## 4 Discussion  
Boron has been reported to be transported passively, driven by the transpiration stream when an optimal supply was provided [36]. In the same manner, B has been shown to enter cells by diffusing through the plasma membrane with no active transport, likely facilitated by channels. According to the B concentration found in the leaves of sweet potatoes tested in the present study, it was observed that it was higher after B application, but to  
Figure 4: Expression analysis by quantitative PCR of NIP aquaporin and BOR genes from _I. batatas_ leaves (C, control; FB, free boron; EB, encapsulated boron). From (**A**–**K**), inclusive, data relative to NIPs aquoronins expression, being, (**A**): IbNIP1;1, (**B**): IbNIP1;2, (**C**): IbNIP1;3, (**D**): IbNIP2;1, (**E**): IbNIP4;1, (**F**): IbNIP4;2, (**G**): IbNIP5;1, (**H**): IbNIP5;2, (**I**): IbNIP5;3, (**J**): IbNIP6;1, (**K**): IbNIP7;1. Additionally, from (**L**–**F**) data relative to BOR genes expression (**(L): IbBOR1, (**M**): IbBOR1, (**N**): IbBOR2, (**O**): IbBOR4 and (**P**): IbBOR7;1). Statistical analysis was performed using SPSS 25.0.0.1. The values are the means \(\pm\) SE of relative expression been 100% the control plants, different letters show statistical differences (\(p<0.05\)). a higher extent when B was supplied in a nanoencapsulated form. This effect has been previously observed in almond trees [24], but these plants were B deficient. The greater penetration and mobility of nanoencapsulated B as compared to the free form observed in previous studies, was related to a higher ease of penetration through the epidermis facilitated by nanovesicles [23]. It was observed that penetration should have occurred through stomatal pores and aqueous pores, producing a greater distribution within the leaf tissues. However, B was observed to penetrate and reach other tissues only when it was encapsulated, producing physiological changes such as an increase in gas exchange, and root hydraulic conductance in relation to the higher expression of aquaporins that transport water. Thus, the experiments conducted in the present study with in vitro cultures of Ipomoea expand our knowledge on the mechanism of action of encapsulated B. In this way, as water transport is very low in these in vitro plants, the movement of encapsulated B must use other mechanisms to get B into foliar leaf tissue, which should account for the movement of the nanovesicles in tissues. Nanofertilizers are starting to be used in crop nutrition via soil or/and via foliar applications, providing a faster and higher transport to different parts of plants [37]. After penetrating the leaf or root cuticle tissue, nanofettilizers can be transported through different parts of the plant, which characterize their effectiveness and final destination [38]. In our experiments, the boron concentration was much higher in leaves when it was encapsulated, demonstrating that penetration was more effective. However, the increase in Mn and Fe was also observed, although it was similar in both B treatments. The application of micronutrient fertilizers has been reported to be a promising strategy for the biofortification of crops [39]. In this way, micronutrient fertilizers can be applied to leaves for improving the concentration and bioavailability of different micronutrients. However, the connection between micronutrients is unknown, and recent studies only showed the concentration due to the enrichment of the micronutrient that was supplied [40]. In this way, the recent investigation in the regulation of micronutrient transporters revealed that plants must have a fine and flexible system to deal with the alteration of the environment for acquiring the specific level of minerals for completing the cellular cycle. In this way, some reports revealed that nutrient transporters are regulated (transcriptionally, translationally, and/or post-translationally) when changes in nutrients occurred.