Effect of waterlogging on root anatomy and nitrogen distribution in pigeonpea (Cajanus cajan (L.) Millsp.)

We studied the effect of waterlogging on root anatomical changes and nitrogen content in pigeonpea, a waterlogging sensitive crop. A pot experiment was conducted with pigeonpea genotypes; ICPL-84023 (waterlogging tolerant) and MAL-18 (waterlogging susceptible). Stress was imposed after 20 days of sowing for 6 days. Aerenchyma development was observed in genotype ICPL-84023 and aerenchyma occupied 12 % root cortical area after 6 days of imposing stress. No change in root anatomy was observed in MAL-18 under waterlogging. Root nitrogen content reduced 40 % in ICPL-84023 (2.47 mg g−1 dry weight) and 51.9 % in MAL-18 (2.06 mg g−1 dry weight) compared to control after 6 days of waterlogging. In stem, nitrogen content was 1.54 and 1.26 mg g−1 dry weight in ICPL-84023 and MAL-18, respectively, after 6 days of stress. Lower leaves abscessed in MAL-18 after 4 days, while, in upper leaves, nitrogen content decreased by 20.4 % in ICPL-84023 and 88.8 % in MAL-18. Waterlogging affected nitrogen uptake and partitioning adversely in both the genotypes. But the ability to maintain high nitrogen content under stress to sustain growth as evident by leaf retention was observed in ICPL-84023. Aerenchyma development is a well known survival strategy facilitating gaseous movement under waterlogging. It was concluded that aerenchyma formation and high nitrogen uptake play an important role in waterlogging tolerance in pigeonpea.