biologia plantarum

Biologia plantarum 50:405-410, 2006 | DOI: 10.1007/s10535-006-0057-6

Waterlogging effect on xylem sap glutamine of nodulated soybean

L. Amarante¹, L. Sodek^1,*

¹ Departamento de Fisiologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, C.P. 6109, Campinas - SP, Brazil

Waterlogging of soybean plants (Glycine max L.) led to impaired symbiotic N₂ fixation and a marked decline in glutamine (Gln) concentration in xylem bleeding sap. Xylem Gln concentration increased during the growth cycle of the plant and was correlated with nodule formation. Treatments known to impair N₂ fixation, such as exposing the root system to pure N₂ gas or a mixture of Ar and O₂ (80:20; v/v), led to specific declines in xylem sap Gln. The decrease in Gln observed during waterlogging was also seen on transfer of nodulated plants to aerated hydroponics, where the decline was highly correlated with ureide content in the xylem sap. Upon flooding the nodulated root system, the specific decline in xylem sap Gln could be detected within 10 min and reached a minimum within 60 min, indicating that waterlogging has an immediate effect on N₂ fixation. It is concluded that xylem Gln arises directly from N₂-fixation and is a useful indicator of N₂ fixation activity of symbiotic soybean plants.

Keywords: Glycine max; hypoxia; nitrogen fixation; nitrogen transport

Subjects: amino acids; Glycine max; hypoxia; nitrogen assimilation; nodules, nodulation; soybean; waterlogging effect; xylem sap

Received: October 15, 2004; Accepted: May 24, 2005; Published: September 1, 2006  Show citation