Using wild-type (WT) leaves and those from an ore9 delayed-senescence Arabidopsis mutant, we investigated the delaying and accelerating effects of benzyladenine (BA) and abscisic acid (ABA), respectively, on the degradation process of the photosynthetic apparatus during dark-induced senescence (DIS). In the mutant, delays were seen for both the breakdown of chlorophyll (ChI) and the decrease in photochemical efficiency of photosystem II (Fv/Fm). Moreover, each step was prolonged in the disassembly process of the Chi-protein complexes. In the presence of HA, Chi degradation was retarded to a similar extent for both the mutant and the WT, but the decrease in Fv/Fm was not. However, in the presence of AHA, the two processes were accelerated in both genotypes. Therefore, although the ore9 mutation causes this functional delayed-senescence, it may not be related to the non-functional delay that happens afterwards. In contrast, HA seems to affect both processes.
