Silicon is a non-essential element but promotes growth in olive plants

Abstract

Silicon (Si) is the second most abundant element in the Earth's crust, so all plants growing in soils contain Si. However, they differ in their ability to accumulate Si, being fruit trees, including the olive, low Si accumulators. Several works have shown that Si nutrition stimulates vegetative growth and nutrients uptake having also other beneficial effects. As a result, some authors have hypothesized Si could be considered essential, but its essentiality has not been proven yet. Therefore, the aim of this work was to study the possible essentiality of Si in olive. Two experiments were performed with ‘Arbequina’ olive seedlings cultivated in a silicon-free medium under controlled conditions. The treatments consisted of the application of different Si doses (0, 10, 20, or 30 mg L−1) by foliar sprays once a week. In both experiments, both shoot growth and plant dry weight was increased, including plants growing in absence of Si (control). Growth showed a quadratic response: the doses of 10 and 20 mg L−1 of Si produced the greatest growth. No differences between plants treated with higher doses of Si or grown in the absence of Si were observed. Also, the low Si dose (10 mg L−1) enhanced stomatal density and size. K nutrition was affected by Si foliar applications too; K concentration in plants increased when they received the dose of 10 or 20 mg L−1, in addition K (Rb) uptake and translocation rates were influenced by Si doses. Since the absence of Si did not prevent plant growth, the results indicate that Si is not an essential element despite it stimulates growth probably because it promotes the uptake and translocation of nutrients, particularly K.