The Effect of Silver Nanoparticle Addition on Micropropagation of Apricot Cultivars (Prunus armeniaca L.) in Semisolid and Liquid Media

Abstract

Silver nanoparticles (AgNPs) are novel compounds used as antimicrobial and antiviral agents. In addition, AgNPs have been used to improve the growth of different plants, as well as the in vitro multiplication of plant material. In this work the effect of AgNPs on in vitro growth of 'Canino' and 'Mirlo Rojo' cultivars, as well as the leaf ion composition, are studied. Different concentrations of AgNPs (0, 25, 50, 75 and 100 mg L^-1) were added to two culture systems: semisolid medium with agar (SSM) in jars and liquid medium in temporary immersion system (TIS). Proliferation (number of shoots), shoot length, productivity (number of shoot × average length), leaf surface, fresh and dry weight were measured. Additionally, the silver and other ion accumulation in the leaves were evaluated by inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. The productivity of 'Canino' and 'Mirlo Rojo' decreased when increasing the concentration of AgNPs in the semisolid medium. However, the use of AgNPs in the TIS improved the proliferation and productivity of 'Canino' and Mirlo Rojo', increasing biomass production, and the concentration of nutrients in the plants, although these effects are genotype-dependent. TISs are the best system for introducing silver into shoots, the optimum concentration being 50 mg L^-1 for 'Canino' and 75 mg L^-1 for 'Mirlo Rojo'. Principal component analysis, considering all the analyzed ions along the treatments, separates samples in two clear groups related to the culture system used. The use of bioreactors with a liquid medium has improved the productivity of 'Canino' and 'Mirlo Rojo' in the proliferation stage, avoiding hyperhydration and other disorders. The amount of metallic silver that penetrates apricot plant tissues depends on the culture system, cultivar and concentration of AgNPs added to the culture medium. Silver ion accumulation measured in the shoots grown in the TIS was higher than in shoots micropropagated in a semisolid medium, where it is barely detectable. Furthermore, AgNPs had a beneficial effect on plants grown in TIS. However, AgNPs had a detrimental effect when added to a semisolid medium.

Keywords: AgNPs; agar culture; clonal propagation; nanobiotechnology; proliferation; temporary immersion system.

Figure 1

Effect of AgNP concentration increase for ion silver content in ‘Canino’ and ‘Mirlo Rojo’ shoots, cultured in both TISs and semisolid media. Polynomial equations are represented by dashed lines.

Figure 2

Principal component analysis of nutrient absorption in ‘Canino’, as a function of AgNP concentration and the culture system. (A) Analysis of variables, (B) analysis of individuals.

Figure 3

Principal component analysis of nutrient absorption in ‘Mirlo Rojo’, as a function of AgNP concentration and the culture system. (A) Analysis of variables, (B) analysis of individuals.

Figure 4

Effect of AgNP concentration on proliferation (A), shoot length (B), productivity (C), fresh weight (D), dry weight (E) and leaf surface (F) of ‘Canino’, both in semisolid media and TIS. When the data followed a significant trend, polynomial equations are represented by dashed lines. Asterisks indicate significant differences between LM and SSM.

Figure 5

Effect of AgNP concentration on proliferation (A), shoot length (B), productivity (C), fresh weight (D), dry weight (E) and leaf surface (F) of ‘Mirlo Rojo’, both in semisolid media and TIS. When the data followed a significant trend, polynomial equations are represented by dashed lines. Asterisks indicate significant differences between LM and SSM.

Figure 6

Apricot plants treated with silver nanoparticles (AgNPs). Effect of AgNP concentration on apricot micropropagation of the ‘Canino’ apricot cultivar in a semisolid medium (A) and the TIS (B). ‘Canino’ plants rooted in vitro (C) and acclimatized in the greenhouse (D,E). The bar represents 5 mm in (A,B).