CHLOROPHYLL FLUORESCENCE AND GAS EXCHANGE RESPONSES OF MAIZE SEEDLINGS TO SALINE-ALKALINE STRESS

DENG, C. N., G X. ZHANG, X. L. PAN and K. Y. ZHAO, 2010. Chlorophyll fluorescence and gas exchange responses of maize seedlings to saline-alkaline stress. Bulg. J. Agric. Sc., 16: 49-58 Responses of photosynthesis rate, stomatal conductance, chlorophyll fluorescence characteristics and chlorophyll content of maize (Zea mays L.) seedlings under combined salinity-alkalinity stress were examined. Investigation revealed that the net photosynthesis rate (P-n) and stomatal conductance (g(s)) decreased rapidly with increasing of salinity-alkalinity stress. The intercellular CO2 concentration (C-i) decreased at low salinity-alkalinity and increased at high salinity-alkalinity. The maximal efficiency of photosystem II (PSII) photochemistry (F-V/F-M) decreased only at high salinity-alkalinity. The comprehensive photosynthesis performance index (PIABS) gradually decreased with increasing of salinity-alkalinity concentration. The JIP test showed that the electric transfer of donor side and acceptor side of PSII in maize seedlings were inhibited by high salinity-alkalinity stress. Stomatal limitation is the main reason of decreased photosynthesis rate at low salinity-alkalinity, and non-stomatal limitation, i.e. decreased photosynthesis activity in PSII plays an important role in decreased photosynthesis rate at high salinity-alkalinity.