The Effect of Bio-Synthesized Silver Nanoparticles on Germination, Early Seedling Development, and Metabolome of Wheat (Triticum aestivum L.)

Abstract

Changes in the metabolome of germinating seeds and seedlings caused by metal nanoparticles are poorly understood. In the present study, the effects of bio-synthesized silver nanoparticles ((Bio)Ag NPs) on grains germination, early seedlings development, and metabolic profiles of roots, coleoptile, and endosperm of wheat were analyzed. Grains germinated well in (Bio)Ag NPs suspensions at the concentration in the range 10–40 mg/L. However, the growth of coleoptile was inhibited by 25%, regardless of (Bio)Ag NPs concentration tested, whereas the growth of roots gradually slowed down along with the increasing concentration of (Bio)Ag NPs. The deleterious effect of Ag NPs on roots was manifested by their shortening, thickening, browning of roots tips, epidermal cell death, progression from apical meristem up to root hairs zone, and the inhibition of root hair development. (Bio)Ag NPs stimulated ROS production in roots and affected the metabolic profiles of all tissues. Roots accumulated sucrose, maltose, 1-kestose, phosphoric acid, and some amino acids (i.e., proline, aspartate/asparagine, hydroxyproline, and branched-chain amino acids). In coleoptile and endosperm, contrary to roots, the concentration of most metabolites decreased. Moreover, coleoptile accumulated galactose. Changes in the concentration of polar metabolites in seedlings revealed the affection of primary metabolism, disturbances in the mobilization of storage materials, and a translocation of sugars and amino acids from the endosperm to growing seedlings.

The Imbibition of Pea (Pisum sativum L.) Seeds in Silver Nitrate Reduces Seed Germination, Seedlings Development and Their Metabolic Profile

“…The elevated level of sucrose in deformed sprouts ( Figure 6 A) was also found earlier in pea seedlings under osmotic stress [ 69 ], dehydration [ 70 ], as well as in pea plants’ response to soil drought [ 15 , 50 ]. Noticeably, the accumulation of sucrose was accompanied with a decrease in the content of glucose and fructose, presumably used for its synthesis ( Figure 6 ).…”

“…On the other hand, the high concentration of these metabolites may also indicate their crucial role as the major sources of carbon skeletons and energy sources providing the metabolism of growing cells/tissues. Homoserine is a characteristic amino acid for pea seedlings, which content is very low in dry seeds, while rapidly increasing during seedlings’ growth [ 49 ] and becomes the main non-protein amino acid in vegetative tissues of pea plants [ 15 , 50 ]. The high contents of homoserine, asparagine and sucrose confirm their role as the main transport forms of nitrogen and carbon in pea seedlings [ 51 , 52 ].…”

“…Since silver causes oxidative stress in plant cells [ 15 , 63 ], proline and GABA can be accumulated as protective compounds, maintaining redox balance [ 64 ] and functioning as antioxidants [ 65 ]. Indeed, our results confirm an accumulation of proline and GABA in sprouts (two-fold higher in deformed seedlings than in normal, Figure 5 A).…”

“…In recent years, there has been an increasing number of reports indicating the effects of Ag NPs on various plant species [ 9 , 10 ], including model plants [ 11 , 12 ] and economically important crops [ 13 , 14 , 15 ]. The effect of Ag NPs on plants depends on their size, shape, coating agents, concentration [ 16 ] and released Ag + ions [ 17 , 18 ].…”

“…Ag NPs and Ag + ions are taken up from the soil by the roots’ epidermal cells, then are translocated between cells through the plasmodesmata (or apoplastically) and later on via vascular bundles to the shoot [ 19 , 20 ]. Both Ag NPs and Ag + ions can be accumulated in cells, causing oxidative stress [ 21 , 22 ] and disturbances in metabolism [ 15 , 23 ], water homeostasis, chlorophyll biosynthesis [ 24 ], mitotic cell division and chromosomal structure [ 10 , 25 , 26 ]. In some plant species, the application of Ag NPs stimulates their growth, which was found in Phaseolus vulgaris and Zea mays [ 27 ], Pisum sativum [ 28 ] and Trigonella foenum-graecum [ 29 ].…”