The interplay of nitrogen metabolism and root attributes in governing yield potential of pea cultivars subjected to simulated acid rain

Acid rain threatens plant productivity, including crop yield. The yield of pea (Pisum sativum) is intimately linked to nodulation, nitrogen (N) assimilation, and fixation processes. While the effects of simulated acid rain (SiAR) on crops have been well documented, the specific impacts on N-assimilation remain inadequately understood. This study aimed to investigate the adaptations exhibited by roots and efficiency of N-metabolism in leaves of two widely cultivated Indian pea cultivars (Samridhi and Nandini) in response to varying levels of SiAR (pH 5.6, 5.0, and 4.5). Both cultivars exhibited altered root morphology under SiAR, with increased relative root growth rate at pH 5.0 and 4.5. Increasing SiAR acidity elicited differential responses in N-assimilation enzyme activities across growth stages in both cultivars. SiAR stimulated the activity of nitrate reductase with reduced nitrite reductase and leghemoglobin content in the reproductive growth stage of both cultivars. Under SiAR, both cultivars showed modified seed yield and quality traits; however, cv. Nandini demonstrated greater resilience due to enhanced glutamate dehydrogenase activity, suggesting more efficient N-metabolism than cv. Samridhi. We conclude that the decrease in yield is primarily attributed to the disruption of N-metabolism, specifically inhibition of the glutamine synthetase and glutamate synthase pathway. These findings have significant implications for agricultural practices, in the selection and development of crop varieties with enhanced nitrogen fixation capabilities, to mitigate the negative effects and improve resilience to acid rain.