Fighting against plant saline stress: Development of a novel bioactive composite based on bentonite and L-proline

Abstract

Soil salinity is one of the most critical environmental stresses that affects crop productivity. In a context in which world demand for food is growing continuously, this problem requires urgent attention. Actions that go beyond traditional agricultural practices are needed. The objective of the current study was to develop a bioactive, economic, and sustainable compound that can increase the tolerance of cultivated plants in saline-stress situations by combining the hosting capacity of natural bentonite nanoclay (Bent) with a phytoactive osmoprotective compound, L-Proline (Pro). The Bent-Pro nanocomposite synthesis method, its final chemical structure, and in vitro bioactivity were addressed here. The results indicated that Bent can retain a maximum of 14.4% (w/w) of Pro. The (001) X-ray diffraction (XRD) peak of Bent shifted to smaller angles in the pattern of Bent-Pro, indicating that Pro has a monolayer arrangement between the Bent layers. The results of transmission electron microscopy (TEM) also supported this result. Pro was also retained on the edges or external surfaces of Bent, as indicated by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). In addition, Pro functional groups identified by Fourier-transform infrared (FTIR) spectroscopy indicated that it was present in its zwitterionic form. The role of Bent-Pro as a protector against plant saline stress was assayed using Arabidopsis thaliana (A. thaliana) as a model, demonstrating that it mitigates the detrimental effects of NaCl-mediated salt stress on seed germination and the leaf chlorophyll level, thus highlighting the relevance of this contribution and the versatility and broad applicability of clays.