Figure 8.

In vivo ³¹P-NMR study of metabolic transitions induced in Medicago truncatula nodules. (A) Proton-decoupled ³¹P-NMR spectra of nodules in normoxia at 21°C, perifused with a nutritive medium at pH 6.0 with successively 21% O₂ (control), 1% O₂, and then 21% O₂. For each line, duration of the treatment is indicated up to the end of the spectrum. (B) Proton-decoupled ³¹P-NMR spectra of nodules in normoxia at 21°C, perifused with a nutritive medium at pH 6.0 containing successively 21% O₂ (control), 1 mM tungstate (Tg) for 5 h, and then 1 mM nitrite (NO₂⁻) for 2 h. For each line, duration of the treatment is indicated up to the end of the spectrum. Each spectrum series is drawn from a representative experiment of eight (A) and five (B) biological replicates. The values indicated next to the G6P and Pi-cyt resonances correspond to the cytosolic pH values. Exponential apodization and zero filling. Pi, inorganic phosphate; G6P, Glucose-6-phosphate; Pi-cyt, cytoplasmic Pi; Pi-vac, vacuolar Pi; UDPG, UDP-glucose.