关键词: 甜高粱, 镉胁迫, 抗氧化酶, 光合作用, 镉富集

Abstract: In order to clarify the effects of cadmium stress on physiological and biochemical indexes of sweet sorghum and the characteristics of cadmium enrichment, Liaotian 1 and 5 different concentrations of cadmium solution (0, 50, 100, 200, 300 μmol·L^-1))were used to simulate the stress environment. The growth index, antioxidant enzyme activity, isoenzyme, photosynthetic parameters, fluorescence parameters, light response curve and cadmium enrichment rate of seedlings under stress were measured and analyzed. The results showed that:① The cadmium stress significantly decreased the fresh weight, plant height, shoot and shoot dry weight of sweet sorghum.② With the increase of stress concentration, superoxide dismutase (SOD) increased first and then decreased, peroxidase (POD) activity increased significantly, catalase (CAT) activity decreased significantly, and ascorbate peroxidase (APX) became lower first, then increase and then lower. In the early stage of stress, multiple bands of SOD and POD zymograms were deepened with the increase of stress concentration, and new S2,P2 bands appeared, while no new bands appeared in CAT and APX zymograms.③ Leaf chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr), leaf primary light energy conversion efficiency (Fv/Fm), photosynthetic electron transport quantum efficiency (φPSⅡ), photochemistry quenching coefficient (qP), maximum net photosynthetic rate (Pmax), apparent quantum efficiency(Q), dark respiration rate (Rd), light saturation point (LSP) decreased significantly, and intercellular CO₂ concentration (Ci), non the photochemical quenching coefficient (NPQ) and the light compensation point (LCP) increased. ④ With the increase of stress concentration, the cadmium concentration in the aboveground and underground parts increased, while the enrichment rates of aboveground, underground and single plant decreased. Therefore, cadmium stress reduced biomass by inhibiting photosynthesis of sweet sorghum. Sweet sorghum maintained its normal cell metabolism by regulating the gene expression of its antioxidant enzymes. The low concentration of cadmium stress was beneficial to enrichment of cadmium in sweet sorghum, and the high concentration of cadmium stress caused sweet sorghum irreversible damage, and the biomass reduced, resulting in a decrease in the enrichment rate of cadmium in sweet sorghum.

Key words: sweet sorghum, cadmium stress, antioxidant enzymes, photosynthesis, cadmium enrichment