Effect of silver nanoparticles on tolerance to drought stress in Thymus daenensis Celak and Thymus vulgaris L. in germination and early growth stages

Introduction Drought is a meteorological event occurring due to the absence of rainfall in a period of time. With the occurrence of drought stress, the water available to the soil is reduced, but the loss of water through evapotranspiration increases continuously. Drought can be effective in reducing the rate of germination and germination percentage, and inadequate The necessity of moisture for germination in soil layers and consequently drought stress in seedling stage is one of the important factors in the lack of desirable seedling establishment in arid regions. Considering the importance and role of medicinal plants in different industries, as well as lack of resources Water and abundance of arid regions in the country, it is necessary by applying techniques on the seeds of these plants, proper management of the production and cultivation of these valuable species, and Increase their performance. The purpose of this study was to investigate and use nanosilver particles in increasing or improving the indices of germination of two important species of Thymus. Materials and methods Seeds of Thymus genotypes Thymus daenensis Celak and Thymus vulgaris L. from Isfahan Seed Packers Company were obtained. This study was carried out in a factorial experiment in 2009 in a completely randomized design with three replications in University of Kashan. Drying treatments were considered at four levels (0, 0.3, -0.6 and -0.9 MPa) and treatments of silver nanoparticles with four concentrations (0, 10, 20 and 30 mg / l).Data were analyzed by SAS statistical software (ver.9). First, the normalization of all the data from different germination traits, including germination percentage, germination speed, root length and stalk length and seedling strain, were evaluated using Kolmogorov-Smirnov test. . Then analysis of variance of data and comparison of means were done using Duncan's test at 5% level. Results and discussion The results showed that the interaction of species, drought stress and nanoparticles on germination rate and shoot length were significant at 5% probability level. The highest germination percentage was observed in both species in control treatment and with increasing dryness, germination percentage, germination rate and seed vigor decreased in both species. Thymus daenensis Celak had a higher rate of germination than the species of Thymus vulgaris L. The species of Thymus vulgaris L in comparison with the species of Thymus daenensis Celak has a relatively low level of roots in terms of the length of its cultivation. On the other hand, silver nanoparticles in non-dry conditions in Thymus vulgaris L.caused an increase in the length of the root, but in the species of Thymus daenensis Celak it was not observed. In general, silver nanoparticles in all traits, with the exception of stem length, had only a mild-to-moderate-particle dose of 30 MPa. Conclusions Under drought stress conditions, silver nanoparticles in all traits, with the exception of stem length, had only a slight increase of -0.3 MPa, which results in the ability of silver nanoparticles to reduce the negative effects of drought stress below -0.3 MPa, especially Proof of nanoparticles with a concentration of 30 mg / l. Due to the favorable germination and rapid seedling growth, better seeding and reduced competition with other plants, the use of nanoparticles in these two important species of thyme can be a good way to produce these two species in drought conditions. In the life span of the plant, rarely favorable conditions are provided in terms of different environmental characteristics, and as a result, the actual germination in the field is less than the predicted value in germination tests. Therefore, seed vigor index can be more effective in determining the seed germination rate in the field. However, increasing the index of seed vigor with the presence of silver nanoparticles at low levels of dryness has been proved in these two species, but to check other characteristics of the above plants, we need additional testing in field conditions.