The influence of silica nanoparticles containing boron on growth of cucumber (Cucumis sativus L.)
Abstract
Boron (B) is one of the essential micronutrients needed for proper growth and high productivity of plants. It performs important functions in the plant life cycle, and both deficiency and excess of B disrupt numerous metabolic and anatomical processes in plants. At the same time, the range of concentrations determining its deficiency or toxicity is relatively narrow [1]. In the soils of Poland and most regions of the world, boron deficiency is quite common. The role of B in plant nutrition is still the least understood of all the nutrients. Boron deficiency in crops is probably more widespread globally than deficiency of any other micronutrient. Probably, the most common and immediate reaction of plants to low B supply is the impairment in root growth and it is species specific [2,3]. Foliar application of nutrients, especially microelements, is a common practice, but the effects depends on many factors: time, humidity, type of solute (hydrophobic/hydrophilic), precipitation, penetration by stomata, accompanying ions [4]. Future research should focus on realistic risk assessment of nanoparticles in plants by measuring the rate of nanoparticles uptake, the size exclusion limit of the apoplast, and understanding the physiological characteristics of plants that promote uptake [5]. The use of many nanomaterials give rise to poisonous effects, which alters morphological, anatomical, and physiochemical changes within the plant system. Many other nanoparticles have been found to have growth regulating properties which brings significant increases in biomass and even improvements in nutritional quality. An issue requiring further research are mechanisms of transport of nanomaterials through plant cells and the entire plant [5-8]. Water suspensions of silica (SiO2) nanoparticles (Ø 20 nm) with boric acid were used as a fertilizer providing plants with B. Applied boron-containing preparations resulted in a significant reduction in the weight of fresh and dry cucumber, both in shoots and roots, while regulating the water content compared to plants grown without B. The concentration of B in plant parts was significantly different. Silica nanoparticles with B applied to the leaf surface resulted in an increase in the B content in plants compared to plants grown without these nanoparticles and treated only with boric acid. Doubling the dose of boron in the preparation with silica resulted in the highest accumulation of B in all tested plant organs.
