Portal de Periódicos da CAPES

Endophytic N2 fixation in sweet potato: responses to N, P, and K inputs and visualization of 15N2 utilizing bacterial cells via Raman spectroscopy

2023; Springer Science+Business Media; Volume: 59; Issue: 3 Linguagem: Inglês

10.1007/s00374-023-01698-5

1432-0789

Risako Ueda, Katsuya Yano,

Plant nutrient uptake and metabolism

Abstract Fertilizer-N strongly limits non-leguminous crop yields; however, sweet potato ( Ipomoea batatas ) is an exception, likely due to its ability to acquire atmospheric N 2 via endophytic diazotrophs. Using Raman spectroscopy, we found that in 15 N 2 -fed sweet potato, some endophytic bacteria contained 15 N, providing direct evidence of N 2 fixation in planta . To assess N 2 -fixing capability, pot experiments were conducted by varying N, P, and K fertilizer inputs. Sweet potato showed higher N content than the non-N 2 -fixing Ipomoea aquatica; additionally, it showed increased N content which was 1.4-fold higher than the fertilizer-N input. Its δ 15 N values were closer to those of N 2 -fixing soybean, with an estimated 11–56% of plant N derived from N 2 . The estimated amount of fixed-N in sweet potato was negligible without fertilizer-N; however, a gradual accumulation leading to an immediate saturation was observed with increasing fertilizer-N. During this state, increasing P supply linearly enhanced the capability, reaching 13 g N m −2 , comparable to that of legumes. However, K inputs affected neither N 2 fixation nor growth owing to strong K acquisition from the soil even without fertilizer-K. Our results indicate extensive N 2 fixation in sweet potato, depending on its nutritional status, particularly P; resonance Raman spectroscopy facilitates the visualization of active N 2 -fixing bacteria on a single-cell scale.