 Water stress substantially increased ABA but reduced zeatin ( Z ) + zeatin riboside ( ZR ) concentrations in the root exudates and leaves . ABA significantly and negatively , while Z+ZR positively , correlated with Pr and Chl of the flag leaves . ABA , not Z+ZR , was positively and significantly correlated with SPS activity and remobilization of pre-stored carbon . Spraying ABA reduced Chl in the flag leaves , and enhanced SPS activity and remobilization of carbon reserves . Spraying kinetin had the opposite effect . The results suggest that both ABA and cytokinins are involved in controlling plant senescence , and an enhanced carbon remobilization is attributed to an elevated ABA level in rice plants subjected to water stress . 