Calcium l-aspartate nanoparticles modify the root ultrastructure and improve plant yield in Brassica napus L

Abstract

Calcium (Ca) is an indispensable nutrient in plant development. Nanoparticles (NPs) are widely used in agricultural production, among which calcium l-aspartate nanoparticles (Ca(l-asp)-NPs), as a new type of Ca fertilizer, have been proven to benefit plant root improvement and stress tolerance. However, the effect of Ca(l-asp)-NPs on the plant root ultrastructure and yield is still not well known. Therefore, in this study, we examined the influence of Ca(l-asp)-NPs on the cellular structure, yield factors, and root nutrients in rapeseed roots. For this purpose, two different experiments were set up: a short-term hydroponic experiment with three treatments: -Ca, no Ca application; NPS-100, 100 mg L⁻¹ Ca(l-asp)-NPs; and Ca-100, 100 mg L⁻¹ Ca(NO<inf>3</inf>)<inf>2</inf>·4H<inf>2</inf>O and a long-term pot experiment with four treatments -Ca, no Ca application; NPS-100, 100 mg kg⁻¹ Ca(l-asp)-NPs; NPS-200, 200 mg kg⁻¹ Ca(l-asp)-NPs; and Ca(NO<inf>3</inf>)<inf>2</inf>, 130 mg kg⁻¹ Ca(NO<inf>3</inf>)<inf>2</inf>·4H<inf>2</inf>O. The results suggested that the application of Ca(l-asp)-NPs had well-organized intracellular cortical thin-walled cells in the root cross-section structure and had increased the diameter of the root system and thickness of the cortex. Moreover, Ca(l-asp)-NPs further improved plant traits, yield-related factors, and the Ca fertilizer utilization rate. In addition, 200 mg kg⁻¹ Ca(l-asp)-NPs increased the uptake of Ca, Mg, and B contents by the root system while decreasing the uptake of Fe, Mn, and Cu elements. Taken together, the application of Ca(l-asp)-NPs positively impacted the root cellular structure and rapeseed yield. This study provides a solid foundation for considering Ca(l-asp)-NPs as a nano fertilizer for soil application aimed at enhancing.