Alternative pathway respiration is associated with ammonium ion sensitivity in spinach and pea plants
2002
Lasa, B. | Frechilla, S. | Aparicio-Tejo, P.M. | Lamsfus, C.
Spinach and pea plants were grown in hydroponic culture with nitrate or ammonium salts as the nitrogen source. Dry matter accumulation and photosynthetic rate declined in spinach plants fed with ammonium salts, whereas they did not change in pea plants compared with nitrate-fed plants. Measurement of organic nitrogen and free amino acid content showed that ammonium ions were assimilated in shoots in spinach plants and in roots in pea plants. Ammonium ion nutrition led to a decline in starch content in both species. Organic acids increased in roots of pea plants fed with ammonium ions whereas they declined in spinach plants. In both species ammonium ions increased root respiration rate but the contribution of both routes (cytochromic and alternative pathway) to this increase was different depending on the species. In spinach plants, ammonium ions increased the cytochromic path and decreased the alternative pathway, whereas in pea plants both routes were stimulated mainly through the alternative pathway. The differences in the sensitivity to ammonium ions between both species are discussed in terms of differences in the availability of C skeletons and energy, which could be due in part to differences in the capacity to stimulate the alternative pathway.
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