关键词: 景观生态安全, 元胞自动机, 城市发展, 东莞市

Abstract: With Indocalamus barbatus as test material, the effects of silicon on the relative content of chlorophyll, diurnal variations of photosynthesis, and chlorophyll fluorescence were examined under simulated acid rain (pH 3.0) stress. The results showed that under acid rain stress, 20 and 500 mg·L^-1 of Na₂SiO₃ could prohibit the decrease of the relative content of chlorophyll to some extent; 100 mg·L^-1 of Na₂SiO₃ could get best effect, with the relative chlorophyll content being 22.7% higher than the control; while 500 mg·L^-1 of Na₂SiO₃ didn’t have any effect. Under the stress, the midday depression of photosynthesis became more serious. The average daily net photosynthetic rate (P_n), stomatal limitation value (L_s), and stomata conductance (G_s) were all decreased significantly, while the intercellular CO₂ concentration (C_i) increased. After treated with 20-100 mg·L^-1 of Na₂SiO₃, the P_n,L_s, and G_s increased to some extent while C_i decreased, and 100 mg·L^-1 of Na₂SiO₃ was most effective, with the average daily P_n increased by 39.2%. The maximum fluorescence of dark adaptation(F_m), maximal photochemical efficiency (F_v/F_m), potential activity (F_v/F_o), effective photochemical efficiency (F_v′/F_m′), maximum fluorescence of light adaptation (F_m′) of PSII, photochemical quenching (q_P), non-photochemical quenching (q_N), and actual photochemical efficiency of PSII (Φ_PSⅡ) were all decreased obviously under simulated acid rain stress, but the minimum fluorescence of dark adaptation (F_o) and the minimum fluorescence of light adaptation (F_o′) increased. 100 mg·L^-1 of Na₂SiO₃ could restrain the changes of fluorescence parameters obviously, with the F_v/F_m, F_v/F_o,F_v′/F_m′ and Φ_PSⅡ increased by 35.2%, 146.2%, 55.0% and 24.3%, respectively, compared with the control. It was suggested that applying appropriate concentration of exogenous silicon to I. barbatus could efficiently relieve the decrease of its photosynthetic activity and the damage of its photosynthetic system caused by acid rain, and thus, improve its photosynthetic ability under the stress.

Key words: landscape ecological security, cellular automata, urban development, Dongguan City.