INSTITUTO DE FISIOLOGIA VEGETAL
Unidad Ejecutora - UE
Is the electrolyte leakage assay an unequivocal test of membrane deterioration during leaf senescence ?
ROLNY NS; COSTA ML; CARRION CA; GUIAMET JJ
PLANT PHYSIOLOGY AND BIOCHEMISTRY
ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
Lugar: Paris; Año: 2011 vol. 49 p. 1220 - 1220
The main symptoms of leaf senescence are the degradation of proteins (which may be accompanied by ammonium accumulation) and chlorophyll, and an increase of electrolyte leakage (EL), which is attributed to leakage of K+ and, presumably, cell membrane damage. The aim of this study was to test the contribution of ammonium accumulation to increased EL in senescing barley (Hordeum vulgare L.) leaves . During senescence of detached leaves (i.e., without N remobilization), there was an early accumulation of ammonium. EL increased early, and it correlated with ammonium leakage (r2= 0.82) and ammonium accumulation in tissues (r2= 0.73), while the correlation with K+ leakage was lower (r2= 0.23). During senescence of attached leaves (i.e., with N remobilization), lower amounts of ammonium accumulated, and this build up occurred later. Changes in EL paralleled ammonium accumulation. Cell viability and the membrane integrity were analyzed using the cell impermeant stain propidium iodide (PI). In detached leaves, EL increased after 3 days in darkness, however cell viability and membrane integrity did not change compared to non-senescing leaves. Detached leaves maintained their capacity to regreen after 3 days of senescence-aceleration in darkness, i.e., membrane integrity was not severely compromised in spite of the increase of EL. EL during the early stages of senescence may be due mainly to ammonium accumulation, possibly resulting from proteolysis, aminoacid deamination, and ammonium efflux , rather than to membrane damage. Therefore, increased EL in senescing leaves should be interpreted with caution.