Photosynthetic responses of Sweet Sorghum cultivars to Cadmium toxicity
Abstract
In this study photosynthetic modification of sweet sorghum was studied in response to heavy metal Cadmium (Cd) under greenhouse conditions. The experiment was concentrated specifically on Keller (KE) and Etian (ET), two cultivars of sweet Sorghum. The plants subjected to 100 mg kg-1 Cd in soil were compared with the control plants without Cd treatment. The results indicated that both cultivars of sweet sorghum display similar photosynthetic responses to Cd exposure. The high Cd concentration resulted in significant decline of photosynthesis net rate (Pn). The Pn of Cd treated plants was reduced compared with control plants, from 5.29% to 16.7 % in KE and from 27.3% to 29.4% in ET. Moreover, Cd treated plants were detected to have lower stomata conductance (gs) but slightly higher intercellular CO2 concentrations (Ci) than control plants. Chlorophyll content also displayed significant difference between the control plants and Cd treated plants. In ET, compared to the controls, the reduction of both chlorophyll-a and chlorophyll-b was observed under Cd stress. In contrast, chlorophyll content was significantly enhanced by Cd stress in KE. An increase of chlorophyll content occurred after Cd exposure, from 5.08 mg/g FW in control plants to 6.43mg/g FW in Cd treated plants.
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