Abstract: Under pot and field culture, the photosynthesis and chlorophyll fluorescence characteristics of citrus plants (Tiancao) were studied. The results showed that the net photosynthesis rate (Pn), stomatal conductance (Gs), intercellular CO₂ concentration (Ci) and transpiration rate (Tr) remained unchanged in the plants grown in large pots as compared to those in field at different photosynthetic photo flux density. However, Pn, Gs and Tr of plants cultured in small pots significantly decreased, while Ci unchanged. The capacity for CO₂ utilization reduced only at high concentration under large pot culture, but it significantly declined at all CO₂ concentration under small pot culture in comparison with the control. Maximal efficiency of PSⅡ photochemistry (Fv/Fm), effective PSⅡ quantum yield (ΦPSⅡ), electron transport rate (ETR) and photochemical quenching (qP) as well as non\|photochemical quenching (NPQ) of plants under large pot culture showed no significant difference as compared to that in the field except that excitation energy capture efficiency of PSⅡ reaction centers (Fv'/Fm') decreased prominently. However, Fv'/Fm', ΦPSⅡ and ETR markedly decreased and NPQ increased in the plants cultured in small pots, which was consistent with the analysis results of the distribution of excitation energy.

Key words: citrus, pot cultivation, photosynthesis characteristic, chlorophyll fluorescence