磺胺对苦草(Vallisneria natans(Lour.)Hara)生理生长及细胞超微结构的影响

以沉水植物苦草为试验材料,通过实验室水培试验,经过不同浓度磺胺(0.01,0.02,0.05,0.08,0.1mg·L~(-1))处理,研究不同浓度磺胺污染对苦草(Vallisneria natans)叶片生理生长及丙二醛(MDA)、可溶性糖(SS)、叶绿素含量、叶绿素a和b含量比值(c_a/c_b)等的影响.结果显示:(1)随着外源磺胺浓度增加,苦草相对生长率降低,叶片叶绿素a和叶绿素b含量呈降低趋势,叶绿素a含量下降速度大于叶绿素b;c_a/c_b先增大后减小.(2)磺胺胁迫下叶片的丙二醛含量与对照组相比变化显著,MDA和SS含量呈先上升后下降的趋势,总体呈上升趋势.(3)透射电镜观察发现,磺胺胁迫使苦草叶细胞中叶绿体被膜破裂至消失,类囊体膨胀、破损;叶细胞中类囊体呈现出分布不均、出现空腔等.当磺胺浓度为0.01m·L~(-1)时,苦草叶片外观形态结构未表现出受害症状,而叶绿体亚显微结构显示,类囊体开始出现轻微的分布不均现象;当营养液中磺胺浓度为0.02mg·L~(-1)时,叶片出现褐色斑点,叶片边缘呈现枯黄至坏死症状,叶绿体超微结构显示类囊体膨胀、变形至空洞现象,线粒体和叶绿体的距离减小至消失.研究结果表明,磺胺胁迫导致苦草叶生理代谢失衡,叶绿素含量下降,叶片亚细胞结构出现不可逆损伤,期望该结果为研究磺胺污染的作用机制及苦草在抗生素污染修复中的应用提供一定的参考.

Physiological responses and ultrastructure changes of Vallisneria natans (Lour.) Hara under sulfonamides stress

Effects of different concentrations of sulfonamides (SAs) (0.01,0.02,0.05,0.08,0.1 mg · L-1) on toxicity symptoms,contents of chlorophyll and malondialdehyde (MDA),soluble sugar (SS),the ration of content of Chl a/Chl b,and subcellular structure in the leaves of Vallisneria natans (Lour.) Hara were studied in this paper.After 15 days exposure to sulfonamides,the results showed that:(1)With the increasing of exogenous SAs concentrations,both contents of chlorophyll a and chlorophyll b in leaves decreased,the decreasing ratio of chlorophyll a was higher than that of chlorophyll b.The tendency of chlorophyll a and chlorophyll b ratio increased first and then decreased.(2) It was a significant change of MDA and SS contents in leaves compared with the control treatment,the contents of MDA and SS increased and then decreased.(3) The aqueous sulfonamides could significantly affect the growth of V.natans when the concentration level of sulfonamides was up to 0.01 mg · L-1,which may cause an adverse effect to the aquatic eco-system.The results indicated that the ultrastructure of the leave cell of V.natans in 0.022 mg · L-1 treatment showed some morphologic changes using transmission electron microscope,compared with the blank treatment.The leave cells ultrastructure showed that chloroplast envelop was damaged,thylakoid swelled and broken ultimately,the thylakoid distribution was uneven or was squeezed to be cable-like.It was concluded that aqueous sulfonamides could disturb the balance of physiological metabolism,and irreversible damage of subcellular structure.The study could provide theory basis for the specific mechanism of sulfonamides stress to aquatic plant,and application of V.natans in antibiotics pollution restoration.