Nitric oxide in plants: pro- or anti-senescence
Résumé
Senescence is a regulated process of tissue degeneration which concerns any plant organ and consists in the degradation and remobilization of molecules to other growing tissues. Senescent organs display microscopic changes as well as internal cellular structure modifications and differential gene expression. A large number of factors influencing senescence have been described including age, nutrient supply and environmental interactions. Internal factors such as phytohormones also affect the timing of leaf senescence. A link between the senescence process and nitric oxide (NO) production in senescing tissues has been noticed for many years. Astonishingly, this link proves to be either a positive or a negative correlation depending upon the organ. NO is a gas signaling or a toxic molecule known to have multiple roles in plants; this review discusses the duality of NO roles in the senescence process of two different plant organs, leaves and root nodules.