| The pot experiment was adopted to study the effects of cadmium（Cd） on biomass, photosynthesis, chlorophyll fluorescence characteristics, chlorophyll content and the accumulation of cadmium in grey poplars（Populus×canescens） and cathay poplars（Populus pseudo-simonii K.）. The substrate was the mixture of soil, vermiculite and worm cast with six concentrations of soil Cd treatment（0 mg·kg-1, 20 mg·kg-1, 70 mg·kg-1, 150 mg·kg-1, 300 mg·kg-1 and 500 mg·kg-1）. The results showed that the lower Cd concentration（20 mg·kg-1） did not significantly inhibit the growth of either poplar, while higher concentrations（≥70 mg·kg-1） had significant inhibition effect. The bioaccumulation capacity in two poplars’ roots were higher than that of leaves and stems, and the bio-concentration factors（BCF） of grey poplars was higher than that of cathay poplars, however, their translocation factors（IF） were approximately equivalent. The contents of chlorophyll a, chlorophyll b and total chlorophyll of the leaves of two poplar seedlings were significantly lower in the Cd treatments than those of control, and the contents were negatively related to the Cd concentrations. In grey poplars, the chlorophyll a/b ratio was higher with higher Cd concentrations, though not significantly; in cathay poplars, however, such value showed a trend of increasing after decreasing, with the addition of Cd in the growth medium also caused significant deleterious effect on the net rate of photosynthesis（Pn）, transpiration rate（Ts） and stomatal conductance（Gs） in both species of poplar seedlings, but the intercellular CO2 concentration（Ci） increased dramatically, indicating that the non-stomatal factor accounted for inhibition of photosynthesis in the leaves of poplar seedlings. The ratio of Fv /Fm and Fv/F0 significantly decreased with increasing Cd concentrations in both plants. The comparison of inhibition rate of two plants indicated that grey poplars were less sensitive to the Cd stress. |
