Foliar Application of Boron Nanoencapsulated in Almond Trees Allows B Movement Within Tree and Implements Water Uptake and Transport Involving Aquaporins

Abstract

Nanotechnology brings to agriculture new forms of fertilizer applications, which could be used to reduce environmental contamination and increase efficiency. In this study, foliar fertilization with nanoencapsulated boron (B) was studied in comparison to an ionic B (non-encapsulated) application in young B-deficient almond trees grown under a controlled environment. B movement within the plant in relation to the leaf gas exchange, water relations parameters, and root hydraulic conductance was measured. Also, the expression of aquaporins (AQPs) [plasma membrane intrinsic protein (PIP) and tonoplast intrinsic protein (TIP)] was studied in relation to water uptake and transport parameters to establish the effectiveness of the different B treatments. The obtained results were associated with a high concentration of observed B with nanoencapsulated B, provided by the higher permeability of carrier nanovesicles, which allowed B to reach the cell wall more efficiently. The increases in water uptake and transport obtained in these plants could be related to the role that this element played in the cell wall and the relationship that it could have in the regulation of the expression of AQPs and their involvement in water relations. Also, an increase in the expression of PIPs (mainly PIP2.2) to the applied nanoencapsulated B could be related to the need for B and water transport, and fine regulation of TIP1.1 in relation to B concentration in tissues provides an important feature in the remobilization of B within the cell.

Nanoencapsulated Boron Foliar Supply Increased Expression of NIPs Aquaporins and BOR Transporters of In Vitro Ipomoea batatas Plants

“…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 a 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].…”

“…This was also observed with the NIPs (NIP1;2, NIP1;3; NIP4;1, NIP4;2, NIP5;1, NIP6;1, and NIP7;1), which only increased in expression with encapsulated B. Therefore, the results could be associated with the decreased mobility of free B into leaves, as compared with encapsulated B [24]. Therefore, the encapsulated B applied to in vitro plants produced changes in the expression related to B, though only when B was able to penetrate and be transported into the leaf tissues.…”

“…The nanoencapsulation of boron has been applied to almond trees [23,24], demonstrating that the efficiency in B transport into tissues was much higher than when free B was applied. In fact, a higher nutrient penetration through the leaf cuticle was demonstrated [23] by the fact that nanocapsules containing fluorescein disodium salt (FNA) were able to penetrate into leaf tissues in 2 h whereas no penetration was observed in free form.…”

Combined Soil Microorganism Amendments and Foliar Micronutrient Nanofertilization Increased the Production of Allium cepa L. through Aquaporin Gene Regulation

“…According to the potential toxicity, new types of nanoencapsulations have been used due to their characteristics as hydrophobic vesicles obtained from biological materials. Nanoencapsulations from agricultural by-products have been tested in different crops, with interesting results observed in terms of bioavailability, compatibility, and efficiency as nutrient nanocarriers [13][14][15], without generating waste or leading to the accumulation of toxic elements in the ecosystem. In this way, the biodegradability of the coating reduces environmental impact and any risk of toxicity.…”

“…Given the essentiality of those proteins in the optimization of existing natural resources, their regulation should occur according to the availability of water and nutrients, which ultimately depends on soil availability and structure. On the other hand, the application of foliar fertilization has been proven to modify the expression of aquaporins at the whole-plant level, and its regulation seemed to be essential in improving water and nutrient immobilization when micronutrients were applied using nanovesicles [15].…”