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Effect of low rhizosphere oxygen on growth, nitrogen fixation and nodule morphology in lucerne
Author(s) -
ArreseIgor C.,
Royuela M.,
Lorenzo C.,
Felipe M. R.,
AparicioTejo P. M.
Publication year - 1993
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1993.tb01786.x
Subject(s) - nitrogen fixation , biology , aerenchyma , rhizosphere , respiration , nodule (geology) , root nodule , agronomy , nitrogenase , oxygen , shoot , frankia , medicago sativa , botany , chemistry , paleontology , genetics , organic chemistry , bacteria
Oxygen shortage in soils can occur following a wide range of natural circumstances, affecting the plant's physiology. In this paper the performance of nodulated lucerne plants under severe hypoxia is examined and the mechanisms involved to achieve this adaptation are discussed. Nodulated lucerne plants ( Medicago sativa L.) were grown with their rooting medium exposed to 1 or 21 kPa oxygen. Final yield, as expressed on a shoot dry weight basis, was unaffected but root and nodule dry weights were reduced by 50%. Water content in roots and nodules was higher at 1 kPa as a result of the formation of aerenchyma. Specific acetylene reduction activity was higher in hypoxic nodules as a consequence of modified nodule structure, although they were more sensitive to the presence of acetylene or nitrate. Root respiration was insensitive to changes in external oxygen supply, therefore providing adequate support for mineral uptake. Nodule respiration rates were 5 times higher in control plants when measured as CO 2 evolution, whereas no differences were observed in O 2 uptake. It is suggested that adaptation of nodulated lucerne to low oxygen concentrations involves changes in photosynthate allocation and nodule morphology, which provide a more efficient nitrogen fixation.