Department of Horticulture, University of Agriculture in Krakow, 29 Listopada 54, 31-425, Kraków, Poland.
Institute of Biology, Pedagogical University of Krakow, Podchorążych 2, 30-084, Kraków, Poland.
BMC Plant Biol. 2023 Jun 21;23(1):329. doi: 10.1186/s12870-023-04305-9.
Most nanoparticles (NPs) have a significant impact on the structure and function of the plant photosynthetic apparatus. However, their spectrum of action varies significantly, from beneficial stimulation to toxicity, depending on the type of NPs, the concentration used and plant genotypic diversity. Photosynthetic performance can be assessed through chlorophyll a fluorescence (ChlF) measurements. These data allow to indirectly obtain detailed information about primary light reactions, thylakoid electron transport reactions, dark enzymatic stroma reactions, slow regulatory processes, processes at the pigment level. It makes possible, together with leaf reflectance performance, to evaluate photosynthesis sensitivity to stress stimuli.
We investigated effects of different metal and metal(oid) oxide nanoparticles on photosynthesis of oakleaf lettuce seedlings by monitoring the chlorophyll a fluorescence light radiation and reflectance from the leaves. Observations of ChlF parameters and changes in leaf morphology were carried out for 9 days in two-day intervals. Spectrophotometric studies were performed at 9 day. Suspensions of NPs with the following concentrations were used: 6% TiO, SiO; 3% CeO, SnO, FeO; 0.004% (40 ppm) Ag; 0.002% (20 ppm) Au. Nanoparticles were applied directly on the leaves which caused small symptoms of chlorosis, necrosis and leaf veins deformation, but the plants fully recovered to the initial morphological state at 9 day. Leaf reflectance analysis showed an increase in FRI for SiO-NPs and CeO-NPs treatments and ARI2 for FeO, however, WBI and PRI coefficients for the latter nanoparticle were lower than in control. Chlorophyll a fluorescence parameters have changed due to NPs treatment. FeO-NPs caused an increase in F/F, PI, ET/RC, DI/RC, ABS/RC in different time points in comparison to control, also Ag, Au and SnO treatment caused an increase in F/F, PI or ET/RC, respectively. On the other hand, TiO-NPs caused a decrease in F/F and F/F parameters, but an increase in DI/RC value was observed. SnO-NPs decreased PI, but increased ET/RC than compared to control. Nanoparticles affected the shape of the O-J-I-P curve in slight manner, however, further analyses showed unfavourable changes within the PSII antenna, manifested by a slowdown in the transport of electrons between the Chl molecules of the light-harvesting complex II and the active center of PSII due to NPs application.
Changes in ChlF parameters and leaf reflectance values clearly proved the significant influence of NPs on the functioning of the photosynthetic apparatus, especially right after NPs application. The nature of these changes was strictly depended on the type of nanoparticles and sometimes underwent very significant changes over time. The greatest changes in ChlF parameters were caused by FeO nanoparticles, followed by TiO-NPs. After slight response of O-J-I-P curves to treatment of the plants with NPs the course of the light phase of photosynthesis stabilized and at 9 day were comparable to the control curve.
大多数纳米颗粒（NPs）对植物光合作用装置的结构和功能有重大影响。然而，它们的作用范围差异很大，从有益的刺激到毒性，这取决于 NPs 的类型、使用的浓度和植物基因型的多样性。光合作用性能可以通过叶绿素 a 荧光（ChlF）测量来评估。这些数据可以间接获得关于初级光反应、类囊体电子传递反应、暗酶基质反应、缓慢调节过程、色素水平过程的详细信息。它与叶片反射率性能相结合，可以评估光合作用对胁迫刺激的敏感性。
我们通过监测叶片的叶绿素 a 荧光光辐射和反射，研究了不同金属和金属（类）氧化物纳米颗粒对生菜幼苗光合作用的影响。在两天的间隔内，进行了 9 天的 ChlF 参数观察和叶片形态变化。在第 9 天进行了分光光度研究。使用了以下浓度的 NPs 悬浮液：6%TiO、SiO；3%CeO、SnO、FeO；0.004%（40ppm）Ag；0.002%（20ppm）Au。纳米颗粒直接应用于叶片，导致叶片出现轻微的黄化、坏死和叶脉变形症状，但在第 9 天，植物完全恢复到初始形态。叶片反射率分析表明，SiO-NPs 和 CeO-NPs 处理的 FRI 增加，而 FeO 的 ARI2 增加，但后者的 WBI 和 PRI 系数低于对照。由于 NPs 处理，叶绿素 a 荧光参数发生了变化。与对照相比，FeO-NPs 在不同时间点引起了 F/F、PI、ET/RC、DI/RC、ABS/RC 的增加，而 Ag、Au 和 SnO 处理分别引起了 F/F、PI 或 ET/RC 的增加。另一方面，TiO-NPs 导致 F/F 和 F/F 参数降低，但观察到 DI/RC 值增加。SnO-NPs 降低了 PI，但与对照相比，ET/RC 增加。纳米颗粒以轻微的方式影响了 O-J-I-P 曲线的形状，但进一步的分析表明，由于 NPs 的应用，PSII 天线内发生了不利的变化，表现为光捕获复合物 II 的叶绿素分子和 PSII 活性中心之间的电子传递减慢。
ChlF 参数和叶片反射率值的变化清楚地证明了 NPs 对光合作用装置功能的重大影响，尤其是在 NPs 应用后不久。这些变化的性质严格取决于纳米颗粒的类型，有时随着时间的推移会发生非常显著的变化。ChlF 参数的最大变化是由 FeO 纳米颗粒引起的，其次是 TiO-NPs。在植物用 NPs 处理后，O-J-I-P 曲线对处理的轻微反应之后，光合作用的光相过程稳定下来，在第 9 天与对照曲线相当。
