微囊藻毒素-LR对生菜非结构性碳水化合物代谢的影响

【目的】研究低质量浓度微囊藻毒素-LR（MC-LR）慢性暴露对生菜（Lactuca sativa）叶片及根系非结构性碳水化合物代谢的影响，为富营养化水体在生菜灌溉中的应用提供理论指导。【方法】以散叶生菜为试验材料，采用土培试验方法，设置不同质量浓度（0（对照组），1，5，10，30 μg/L）MC-LR的水溶液灌溉生菜30 d，通过分析生菜叶片及根系中可溶性糖（葡萄糖、果糖和蔗糖）及淀粉含量、蔗糖和淀粉代谢相关酶活性的变化，探讨生菜非结构性碳水化合物代谢对MC-LR慢性暴露的响应。【结果】10和30 μg/L MC-LR组生菜对MC-LR的富集系数较5 μg/L MC-LR组分别显著上升10.85%和17.83%（P＜0.05），而对MC-LR的转运系数分别显著下降17.46%和13.85%（P＜0.05）。与对照组相比，1 μg/L MC-LR组生菜净光合速率显著提高了9.17%（P＜0.05），叶片中果糖含量及根系中葡萄糖含量和淀粉酶（AMS）活性分别显著增加了52.71%，19.13%和37.01%（P＜0.05）；5，10和30 μg/L MC-LR组生菜净光合速率提高，但差异不显著（P＞0.05），叶片和根系中葡萄糖、果糖和蔗糖含量均显著增加（P＜0.05），叶片中性转化酶（NI）活性分别显著降低了27.10%，38.01%和37.29%（P＜0.05），淀粉合成酶活性分别显著增加20.92%，24.57%和30.28%（P＜0.05），根系蔗糖合成酶、蔗糖磷酸合成酶（SPS）和AMS活性均显著增加（P＜0.05）。【结论】1 μg/L MC-LR水溶液灌溉对生菜叶片和根系中非结构性碳水化合物的分布和代谢影响较弱；而5～30 μg/L MC-LR水溶液灌溉通过促进生菜根系淀粉分解和蔗糖代谢活性，维持体内较高浓度的可溶性糖，从而提高生菜的抗逆性。

Effect of microcystin-LR on non-structural carbohydrate metabolism in Lactuca sativa

【Objective】This study investigated the effects of chronic exposure to low concentrations of microcystin LR (MC LR) on metabolism of non-structural carbohydrates in lettuce (Lactuca sativa) leaves and roots to provide guidance for the application of eutrophic water bodies in lettuce irrigation.【Method】Soil culture experiment was carried out to irrigate loose leaf lettuce with MC-LR solutions at different concentrations (0 (control group),1,5,10 and 30 μg/L) for 30 days.The response of non-structural carbohydrate metabolism after chronic exposure to MC-LR was analyzed through the changes in contents of soluble sugars (glucose,fructose and sucrose) and starch and activities of enzymes related to sucrose and starch metabolism in leaves and roots.【Result】After 30 days of irrigation with MC-LR solutions at concentrations of 10 and 30 μg/L,the enrichment factors of MC-LR were significantly increased by 10.85% and 17.83% (P＜0.05) in comparison to that of 5 μg/L,while the translocation factors were significantly decreased by 17.46% and 13.85%(P＜0.05),respectively.Compared with the control group,the net photosynthetic rate of lettuce in the group with 1 μg/L MC-LR was significantly increased by 9.17% (P＜0.05),fructose content in leaves,glucose content and amylase (AMS) activities in roots were increased by 52.71%,19.13% and 37.01%,respectively (P＜0.05).The net photosynthetic rates of lettuce with 5,10 and 30 μg/L MC-LR were increased insignificantly (P＞0.05),glucose,fructose and sucrose contents in leaves and roots were increased significantly (P＜0.05),while leaf neutral invertase (NI) activities were decreased by 27.10%,38.01% and 37.29% (P＜0.05),respectively.Starch synthase activities were significantly increased by 20.92%,24.57%,and 30.28% (P＜0.05),and root sucrose synthase,sucrose phosphate synthase (SPS) and AMS activities were significantly increased (P＜0.05).【Conclusion】Irrigation with 1 μg/L MC-LR aqueous solution had weak effects on distribution and metabolism of non-structural carbohydrates in lettuce leaves and roots,while irrigation with 5-30 μg/L MC-LR aqueous solutions maintained high concentrations of soluble sugars by promoting amylolytic and sucrose metabolic activities in lettuce roots,so as to improve the resistance and adaptability of lettuce to adversity stress.