Photosynthetic physiology characteristics of different Catalpa bungei clones under antimony stress

To study the effects of antimony stress on photosynthetic physiology of different antimony tolerance clones of Catalpa bungei.

Two kinds of C. bungei clones with different antimony tolerance were studied, namely sensitive clones (1-1) and tolerant clones (5-8). Three antimony stress concentrations (calculated by antimony element) were set up in a pollution-free red soil as the substrate for pot stress tests. The concentrations of antimony were 0 mg/kg, 1 200 mg/kg and 3 000 mg/kg. The growth, relative content of chlorophyll in leaves, chlorophyll fluorescence parameters and photosynthetic parameters of the two clones were determined at 0 d, 20 d and 40 d, respectively.

1) Under the same conditions, the growth of sensitive clones (1-1) was more affected than that of tolerant clones (5-8). 2) Under antimony stress, the relative content of chlorophyll in the leaves of both clones decreased, and the relative content of chlorophyll in the leaves gradually decreased with the extension of stress concentration and time, but the decrease range of tolerant clones was much less than that of sensitive clones. 3) The chlorophyll fluorescence parameters of the two clones were different under antimony stress. At the same time, the variable fluorescence, maximum photochemical efficiency of PSII and potential activity of PSII all decreased with the increase of antimony stress concentration, and the tolerant clones were less affected.4) Under antimony stress, the net photosynthetic rate of both clones decreased and the intercellular CO₂ concentration increased, indicating that antimony stress was caused by non-stomatal factors.

Under high concentration of antimony stress, the tolerant clones (5-8) had higher chlorophyll content than the sensitive clones (1-1), and the photosynthetic system was less affected by the damage, so they could better cope with antimony stress.