Our results also showed that UV-B radiation decreased seed ABA level that was correlated with seed growth rate, resulting in smaller seed size. This indicates that seed ABA concentration is involved in the control of the rate of dry matter accumulation. Morandi et al. (1990) suggested that ABA may increase the assimilate availability during the critical cell division period, and thus may regulate cotyledon cell number and seed growth rates. Ackerson (1984) also found that ABA could regulate cell divisionduring early embryo development, thus influencing potential cell storage capacity