Instituto de Fisiología Vegetal, UNLP-CONICET (FCAyF), cc 327, 1900, diagonal 113 y calle 61, N° 495, La Plata, Argentina.
Plant Physiol Biochem. 2011 Oct;49(10):1220-7. doi: 10.1016/j.plaphy.2011.06.010. Epub 2011 Jul 13.
The main symptoms of leaf senescence are the degradation of chlorophyll and proteins (which may be accompanied by ammonium accumulation), and an increase of electrolyte leakage (EL), which has been traditionally attributed to disruption of cell membranes. The aim of this study was to determine if ammonium efflux contributes to the increase EL in senescing barley leaves. During senescence of detached leaves the increase of EL correlated with ammonium leakage (r(2) = 0.82) and ammonium content in tissues (r(2) = 0.73), but not with K(1+) leakage (r(2) = 0.23). Although lower amounts of ammonium accumulated in senescing attached leaves, again changes in EL paralleled ammonium accumulation. EL increased early during senescence even though ion leakage was selective (leaves leaked proportionally more ammonium than K(1+)), and membranes appeared intact as judged from staining with the cell impermeant stain propidium iodide. Detached leaves maintained their capacity to regreen after 3 days of senescence-acceleration in darkness, i.e., membrane integrity was not severely compromised. During the early stages of senescence, EL increases due to ammonium accumulation (possibly resulting from protein degradation) even if there is no massive disruption of cell membranes. Therefore, increased EL in senescing leaves is not an unequivocal symptom of cell membrane damage.
叶片衰老的主要症状是叶绿素和蛋白质的降解（可能伴随着铵积累），以及电解质泄漏（EL）的增加，这传统上归因于细胞膜的破坏。本研究旨在确定铵流出是否有助于衰老大麦叶片中 EL 的增加。在离体叶片衰老过程中，EL 的增加与铵泄漏（r² = 0.82）和组织中铵含量（r² = 0.73）相关，但与 K(1+)泄漏无关（r² = 0.23）。尽管衰老附着叶片中积累的铵量较少，但 EL 的变化再次与铵积累平行。衰老早期 EL 增加，尽管离子泄漏具有选择性（叶片泄漏的铵比 K(1+)多），并且根据细胞不可渗透染料碘化丙啶的染色判断，膜似乎完整。在黑暗中加速衰老 3 天后，离体叶片仍保持重新变绿的能力，即膜完整性未受到严重损害。在衰老的早期阶段，EL 的增加是由于铵的积累（可能是由于蛋白质的降解）引起的，即使没有细胞膜的大规模破坏。因此，衰老叶片中 EL 的增加并不是细胞膜损伤的明确症状。
