## 3 Results and Discussion
### Uptake and Distribution of Pyr@MSN in Cucumber Plants  
The plant root system is one of the most important parts in which pesticides enter the plant. In this study, the distribution behavior of Pyr@M and Pyr in cucumber plants was studied under roots application. Figure 7a showed that the uptake of Pyr was much higher than Pyr@M at the roots of cucumber. After the root application, pesticides were deposited or adsorbed on plant roots, then infiltrated into the cuticle and epidermis, and then migrated to the vascular tissues through the symplast or extracellular pathway. At this point, infiltration depended on the concentration of pesticides and particle size in the environment. The higher the concentration and the smaller the particle size, the easier it was to be absorbed by the roots. In this study, Pyr TC was first dissolved by acetone and then dispersed in water, as 5 mg/kg homogenous solution. However, Pyr@M enshrouded Pyr and kept it as suspension, so the concentration of Pyr around the roots was lower than the homogenous solution of Pyr, when Pyr@M was used. As a result, the concentration of Pyr in roots was lower than when Pyr@M was used.  
On the other hand, it could be seen from the concentration levels of Pyr shown in Figure 7 that the pesticide could be found in the leaves and roots during the period of 2 h to 10 d. The results showed that the concentration was related to the size of Pyr@M. The cellular uptake was highly particle-size-dependent in the order Pyr@M15 > Pyr@M100 > Pyr@M200. Some studies report that only particles with a diameter of less than or equal to 50 nm can pass through the cells walls in the root systems of most plants [26; 27], and in our previous study, it was observed that MSN with a particle size between 200-300 nm could also be absorbed by the cucumber leaves [29], but the dose in roots was very low. In roots, the uptake of Pyr@M15 was approximately 1.5 times that of Pyr@M100, and 2.5 times that of Pyr@M200. In leaves, the uptake of Pyr@M15 was approximately 1.7 times that of Pyr@M100, and 1.9 times that of Pyr@M200. Due to the smaller particle size, Pyr@M showed a better dispersion performance in water [43], and it became much easier for Pyr to be adsorbed by cucumber roots.  
Figure 8 summarized the transfer rate of Pyr from the cucumber roots to leaves, which was calculated as the ratio of leaves concentration to root concentration. The results indicated that the Pyr@M had a significantly higher transfer rate than Pyr (\(p<0.05\)). It was also shown that Pyr@M15 had the best transfer rate, which indicated that MSN with the smallest size would give the best transportation performance, as carriers. From the data, it was seen that the top transport capacity of Pyr was poor, with a maximum of 2.25%. [PERSON] also reported that the Pyr had a poor transport performance on leaves and poor absorbability in cucumber and rice root [37]. After pesticide loading with mesoporous silica, the transfer rate of Pyr was increased by about 3.5 times, which further proved that the drug loading of mesoporous nanometer silica could improve the internality of pesticide. In our previous study it was also reflected that MSN could enhance the dose transfer of pesticide in plants [38; 39]. The application of nanomaterial improves the internal conductivity of pesticides. The size had a great effect on the uptake and transportation performance of pesticide in plants.  
Figure 7: Concentrations of Pyr in cucumber root (**a**) and leaves (**b**) in certain intervals.