镉胁迫对姬松茸菌丝生理指标与镉吸收的影响

为了比较镉胁迫对不同姬松茸菌株(J1、J77)菌丝生长与镉吸收的影响,通过室内培育试验,设立0～75 mg·kg-1的不同镉胁迫浓度梯度,测定其对姬松茸菌丝生理指标与镉含量的影响。结果显示,不同镉浓度胁迫处理对J77和J1菌丝抗氧化系统的影响各异。当镉浓度为5 mg·L~(-1)时,J1与J77菌丝SOD酶活性分别增加121.5%、157.5%;当镉浓度高于5 mg·L~(-1)时,两个菌株菌丝SOD酶活性均开始降低。在10～75 mg·L~(-1)中高镉浓度胁迫范围,J77、J1菌丝的POD酶活性分别减少92.7%、95.3%。在5～50 mg·L~(-1)镉浓度胁迫范围,J77、J1菌丝的CAT酶活性分别减少40.9%、60.4%,随着镉胁迫浓度增加,J1的镉毒害更为严重。在0～2 mg·L~(-1)镉浓度范围内,J1与J77菌丝的APX酶活性分别增加7.9、13倍,两菌株相差近5倍,J77菌丝APX酶活性反应大于J1菌丝。不同浓度镉胁迫处理条件下(0～75 mg·L~(-1)),J1菌丝丙二醛(MDA)显示了较大幅度的提升,氧化程度比较剧烈,而J77在整个过程则提升幅度较缓,氧化应激程度相对较低。当镉胁迫浓度为10 mg·L~(-1)时,J1菌丝MDA含量比对照高1.6倍并达到最大值;当镉浓度为15mg·L~(-1)时,J77菌丝MDA含量比对照高60%并达到最大值,J1、J77的MDA最大值相差近1倍,J1菌丝细胞膜过氧化反应比J77更为强烈。在0～75 mg·L~(-1)浓度范围内,J77与J1菌丝中镉含量的浓度均随着外源镉含量的提高而增加。当镉浓度在2.5～50 mg·L~(-1)范围内,J1、J77菌丝镉含量分别增长了17.2、19.1倍;但就镉吸收累积量而言,J1菌丝比J77菌丝镉含量高近2.3倍;J77不仅对高镉胁迫的耐受程度高于J1,而且J77抵制镉吸收能力高于J1。结果表明,姬松茸J1和J77菌丝SOD、POD、CAT、APX酶活性及MDA含量随镉含量变化均表现为"低促高抑"的现象,J77菌丝镉含量低于J1,J77具有抵制镉吸收的潜力。

Effects of cadmium stress on mycelium physiological indexes and cadmium absorption in Agaricus brasiliensis

To compare the effects of cadmium(Cd)stress on mycelia growth and Cd absorption of Agaricus brasiliensis strains J77 and J1, Cd was added to A. brasiliensis culture medium at concentrations ranging from 0 to 75 mg·L^-1, and the physiological indexes and Cd content of the mycelia were measured. The results showed that the effects of Cd stress on the J77 and J1 mycelia antioxidant systems were different. As the Cd concentration(i.e., stress)increased, the activities of superoxide dismutase(SOD), peroxidase(POD), catalase(CAT), ascorbate peroxidase(APX), and malondialdehyde(MDA)in the mycelia increased then decreased in both strains. At Cd concentrations greater than 5 mg·L^-1, the SOD and POD activities of both strains decreased. POD activity of J77 and J1 mycelia decreased by 92.7% and 95.3%, respectively. When the Cd concentration was between 5 and 50 mg·L^-1, CAT activity in J77 and J1 decreased by 40.9% and 60.4%, respectively, indicating greater sensitivity to Cd during J1 growth. When the Cd concentration was between 0 and 2 mg·L^-1, APX activity increased in both strains as the concentration increased; J77 was 13 times higher, and J1 was 7.9 times higher. The J77 APX activity increase was nearly 5 times greater than J1. Under the same treatment conditions(0 to 75 mg·L^-1 Cd), the MDA content in the mycelia was higher in J1 in than J77. In addition, a rapid increase of MDA and severe oxidation were observed in the J1 strain, while opposite patterns were observed in J77. The mycelia MDA content peaked at 15 mg·L^-1 Cd in J77(60% higher than that of the control)and at 10 mg·L^-1 Cd in J1(1.6 times higher than that of the control). These differences indicated that the cell membrane peroxidation of J1 mycelia was more severe. The Cd concentration in the mycelia increased with increasing environmental Cd(0 to 75 mg·L^-1)in both strains. When the environmental Cd concentrations were between 2.5 and 50 mg·L^-1, the Cd in J1 and J77 mycelia increased by 17.2 and 19.1 times, respectively. The Cd growth rate in the J77 mycelia was higher than J1, but the overall Cd content of the J1 mycelia was nearly 2.3 times higher. These results show that J77 has a higher tolerance to Cd stress and greater resistance to Cd absorption than J1. As the Cd content of the J77 and J1 strains increased, the SOD, POD, CAT, and APX enzyme activities, and MDA content increased then decreased. The Cd content in the J77 mycelia was lower than J1, indicating that J77 has low cadmium absorption potential.