Abstract: The cut flower chrysanthemum ‘Jinba’ was respectively treated with lower temperature and weaker light (16 ℃/ 12 ℃, PFD 100  μmol·m^-2·s^-1) and critical low temperature and weak light (12 ℃/8 ℃, PFD 60 μmol·m^-2·s^-1 ) for 11 days, and then transferred to normal condition (22 ℃/18 ℃, PFD 450 μmol·m^-2·s^-1) for 11 days, aimed to study the low temperature and weak light stress and its recovery on the photosynthesis and chlorophyll fluorescence of chrysanthemum leaves. Under the stress of lower temperature and weaker light, the net photosynthetic rate (P_n) and stomatal limitation (L_s) of chrysanthemum leaves decreased while the intercellular CO₂ concentration (C_i) increased, the maximal photochemical efficiency of
PSⅡ(F_v/F_m) in dark and the initial fluorescence (F_o) had no obvious change, but the maximal photochemical efficiency of PSⅡ (F_v'/F_m′) in light increased after an initial decrease. Contrarily, under the stress of critical low temperature and weak light, the F_o increased, and the F_v/F_m and F_v'/F_m' decreased significantly. The quantum yield of PSⅡelectron transport (Φ_PSⅡ), photochemical quenching (q_P),and apparent photosynthetic electron transfer rate (ETR) of chrysanthemum leaves decreased with increasing stress and time, and recovered quickly after the release of lower temperature and weaker light stress but more slowly after the release of critical low temperature and weak light stress. At the same time,the photochemistry react rate (Prate) decreased, but the hot dissipation of antenna (Drate) and the energy dissipation of PSⅡ (Ex) increased under the stress conditions. Drate was the main pathway of superfluous light allocation.

Key words: chrysanthemum, low temperature, weak light, photosynthesis, chlorophyll fluorescence parameter, temperate grassland, bacterial diversity, bacterial community structure, nitrogen deposition, precipitation.