| Soil texture is an important factor to effect the toxicity of heavy metal on crop plants. In order to investigate the effects of three textures of soil including loam soil, clay soil and sandy soil on the photosynthetic characteristics of wheat flag leaves under chromium stress, traits of morphology and photosynthesis of wheat, such as plant biomass, length and numbers of root, photosynthetic rate(Pn), stomata conductance(Gs), intercellular CO2 concentration(Ci), transpiration rate(Tr), water utilization efficiency(WUE), and relative content of chlorophyll were studied during grain-filling stage. The results showed that, with the increasing of chromium concentration, the length of root decreased in clay soil, while it was shown as the trend of increasing first and then decreasing in loam soil and sandy soil, which reaching the peak at the chromium concentration of 100 mg·kg-1. In three soil textures,lateral root numbers were all reduced as the chromium concentrations increasing; biomass of different organs were decreased also; the Pn decreased in loam soil and showed the trend of increasing first and then decreasing in clay soil and sandy soil, which reached the peak as chromium concentrations was 100 and 200 mg·kg-1, respectively; the Gs, Ci, Tr and relative content of chlorophyll of flag leaves showed a trend of increasing first and then decreasing, and to their peak at the chromium concentration of 100 mg·kg-1 in loam soil and clay soil, and at 200 mg·kg-1 in sandy soil; the WUE increased at first and then decreased in clay soil, showing rising trend in sandy soil and little fluctuation in loam soil. To sum up, there were distinct inhibitions or increasing first and then decreasing trends of photosynthetic indexes of wheat flag leaves during grain-filling stage with chromium stress. While chromium concentration was more than 200 mg·kg-1, theses stress effects on wheat were showed more and more obviously, such as reduction of root length and root number, decrease of Gs, Ci, Tr and relative content of chlorophyll of flag leaves, as well as the biomass of different organs. Additionally, in the three soil textures, photosynthesis indexes of the flag leaves of wheat during grain-filling stage declined in different degrees with chromium stress, but these decreasing trends were more obvious in sandy soil than that in loam soil and clay soil. |
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