Abstract: hlorophyll fluorescence in PS II of the leaves of maize (Zea mays L. ) seedlings under stress was measured with a newly developed pulse modulation fluorometer. Water stress had no effect on the initial fluorescence (Fo) but slightly inhibited the maximum fluorescence (Fm), variable fluorescence(Fv), Photochemical efficiency (Fv/Fm) and the effective activity of PS Ⅱ (Fv/Fo). In the first minute of saturated flash, some changes in photochemical quenching (qp) occurred. However, when leaves that had been subjected to water stress were illuminated again with intense light (1100 μmol · m-2· s-1) for 30 min, fluorescence yield, fluorescence kinetics, photochemical and non-photochemical quenching(qE) all changed significantly. Pretreatment of the leaves with scavengers of activated oxygen butylated hydroxytoluene (BHT), ascorbic acid(ASA) and 6-BA could change to a certain extent the effect of water stress on Q-quenching and E-quenching. It might be concluded that: (1) light enhanced the damage of water stress on photosynthetic apparatus; and (2) such damage could be relieved by ASA and 6-BA.

Key words: Zea mays, Water stress, Antioxidant, Chlorophyll fluorescence