Stimulation of dark carbon fixation in rice and tomato roots by application of ammonium nitrogen

The influence of root assimilated inorganic carbon on nitrogen acquisition/assimilation and carbon partitioning

“…Incorporation of DIC enables synthesis of organic acids, which may in turn be utilized for amino acid synthesis (Schweizer & Erismann, 1985;Ikeda et al ., 1992;Vuorinen & Kaiser, 1997), exudation (e.g. for chelation of aluminium (Al); Cramer & Titus, 2001) and other processes dependant on organic acids.…”

Carbon skeletons for amide synthesis during ammonium nutrition in tomato and wheat roots

“…As mentioned above, the carbon skeleton of asparagine is easily synthesized through the carboxylation of PEP, an intermediate product in glycolysis. Ammonium supply stimulates dark carbon fixation that is catalyzed by PEP carboxylase in roots of several plant species (Ikeda et al 1992;Cramer et al 1993;Koga and Ikeda 2000b). Wheat roots displayed a higher PEP carboxylase activity than tomato roots when ammonium nitrogen was supplied (Koga and Ikeda 1997), which might possibly account partly for the remarkable accumulation of asparagine in wheat roots.…”

“…cv Oogatafukujyu) and wheat (Triticum aestivum L. cv Chikushikomugi) seeds were germinated in sand at 25°C and in vermiculite at 20°C, respectively. After full expansion of the first leaf, seedlings were transferred into one-eighth to one-fourth strength modified Hoagland nutrient solution (pH 6.0) containing 2 to 4 mM NaN0 3 as the N source at 25T for tomato and at 20°C for wheat under natural light conditions at the Biotron Institute, Kyushu University (Downs and Hellmers 1975;Ikeda et al 1992). These plants were used for the following three experiments, which were conducted in triplicate.…”

“…In several reports, it was shown that dark carbon fixation in roots was enhanced following the supply of ammonium nitrogen (Ikeda et al 1992;Cramer et al 1993). Popp and Summons (1983) reported that a greater proportion of !3C from labeled bicarbonate appeared in amino acids, especially asparagine, in wheat roots treated with ammonium compared to those exposed to low salt concentrations.…”

“…Popp and Summons (1983) reported that a greater proportion of !3C from labeled bicarbonate appeared in amino acids, especially asparagine, in wheat roots treated with ammonium compared to those exposed to low salt concentrations. In tomato roots supplied with 14C-bicarbonate, 14C was incorporated similarly into the aspartate and asparagine (C4) and glutamate and glutamine (C5) fractions (Ikeda et al 1992). It was reported that the asparagine concentration increased relative to the concentrations of other amino acids in the shoot and roots of rice seedlings grown with ammonium nitrogen (Oji and Izawa 1974;Marwaha and Juliano 1976).…”