镉胁迫对矮牵牛种子萌发、幼苗生长及抗氧化酶活性的影响

采用营养液培养的方法研究了不同浓度镉Cd（0、1、2和4 mmol·L^-1）处理对矮牵牛（Petunia hybrida）种子萌发、幼苗生长及生理特性的影响。结果发现：与对照相比，较低浓度（1 mmol·L^-1）Cd处理下矮牵牛种子萌发和幼苗生长均显著被抑制，当Cd浓度增至4 mmol·L^-1时完全抑制了矮牵牛种子的萌发。Cd胁迫在低浓度时激活矮牵牛幼苗叶片过氧化物酶（POD）、过氧化氢酶（CAT）活性,而高浓度产生抑制效应；抗坏血酸过氧化物酶（APX）和超氧化物歧化酶（SOD）活性与对照相比均显著升高，丙二醛（MDA）含量无显著变化。不同浓度的乙二胺四乙酸(EDTA)的加入使4 mmol·L^-1 Cd胁迫下矮牵牛幼苗叶片POD和APX活性增加，但不影响SOD和CAT活性；此外，6 mmol·L^-1 EDTA使Cd胁迫下矮牵牛幼苗叶片中MDA含量增加。结果表明，Cd胁迫抑制矮牵牛种子萌发和幼苗生长，却使幼苗叶片POD、CAT和APX活性增加，EDTA的加入能够进一步提高Cd胁迫幼苗POD和APX活性。因此，矮牵牛幼苗在Cd胁迫下具有较强的抗氧化损伤的能力。

Effects of Cd Stress on the Seed Germination,Seedling Growth and Activities of Antioxidant Enzymes in Petunia hybrida

Effects of different cadmium (Cd) concentrations (0, 1, 2 and 4 mmol·L^-1) on the seed germination, seedling growth and physiological property of Petunia hybrida were studied. In comparison with the control, seed germination and seeding growth exhibited a significant decrease at low level of Cd²⁺ concentration(1 mmol·L^-1), and these factors were all completely restrained at high concentration(4 mmol·L^-1). Compared to the control, the activities of peroxidase (POD) and catalase (CAT) were enhanced in P.hybrida seedings exposed to low Cd concentrations but inhibited at higher concentrations; the activities of ascorbate peroxidase (APX) and superoxide dismutase (SOD) could be increased in response to different Cd concentrations, no significant change in the malonaldehyde (MDA) content was observed. Ethylene-aminetetraacetic acid (EDTA) could stimulate the activities of POD and CAT in P.hybrida seedlings exposed to 4 mmol·L^-1 Cd treatment, and MDA content was also enhanced when seedlings were treated with 4 mmol·L^-1 Cd in the presence of 6 mmol·L^-1 EDTA. In conclusion, these results indicate that Cd stress significantly inhibit P.hybrida seed germination and seedling growth, but stimulate the activities of POD, CAT and APX in the leaves of seedlings; the application of EDTA further enhance the activities of POD and APX in Cd-treated P.hybrida seedlings. Therefore, higher activities of antioxidative enzymes may protect P.hybrida seedlings against Cd-induced oxidative change.