“…It has been suggested that conversion of chloroplasts to gerontoplasts, and therefore leaf senescence, may be reversible in several species if the senescing tissue is exposed to conditions favoring re-greening (e.g., exogenous application of cytokinins). However, this reversal is only possible before the terminal phase has been initiated and if the "point of no return" is not surpassed (Karagiannis and Pappelis, 1994;Bhattacharya et al, 1996;Olah and Masarovicova, 1998;Zavaleta-Mancera et al, 1999a, b). The 'point of no return' is that point at which, once passed, the leaf is committed to death.…”