砷胁迫下不同砷富集能力植物内源生长素与抗氧化酶的关系

采用室内土培法,研究了砷胁迫(0,50,100和200 mg/kg)对凤尾蕨属中砷超富集植物大叶井口边草(Pteris cretica var.nervosa)和非砷超富集植物剑叶凤尾蕨(Pteris ensiformis)生物量、株高、叶片内源3-吲哚乙酸(IAA)含量、IAA氧化酶(IAAO)活性、砷含量、抗氧化酶(超氧化物歧化酶SOD、过氧化物酶POD、过氧化氢酶CAT)活性以及细胞膜脂过氧化产物丙二醛(MDA)含量的影响,并用逐步回归法分析了IAA含量与砷含量、抗氧化酶活性、MDA含量之间的关系。此外,研究了100 mg/kg砷处理下IAA、IAAO、3种抗氧化酶和MDA的时间动态。结果表明,与对照(不加砷)相比,加砷处理下大叶井口边草的株高和生物量未出现显著变化,但剑叶凤尾蕨在中、高浓度砷胁迫下则显著降低;中、高浓度砷胁迫均使2种植物叶片含砷量、IAA含量显著增加和IAAO活性显著下降,但这种改变在大叶井口边草中更为显著;加砷处理使大叶井口边草叶片3种抗氧化酶活性维持或增加,剑叶凤尾蕨中SOD和CAT活性虽能维持,但POD活性则显著下降,说明砷胁迫下大叶井口边草具有更强的抗氧化能力。逐步回归分析结果显示,2种植物叶片IAA含量均与砷含量成显著正相关,但在大叶井口边草中,IAA含量还与CAT活性成显著负相关。时间动态研究表明,第13天,大叶井口边草具有最高的IAA含量、最低的IAAO活性以及最低的CAT活性,而剑叶凤尾蕨中的变化规律则不明显。因此,叶片保持较高的IAA含量、较低的IAAO和CAT活性有助于大叶井口边草超量富集砷。

The relationship between endogenous auxin and antioxidative enzymes in two plants with different arsenic-accumulative ability under arsenic stress

Up to now, 11 arsenic hyperaccumulators and 4 non-hyperaccumulators in Pteris genus have been reported. The non-hyperaccumulators could be used as controls to reveal the responsive mechanisms of hyperaccumulators to arsenic pollution. Auxin plays an important role in plant cell growth, differentiation and division. In the present research, one arsenic hyperaccumulator (Pteris cretica var. nervosa)and one non-hyperaccumulator (Pteris ensiformis) were selected from Pteris genus to evaluate the effects of arsenic stress (0, 50, 100 and 200 mg/kg) on the plant biomass, height, frond indole-3-acetic acid (IAA) contents, arsenic accumulation, the activities of IAA oxidase and antioxidative enzymes (superoxide dismutase SOD, peroxidase POD and catalase CAT), as well as the content of malondialdehyde (MDA, a per-oxidation product of cell membrane lipid) using a pot experiment. The relationship among the contents of IAA, arsenic concentration, activities of 3 antioxidative enzymes and MDA contents in the fronds of two plants were also analyzed by step regression statistical method. In addition, the variation of IAA, IAAO, SOD, POD, CAT and MDA in two plants exposed to 100 mg/kg arsenic with culture time was examined. No significant difference was observed in the biomass and height of P. cretica var. nervosa under arsenic stress compared to the control (0 mg/kg), but a significant decrease was noted in P. ensiformis under medium or high arsenic stress. The concentrations of arsenic and IAA increased but the activity of IAAO decreased in the fronds of two plants exposed to medium or high arsenic stress, but this change was more significant in P. cretica var. nervosa. The activities of 3 antioxidative enzymes could maintain or increase in the fronds of P. cretica var. nervosa exposed to arsenic stress, but a significant decrease of POD was observed in P. ensiformis, in which the activities of SOD and CAT could maintain. Therefore, much stronger antioxidative ability was shown in P. cretica var. nervosa exposed to arsenic stress. The results from step regression analysis showed a significantly positive correlation between the IAA contents and arsenic concentrations in the fronds of two plants, and a significantly negative correlation was also observed between the IAA contents and CAT activities in the fronds of P. cretica var. nervosa. The result from time-course effect research showed that the highest IAA contents, the lowest IAAO and CAT activity were found in the 13th days in the culture process of P. cretica var. nervosa exposed to 100 mg/kg, but similar result was not observed for P. ensiformis. Therefore, a higher IAA contents, a lower IAAO and CAT activities may have contributed to arsenic hyperaccumulation in P. cretica var. nervosa.