Influence of plant age and growth conditions on nitrate assimilation in roots of Lotus japonicus plants

Functional Plant Biology - Tập 29 Số 4 - Trang 485 - 2002
Purificación Pajuelo1, Eloísa Pajuelo1, Alicia Orea2, J. Romero3, Antonio J. Márquez4
1Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Química, Universidad de Sevilla, Apdo. 553, 41080-Sevilla, Spain.
2Consejo Superior de Investigaciones Científicas, Madrid, Spain
3Instituto de Bioquı́mica Vegetal y Fotosı́ntesis, Centro de Investigaciones Cientı́ficas ‘Isla de la Cartuja’, Avda Américo Vespucio s/n, 41092 Sevilla, Spain
4Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Química, Universidad de Sevilla, Apdo. 553, 41080-Sevilla, Spain.Corresponding author; email:

Tóm tắt

In roots of Lotus japonicus (Regel) Larsen cv. Gifu, the level of NADH-nitrate reductase (NR) activity and protein, as well as ferredoxin-nitrite reductase activity and nitrate accumulation, were higher in roots of young plants, and decreased in mature plants grown in seed trays. When plants were grown in larger pots, the decrease in NR activity and nitrate accumulation took place at a later stage of growth, suggesting that the cessation of nitrate assimilation in mature plants could be related to both ageing and a lower availability of space for roots. Low NR activity was detected in leaves, whereas nitrate accumulation in this tissue could reach relatively high levels. NR activity and protein, and nitrate accumulation, also decreased in leaves of mature plants, indicating that the diminution in nitrate accumulation and NR in roots from mature plants is not related to a shift of the nitrate assimilation process from roots to leaves. Measurement of the extent of total and active NR according to the phosphorylation/dephosphorylation inactivating mechanism described for spinach leaf NR, indicates that this mechanism is operative on NR from L. japonicus roots, being responsible for a great proportion of inactive NR protein. The amount of inactive NR protein in roots due to the aforementioned phosphorylation mechanism also increased in mature plants.

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Functional Plant Biology

Tập 29 Số 4

485

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