Cadmium (Cd) is a common heavy metal pollutant in the aquatic environment, generally toxic to plant growth and leading to growth inhibition and biomass reduction. To study the oxidation resistance in Sargassum fusiforme seedlings in response to inorganic Cd stress, we cultured the seedlings under two different Cd levels: natural seawater and high Cd stress. High Cd stress significantly inhibited the seedlings growth, and darkened the thalli color. Additionally, the pigment contents, growth rate, peroxidase (POD) activity, dehydroascorbic acid (DHA) content, and glutathione reductase (GR) activity in S. fusiforme were significantly reduced by high Cd treatment. Contrarily, the Cd accumulation, Cd2+ absorption rate, dark respiration/net photosynthetic rate (Rd/Pn), ascorbic acid (Vc) content, soluble protein (SP) content, glutathione (GSH), and the activities of superoxide dismutase (SOD) and catalase (CAT) of S. fusiforme under Cd treatment significantly increased compared to the control group. The decrease of malondialdehyde (MDA) was not significant. Although S. fusiforme seedlings increased the antioxidant activities of POD, SOD, Vc, and the AsA-GSH cycle to disseminate H2O2 and maintain healthy metabolism, high Cd stress caused Cd accumulation in the stem and leaves of S. fusiforme seedlings. The excessive Cd significantly restricted photosynthesis and reduced photosynthetic pigments in the seedlings, resulting in growth inhibition and deep morphological color, especially of the stems. High levels of Cd in seawater had toxic effects on commercial S. fusiforme seedlings, and risked this edible seaweed for human food.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |