Determination of Optimal Acidity and Concentration of Nano and Micro Sodium Silicate on Efficiency of Foliar Application of Potato Plantlets

Silicon (Si) is one of the most abundant elements in Earth’s crust. It has been regarded as an essential element in a number of species of the Poaceae and Cyperaceae, however it has not been possible to demonstrate that it is essential to all higher plants because direct evidence is still lacking that it is part of the molecule of an essential plant constituent or metabolite. Recently, the role of Si in plant metabolism has received increasing attention. It has been suggested that Si may be involved in metabolic or physiological and/or structural activity in higher plants in normal condition and exposed to abiotic and biotic stresses. In many researches, it has been found that Si improved water use efficiency, photosynthesis, membrane stability index and yield in crops. The use of nano-compound material has been given a lot of attention by the agricultural researchers, especially by those who examine the characteristics of the seeds, although the exact mechanism of their actions is not well understood. Nanomaterials, because of their tiny size, show unique characteristics. Previous work reported that nano sodium silicate was affected on physiological and yield of potato seedlings in greenhouse. Acidity was determinant factor in foliar application of solutions. However, studies have not been paid attention to this factor.
This research was conducted as a factorial experiment based on a randomized complete block design with three replications at the faculty of agriculture’s research greenhouse, Ferdowsi University of Mashhad, in 2013. Plantlets of Agria cv. produced from nodal tissue culture in Murashinge and Skoog (MS) medium. After 25 days, Free disease and uniform plantlets exported to plastic pots with 12 cm diameter and 30 cm height. Perlite, cocopite and sand with 3:3:4 ratios, formed the substrate. Potato plantlets were fed with corrected Hoagland solution. In the first experiment, Treatments were particle size of sodium silicate (nano and micro) and eleven concentrations (Non-spraying, Distilled water, 100, 200, 300, 400, 500, 600,700, 800 and 900 mg l-1). The pH of Concentrations were measured and was in the range of 7.5 (distilled water) and 11.6. In the second experiment, the optimal concentrations nano and micro particles of first experiment and three pH levels (5, 7 and 11.3) were used. In both experiments, membrane stability index, photosynthesis parameters, chlorophyll a, b and cartenoids, shoot dry weight, silicon concentration and amount, yield and yield components of minituber were measured.
In the first experiment, the results showed that with increasing silicon concentration up to 400 mg l-1, photosynthesis, chlorophyll a and yield of potato minituber, significantly increased. Membrane stability index increased, transpiration reduced, water use efficiency increased, chlorophyll a and cartenoids of potato leaves increased as a result of nano and micro silicon foliar application up to 400 mg l-1and effects of nano particles on traits more than of micro particles. But, both of silicon particle sizes had a negative effect on traits in higher concentrations. In second experiment, effect of nano silicon particles to improve membrane stability index, chlorophyll b, mean of minituber weight and shoot dry weight traits was higher than the micro particles by 5.4, 9.7, 9 and 12 percentages, respectively. Also, membrane stability index, shoot dry weight and water use efficiency trials, improved in foliar application with pH 5 compared to 11.3 by 8.8, 6.11 and 21.3 percentage, respectively. Reducing the acidity of nano and micro-particles sprayed silicon was caused to increasing of photosynthesis, decreasing of transpiration, increasing of silicon amount of shoot significantly.
Optimal concentration was obtained to foliar application of nano and micro Sodium silicate particles. Overall, the best treatments were 400 mg l-1 sodium silicate and pH=5.