不同光强下镉胁迫对紫茉莉光合作用和抗氧化系统的影响

通过土培实验,比较分析了3种光强(全光照(HL)、50%全光照(ML)和10%全光照(LL))下镉胁迫(30 mg·kg-1)对紫茉莉植株生长、光合作用、光合色素、镉、镁、铁和钾含量、脂质过氧化、抗氧化酶活性、抗坏血酸和谷胱甘肽含量的影响.结果发现,镉胁迫显著降低紫茉莉叶片的净光合速率,对HL植株的抑制程度高于ML和LL植株;HL和LL植株最大光化学效率在镉胁迫下显著降低,而ML植株所受影响不明显;镉胁迫显著提高了紫茉莉叶片的暗呼吸速率,ML植株提高幅度最大.镉胁迫对紫茉莉植株生长的抑制作用显著,对HL植株的抑制最大.镉胁迫显著增加了紫茉莉叶片的镉含量,减小叶片叶绿素、类胡萝卜素、Mg、Fe和K的含量,对HL植株影响最大.镉胁迫下,HL植株超氧化物歧化酶和过氧化物酶活性增强,过氧化氢酶和抗坏血酸过氧化物酶活性降低,谷胱甘肽和抗坏血酸含量减小,过氧化氢和丙二醛含量、超氧阴离子产生速率增高,电解质渗漏加重.上述结果表明,镉加重了叶片氧化胁迫程度和强化了对紫茉莉生长的抑制,特别在高光强条件下.

Effects of cadmium stress on photosynthesis and antioxidant systems in Mirabilis jalapa under different light intensities

The effects of excessive cadmium (30 mg·kg-1 in soils) on plant growth, photosynthesis, lipid peroxidation, the activities of antioxidant enzymes, the contents of photosynthetic pigments, Cd, Mg, Fe, K, ascorbic acid (AsA) and glutathione (GSH) in Mirabilis jalapa plants were investigated and compared under high light (HL, fully exposed to ambient sunlight), intermediate light (ML, about 50% of full ambient sunlight) and low light (LL, about 10% of full ambient sunlight) conditions. The net photosynthetic rate (Pn) in the presence of excessive Cd in soils decreased more under HL treatment than under ML and LL treatments. Excessive Cd significantly reduced the maximal photochemical efficiency (Fv/Fm) under HL and LL treatments, but did not affect Fv/Fm under ML treatment. Excessive Cd remarkably increased the dark respiration rate (Rd), especially under ML treatment. The growth of plants was significantly inhibited in the presence of excessive Cd, especially under HL treatment. Excessive Cd greatly increased the Cd content, and reduced the contents of chlorophyll, carotinoid, Mg, Fe and K in the leaves, particularly under HL treatment. Under HL treatment, excessive Cd greatly increased the activities of superoxide dismutase (SOD) and guaiacol peroxidase (POD), the contents of hydrogen peroxide (H2O2), superoxide (O-·2) and malondialdehyde (MDA), and electrolyte leakage, whereas it decreased the activities of catalase (CAT) and ascorbate peroxidase (APX), and the contents of GSH and AsA. The results indicate that excessive Cd enhanced oxidative stress and growth inhibition to Mirabilis jalapa plants, especially under HL treatment.