Nanoparticles-Based Delivery Systems for Salicylic Acid as Plant Growth Stimulator and Stress Alleviation

Abstract

The population growth tendency leads to an increase in demand for food products, and in particular, products obtained from the processing of plants. However, there are issues of biotic and abiotic stresses that can significantly reduce crop yields and escalate the food crisis. Therefore, in recent years, the development of new methods of plant protection became an important task. One of the most promising ways to protect plants is to treat them with various phytohormones. Salicylic acid (SA) is one of the regulators of systemic acquired resistance (SAR) signaling pathways. These mechanisms are able to protect plants from biotic and abiotic stresses by increasing the expression of genes that encode antioxidant enzymes. However, salicylic acid in high doses can act as an antagonist and have the negative rebound effect of inhibition of plant growth and development. To maintain optimal SA concentrations in the long term, it is necessary to develop systems for the delivery and slow release of SA in plants. The purpose of this review is to summarize and study methods of delivery and controlled release of SA in a plant. Various carriers-based nanoparticles (NPs) synthesized from both organic and inorganic compounds, their chemical structure, impacts on plants, advantages, and disadvantages are comprehensively discussed. The mechanisms of controlled release of SA and the effects of the use of the considered composites on the growth and development of plants are also described. The present review will be helpful to design or fabricate NPs and NPs-based delivery systems for salicylic acid-controlled release and better understating of the mechanism of SA-NPs interaction to alleviate stress on plants.

Keywords: delivery systems; nanoparticles; phytohormone; plant defense; salicylic acid; systemic acquired resistance.

Figure 1

Salicylic acid structure.

Figure 2

Functions of salicylic acid in plant growth and development. ROS–reactive oxygen species, ABA–abscisic acid, GA–gibberellins, NPR1–gene nonexpressor of PR-1, and NADPH/NADP+–a protonated and deprotonated form of nicotinamide adenine dinucleotide phosphate, respectively. Adapted from [48].

Figure 3

Hypothetical representation of the salicylic acid-chitosan complex structure. Adapted from [55].

Figure 4

Cellulose-based nanogel synthesis process and its adaptive behavior in an environment with different pH and in the presence of glutathione. Adapted from [58].

Figure 5

Scheme of the silica functionalization and SA loading/release processes. Adapted from [59].

Figure 6

Synthesis scheme and structure of NPs functionalized with decanethiol MSN loaded with SA. The process of the removal of the gatekeepers under the influence of GSH in an aqueous solution. Adapted from [60].