Utilization of 15NO3 − by nodulated soybean plants under conditions of root hypoxia

Abstract

Waterlogging of soils is common in nature. The low availability of oxygen under these conditions leads to hypoxia of the root system impairing the development and productivity of the plant. The presence of nitrate under flooding conditions is regarded as being beneficial towards tolerance to this stress. However, it is not known how nodulated soybean plants, cultivated in the absence of nitrate and therefore not metabolically adapted to this compound, would respond to nitrate under root hypoxia in comparison with non-nodulated plants grown on nitrate. A study was conducted with 15 N labelled nitrate supplied on waterlogging for a period of 48 h using both nodulated and non-nodulated plants of different physiological ages. Enrichment of N was found in roots and leaves with incorporation of the isotope in amino acids, although to a much smaller degree under hypoxia than normoxia. This demonstrates that nitrate is taken up under hypoxic conditions and assimilated into amino acids, although to a much lesser extent than for normoxia. The similar response obtained with nodulated and non-nodulated plants indicates the rapid metabolic adaptation of nodulated plants to the presence of nitrate under hypoxia. Enrichment of N in nodules was very much weaker with a distinct enrichment pattern of amino acids (especially asparagine) suggesting that labelling arose from a tissue source external to the nodule rather than through assimilation in the nodule itself.

Short-term root flooding and recovery conditions—affected photosynthetic process of common bean plants

“…Besides limitation in CO 2 assimilation by plants, lower Chl indexes can be a result of Chl degradation and low turnover rates along the recovery time (up to 7 days of recovery), due to a reduction in mineral nutrient uptake and transport through xylem sap to the shoot, mainly nitrogen forms (Lanza et al 2014;Garcia et al 2020). Decreases in photosynthetic pigments led to a reduction in energy absorption and an imbalance in electron transport chain (ETC), which was prolonged over 7 days of the recovery period.…”

Changes in soluble amino acid composition during Canavalia ensiformis development: responses to nitrogen deficiency

“…In fact, the internal pool of soluble amino acids in plant tissues indicates the N status by providing a signal that can regulate nitrate uptake by the plant root system (Miller et al 2008;Fan et al 2009). Therefore, environmental changes may impair metabolism and the exportation of N from the roots to the shoots (Justino and Sodek 2013;Lanza et al 2014). For instance, reduction of glutamine and increase of alanine in xylem sap were observed in nodulated soybean plants under waterlogging stress (Amarante et al 2006;Justino and Sodek 2013).…”