Abstract: 【Objective】 Considering the heavy metal pollution in the distribution area of Indocalamus barbatus McClure, the response of its photosynthetic characteristics to chromium(Cr)stress was evaluated. This should provide a basis for the study of physiological response mechanisms of I. barbatus under Cr stress and as a reference for ecological restoration in Cr-contaminated areas.【Method】 A pot culture experiment was used to study the effects of different Cr concentrations(0, 100, 400 and 800 mg/kg)on the photosynthetic characteristics of I. barbatus, using K₂Cr₂O₇ as the Cr source. A Cr solution was prepared in distilled water and applied to the soil at 17:00 with two times. Plant growth was then observed regularly for two months. The relative chlorophyll content(SPAD), photosynthetic gas exchange parameters, and chlorophyll fluorescence parameters were determined using a portable SPAD-502 chlorophyll meter and the Li-6400XT portable photosynthesis system.【Result】 Plants treated with a low concentration of Cr grew normally and had green leaves. Under the high concentration treatment, the leaves showed chlorotic changes and yellowing, and some were curled or dead. SPAD, net photosynthetic rate(P_n), stomatal conductance(G_s)and transpiration rate(T_r)initially increased and then decreased with increasing Cr concentrations, whereas intercellular CO₂ concentration(C_i)showed an opposite trend. P_n was promoted at low Cr concentrations and was inhibited at the high Cr concentrations; the non-stomatal limiting factor was the main reason for the change in P_n. At the low Cr concentration, fluorescence parameters for the PSⅡ maximal photochemical efficiency(F_v/F_m), PSⅡ potential activity(F_v/F₀), PSⅡ effective photochemical efficiency(F_v'/F_m'), PSⅡ actual photochemical efficiency(η_ΦPSⅡ), electron transmission rate(R_ETR), and photochemical quenching(C_PQC)increased, whereas those for non-photochemical quenching(C_NPQ)decreased. This suggested that the improved P_n was related to the stimulation in photochemical activity and enhanced light-utilization efficiency in mesophyll cells. The increased “open” proportion of the PSⅡ reaction center and low heat dissipation were the main reasons for the improved light utilization. As Cr concentration and exposure time increased, F_v/F_m, F_v/F₀, F_v'/F_m', η_ΦPSⅡ, C_PQC, and R_ETR generally presented a downward trend, whereas C_NPQ showed an opposite pattern. These results indicated that long-term treatment with high concentrations of Cr damaged the photosynthetic apparatus, decreased photochemical activity, and resulted in significant photo-inhibition. The increase in C_NPQ indicated that excess excitation energy could be dissipated in the form of heat energy, thereby protecting the photosynthetic apparatus from light damage and improving the resistance of plants to high concentrations of Cr. The enhanced C_NPQ caused by the high Cr concentration led to a reduction in light-energy utilization efficiency; however, this is an important defense mechanism for light destruction in leaves. The dynamic changes in fluorescence parameters under stress showed that F_v/F₀ and C_NPQ were sensitive to the Cr concentration, and this variation presented a relatively broad range. Therefore, these two parameters could be used as a sensitive indicator to measure Cr stress induced damage and the degree of photo-inhibition. 【Conclusion】 Low levels of Cr stress could promote photosynthesis in I. barbatus, whereas long-term exposure to high levels of Cr stress damaged the photosynthetic apparatus, decreased photochemical activity, and caused significant photo-inhibition. Enhanced heat dissipation is an important protective mechanism against the photo-destruction of I. barbatus leaves under high Cr concentrations. Indocalamus barbatus McClure can adapt to certain concentrations of Cr stress in the environment and presents different photosynthetic response adjustment to different concentrations of Cr stress. Thus, Indocalamus barbatus McClure is a suitable plant material for the ecological restoration of Cr polluted areas.