Differential root and shoot biomass recovery in wheat and barley with transient waterlogging during preflowering

Wheat and barley plants exposed to waterlogging reduced their growth, but the final impact on grain yield depends on the capacity of the plant to recover after stress. The aim of this study was to evaluate shoot and root biomass accumulation in wheat and barley plants during waterlogging events applied at different stages during preflowering and after stress removal. Wheat and barley plants were waterlogged for 15-20 days at four consecutive periods during phenological cycle from emergence to flowering. Waterlogging produced a delayed effect on shoot biomass, as biomass reductions were detected 20 days after waterlogging was released. The highest relative reductions of shoot biomass (60% in wheat and 68-74% in barley regarding control) occurred when waterlogging was applied early in the cycle (from emergence to tillering). Waterlogged plants showed a remarkable capacity to recover from early waterlogging (reaching similar shoot biomass as control plants at flowering), but recovery capacity decreased when waterlogging occurred later in the phenological cycle. For both species green leaf area and photosynthetic rate were reduced and water soluble carbohydrates increased when waterlogging ended, however the general trend showed values at flowering similar to the control plants. The impact of waterlogging on roots was generally higher than the one on shoots and the effect was detected immediately after treatment. The root system capacity to recover after waterlogging was lower than the one for shoots, and was higher in barley than in wheat. Waterlogging first damaged root biomass while effects on shoots were delayed. Shoot recovery at flowering was possible for waterlogging events previous to stem elongation, but root recovery was lower, especially for wheat.