# Impact of Silicon-Based Biostimulant on Improving Growth and Morpho-Physiological Traits of Sweet Basil (Ocimum basilicum L.) in a Glasshouse Production System

## TL;DR

This study shows that silicon-based biostimulants can improve sweet basil growth and health in glasshouse conditions, but the right dose and formulation are crucial.

## Contribution

The study identifies optimal application rates and formulation effects of silicon-based biostimulants for sweet basil in controlled environments.

## Key findings

- Lower doses of silicic acid tetraethyl ester improved 7 out of 12 traits in sweet basil.
- Higher doses of silicon reduced leaf size and morphology but improved stress resistance indicators.
- Root-to-shoot ratios were low with the SiO2 and chelated iron formulation across all treatments.

## Abstract

Silicon-based biostimulants are gaining increasing interest for their ability to enhance plant performance and stress tolerance. In protected cultivation, where environmental conditions are already carefully managed, it remains unclear whether adding biostimulants provides meaningful benefits and how they should be used. This study examines whether silicon (Si) biostimulants can enhance the growth and morpho-physiological traits of sweet basil (Ocimum basilicum L.) in glasshouse production and which application rates are most effective. Two Si-based products with similar silicon content and different formulations were applied as soil drenches at four rates (10 mL, 100 mL, 1 L, and 2 L per hectare). Plant growth, biomass, photosynthetic performance, and physiological traits including membrane stability and electrolyte leakage were measured. Overall, silicon treatments improved most traits compared with untreated plants. Basil receiving Si showed longer shoots and roots, greater fresh and dry weight, and healthier leaves with better photosynthetic activity, as reflected by higher SPAD values and chlorophyll content. The response often depended on the dose: lower rates (10 mL and 100 mL h−1) of the silicic acid tetraethyl ester (21% Si) led to clear improvements in 7 of 12 measured traits, while higher rates (especially 2 L ha−1) reduced leaf size and morphology. However, root length: shoot length ratios were low across all treatments with the second biostimulant product: SiO2 with chelated iron (T5–T9). Certain results are paradoxical, suggesting a trade-off in growth and defense. In some instances, low doses promote growth but potentially worsen some physiological indicators, while high doses inhibit growth but improve stress resistance indicators. The conclusion indicates that silicon-based biostimulants are valuable to include in single-harvest basil production systems, when applied at a suitable rate. Choosing the correct formulation and dose requires testing and optimization to the crop and growing system.