摩西球囊霉对三叶鬼针草保护酶活性的影响

旱地农田入侵杂草三叶鬼针草(Bidens pilosa L.)与摩西球囊霉(Glomus mosseae)(AM真菌)经常形成长效的共生体,该霉菌对三叶鬼针草的入侵能力起到促进作用,但机理并不清楚。盆栽试验对正常浇水、中度干旱和重度干旱条件下接种AM真菌的三叶鬼针草植株与未接种植株之间叶片丙二醛(MDA)含量及超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸氧化酶(ASP)和过氧化物酶(POD)等保护酶活性进行了比较研究。结果表明,干旱胁迫导致三叶鬼针草叶片内MDA含量升高,SOD、CAT、ASP和POD的活性升高;正常浇水条件下,接种G. mosseae 对MDA含量,SOD、ASP和CAT活性影响不显著;中度干旱条件下,接种没有显著影响ASP活性,但对SOD和CAT活性影响显著;在处理前期(7,14,21d)POD活性影响不显著,在处理后期(28,35d)接种植株显著低于未接种植株;重度干旱条件下,未接种植株MDA含量、CAT活性显著高于接种植株,POD活性差异不显著。ASP活性在21d前差异不显著,之后,未接种植株显著高于接种植株。因此,AM真菌G. mosseae 有效地降低了干旱胁迫对三叶鬼针草的伤害程度,随着土壤含水量的严重亏缺和胁迫时间的延长,摩西球囊霉对三叶鬼针草的保护作用逐渐减弱。由于三叶鬼针草和AM真菌之间普遍存在着共生关系,该共生关系可能是三叶鬼针草入侵能力强的关键生物因子之一。

Analysis of the activities of protective enzymes in Bidens pilosa L. inoculated with Glomus mosseae under drought stress

Biological invasion not only led to the loss of species biodiversity and the destruction of ecological balance but also resulted in the significant economic losses. Biden (Bidens pilosa L.), originating from south America, is recorded as a tenacious annual weed in many countries and has been spread into the most tropical and subtropical areas of China. Previous studies have shown that Glomus mosseae (one of AM fungi) can form a long-lasting symbiosis with biden. Under drought stress, this AM fungus greatly increased stomatal conductance and carboxylation efficiency, which improved plant growth and productivity. The objective of this study was to clarify the drought resistance ability of biden under a symbiotic relationship with AM fungus and gave support to the invasive mechanism of biden. The experiment was carried out at the ecological farm located at Southwest University, Chongqing and included three treatments including well-watered (as control), moderate drought stress, and severe drought stress companied with AM fungus inoculation. The lipid peroxidation and antioxidant system from the AM and non-AM seedlings were analyzed under the controlled drought stress conditions. Our results showed that drought stress led to the accumulation of reactive oxygen species, subsequently resulted in the rise of MDA content and the significant increase of the antioxidative enzymes (SOD, CAT, ASP and POD) activities. The MDA content within leaf was significantly higher in the moderate and severe drought stress treatments than that in well-watered (control) after seven days treatment both in the AM and non-AM plants. Only under severe stress, the MDA content was significantly higher in non-AM seedlings than that in AM seedlings after 14 days drought stress treatment. The antioxidant enzymes (SOD, CAT, ASP and POD) activities were also significantly higher in the moderate and severe drought stress treatments than those in control after seven days treatments or during the whole experimental period, and the difference increased dramatically with the aggravation of drought stress both in the non-AM and AM seedlings. Under the control condition, there was no significantly difference on the activities of antioxidant enzymes (SOD, ASP and CAT) between the non-AM and AM plants, while the POD activity was dramatically lower in AM seedlings than that in non-AM seedlings after 21 days drought treatment. Under the moderate drought stress, the activities of CAT and SOD in non-AM plants were significantly higher than those in AM plants within the whole experimental period, while the increased activity of POD in non-AM plants was only observed 28 days after drought stress treatment. Under the severe stress treatment, the AM inoculation only led to the decrease of ASP and CAT activity, and did not affect the activity of SOD and POD. The ASP activity was greatly higher in non-AM plants than that in AM plants 28 days after drought treatment. While the increased CAT activity during the whole treatment time. Our results indicated that this AM fungus greatly decreased the damage of plant cell membrane through adjusting the antioxidant system and reactive oxygen species, thus it accelerated B. pilosa growth and improved plant vigor under the drought stress. These results suggested that the prevalent symbiotic relationship between B. pilosa and the AM fungus was presumably one of the key biological factors affecting the tenacious invasive ability of B. pilosa weeds.