Nanoplastic pollution has become an increasing problem due to over-consumption and degradation in ecosystems. A little is known about ecological toxicity and the potential risks of nanoplastics on plants. To better comprehend the hormetic effects of nanoplastics, the experimental design was conducted on the impacts of polymethyl methacrylate (PMMA) on water status, growth, gas exchange, chlorophyll a fluorescence transient, reactive oxygen species (ROS) content (both content and fluorescence visualization), lipid peroxidation and antioxidant capacity (comparatively between leaves and roots). For this purpose, PMMA (10, 20, 50 and 100 mg L⁻¹) was hydroponically applied to Lactuca sativa for 15 days(d). PMMA exposure resulted a decline in the growth, water content and osmotic potential. As based on assimilation rate (A), stomatal conductance (g_s), and intercellular CO₂ concentrations (C_i), the decreased stomatal limitation (L_s) and, A/C_i and increased intrinsic mesophyll efficiency proved low carboxylation efficiency showing impaired photosynthesis as a non-stomatal limitation. PMMA toxicity increased the trapping fluxes and absorption with a decrease in electron transport fluxes caused the disruption in reaction centers of photosystems. The leaves and roots had a similar effect against PMMA toxicity, with increased superoxide dismutase (SOD) activity. Although, catalase (CAT) and peroxidase (POX) of leaves increased under 10 mg L⁻¹ PMMA, these defense activities failed to prevent radicals from attacking. Compared to the leaves, the lettuce roots showed an intriguing result for AsA-GSH cycle against PMMA exposure. In the roots, the lowest PMMA application provided the high ascorbate/dehydroascorbate (AsA/DHA), GSH/GSSG and the pool of AsA/glutathione (GSH) and non-suppressed GSH redox state. Also, 10 mg L⁻¹ PMMA helped remove high hydrogen peroxide (H₂O₂) by both glutathione peroxidase (GPX) and glutathione S-transferase (GST). Since this improvement in the antioxidant system could not be continued in roots after higher applications than 20 mg L⁻¹ PMMA, TBARS (Thiobarbituric acid-reactive substances), indicating the level of lipid peroxidation, and H₂O₂ increased. Our findings obtained from PMMA-applied lettuce provide new information to advance the tolerance mechanism against nanoplastic pollution.

由于过度消耗和生态系统退化，纳米塑料污染已成为一个日益严重的问题。人们对纳米塑料对植物的生态毒性和潜在风险知之甚少。为了更好地理解纳米塑料的毒效效应，实验设计了聚甲基丙烯酸甲酯（PMMA）对水状态、生长、气体交换、叶绿素a荧光瞬态、活性氧（ROS）含量（含量和荧光可视化）的影响）、脂质过氧化和抗氧化能力（叶和根之间的比较）。为此，将PMMA（10、20、50和100mg L ^-1 ）水培到莴苣上15天（d）。 PMMA 暴露导致生长、含水量和渗透势下降。根据同化率 (A)、气孔导度 ( _gs ) 和细胞间 CO ₂浓度 (C _i )，气孔限制 (L _s ) 和 A/C _i的降低以及内在叶肉效率的增加证明了低羧化效率光合作用受损是一种非气孔限制。 PMMA 毒性增加了捕获通量和吸收，同时电子传输通量减少，导致光系统反应中心的破坏。叶子和根对 PMMA 毒性具有类似的作用，具有增加的超氧化物歧化酶 (SOD) 活性。尽管10 mg L ^-1 PMMA下叶片的过氧化氢酶（CAT）和过氧化物酶（POX）有所增加，但这些防御活性未能阻止自由基的攻击。与叶子相比，生菜根针对 PMMA 暴露的 AsA-GSH 循环显示出有趣的结果。 在根部，最低的 PMMA 应用提供了高抗坏血酸/脱氢抗坏血酸 (AsA/DHA)、GSH/GSSG 以及 AsA/谷胱甘肽 (GSH) 库和未抑制的 GSH 氧化还原状态。此外，10 mg L ^-1 PMMA 有助于通过谷胱甘肽过氧化物酶 (GPX) 和谷胱甘肽 S-转移酶 (GST) 去除高过氧化氢 (H ₂ O ₂ )。由于施用高于20 mg L ^-1 PMMA、TBARS（硫代巴比妥酸反应物质）后，根部抗氧化系统的这种改善无法持续，表明脂质过氧化水平和H ₂ O ₂增加。我们从应用 PMMA 的生菜中获得的研究结果为推进纳米塑料污染的耐受机制提供了新的信息。