The effect of bicarbonate on iron (Fe) and zinc (Zn) uptakes by soybean varieties

Bicarbonate anion, has a very high concentration in the calcareous soil, and in fact, is the main cause of chlorosis in calcareous soils. This study was conducted to evaluate eight soybean cultivars with iron deficiency and bicarbonate presence. The present research was carried out with the aim of assessing the effect of irrigation with water containing bicarbonate on enzyme activities and Fe and Zn uptakes in soybean. We also compared Fe-efficient and non-Fe-efficient varieties regarding their tolerance against bicarbonate stress. This experiment was done in two parts; the first part was performed in order to identify Fe-efficient and non-Fe-efficient varieties (8 soybean varieties: ‘Perishing’, ‘Zaan’, ‘Clark’, ‘Williams’, ‘M7’, ‘M9’, ‘B.P’, and ‘L17’). ‘Perishing’, with an Fe efficiency index of 0.98, was considered Fe-efficient, and ‘Clark’, with an Fe efficiency index of 0.43, was identified as non-Fe-efficient. In the second part, the treatments included two levels of Fe, four levels of bicarbonate (0, 10, 20, and 40 mM), and two varieties different in terms of Fe uptake (Fe-efficient [‘Perishing’] and non-Fe-efficient [‘Clark’]) were selected. The results showed that under conditions of bicarbonate stress caused by the irrigation water, the Fe-efficient variety (‘Perishing’) had more resistance than the non-Fe-efficient variety (‘Clark’). Zinc uptake by ‘Perishing’ was greater than that by ‘Clark’. The activity of catalase enzyme decreased with increasing the bicarbonate concentration, while that of super oxide dismutase increased in both varieties, but more strongly in ‘Perishing’.