Differential Responses of Two Lactuca sativa Varieties to Bicarbonate-Induced Iron Deficiency

Abstract

Iron chlorosis induced by bicarbonate is very common in calcareous soils, where bicarbonate (HCO3-) ions are present at high concentrations. In this study, morpho-physiological and biochemical responses of two Lactuca sativa varieties (Romaine and Vista) to bicarbonate induced iron deficiency were investigated. The culture was conducted on nutrient solution containing 5 µM Fe and 10 mM NaHCO3, in a growth chamber with controlled conditions. After 14 days of bicarbonate treatment, the two varieties seedling showed a slight yellowing of young leaves associated with a significant decline of plant biomass, leaf number and area. Furthermore, the concentrations of the nutrient elements (potassium, magnesium, iron and calcium) in leaves and roots of two lettuce varieties were modified. In roots of bicarbonate treated plants, the Fe-chelate reductase activity was increased as compared to control in both varieties. PEPC activity was enhanced only in Vista variety. Moreover, Fe deficiency induced a small change in the photosynthetic parameters and chlorophyll fluorescence, especially in Romaine variety. These changes are accompanied by decreases in ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) activity. These findings indicated that Vista variety could survive at low iron supply.

Keywords

• Lactuca sativa
• bicarbonate
• iron deficiency
• photosynthetic activity