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IAA (indole-3-acetic acid), can regulate plant growth and development, and it can involve in regulation of abiotic stresses. In the present study, the effects of spraying different concentrations (0, 25, 50, 100 and 200 μmol/L) of IAA on the photosynthesis physiology in lettuce were investigated. The lettuce (Lactuca sativa) exposed to cadmium (Cd) exhibited a substantial change in photosynthetic pigment content and photosynthetic parameters. Spraying exogenous IAA resulted in alleviating the inhibitory of Cd toxicity to lettuce. The photosynthetic pigment content in shoot of lettuce increased by spraying with IAA compared with the Cd treatment alone. Cd stress caused reductions (P < 0.05) in Pn and Ls, respectively, whereas Gs, Ci, and Tr were increased, compared with the control. Spraying exogenous IAA resulted that the Pn increased and the Ls, Gs, Ci, Tr showed different trend. Therefore, spraying IAA effectively changed the photosynthetic pigment contents and photosynthesis parameters in lettuce.

Lettuce (Lactuca sativa) is one of the most common green leafy vegetables, which is widely cultivated all over the world, but extremely sensitive to cadmium (Cd) contaminated in soil. The effects of three hyperaccumulator plants straw (Solanum nigrum, Bidens pilosa and Galinsoga parviflora) on the antioxidant enzyme activities and osmotic regulators and malondialdehyde (MDA) content under Cd stress were studied by pot culture. Compared with no straw, three kinds of hyperaccumulator straw of S. nigrum straw, B. pilosa straw and G. parviflora straw increased the content of soluble protein and proline in lettuce, the activity of peroxidase (POD) and catalase (CAT) in lettuce was also increased, and the content of MDA was decreased. The stress resistance of lettuce was improved and the toxicity of Cd to lettuce was alleviated by using three kinds of hyperaccumulator plant straw.