat adapts to environmental pH by changing H+ net flux in roots at the seedling stage

Changes in rhizosphere pH play an important role in wheat growth. To investigate the relationship between changes in rhizosphere pH and the growth of winter wheat roots and to explore the regulatory mechanism of acid and alkali resistance in winter wheat roots, the semi-winter wheat varieties Aikang 58 (AK58) and Bainong 4199 (BN4199) were used as materials for hydroponic experiments. Three pH levels (4.0, 6.5, and 9.0, with 6.5 as control) were applied during the wheat seedling stage. The results showed that the shoot and root biomass of the plants significantly decreased compared with the control under acid-base stress, with a more significant decrease with acid stress than alkali stress. Compared with the control, the root/shoot ratio increased under alkali stress and decreased under acid stress. The wheat root system showed H+ net efflux at pH 6.5 and 9.0, and the H+ net efflux rate at pH 4.0 was significantly lower than the control. The root activity of wheat was higher than the control at pH 9.0 and lower at pH4.0. The change of root pH was showed pH 4.0 < pH 6.5 < pH 9.0. Correlation analysis showed that changes in H+ net flux were significantly positively correlated to root activity and root pH. The H+ efflux rate and root activity of BN4199 were highe r than AK58 under acid and alkali stress, and the root/shoot ratio was relatively high, indicating strong acid and alkali resistance. We conclude that wheat could adapt to poor acid-base environments by adjusting root H+ net flux, and in practice, the root/shoot ratio could be used as index for the rapid determination of acid-base tolerance in wheat at the seedling stage.