BRs have various physiological and morphological effects on plants, including ethylene production which is the cause of senescence. BL retarded abscission of leaves of Citrus was reported (Iwahori et al., 1990). BRs increase chlorophyll breakdown (Vardhini & Rao,2002) but inhibit anthocyanin biosynthesis (Brosa, 1999). On the contrary, BRs accelerate senescence (He et al., 2001; Rao et al., 2002) but the studies about this topic are not enough to clarify their effect in regulating
senescence process.